ComparisonoftheEfficiencyofUltraviolet/ZincOxide (UV/ZnO

Research ArticleComparison of the Efficiency of UltravioletZinc Oxide(UVZnO) and OzoneZinc Oxide (O3ZnO) Techniques asAdvanced Oxidation Processes in the Removal ofTrimethoprim from Aqueous Solutions

Moayede Taie 1 Abdolmajid Fadaei 2 Mehraban Sadeghi 2

Sara Hemati 3 and Gashtasb Mardani 2

1Studentsrsquo Research Committee Research Center Shahrekord University of Medical Sciences Shahrekord Iran2Department of Environmental Health Engineering School of Health Shahrekord University of Medical SciencesShahrekord Iran3PhD Student of Environmental Health Engineering Department of Environmental Health Engineering School of HealthShahrekord University of Medical Sciences Shahrekord Iran

Correspondence should be addressed to Abdolmajid Fadaei ali2fadaeyahoocom

Received 14 April 2021 Revised 30 May 2021 Accepted 10 June 2021 Published 18 June 2021

Academic Editor Sebastien Deon

Copyright copy 2021Moayede Taie et al+is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Nowadays advanced oxidation processes particularly photocatalyst process and catalytic ozonation by ZnO nanoparticles are themost efficient method of eliminating pharmaceuticals +e purpose of this study was to compare the efficiency of ultravioletzincoxide (UVZnO) and ozonezinc oxide (O3ZnO) techniques as advanced oxidation processes in the removal of trimethoprim(TMP) from aqueous solutions +e process consisted of 06 gL of ozone (O3) pH 75plusmn 05 TMP with a concentration of05ndash5mgL ZnO with a dose of 50ndash500mgL 5ndash30min reaction time and 30ndash180min contact time with UV radiation (6W256 nm) in a continuous reactor +e high removal efficiency was achieved after 25 minutes when ZnO is used in 1mgL TMPunder an operational condition at pH 75 When the concentration of the pollutant increased from 05 to 1 the average removalefficiency increased from 78 to 94 and then it remained almost constant An increase in the reaction time from 5 to 25minutes will cause the average elimination to increase from 84 to 94+e results showed that the efficiency of O3ZnO processin the removal of TMP was 94 while the removal efficiency of UVZnO process was 91+e findings exhibited that the kineticstudy followed the second-order kinetics both processes With regard to the results the photocatalyst process and catalyticozonation by ZnO nanoparticles can make acceptable levels for an efficient posttreatment Finally this combined system is provento be a technically effective method for treating antibiotic contaminants

1 Introduction

Today water crisis throughout the world is evident+ereforereusing the drinking water is very important One of thechallenges related to water reuse is the removal of emergingcontaminants (eg pharmaceuticals personal care products)[1] Antibiotics which are one of the biggest groups of drugsprincipally enter water sources by discharging from phar-maceutical industries and hospitals and urban wastewatereffluents [2] +e accumulation and persistence of antibiotics

in the environment can cause a potential hazard to theecosystems Actually some of these materials are genotoxicand mutagenic and cause cancer [3] Long-term exposure tolow doses of antibiotics leads to the selective amplification ofresistant bacteria which could shift to other strains [4]Trimethoprim has been reported to cause disorders in humanhealth and environment (ecotoxicological chronic ecotox-icity) modifying the breeding of animals and plants [5]

Trimethoprim (TMP) has been reported as one of theantibiotics currently detected in urban wastewaters and

HindawiInternational Journal of Chemical EngineeringVolume 2021 Article ID 9640918 11 pageshttpsdoiorg10115520219640918

surface waters [1] +is antibiotic concentration in surfacewaters and effluents was observed up to several hundred ngL [6] Concerns about trimethoprim are related to the po-tential for creating drug resistance [7] because of thewidespread use in the treatment of infections in the upperrespiratory tract and lower urinary tract and for kidneygastrointestinal and other bacterial infections since 1968 Itis also used for prophylaxis and treating veterinary infections[8] It is considered that trimethoprim is highly water solubleand provides low sorption to the sludge and easily enters andaccumulates in aquatic resources [5] +e elimination oftrimethoprim with the treatment of flocculation adsorptionand oxidation showed different trends and had an efficiencyof 10 50 and lower than 90 percent respectively [6] TMP isthe white powder that has high solubility in water [6] and itsstructure is illustrated [9] in Figure 1 Most of the currentlyused wastewater treatment techniques are not effective inremoving these compounds completely [4] For instanceozonation was found to be effective for the removal of TMPin the drinking water treatment process [10] Additionallyphotocatalytic processes that are based on absorption of lightfor generation of active radicals have become an alternativefor water clarification mechanism leading to mineralizationof organic compounds [11] Six intermediates were identi-fied during the photocatalytic decomposition of TMP +eexocyclic amino groups of the diaminopyridine ring andbridging methylene group are the potential active reactionsites in the TMP molecule [12] Advanced oxidation pro-cesses (AOPs) have been shown to have a high efficiency inthe elimination of various organic contaminants fromdrinking water and wastewater [1] It is evident that researchhas recently been directed toward the application of AOPsdue to their high performance in the decomposition of theorganic matter [13] Among various AOPs ozonation wasemployed as one of the most popular AOPs Ozonation hasbeen traditionally employed in drinking water treatment forodor and taste control and disinfection and for wastewaterdisinfection Today advanced oxidation processes for theelimination of pharmaceuticals in waters with emphasis onthe use of catalysts have begun to enhance [14] Instances ofheterogeneous catalysts used in the advanced oxidationprocesses can be metal oxides such as ZnO and TiO2 that areinexpensive commercially available in various crystallineforms and particle characteristics nontoxic and photo-chemically stable [15] TiO2 and ZnO semiconductors arethe most effective ZnO has a wide band gap with an energygap (EG) of about 33 eV As a photocatalyst ZnO has someimportant advantages such as low price and high photo-catalytic activity (sometimes activity bigger than TiO2) +ebiggest advantage of ZnO is that it absorbs a larger fractionof the UV spectrum compared with TiO2 [16] Unfortu-nately these process measures have their own disadvantageslike the difficulty in reusability of the adsorbent the for-mation of degradation by-products poor stability high costand lack of practicality [17]

In this work we compared the following two techniquesused for trimethoprim degradation ozonezinc oxide (UVZnO) and ozonezinc oxide (O3ZnO) +e objective of thisstudy is to investigate and compare the efficiency of

ultravioletzinc oxide (UVZnO) and ozonezinc oxide (O3ZnO) techniques as advanced oxidation processes in theremoval of trimethoprim from aqueous solutions+e effectsof ozone concentration TMP concentration ZnO dose andresidence time on removal efficiency were also explored

2 Materials and Methods

21 Chemicals TMP (standard gt98) was purchased fromSigma-Aldrich with CAS number 738-70-5 HPLC-grademethanol and ACN were supplied by Merck (Germany) AMilli-Q ultrapure water system (USA) was used to obtainHPLC-grade water NaOH and H2SO4 were used as pHadjustment chemicals ZnO (99 purity Merck) was usedfor all experiments as received Zinc oxide nanoparticleswith 99 purity 10ndash30 nm particle size 20ndash60m2g speciallevel nearly spherical and milky white were used ZnO wasprovided from Isfahan Science and Technology Town inIsfahan Figure 2 illustrates the SEM of ZnO nanoparticlesX-ray diffraction (XRD) (Siemens D5000 Germany) wasused to investigate the crystalline phase and solid structureof the ZnO nanoparticles (at 200 keV)

