Adsorptive Removal of Zinc from Waste Water by Natural …ijesi.org/papers/Vol(3)6/Version-3/K0363060080.pdf · · 2014-06-26the removal of zinc from ... Table1.2 Typical concentration

International Journal of Engineering Science Invention

ISSN (Online): 2319 – 6734, ISSN (Print): 2319 – 6726

www.ijesi.org Volume 3 Issue 6ǁ June 2014 ǁ PP.60-80

www.ijesi.org 60 | Page

Adsorptive Removal of Zinc from Waste Water by Natural

Biosorbents

Sunil Rajoriya1, Balpreet kaur

2

1(Chemical engineering,

1Doon Group of Colleges, India)

2(Chemical engineering, SBSSTC Ferozepur, India)

ABSTRACT: Zinc is a toxic metal and is present in high concentration in wastewater of various industries like

galvanizing, metallurgical, electroplating, mining, paints, pigments, pulp and paper and pharmaceuticals. There

are various conventional treatment techniques available for the removal of zinc from wastewater like chemical

precipitation, ion exchange, reverse osmosis, electro dialysis, electrochemical treatment, membrane separation

process and adsorption. Among these methods, adsorption has been found to be one of most popular process for

the removal of zinc from wastewater due to its low initial cost and sludge free environment.Increasing demand

for eco-friendly techniques promotes the interest to natural and bio-degradable adsorbents. In this work, lemon

peel and banana peel have been used as biosorbents to achieve the desired objective. To study the adsorption of

zinc ions, batch experiments were performed. The characterization of both adsorbents was carried out using

FTIR. The effects of various process parameters like biosorbent concentration, contact time, pH, various initial

zinc concentration and temperature on the removal of zinc from wastewater have been investigated and

optimized. Adsorbent concentration for both biosorbents for the maximum removal of zinc at optimum pH of 4

and temperature of 300C is found to be 1g/100ml. The optimum contact time for the equilibrium condition is 260

min for the removal of zinc.

KEYWORDS: Adsorption, Batch studies, magnetic stirrer (300C), Natural Bio-sorbents.

I. INTRODUCTION 1.1 General

Environmental pollution is one of the main problems of the society in the 21st century. The major

pollutants include toxic metals, the quantity of which permanently increases in the environment as the result of

increased industrial activity. Zinc is one of these toxic metals and is present in high concentration in wastewater

of various industries like galvanizing, metallurgical, electroplating, mining, paints & pigments, pharmaceuticals,

fiber production, ground wood pulp, newsprint paper, batteries, petroleum and petrochemical (Naiya et al.,

2009, King et al., 2008 and Deliyanni et al., 2009). Zinc metal ions do not degrade and thus are carried away to

the food chain and finally get accumulated in the living organisms, causing several diseases and disorders

(Deliyanni et al., 2009). Waste water treatments would not only be economical but will also help to maintain the

quality of the environment. The heavy metals, having hazardous effects on health, can be treated from

wastewater by using various physicochemical methods. The release of large quantities of heavy metals into the

natural environment has resulted in a number of environmental problems.

1.2 Major sources of zinc in waste water Zinc enters into water through natural as well as anthropogenic sources (anthropogenic effects,

materials or process are those that are derived from human activities as opposed to occurring in natural

environments without human influence). Erosion of soil and rocks has been found to be responsible for natural

zinc contamination in water (Elinder et al., 1986).

Adsorptive Removal Of Zinc From Waste…


Table 1.1 Typical concentration of zinc in waste water of various industries

Table1.2 Typical concentration of heavy metals presents in copper smelter wastewaters (Basha et al.,

2008)

Heavy metal Average zinc concentration (mg/L)

Arsenic 1979

Zinc 300

Copper 164.48

Iron 88

Bismuth 85

Cadmium 76

Nickel 12

Lead 4.6

Chromium 2.3

1.3 Permissible limit and Mechanism of zinc toxicity

The permissible concentration of zinc in drinking water is 5 mg/l, According to US EPA (Naiya et al.,

2009), WHO (Mohan et al., 2002), IS 10500 (Naiya et al., 2009). zinc is initially concentrated in the liver after

ingestion, and is subsequently distributed throughout the body. The liver, pancreas, bone, kidney, and muscle

are the major tissue storage sites.