22Experiments Stock solutions were prepared in ultrapurewater by constant stirring over 30min by ultrasonic batch[18] +e concentration of TMP in the stock solution was1000mgL [6] In this study several parameters were ex-amined including catalyst doses (5 250 and 500mgL) andconcentrations of TMP (05 1 and 5mgL) in a syntheticwater model and contact time in order to investigate theinfluence of these parameters on the removal process [6]Before reaction the heterogeneous mixture was equilibratedfor 15min Its pH value was maintained at 75plusmn 05 and thereaction temperature was maintained at 25plusmn 05degC Con-tinuous experiments were performed in a glass cylinder witha height of 75 cm and a capacity of 11 L +e solution wascirculated through a peristatic pump Ozone dose was set on06mgL +e ozone was generated from pure oxygen(gt9999) using an ozone generator (Model OZ1-BTUOzotech CA USA) which was calibrated by an iodometrymethod [19] as in

O3mgmin

(A + B) times N times 24

T(min) (1)

where A mL of thiosulfate consumed in the first gas B mLof thiosulfate consumed in the second gas T ozonation timein minutes and N normality of sodium thiosulfate

NH2

H2N

N

N

O

O

O

Figure 1 Trimethoprim structure

2 International Journal of Chemical Engineering

Ozone flow was transferred from a Venturi tube in thedrift pump and was injected into the solution from thesintered diffuser for the maximum distribution and disso-lution of gaseous ozone [20 21] +e ozone contact timeranged from 5 to 30min Aliquots of samples were taken atpredetermined time intervals (5 10 15 20 25 and 30min)[18] +e semicontinuous photoreactor consisted of a ver-tical reactor with a total volume of 1 L a UV lamp and amagnetic stirrer in safety pilot +e source of radiation was alow-pressure mercury lamp (6W) with a wavelength of254 nm and a quartz glass tube made by Arda France [22]+e suspension was continuously stirred using a magneticstirrer Subsequently the solution was irradiated for180min Aliquots of samples were taken at predeterminedtime intervals (30 60 90 120 150 and 180min) [18]

23 Analysis Solid-phase extraction using Oasis HLB car-tridges (200mg) was applied to samples to reduce the saltcontent in the matrix before the chromatographic analysisCartridges were conditioned with 4mL of methanol and3mL of water and loaded with a 50mL of the samples +ecartridges were washed with 5mL of Milli-Q water and theneluted with two aliquots of 5mL of methanol Before in-jection extracts were diluted with 90 10 (H2Omethanol) torecover the initial concentration [23]

24 Analytical Equipment and Methods +e concentrationof TMP was monitored by HPLC (series1200 AgilentTechnologies) equipped with C18 analytical columns (150mmtimes 46 mm 5 μm) used in isocratic mode (1mLmin)with a FID detector +e mobile phase included methanoland water (1090 VV) with a flow rate of 1mLmin +emineralization content of TMP was determined on the basisof the TOC measurements TOC measurements were per-formed by using a total organic carbon analyzer (ShimadzuTOC-VCSH) +e ultraviolet spectrophotometric screeningmethod (Shimadzu 1700 Japan) was used to measure nitrateand ammonium ions during the photodegradation of TMP

25 PrecisionandAccuracy All reagents were obtained fromSigma-Aldrich and Merck Net purification water was usedfor purification of samples and standards during the studyAll glass and plastic containers were washed with 10HNO3overnight and then washed with deionized water to

minimize contamination +e limit of detection (LOD) forTMP was 001 microgL +e concentration of the TMP wasrecorded as zero if it was lower than the limit of detectionFor study method validation the TMP concentration wastested in spiked deionized water

26OzoneDecomposition +e residual ozone concentrationin samples was determined by spectrophotometry using theindigo method [24] by equation (2) +e concentration ofgaseous ozone was determined by iodometry using potas-sium iodide solutions and the residual ozone concentrationwas determined in the gas phase +e amount of ozonedecomposition was defined as the difference between theinitially applied ozone dose and the sum of the residualozone doses in the water and gas [24]

ozone concentration inmgO3

l A 100f b V

(2)

where A difference in absorbance between sample andblank b path length of the cuvette in cm V volume of thesample added in mL (normally 90mL) and f 042

3 Results and Discussion

31 Preliminary Experiments with TMP +e observationsshowed that ZnO nanopowders alone did not degrade TMPbut removal efficiency of ozonation alone was shown to be89 However O3ZnO removed about 99 of TMP within30 min of reaction time (Figure 3) +e decomposition ofTMP is very high in the presence of the ZnO catalystcompared with when the catalyst was not used Ozone isunstable in water Depending on the water quality the half-life of ozone is in the range of seconds to minutes +eprincipal secondary oxidant formed from ozone decom-position in water is the OH radical +e stability of ozonelargely depends on the water matrix especially its pH thetype and content of natural organic matter (NOM) and itsalkalinity In the experiments the synthetic water model wasin Milli-Q water and pH value was maintained at 75plusmn 05[25]

It seems that ZnO nanopowder alone did not degradeTMP (05mgL) and the degradation of antibiotics by UVirradiation alone has removal efficiency of about 27(Figure 4) As well as the UVZnO photocatalytic processremoved about 91 of TRI within 180min of irradiation+e present results agree with a number of various previousAOP studies that have the discussion on the removal ofpollutants by the similar method Advanced oxidationprocesses (AOPs) through the production of hydroxylradicals (HObull) have been considered to be very hopefulalternative techniques to water decontamination [13] +eseexperiments exhibited that both UV light and a photo-catalyst such as ZnO were required for the effective removalof pollutants because the photocatalytic destruction of or-ganic matters in solutions is started by photoexcitation of thesemiconductor and after that formation of an electron-holepair on the surface of catalyst [26] Similarly for a study onCI Acid Orange 7 and diazinon photocatalyst degradation

Figure 2 +e SEM image of ZnO nanoparticles

International Journal of Chemical Engineering 3

of TMP was negligible when ZnO nanopowder and UV lightwere used on their own [26]

In the UVZnO photocatalyst process zinc oxide whenilluminated by photons having an energy level that surpassestheir band gap vitality excites electrons (eminus ) from the valenceband to the conduction band thus creating holes (h+) in thevalence band +e photogenerated valence band holes reactwith either water (H2O) or hydroxyl ions (OHminus ) adsorbed onthe catalyst surface to create hydroxyl radicals (bullOH) whichare powerful oxidants and degrade TMP +e hydroxylradical formation caused by radiation to the ZnO surface isshown in [27]

ZnO + h⟶ ZnO eminus

+ h+

( 1113857 (3)

h+

+ TMP⟶ TMP0+⟶ oxidation of the TMP (4)

h+

+ H2O⟶ H++ OH0

(5)

h+

+ OHminus+ ⟶ OH0

(6)

+e biggest advantage of ZnO is its ability to absorb arange of electromagnetic and photocatalytic capabilitiesunder UVA radiation In fact ZnO is nontoxic withchemical stability at high temperatures and able to producechemical oxidation [28]

32 Effect of theCatalyst Doses Increasing the concentrationof the catalyst has a slight effect on the increase of the re-moval average rate Results of the comparison of the meanvalues of the removal efficiency in Figure 5 show that in-creasing the dose of the catalyst has achieved faster de-struction rates and higher overall decomposition of TMP+us the efficiency of removal was 8749 when 50mgL ofZnO was used whereas 904 was achieved by increasingthe catalyst dose to 250mgL and 9238 when 500mgL ofcatalyst was used +e catalytic ozonation process has twomechanisms direct oxidation of pollutants by ozone mol-ecules and indirect oxidation by hydroxyl radicals generatedfrom the molecular ozone [29] +e increase of ZnO leads tothe increase of the ozone decomposition rate and the in-crease of OH production there upon the highest removal isachieved (Figure 4) Also results of a similar study haveshown that the high reactivity of hydroxyl radicals that weregenerated in high ZnO concentrations during the oxidationprocess effectively degraded TCP and thus confirms thefindings [30] Another study showed that the most effectiveTiO2 dose was recognized as 100mgL in terms of TMPdecomposition [12] Another study showed that TiO2 dose of200mgL was most effective in terms of TMP decomposition[23] Abellan et al reported that degradation of SMX andTMP was improved when the TiO2 concentration was in-creased up to 500mgL [31]

+e observations showed the degradation of TMP in-creased with the enhancement of ZnO dosage (P val-ue 0006) presumably due to the increase in bullOHproduction +e most effective ZnO dose was recognized tobe 500mgL in terms of TMP destruction (Figure 4) +eefficiency increased slightly from 831 at ZnO dose of50mgL to about 91 at 500mgL of ZnO It has beenconjectured there was no improvement with the furtherincrease in the catalyst doses probably +e results provedwere similar to degradation of other contaminants (anti-biotics pesticides and dyes) TMP removal is signally af-fected by catalyst dosage and the photodegradationefficiency increases with an increase in ZnO dosageHowever at high dosage the increase of the rate was de-creased gradually Previous studies compared the catalyticactivity of ZnO and TiO2 for the degradation of sulfame-thazine and chloramphenicol respectively and reported thatZnO was slightly more effective than TiO2 [14]

It can be seen that the destruction of antibiotics with theenhancement of ZnO concentration was probably due to theincrement in OH generation However increasing ZnO

0

20

40

60

80

100

5 10 15 20 25 30

Effic

ienc

y (

)

Time (min)

O3ZnOZnOO3

Figure 3 TMP removal by different treatment processes(ZnO 500mgL)

0

20

40

60

80

100

Effic

ienc

y (

)

30 60 90 120 150 180Time (min)

UVZnOZnOUV

Figure 4 TMP removal by different treatment processes(TMP 05mgL) (P value 0032)


concentration above 500mgL did not deliver any criticalchange in antibiotics degradation +is may be due to di-minishing UV light penetration as a consequence of anincrease in turbidity and thus decreasing the photoactivatedvolume of the suspension [32] In previous studies on otherpollutants by expanding the initial ZnO dosage from 00 to50 gL mineralization of amoxicillin ampicillin andcloxacillin and also degradation of CI Acid Orange 7 ad-ditionally expanded until reaching a certain level [26]According to the previous investigations and our work theincrease in the amount of catalyst added increased thenumber of active sites on the photocatalytic surface whichthus expanded the number of hydroxyl and superoxideradicals Also after getting the optimal level of the photo-catalyst further expanding photocatalyst dosage does notincrease removal efficiency [33] Hence after that furthercatalyst loading does not influence the degradation signif-icantly often +is observation can clarify as far as acces-sibility of active sites on the catalyst surface and the influx ofUV light into the solution +e total active surface areaincreases with an increase in the catalyst dosage At the sametime due to the increase in the turbidity of the solutionthere is a reduction in UV light influx as a result of increaseddispersion effect and hence the photoactivated volume ofthe solution decreases Furthermore at high catalyst loadingit is hard to maintain the homogeneity of the solution due toparticles agglomeration which diminishes the quantity ofactive sites [26] +e photocorrosion of ZnO is complete atpH lower than 4 and at pH higher than 10 and no pho-tocorrosion of ZnO takes place at pH 7 [34] Shankaraiahet al reported that the UVTiO2 process removed 61 to 90of norfloxacin [35] Another study showed that TiO2 pho-tocatalysis was the most effective method for removingβ-lactam antibiotics [36] Aissani et al indicated that theUVTiO2 process removed 41 of sulfamethazine (+ecombination of photocatalysis process [34]

One study indicated that a nanoparticle TiO2-basedphotoelectrocatalytic process has high potential to be uti-lized as an appropriate treatment method for pharmaceu-tical effluents containing cefotaxime antibiotics [37] One ofthe most important problems of this process is recycling of

nanoparticles which can be addressed by doping andcodoping of metal oxide nanomaterials immobilization ofnanoparticles on appropriate matrices and nano-basedfilters through the combination of clayZnO nano-composites [38 39]

33 Effect of Initial TMP Concentrations +e effect of theinitial TMP concentration was an assessment Figure 7shows the rate of decomposition was greater for higherTMP concentrations +e catchment of ozone is greater in amore concentrated solution obviously ozone is in exposurewith more pollutant molecules and more of trimethoprimantibiotic molecules are decomposed by ozone

+e results of the comparison of the mean values of theremoval efficiency show that with increasing the initialconcentration of TMP the efficiency of removal has in-creased Hence the removal efficiency was 7889 when theinitial concentration of trimethoprim was 05mgL and thisamount increased to 9406 for 1mgL TMP and was9688 when 5mgL of pollutant was used Hence forachieving high removal efficiency in a few minutes it isbetter to use catalytic ozonation in a high concentration ofcontamination or the concentrated solution +e ozonationefficiency increases in higher concentrations of trimetho-prim and zinc oxide Passing through more concentratedsolutions ozone molecules are encountered with morepollutants Hence the catchment and consumption of theozone solution are greater in more concentrated solutionsand as a result the direct oxidation of the pollutants occursmore by the ozone molecules Shabani et al [20] concludedthe same in their research by using a new reactor systemcontaining a centrifuge pump and a Venturi tube and thecapability of ozonation in the treatment of the leachategenerated in the landfill indicated that efficiency is muchgreater in more concentrated leachates [20] +e effect of theinitial TMP concentration was also been evaluated and theresults are shown in Figure 7 +e rate of photodegradationwas higher for lower TMP concentrations (P value 0006)which the reason for the interfering effect of turbidityprobably +is process has improved in lower TMP con-centrations (more dilute solutions) because turbidity in-terferes with the UV irradiation It took less than 120min tobreak down the TMP compound if we want to save oureconomy and time [9] As for dyes [33] and insecticides [26]in previous similar studies the rate of degradation reduceswith increasing initial concentration of a model solution+e level of photodegradation diminished with expandingthe concentration of pollutants Also when the initialconcentration is increased more organic substances areadsorbed on the surface of ZnO Along these lines there arejust a less number of active sites for adsorption of hydroxylions so the production of hydroxyl radicals will be de-creased Furthermore as the concentration of a pollutantsolution increased the photons get intercepted before theyreach the catalyst surface thus the absorption of photons bythe catalyst diminishes and subsequently the degradationpercent is decreased [40ndash42]