1.4 Biosorption

Biosorption is an emerging technology that uses biological materials such as dead biomass and living

microbial cells to remove pollutants from solution. Biosorption is a rapid, reversible, economical and in contrast

to physico-chemical methods used for removal of heavy metals from wastewater. Other advantages of

biosorption over physico-chemical techniques include low cost, high efficiency, minimization of chemical or

biological sludge, no additional nutrient requirement, possibility of regeneration of biosorbent and metal

recovery (Norton et al., 2004).

Physico-chemical methods for zinc removal from wastewater

The removal of zinc include coagulation- flocculation, chemical precipitation, membrane filtration,

flotation, ion exchange, reverse osmosis, liquid extraction, activated carbon adsorption and electrochemical

treatment by various physico-chemical techniques (Gupta et. al., 2010).

The above mentioned conventional processes are briefly discussed below:

Available techniques for zinc removal

from water

Figure1.1 Available techniques for zinc removal from water

Industrial wastewater Average concentration (mg/L)

Copper smelter 50-300

Electroplating 9-41

Hot-dip galvanizing 81.86

Rubber thread 81.6

Petrochemical 2.2

Battery 0.18-7.27

Paint 20

Pulp and paper 1.3

Pharmaceutical 0.12

Coagulation-

flocculation

Chemical

precipitation

Flotation Membrane

filtration

Electrochemical

treatment

Activated carbon

adsorption



II. LITERATURE REVIEW Mohan et al., 2002 investigated the use of low-cost activated carbon derived from bagasse, an

agricultural waste material has as a replacement for the current expensive methods of removing heavy metals

from wastewater. These studies were carried out at the initial concentration of 200 mg/l for Cd+2

and Zn+2.

The

adsorption of Cd+2

and Zn+2

on the prepared adsorbent increases with the increase in pH. The adsorption of Cd+2

and Zn+2

is very low at pH- 2; it increases from 90% to 95% at pH 4.0–6.0. At pH greater than 8.0 the removal

takes place by adsorption as well as precipitation i.e. the OH- ions from the solution formed some complexes

with Cd+2

and Zn+2

. The removal of Cu+2

, Zn+2

and Ni+2

from solutions using biosorption in cork powder was

described. It was concluded that the adsorption of the heavy metals was favored by an increase in pH (Chubar et

al., 2004). The biosorption of zinc ions from aqueous solution by Tectona grandis L.f. was studied in a batch

adsorption system (Kumar et al., 2006). Nasir et al., 2007 studied that the removal of lead and zinc from

aqueous solutions using chemically modified distillation sludge of rose (Rosa centifolia) petals. Maximum

adsorption of both metal ions was observed at pH 5. Kinetic data was better described by pseudo second order

model rather than pseudo first order kinetic model. The equilibrium studies were carried out at a temperature

300C. The initial metal ion concentration was taken as 100 mg/l. Adsorption capacity of biomass tends to be in

the order Pb+2

(87.74 mg/g) > Zn+2

(73.8 mg/g) by NaOH pretreated biomass. (Srivastava et al., 2008) studied

that adsorptive removal of cadmium and zinc ions from binary systems using rice husk ash (RHA), The

optimum pH for the removal of Cd+2

and Zn+2

ions by RHA is found to be 6.Biosorption experiments were

carried out at 300C.

Arshad et al., 2008 utilized the mature leaves and stem bark of the Neem tree for removing zinc from

water. Adsorption was carried out in a batch process with several different concentrations of zinc by varying pH.

The uptake of metal was very fast initially, but gradually slowed down indicating penetration into the interior of

the adsorbent particles. Biosorption experiment was carried out at 250C. The optimum pH for efficient

biosorption of zinc by Neem leaves and stem bark was 4 and 5, respectively. The maximum adsorption capacity

for zinc is147.08 mg Zn/g for Neem leaves and 137.67 mg Zn/g Neem bark. The obtained results show that pH,

adsorbent particle size, adsorbent dose, initial metal concentration and contact time highly affect the overall

metal uptake capacity of biosorbents. Due to its outstanding zinc uptake capacity, the Neem tree was proved to

be an excellent biomaterial for accumulating zinc from aqueous solutions. Salamatinia et al., 2008 studied that

the sorption of Cu and Zn onto NaOH-treated oil palm frond [OPF] in a fixed-bed up flow column operated in

continuous mode at hydraulic retention times of 6, 12 and 18 mins. The percent removal of 90 % for

Zn+2

adsorption was achieved at optimum pH value. According to Marin et al., 2008, the biosorption of several

metals mainly Cd+2

, Zn+2

and Pb+2

by orange wastes has been investigated in binary systems. Orange waste

consists mainly of cellulose, hemicelluloses, pectin, limonene and many other low molecular weight

compounds. Biosorption experiment was carried out at 250C. The optimum pH for efficient biosorption of zinc

was 5. Naiya et al., 2009 studied that the various physico-chemical parameters such as pH, initial metal ion

concentration, adsorbent dosage level and equilibrium contact time. The optimum pH for adsorption was found

to be 5 for Zn+2

and the initial metal ion concentration obtained was 25 mg/l. Hawari et al., 2009 studied that the

equilibrium batch dynamics using olive oil mill solid residues as an adsorbent for zinc removal from aqueous

solutions. It was found that the maximum adsorption capacity of zinc was attained at a pH value of 5.0. It was

found that qmax for zinc ions, was 5.63, 6.46, and 7.11mg/g at temperature values of 298, 308, and 328 K,

respectively. At optimum pH a percentage removal of 95 % was achieved. Adsorption experiments were carried

out using waste rice straw of several kinds as a biosorbent to adsorb Cu+2

, Zn+2

, Cd+2

and Hg+2

ions from aqueous

solutions at room temperature. The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for

the removal of Cd+2

and Zn+2

metal ions from aqueous solution has been investigated (Mohammada et al.,

2010). It has been found that the amount of adsorption for both Cd+2

and Zn+2

increased with the increase in

initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic

range), but decreased with the increase in the particle size of the adsorbent.

III. PRESENT WORK 3. 1 experimental set-up and instrumentation Removal of zinc was carried out by batch process. In this chapter, analytical and auxiliary instruments

used in the present work have been described.

3.1.1 Batch study

Experiments were conducted with two adsorbents namely banana peel and lemon peel. 100 ml of the

sample volume was taken for each experiment. Batch study was undertaken for the optimization of process

parameters and to extract design parameters like rate constants and isotherm constants.



3.1.2Analytical instruments used in the present study

(i) Atomic Absorption Spectroscopy (AAS)

Used for the determination of Zn (II) in standard and treated solution.

Figure 3.1 AAS, GBC, Avanta, Australia

(ii) Fourier Transform Infrared Spectroscopy (FTIR)

To determine the type of functional groups present on the adsorbents surface before and after adsorption and

thus, to find out the ions responsible for metal adsorption.

Figure 3.2 FTIR, Thermo model AVATR 370 Australia

3.1.3 Auxiliary equipments used in the present study

pH meter, muffle furnace, autoclave, digital camera, weighing balance, oven etc.

3.2 experimental methodology

Banana peel and lemon peel were used as bio-sorbents for the removal of zinc

from waste water. The preparation and characterization of adsorbents, experimental procedure & data recording

for adsorptive removal of zinc from wastewater as well as the bio removal of zinc supplemented with adsorption

are discussed hereunder.

3.2.1 Availability of adsorbents

Lemon peel and Banana peel were used as the low cost natural bio-sorbents. These were sourced from

local market in Dehradun, India.