6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)

ZnO = 50mgLZnO = 250mgLZnO = 500mgL

Figure 5 Effect of initial ZnO dose on degradation duringtreatment processes UV 6W TMP 05mgL and pH 75plusmn 05


34 Effect of Reaction Time In this study the removal ef-ficiency has increased over time +e results of the com-parison of the mean values of removal efficiency in Figure 3show that with increase in the time due to a greater op-portunity for contact of hydroxyl radicals and trimethoprimmolecules the removal efficiency increases from 8463 inthe first 5 minutes to 9419 after 25 minutes However theslope of the curve decreased in the latter times and finallyafter 30 minutes the efficiency of the elimination decreasedto 9294 percent At 2 hours the slope of the graph washigher than the remaining time It was reduced after this120min and the removal efficiency obtained was around thesame removal efficiency obtained at 120min +e rate ofphotodegradation increased slightly from 0 in the initial timeto about 90 at 120min when the initial TMP concentrationwas 05mgL and catalyst dose was 500mgL Overallperformance increases with increasing contact time In astudy by Adhami to evaluate the efficacy of the UVZnOphotocatalytic process in removing antibiotic cefalexin fromaqueous solutions they increased the removal efficiency byincreasing the contact time due to the production of

hydroxyl radicals [43] Another study showed that removalefficiency was increased with increasing contact time [44]

35 Kinetics Determining the Reaction +e decompositionrate of TMP was evaluated in the photocatalytic oxidationprocess +e photodegradation data of TMP show thesecond-order reaction rate in this experiment and Figure 8shows the photodegradation rate for TMP Ct is the tri-methoprim concentration at the desired time R2 09675and K 00703 (Lmg s) +e O3ZnO process data of TMPare presented in Table 1 In a study by Elmolla andChaudhuri the degradation of amoxicillin ampicillin andcloxacillin antibiotics in aqueous solutions by the UVZnOphotocatalytic process followed a pseudo-first-order kinetics[32]

36 Mineralization Studies In order to study the mineral-ization of TMP the TOC and concentrations of NO3

minus andNH4

+ ions were measured Table 2 shows that the TOC of thesolution (C0 05mgL ZnO 500mgL and pH 75) hasdecreased about 91 after 180min +e reduction of TOCand the increase of ionsrsquo concentrations in the solutionrepresent the mineralization of TMP solution +e mea-surement of UV absorption of TMP solution at 220 and275 nm in the presence of HCl as a reagent enables rapiddetermination of nitrate For determination of ammoniumions a solution of TMP was prepared using different re-agents such as ZnSO4 NaOH and Rochelle(KNaC4H4O64H2O) and after 10min the intensity ofabsorbance peak was measured by a spectrophotometricmethod [45] +e results are shown in Table 3

37 Ozone Decomposition +e consumed ozone outletozone and residual ozone were measured at differentconcentrations of the catalyst and trimethoprim and someof their results are shown in Figures 9 and 10 +ese graphsindicate that the increase in the initial concentration oftrimethoprim has reduced the amount of ozone depletedfrom the reactor and increased the amount of soluble ozoneand consumed ozone Also the increase in the catalyst dosehas reduced the amount of ozone depleted from the reactorand slightly increased the amount of ozone and the ozonesolution and consumed ozone +e transfer efficiency ofozone and the transferred dose are shown in Table 2 Anegative sign indicates that the consuming ozone for 05mgL TMP is less than the outlet ozone Using the ozoneconcentration average in the solution the ozone concen-tration average in the outlet gas of reactor and the consumedozone concentration average the transfer efficiency of ozonewas calculated using equation (7) By measuring the averagecumulative ozone depleted from the reactor and the averagecumulative ozone consume the transfused dose was cal-culated using [46]

0

20

40

60

80

100Ef

ficie

ncy

()

0 2 4 6TMP concentration (mgL)

Figure 6 Effect of initial TMP concentrations on the UVZnOprocess

6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)

TMP = 05ppmTMP = 1ppmTMP = 5ppm

Figure 7 Effect of initial TMP concentrations on degradationduring treatment processes UV 6W ZnO 500mgL and pH75plusmn 05


0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)

Figure 8 Effect of catalyst dose on ozone decomposition (TMP 05mgL) bull consumed ozone residual ozone and outlet ozone

Table 1 Summary of the kinetic analysis results of TMP removal for O3ZnO process

Kinetics K R2

Zero order 0018 (mgL s) 07553First order 0008 (Ls) 09000Second order 0041 (Lmg s) 09720

Table 2 TOC and ion measurements for degradation of trimethoprim using UVZnO process

Time (min) 0 90 180TOC 420 084 047NOminus

3 concentration (mgL) 079 67 164NH+

4 concentration (mgL) 004 13 329

Table 3 +e transfer efficiency of ozone and transferred dose

ZnO 500 (mgL) ZnO 250 (mgL) ZnO 50 (mgL) TMP (mgL)4966 4583 3833 05 Transfer efficiencyminus 885 minus 1561 minus 3114 05 Transferred dose6933 645 5766 1 Transfer efficiency2703 1684 491 1 Transferred dose8433 83 8083 5 Transfer efficiency4877 4670 4359 5 Transferred doselowastA negative sign indicates that the consuming ozone for 05mgL TMP is less than the outlet ozone

y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)

Figure 9 +e second-order reaction rate in TMP photo-degradation oxidation process

005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)

TMP concentration (mgL)

Figure 10 Effect of initial TMP concentrations on ozone de-composition (ZnO 50mgL) bull consumed ozone residualozone and outlet ozone


() the transfer efficiency of ozone inlet gas minus gas outlet

inlet gastimes 100 (7)

mgLmin

1113874 1113875 transferred dose (mgLmin)gas consumed minus (mgLmin)gas outlet

(l)reactor volumetimes(min)examination time (8)

Ozone decomposition is a function of catalyst concen-tration and with increasing the concentration the rate ofdecomposition increases especially at the early stages of theprocess As already mentioned it shows the catalytic role ofdecomposition of ozone and the formation of hydroxylradicals [47] Increasing the concentration of contaminantsalso increases the decomposition of ozone molecules be-cause in the more concentrated solution the ozone mole-cule is more closely contacted with trimethoprim moleculesIn addition to radical hydroxyl production the reactionoccurs between the ozone and the trimethoprim Hence wehave high ozone consumption and more pollutant removalwhile in the dilute solution this direct reaction is less [48]+e results of transfer efficiency of ozone and transferreddose of ozone can be related to the type of the system usedfor ozonation +e system used in this research includes aVenturi tube with a peristaltic pump with return solutionSince in this case ozone is injected by pressure into theeffluent after passing through the Venturi tube and througha structure similar to a glass diffuser the injection of the gasin this system makes the gas bubbles smaller and so theoverall contact area of the gas bubbles with the liquid phaseincreases +erefore it can be expected that ozone de-composition and removal efficiency can be improved withincreasing the solution concentration Here the effect of anincrease in the initial concentration of antibiotics is greaterthan the increase in the catalyst dose [20 46] Similar re-search has shown that the ratio of ozone consumption toantibiotic degradation is low in the early minutes of thereaction in the ozonation process and gradually increasesHowever high ozone consumption per unit of the pollutant

can be related to the competition of trimethoprim withintermediates in combination with oxidizing agents Per-haps the other reason is to reduce the efficiency of the ozonemolecules at the end of the process due to the reducedreaction rate of the carbonic acid produced [49]

38 Chemicals +e results of the SEM image showed thatthe Zn nanoparticle size in this study was less than 150 nmand the SEM technique showed no impurity in the zincoxide nanoparticle used in this study (Figure 2) X-raydiffraction (XRD) was conducted to characterize thestructural properties of catalyst (characterization of con-stituent phases and crystalline size of nanoparticle) (Fig-ure 11) +e peaks of the XRD patterns of the ZnOnanoparticles are quite sharp indicating the crystallinenature of the nanoparticles

39 Comparison of O3ZnO and UVZnO Processes +eresults indicated inefficient adsorption of TMP by ZnOalone (9) In fact the adsorption process was an inefficienttreatment method to be used for the removal of TMP as anindependent process (Figures 3 and 4) Totally the ad-sorption process only transfers the contaminant from theliquid to the solid phase (adsorbent construction) and doesnot change its toxic character According to the resultsunder similar conditions including ZnO dose concentra-tion of TMP and experiment location the O3ZnO processshowed greater removal efficiency than the UVZnO process(Figures 3 and 4) +e optimal conditions for removal ofTMP were 05mgL of TMP 500mgL of ZnO dose 06 gL

Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)

Figure 11 +e X-ray diffraction (XRD) patterns of the ZnO nanoparticles


of ozone concentration and pH 75 Under these condi-tions removal efficiency of UVZnO and O3ZnO processeswas obtained as 91 and 94 respectively +e result ob-tained was found similar or even better than those reportedby other authors (Table 4)

4 Conclusions

+is study indicated that the presence of nano-ZnO with O3showed a significant increase in the degradation of TMPthan with ozonation alone +ere is a direct relationshipbetween TMP concentration ZnO concentration andcontact time with the removal efficiency +e increase ofZnO concentration from 05 to 500mgL will also lead to theincrease of the ozone decomposition efficiency thereforeproduction of OH increases which leads to an increase inthe degradation of antibiotics and removal efficiency in ashort time

Because the catchment and consumption of ozone in themore concentrated solution are much greater ozone hasexposure to more pollutants therefore ozonation efficiencyhas increased Of course type of the ozonation system andthe structure of the pollutant are very influential in ozonetransfer efficiency and doses and subsequently in the de-composition and consumption of ozone and removal of thecontaminants By UV irradiation alone degradation of TMPconcentrations was low while the mineralization by UVZnO photooxidation occurred in over time All resultsobtained from the present study clearly showed that ZnOconcentration TMP concentrations and contact timeplayed key operating factors in the removal of antibiotics+ere is a direct relationship between ZnO dose and contacttime with removal efficiency while this is reverse for TMPconcentration Based on the findings the removal efficiencyof the O3ZnO process was higher than that of the UVZnOprocess +erefore this method is suitable for the removal of

TMP because of its low cost safety and biocompatibilityand combination of UVZnO process with renewable energysources in order to reduce both economic and environ-mental impacts is recommended

Data Availability

+e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

+e authors declare that they have no conflicts of interest

Acknowledgments

+e authors thank the Shahrekord University of MedicalSciences (grant number 2757) for supporting this study

References

[1] F L Rosario-Ortiz E C Wert and S A Snyder ldquoEvaluationof UVH2O2 treatment for the oxidation of pharmaceuticalsin wastewaterrdquoWater Research vol 44 no 5 pp 1440ndash14482010

[2] G Z Kyzas J Fu N K Lazaridis D N Bikiaris andK A Matis ldquoNew approaches on the removal of pharma-ceuticals from wastewaters with adsorbent materialsrdquo Journalof Molecular Liquids vol 209 pp 87ndash93 2015

[3] C G B Brenner C A Mallmann D R Arsand F M Mayerand A F Martins ldquoDetermination of sulfamethoxazole andtrimethoprim and their metabolites in hospital effluentrdquoCLEANmdashSoil Air Water vol 39 no 1 pp 28ndash34 2011

[4] A L Batt I B Bruce and D S Aga ldquoEvaluating the vul-nerability of surface waters to antibiotic contamination fromvarying wastewater treatment plant dischargesrdquo Environ-mental Pollution vol 142 no 2 pp 295ndash302 2006

Table 4 Comparison of removal efficiency of antibiotics in aqueous solution by advanced oxidation processes

Antibiotic Environment Process Operation conditions Removalefficiency Reference

Trimethoprim Synthetic watermodel UVZnO O3ZnO

Ozonation rate 06 gL ZnO 500mgLlow-pressure UV (6W 254 nm) 91 94 +is

studyTrimethoprim Spiked STP effluent O3 01ndash03mM O3 pH 72 85 [50]Trimethoprim andciprofloxacin

25mM phosphatebuffer saline pH 7 O3H2O2UV

O3 01mMH2O2 005ndash01mM mediumpressure gt90 [51]

Ciprofloxacin Ultrapure water UVTiO2 Dose catalyst (035 gL) low-pressure UV 100 in45min [52]

Metronidazole Complex aqueousmatrix UVTiO2

TiO2 15 gL UV light intensity 65mWcmminus 2

88 in30min [53]

Tetracycline Deionized water USZnO+nanocomposite

ZnONC 488mg US frequency andpower 37 kHz and 256W

876 in45min [54]

Ciprofloxacin andtrimethoprim Ultrapure water UVO3

2ndash20mM O3 medium-pressurepolychromatic UV lamp sim100 [51]

CiprofloxacinSynthetic andsimulated

wastewater samplesO3CaO2

CaO2 0025mgL temperature 25degCozonation rate 1 gmin

956 and854 [55]

Ciprofloxacin Synthetic watermodel O3UVZnO

Ozonation rate 4 Lmin UV lamp 6W andlow pressure ZnO 03 gL

96 in30min [44]


[5] S Oros-Ruiz R Zanella and B Prado ldquoPhotocatalyticdegradation of trimethoprim by metallic nanoparticles sup-ported on TiO2-P25rdquo Journal of Hazardous Materialsvol 263 pp 28ndash35 2013

[6] D Ho S Vigneswaran H H Ngo et al ldquoPhotocatalysis oftrimethoprim (TRI) in waterrdquo Sustainable Environment Re-search (Formerly J Environmental Engineering and Man-agement) vol 21 no 3 pp 149ndash154 2011

[7] C C Ryan D T Tan and W A Arnold ldquoDirect and indirectphotolysis of sulfamethoxazole and trimethoprim in waste-water treatment plant effluentrdquoWater Research vol 45 no 3pp 1280ndash1286 2011

[8] A F Martins C A Mallmann D R Arsand F M Mayerand C G B Brenner ldquoOccurrence of the antimicrobialssulfamethoxazole and trimethoprim in hospital effluent andstudy of their degradation products after electrocoagulationrdquoCLEANmdashSoil Air Water vol 39 no 1 pp 21ndash27 2011