3.2.2 Preparation of adsorbents

Banana peel and lemon peel were washed with distilled water 3-4 times and Thereafter both these peels

(lemon peel and banana peel) were dried in sun light for 5 days and then in an oven at 900C for 10 hours. The

adsorbents after drying were used for adsorption studies. They were washed with distilled water several times in

order to remove unreacted citric acid and other soluble substances. The final product was dried in an air oven at



1000C for 5 hours, later the product was cooled at room temperature in desiccators and stored in air tight

polythene bag. Prepared bio-sorbents are shown in figure below:

Figure 3.4 Prepared bio-sorbents

Figure 3.5 Flow diagram showing various steps of worked carried out



3.2.3 Characterization of the adsorbents prepared

For the characterization of adsorbents, FTIR spectrometer was employed to determine the type of

functional groups present on the adsorbents surface before and after adsorption and thus, to find out the ions

responsible for metal adsorption. Pellets of adsorbent were made with 1 % KBR and 4,000 to 400 cm−1

wavelength was used.

3.2.4 Preparation of zinc metal solution

The stock solution containing 1g/L of standard Zn (II) was prepared by dissolving 2.08 g of AR grade

ZnCl2 in 1000 ml of distilled water. In order to prevent precipitation of metals by hydrolyzing, two drops of HCl

were added to the stock solution. All experimental solutions were prepared by diluting the stock solution with

distilled water.

3.2.5 Batch adsorption studies

Batch adsorption studies were carried out at the desired pH value, contact time and adsorbent dosage

for both the adsorbents. Various initial concentrations of metal solutions were prepared by proper dilution from

stock 1000 mg/L zinc solution standard. pH of the solution was monitored by adding 0.1M HCl and 0.1M

NaOH solution. 100 ml of zinc solution was mixed with calculated amount of adsorbent in a 500 ml conical

flask and the adsorption was carried out in magnetic stirrer at 30°C. After the completion of adsorption, the

sample was filtered and filtrate was analyzed by atomic absorption spectrophotometric method for metal ion

concentration. The amount of metal ion adsorbed per unit mass of the adsorbent was evaluated by using the

same following mass balance equation

qe = ( Co - Ce)

where, qe is the adsorption capacity in mg pollutant/g adsorbent, Co is the initial concentration of pollutant in

solution, Ce is the concentration of the pollutant in solution after equilibrium has been reached, V is the

volume of the solution to which the adsorbent mass is exposed, and M is the mass of the adsorbent.



Figure 3.6 Batch Experiments

3.2.6 Experimental procedure and data recording

3.2.6.1 Procedure on zinc removal at various pH values

Synthetic solution (containing 50 mg/l of zinc) was prepared from stock solution of zinc. Single

Distilled water was used to prepare the solutions. 100 ml of the above stated synthetic solution was taken in

each of the 5 different 100 ml plastic bottles. The pH of this solution was adjusted to 2, 3, 4, 5, and 6 using 0.1M

HCl and 0.1M NaOH solution. For each adsorbent, 5 set of experiments were conducted at different pH 2, 3, 4,

5, and 6 to study the effects of pH on the removal of zinc. 1 g of biosorbent was added to each of these flasks.

Thereafter, these 100 ml plastic bottles were agitated for 6 hr in magnetic stirrer at 300C. After 360 min of

agitation, the solutions were filtered through filter paper (whatman no.41, 125mm). The filtrate obtained was

diluted using distilled water. The analysis of Zn (II) was done by AAS. The calibration curves for zinc

measurement by AAS have been provided in Appendix (graph-2).