[9] J N Bhakta and Y Munekage ldquoDegradation of antibiotics(trimethoprim and sulphamethoxazole) pollutants using UVand TiO2 in aqueous mediumrdquo Modern Applied Sciencevol 3 no 2 p p3 2009

[10] Y Ji W Xie Y Fan Y Shi D Kong and J Lu ldquoDegradationof trimethoprim by thermo-activated persulfate oxidationreaction kinetics and transformation mechanismsrdquo ChemicalEngineering Journal vol 286 pp 16ndash24 2016

[11] M Malakootian N Olama and M Malakootian A NasirildquoPhotocatalytic degradation of metronidazole from aquaticsolution by TiO2-doped Fe3+ nano-photocatalystrdquo Interna-tional Journal of Environmental Science and Technologyvol 16 no 8 pp 4275ndash4284 2019

[12] Q Cai and J Hu ldquoDecomposition of sulfamethoxazole andtrimethoprim by continuous UVALEDTiO2 photocatalysisdecomposition pathways residual antibacterial activity andtoxicityrdquo Journal of Hazardous Materials vol 323 pp 527ndash536 2017

[13] I Michael E Hapeshi V Osorio et al ldquoSolar photocatalytictreatment of trimethoprim in four environmental matrices ata pilot scale transformation products and ecotoxicity eval-uationrdquo Science of the Total Environment vol 430 pp 167ndash173 2012

[14] M Klavarioti D Mantzavinos and D Kassinos ldquoRemoval ofresidual pharmaceuticals from aqueous systems by advancedoxidation processesrdquo Environment International vol 35no 2 pp 402ndash417 2009

[15] M Samarghandi G Asgari S Chavoshi Z Ghavami andJ Mehralipour ldquoPerformance of catalytic ozonation by FeMgO nanoparticle for degradation of cefazolin from aqueousenvironmentsrdquo Journal of Mazandaran University of MedicalSciences vol 25 no 128 pp 77ndash90 2015

[16] A Hassani A Khataee S Karaca C Karaca and P GholamildquoSonocatalytic degradation of ciprofloxacin using synthesizedTiO2 nanoparticles on montmorilloniterdquo Ultrasonics Sono-chemistry vol 35 pp 251ndash262 2017

[17] Y Shi Y Zhang Y Cui et al ldquoMagnetite nanoparticlesmodified β-cyclodextrin polymercoupled with KMnO4 oxi-dation for adsorption and degradation of acetaminophenrdquoCarbohydrate Polymers vol 222 Article ID 114972 2019

[18] U I Gaya A H Abdullah M Z Hussein and Z ZainalldquoPhotocatalytic removal of 2 4 6-trichlorophenol from waterexploiting commercial ZnO powderrdquo Desalination vol 263no 1-3 pp 176ndash182 2010

[19] Y Huang Y Yang J Jiang Z Xu C Zhu and L Li ldquoVisiblelight photocatalytic ozonation of oxalic acid by MnOx-g-

C3N4 compositerdquo Journal of Environmental Engineeringvol 144 no 8 Article ID 04018063 2018

[20] M Shabani F Essmaeil A Khoshfetrat andD Kahforoushan ldquo+e application of ozonation process forthe treatment of landfill leachaterdquo Journal of Civil and En-vironmental Engineering vol 44 no 76 pp 39ndash45 2014

[21] Y D Shahamat M Farzadkia S Nasseri A H MahviM Gholami and A Esrafili ldquoMagnetic heterogeneous cata-lytic ozonation a new removal method for phenol in in-dustrial wastewaterrdquo Journal of Environmental Health Scienceamp Engineering vol 12 no 1 p 50 2014

[22] C Baeza and D R U Knappe ldquoTransformation kinetics ofbiochemically active compounds in low-pressure UV pho-tolysis and UVH2O2 advanced oxidation processesrdquo WaterResearch vol 45 no 15 pp 4531ndash4543 2011

[23] C Sirtori A Aguera W Gernjak and S Malato ldquoEffect ofwater-matrix composition on trimethoprim solar photo-degradation kinetics and pathwaysrdquo Water Research vol 44no 9 pp 2735ndash2744 2010

[24] H Bader ldquoDetermination of ozone in water by the indigomethod a submitted standard methodrdquo Ge Journal of theInternational Ozone Association vol 4 no 4 pp 169ndash1761982

[25] K A H Buchan D J Martin-Robichaud and T J BenfeyldquoMeasurement of dissolved ozone in sea water a comparisonof methodsrdquo Aquacultural Engineering vol 33 no 3pp 225ndash231 2005

[26] N Daneshvar S Aber M Seyeddorraji A Khataee andM Rasoulifard ldquoPhotocatalytic degradation of the insecticidediazinon in the presence of prepared nanocrystalline ZnOpowders under irradiation of UV-C lightrdquo Separation andPurification Technology vol 58 no 1 pp 91ndash98 2007

[27] M H Dehghani B Heibati A Asadi I Tyagi S Agarwal andV K Gupta ldquoReduction of noxious Cr (VI) ion to Cr (III) ionin aqueous solutions using H2O2 and UVH2O2 systemsrdquoJournal of Industrial and Engineering Chemistry vol 33pp 197ndash200 2016

[28] T Razavi A Fadaei M Sadeghi and S Shahsavan markadehldquoStudy of the impact of combination of ZnO nanoparticleswith ultraviolet radiation (photocatalytic process) on theremoval of anionic surfactant linear alkyl benzene sulfonate(LAS) from aqueous solutions using taguchi statisticalmethodrdquo Desalination and Water Treatment vol 57 no 59pp 28755ndash28761 2016


[30] W-J Huang G-C Fang and C-CWang ldquoA nanometer-ZnOcatalyst to enhance the ozonation of 2 4 6-trichlorophenol inwaterrdquo Colloids and Surfaces A Physicochemical and Engi-neering Aspects vol 260 no 1 pp 45ndash51 2005

[31] M Abellan J Gimenez and S Esplugas ldquoPhotocatalyticdegradation of antibiotics the case of sulfamethoxazole andtrimethoprimrdquo Catalysis Today vol 144 no 1-2 pp 131ndash1362009

[32] E S Elmolla and M Chaudhuri ldquoDegradation of amoxicillinampicillin and cloxacillin antibiotics in aqueous solution bythe UVZnO photocatalytic processrdquo Journal of HazardousMaterials vol 173 no 1-3 pp 445ndash449 2010

[33] I T Peternel N Koprivanac A M L Bozic and H M KusicldquoComparative study of UVTiO2 UVZnO and photo-fentonprocesses for the organic reactive dye degradation in aqueous


solutionrdquo Journal of Hazardous Materials vol 148 no 1-2pp 477ndash484 2007

[34] T Aissani I Yahiaoui F Boudrahem S Ait ChikhF Aissani-Benissad and A Amrane ldquo+e combination ofphotocatalysis process (UVTiO2 (P25) and UVZnO) withactivated sludge culture for the degradation of sulfametha-zinerdquo Separation Science and Technology vol 53 no 9pp 1423ndash1433 2018

[35] G Shankaraiah S Poodari D Bhagawan V Himabindu andS Vidyavathi ldquoDegradation of antibiotic norfloxacin inaqueous solution using advanced oxidation processes(AOPs)mdasha comparative studyrdquo Desalination and WaterTreatment vol 57 no 57 pp 27804ndash27815 2016

[36] E A Serna-Galvis J Silva-Agredo A L GiraldoO A Florez-Acosta and R A Torres-Palma ldquoComparativestudy of the effect of pharmaceutical additives on the elim-ination of antibiotic activity during the treatment of oxacillinin water by the photo-fenton TiO2 -photocatalysis andelectrochemical processesrdquo Science of the Total Environmentvol 541 pp 1431ndash1438 2016

[37] Q Jiang R Zhu Y Zhu and Q Chen ldquoEfficient degradationof cefotaxime by a UV+ ferrihydriteTiO2 +H2O2 process theimportant role of ferrihydrite in transferring photo-generatedelectrons from TiO2 to H2O2rdquo Journal of Chemical Technologyamp Biotechnology vol 94 no 8 pp 2512ndash2521 2019

[38] M Malakootian H Mahdizadeh A Dehdarirad andM Amiri Gharghani ldquoPhotocatalytic ozonation degradationof ciprofloxacin using ZnO nanoparticles immobilized on thesurface of stonesrdquo Journal of Dispersion Science and Tech-nology vol 40 no 6 pp 846ndash854 2019

[39] S Mustapha M Ndamitso A Abdulkareem et al ldquoAppli-cation of TiO2 and ZnO nanoparticles immobilized on clay inwastewater treatment a reviewrdquo Applied Water Sciencevol 10 no 1 pp 1ndash36 2020

[40] M Malakootian A Nasiri A N Alibeigi H Mahdizadehand M Amiri Gharaghani ldquoSynthesis and stabilization ofZnO nanoparticles on a glass plate to study the removal ef-ficiency of acid red 18 by hybrid advanced oxidation process(ultravioletZnOultrasonic)rdquo Desalination and WaterTreatment vol 170 pp 325ndash336 2019

[41] M Malakootian M Yaseri and M Faraji ldquoRemoval of an-tibiotics from aqueous solutions by nanoparticles a sys-tematic review andmeta-analysisrdquo Environmental Science andPollution Research vol 26 no 9 pp 8444ndash8458 2019

[42] A Nasiri F Tamaddon M H Mosslemin M Amiri Ghar-aghani and A Asadipour ldquoMagnetic nano-biocompositeCuFe2O4 methylcellulose (MC) prepared as a new nano-photocatalyst for degradation of ciprofloxacin from aqueoussolutionrdquo Environmental Health Engineering and Manage-ment vol 6 no 1 pp 41ndash51 2019

[43] S Adhami M Fazlzadeh and S Hazrati ldquoPhotocatalyticremoval of cephalexin by UVZnO process from aqueoussolutionsrdquo Journal of Environmental Health Engineeringvol 5 no 2 pp 173ndash183 2018

[44] M Malakootian M A Gharaghani A Dehdarirad et alldquoZnO nanoparticles immobilized on the surface of stones tostudy the removal efficiency of 4-nitroaniline by the hybridadvanced oxidation process (UVZnOO3)rdquo Journal of Mo-lecular Structure vol 1176 pp 766ndash776 2019

[45] S Aghdasi and M Shokri ldquoPhotocatalytic degradation ofciprofloxacin in the presence of synthesized ZnO nano-catalyst the effect of operational parametersrdquo Iranian Journalof Catalysis vol 6 no 5 pp 481ndash487 2016

[46] M Sadeghi A Mesdaghinia A Badkoobi and R NabizadehldquoEnhancement of the biodegradability of methyl tert-butylether (MTBE) by advanced oxidationrdquo Water Wastewatervol 58 pp 54ndash61 2005

[47] B Legube and N K V Leitner ldquoCatalytic ozonation apromising advanced oxidation technology for water treat-mentrdquo Catalysis Today vol 53 no 1 pp 61ndash72 1999

[48] K He Y M Dong Z Li L Yin A M Zhang andY C Zheng ldquoCatalytic ozonation of phenol in water withnatural brucite and magnesiardquo Journal of Hazardous Mate-rials vol 159 no 2 pp 587ndash592 2008

[49] Y Dadban Shahamat M Farzadkia S Nasseri A H MahviM Gholami and A Esrafily ldquoEvaluation of toxicity reduc-tion mineralization and treatability of phenolic wastewatertreated with combined system of catalytic ozonation processbiological reactor (SBR)rdquo Iranian Journal of Health amp En-vironment vol 8 no 3 2015

[50] T A Ternes J Stuber N Herrmann et al ldquoOzonation a toolfor removal of pharmaceuticals contrast media and muskfragrances from wastewaterrdquo Water Research vol 37 no 8pp 1976ndash1982 2003

[51] Y Lester D Avisar I Gozlan and H Mamane ldquoRemoval ofpharmaceuticals using combination of UVH2O2O3 ad-vanced oxidation processrdquo Water Science and Technologyvol 64 no 11 pp 2230ndash2238 2011

[52] X Zheng S Xu Y Wang X Sun Y Gao and B GaoldquoEnhanced degradation of ciprofloxacin by graphitizedmesoporous carbon (GMC)-TiO2 nanocomposite strongsynergy of adsorption-photocatalysis and antibiotics degra-dation mechanismrdquo Journal of Colloid and Interface Sciencevol 527 pp 202ndash213 2018

[53] M L Tran C-C Fu and R-S Juang ldquoEffects of water matrixcomponents on degradation efficiency and pathways of an-tibiotic metronidazole by UVTiO2 photocatalysisrdquo Journal ofMolecular Liquids vol 276 pp 32ndash38 2019

[54] R D C Soltani M Mashayekhi M Naderi G BoczkajS Jorfi and M Safari ldquoSonocatalytic degradation of tetra-cycline antibiotic using zinc oxide nanostructures loaded onnano-cellulose from waste straw as nanosonocatalystrdquo Ul-trasonics Sonochemistry vol 55 pp 117ndash124 2019

[55] N Javid Z Honarmandrad and M Malakootian ldquoCipro-floxacin removal from aqueous solutions by ozonation withcalcium peroxiderdquo Desalination and Water Treatmentvol 174 pp 178ndash185 2020