3.2.6.2 Procedure on zinc removal at various adsorbent concentrations

Synthetic solution (containing 50 mg/l of zinc) was prepared from stock solution of zinc. Distilled

water was used to prepare the solutions. The pH of this solution was adjusted to 4.0 using 0.1M HCl and 0.1M

NaOH solution. For each adsorbent, 5 set of experiments were conducted using the adsorbent concentrations of

2.5, 5.0, 10, 20 and 30 g/l to study the effects of adsorbent concentration on the removal of zinc. 100 ml of the

above stated synthetic solution was taken in each of the 5 different 100 ml plastic bottles and was added with

calculated amount of the adsorbent as mentioned above. Thereafter, these 100 ml plastic bottles were agitated

for 6 hr in magnetic stirrer at 300C. After 360 min of agitation, the solutions were filtered through filter paper

(whatman no.41, 125mm). The filtrate obtained was diluted using distilled water and analysis of Zn (II) was

done by AAS. The calibration curves for zinc measurement by AAS have been provided in Appendix (graph-3).

3.2.6.3 Procedure on zinc removal at various temperatures

For each adsorbent five set of experiments were conducted at different temperature to study the effects

of temperature on the removal of zinc. 100 ml of the Synthetic solution was taken in each of the five different

100 ml plastic bottles and the pH of this solution was adjusted to 4.0 using 0.1M HCl and 0.1M NaOH solution.

1 g of adsorbent was added to each bottle. Experiments were conducted with five bottles at five different

temperatures i.e., 30, 35, 40, 45 and 500C respectively. After the addition of the adsorbent in the solution in 100

ml plastic bottles (pH adjusted initially), Thereafter, these 100 ml plastic bottles were agitated for 6 hr in

magnetic stirrer at 300C. After 360 min of agitation, the solutions were filtered through filter paper (whatman

no.41, 125mm). The filtrate obtained was diluted using distilled water and analysis of Zn (II) was done by AAS.

The calibration curves for zinc measurement by AAS have been provided in Appendix (graph-4).

3.2.6.4 Procedure on zinc removal at various contact times

Experiments have been conducted by batch process to study the effect of contact time on the removal of zinc.

100 ml of the zinc synthetic solution was taken in each of the 12 different 100 ml plastic bottles. The pH of this

solution was adjusted to 4.0 using 0.1M HCl and 0.1M NaOH solution. 1 g of adsorbent was added to each

bottle. Thereafter, these 100 ml plastic bottles were agitated for 6 hr in magnetic stirrer at 300C. After 15 min,

bottle numbered 1 was taken out and the solution was filtered through filter. Similarly after every 15 min bottles

numbered 2-4 were taken out and solution was filtered. Similarly after every 30 min bottles numbered 5-9 were



taken out and solution was filtered. Similarly after every 50 min bottles numbered 10-12 were taken out and

solution was filtered through filter paper (whatman no.41, 125mm). Then the solution was diluted using distilled

water and analysis of Zn (II) was done by AAS. The calibration curves for zinc measurement by AAS have been

provided in Appendix (graph-5).

3.2.6.5 Procedure on zinc removal at various initial zinc concentrations For each adsorbent four set of experiments were conducted at different initial zinc concentration to

study the effect of initial zinc concentration on the removal of zinc by batch process. 100 ml of the synthetic

solution was taken in each of the four different 100 ml plastic bottles and the pH of this solution was adjusted to

4.0 using 0.1M HCl and 0.1M NaOH solution.

The initial zinc concentration used was 50, 100, 200, and 300 mg/l. After the addition of the adsorbent

in the solution in 100 ml plastic bottles (pH adjusted initially to 4), Thereafter, these 100 ml plastic bottles were

agitated for 6 hr in magnetic stirrer at 300C. After 360 min of agitation, the solutions were filtered through filter

paper (whatman no.41, 125mm). The filtrate obtained was diluted using distilled water and analysis of Zn (II)

was done by AAS. The calibration curves for zinc measurement by AAS have been provided in Appendix

(graph-6).