surface waters [1] +is antibiotic concentration in surfacewaters and effluents was observed up to several hundred ngL [6] Concerns about trimethoprim are related to the po-tential for creating drug resistance [7] because of thewidespread use in the treatment of infections in the upperrespiratory tract and lower urinary tract and for kidneygastrointestinal and other bacterial infections since 1968 Itis also used for prophylaxis and treating veterinary infections[8] It is considered that trimethoprim is highly water solubleand provides low sorption to the sludge and easily enters andaccumulates in aquatic resources [5] +e elimination oftrimethoprim with the treatment of flocculation adsorptionand oxidation showed different trends and had an efficiencyof 10 50 and lower than 90 percent respectively [6] TMP isthe white powder that has high solubility in water [6] and itsstructure is illustrated [9] in Figure 1 Most of the currentlyused wastewater treatment techniques are not effective inremoving these compounds completely [4] For instanceozonation was found to be effective for the removal of TMPin the drinking water treatment process [10] Additionallyphotocatalytic processes that are based on absorption of lightfor generation of active radicals have become an alternativefor water clarification mechanism leading to mineralizationof organic compounds [11] Six intermediates were identi-fied during the photocatalytic decomposition of TMP +eexocyclic amino groups of the diaminopyridine ring andbridging methylene group are the potential active reactionsites in the TMP molecule [12] Advanced oxidation pro-cesses (AOPs) have been shown to have a high efficiency inthe elimination of various organic contaminants fromdrinking water and wastewater [1] It is evident that researchhas recently been directed toward the application of AOPsdue to their high performance in the decomposition of theorganic matter [13] Among various AOPs ozonation wasemployed as one of the most popular AOPs Ozonation hasbeen traditionally employed in drinking water treatment forodor and taste control and disinfection and for wastewaterdisinfection Today advanced oxidation processes for theelimination of pharmaceuticals in waters with emphasis onthe use of catalysts have begun to enhance [14] Instances ofheterogeneous catalysts used in the advanced oxidationprocesses can be metal oxides such as ZnO and TiO2 that areinexpensive commercially available in various crystallineforms and particle characteristics nontoxic and photo-chemically stable [15] TiO2 and ZnO semiconductors arethe most effective ZnO has a wide band gap with an energygap (EG) of about 33 eV As a photocatalyst ZnO has someimportant advantages such as low price and high photo-catalytic activity (sometimes activity bigger than TiO2) +ebiggest advantage of ZnO is that it absorbs a larger fractionof the UV spectrum compared with TiO2 [16] Unfortu-nately these process measures have their own disadvantageslike the difficulty in reusability of the adsorbent the for-mation of degradation by-products poor stability high costand lack of practicality [17]

In this work we compared the following two techniquesused for trimethoprim degradation ozonezinc oxide (UVZnO) and ozonezinc oxide (O3ZnO) +e objective of thisstudy is to investigate and compare the efficiency of

ultravioletzinc oxide (UVZnO) and ozonezinc oxide (O3ZnO) techniques as advanced oxidation processes in theremoval of trimethoprim from aqueous solutions+e effectsof ozone concentration TMP concentration ZnO dose andresidence time on removal efficiency were also explored

2 Materials and Methods

21 Chemicals TMP (standard gt98) was purchased fromSigma-Aldrich with CAS number 738-70-5 HPLC-grademethanol and ACN were supplied by Merck (Germany) AMilli-Q ultrapure water system (USA) was used to obtainHPLC-grade water NaOH and H2SO4 were used as pHadjustment chemicals ZnO (99 purity Merck) was usedfor all experiments as received Zinc oxide nanoparticleswith 99 purity 10ndash30 nm particle size 20ndash60m2g speciallevel nearly spherical and milky white were used ZnO wasprovided from Isfahan Science and Technology Town inIsfahan Figure 2 illustrates the SEM of ZnO nanoparticlesX-ray diffraction (XRD) (Siemens D5000 Germany) wasused to investigate the crystalline phase and solid structureof the ZnO nanoparticles (at 200 keV)

22Experiments Stock solutions were prepared in ultrapurewater by constant stirring over 30min by ultrasonic batch[18] +e concentration of TMP in the stock solution was1000mgL [6] In this study several parameters were ex-amined including catalyst doses (5 250 and 500mgL) andconcentrations of TMP (05 1 and 5mgL) in a syntheticwater model and contact time in order to investigate theinfluence of these parameters on the removal process [6]Before reaction the heterogeneous mixture was equilibratedfor 15min Its pH value was maintained at 75plusmn 05 and thereaction temperature was maintained at 25plusmn 05degC Con-tinuous experiments were performed in a glass cylinder witha height of 75 cm and a capacity of 11 L +e solution wascirculated through a peristatic pump Ozone dose was set on06mgL +e ozone was generated from pure oxygen(gt9999) using an ozone generator (Model OZ1-BTUOzotech CA USA) which was calibrated by an iodometrymethod [19] as in

O3mgmin

(A + B) times N times 24

T(min) (1)

where A mL of thiosulfate consumed in the first gas B mLof thiosulfate consumed in the second gas T ozonation timein minutes and N normality of sodium thiosulfate

NH2

H2N

N

N

O

O

O

Figure 1 Trimethoprim structure









l A 100f b V

(2)










+ h+

( 1113857 (3)

h+


h+

+ H2O⟶ H++ OH0

(5)

h+

+ OHminus+ ⟶ OH0

(6)





0

20

40

60

80

100

5 10 15 20 25 30

Effic

ienc

y (

)

Time (min)

O3ZnOZnOO3


0

20

40

60

80

100

Effic

ienc

y (

)

30 60 90 120 150 180Time (min)

UVZnOZnOUV








6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)








minus andNH4



0

20

40

60

80

100Ef

ficie

ncy

()



6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)




0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)



Kinetics K R2








y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)


005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)






mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]
































































l A 100f b V

(2)










+ h+

( 1113857 (3)

h+


h+

+ H2O⟶ H++ OH0

(5)

h+

+ OHminus+ ⟶ OH0

(6)





0

20

40

60

80

100

5 10 15 20 25 30

Effic

ienc

y (

)

Time (min)

O3ZnOZnOO3


0

20

40

60

80

100

Effic

ienc

y (

)

30 60 90 120 150 180Time (min)

UVZnOZnOUV








6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)








minus andNH4



0

20

40

60

80

100Ef

ficie

ncy

()



6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)




0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)



Kinetics K R2








y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)


005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)






mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]




























































+ h+

( 1113857 (3)

h+


h+

+ H2O⟶ H++ OH0

(5)

h+

+ OHminus+ ⟶ OH0

(6)





0

20

40

60

80

100

5 10 15 20 25 30

Effic

ienc

y (

)

Time (min)

O3ZnOZnOO3


0

20

40

60

80

100

Effic

ienc

y (

)

30 60 90 120 150 180Time (min)

UVZnOZnOUV








6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)








minus andNH4



0

20

40

60

80

100Ef

ficie

ncy

()



6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)




0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)



Kinetics K R2








y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)


005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)






mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]






























































6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)








minus andNH4



0

20

40

60

80

100Ef

ficie

ncy

()



6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)




0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)



Kinetics K R2








y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)


005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)






mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]





























































minus andNH4



0

20

40

60

80

100Ef

ficie

ncy

()



6065707580859095

0 30 60 90 120 150 180

Effic

ienc

y (

)

Time (min)




0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)



Kinetics K R2








y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)


005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)






mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]

























































0

05

1

15

2

25

3

35

0 100 200 300 400 500 600

Ozo

ne co

ncen

trat

ion

(mg

L)

Catalyst dose (mgL)



Kinetics K R2








y = 00703x + 10399R2 = 09675

10

15

20

25

0 30 60 90 120 150 180

1Ct

Time (min)


005

115

225

335

4

0 2 4 6

Ozo

ne co

ncen

trat

ion

(mg

L)






mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]



























































mgLmin







Inte

nsity

(au

)

20 40 60 80 100 1202theta (degree)




4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]


























































4 Conclusions




Data Availability




Acknowledgments


References















88 in30min [53]



876 in45min [54]






956 and854 [55]



96 in30min [44]








































































































































Documents

ComparisonoftheEfficiencyofUltraviolet/ZincOxide (UV/ZnO