IV. RESULTS AND DISCUSSIONS This Chapter covers the discussion and interpretation of results of the present study. Studies in this

chapter have been divided into two Sections as stated below:

Section 4.1 Characterization of the adsorbents

Section 4.2 Adsorptive removal of zinc from synthetic wastewater

4.1 Characterization of the adsorbents Characterization of the adsorbents is discussed in the subsequent

sections:

4.1.1 FT-IR spectra FTIR spectra of lemon peel and banana peel before metal ion adsorption are shown in figure 4.1 (a) and

(b) respectively. FTIR study revealed that functional groups like amide, hydroxyl, methyl, and carboxyl

vibrations were present in significant amplitude in both biosorbent samples. Strong vibration peaks in between

3,500-3,000 cm-1

were demarcated as the vibrations of O-H and −N-H functional groups (Zakaria et al., 2009;

Norton et al., 2004). Weaker –CH stretch bands are superimposed onto the side of the broad –OH band at 3,000-

2,800 cm-1

. Vibrations at 2,923.57; 2,921.66; 2,852.93; and 2,851.67 cm-1 in figure 4.1 (a) and (b), respectively,

are caused due to the presence of symmetric or asymmetric CH stretching of aliphatic acids (Yao et al., 2008).

Peaks between 1,800-1,300 cm−1

are caused due to the presence of C=C in aromatic rings and C=H stretching

(Rocha et al., 2009). The peak at approximately 1,020 cm-1

is either due to the C=O stretch of the –OH bend.

Absorbance peaks generated due to weak reflectance in between 1,000-500 cm−1

and 700 cm−1

indicated the

presence of miscellaneous oxides and symmetrical vibrations of Si–O (Das and Guha, 2009; Rocha et al., 2009),

respectively. Figure 4.2 (a) and (b) represent FTIR spectra of metal ion loaded lemon peel and banana peel

respectively.

From FTIR spectra of metal loaded biosorbents it was observed that there was a shift in wave number

of dominant peaks associated with the loaded metal. This shift in the wavelength showed that there was a metal

binding process taking place at the surface of biosorbents. There was a major shift in wave number from 1,446

cm-1

for raw lemon peel to 1,456.07 cm-1

for metal loaded lemon peel. Also some of the metal binding groups

present on the surface of biosorbents get diminished or disappeared after metal loading. Strong vibration peaks

in between 3,500-3,000 cm-1

got diminished after metal loading. Also C–O stretch of the –OH bend in range of

1,400 to 1,020 cm−1

almost disappeared from adsorbed biosorbents. Analysis of the FTIR provides the evidence

that functional groups like carboxyl, hydroxyl, carbonyl and other aromatic vibrations were involved in metal

ion adsorption onto biomass surface.



Figure 4.1 FTIR spectra before metal ion adsorption (a) lemon peel (b) banana peel



Figure 4.2 FTIR spectra after metal ion adsorption for (a) lemon peel (b) banana peel

4.2 Adsorptive removal of zinc from synthetic wastewater

This section consists the observations on the removal of zinc from synthetic wastewater by batch

process using biosorbents. Effects of various process parameters such as adsorbent concentration, agitation time,

pH and temperature on the removal of zinc have been studied to select the process parameters for optimum

removal of zinc in batch reactors. Results on these batch studies are discussed below:



4.2.1 Effect of pH on zinc removal

The effect of pH on percentage removal of zinc by lemon and banana peel is shown in figure4.4 (a),

(b). It is shown from figure 4.4 (a) that the percentage removal of Zn (II) increases slowly with increasing pH

from 2 to 4, and thereafter drops slowly. The maximum percentage removal of zinc by lemon peel and banana

peel was 87.5 % and 90.5 % respectively. The optimum pH value for adsorption of Zn (II) by both lemon peel

and banana peel was found to be 4.0. At lower pH, there is net positive charge on the biomass cells, which

results in higher electrostatic repulsion between the metal ions and the H+

ion during the uptake of metal ion

(Naiya et al., 2009). Whereas at higher pH, there is net negative charge on the biomass, which results in

decrease in the electrostatic repulsion and thus increases the biosorption. Similar trend was reported for the

biosorption of Zn (II) on Neem biomass (Arshad et al., 2008) when the extent of biosorption increased from 0 to

86.48% in pH range of 1.0-6.0. According to the results of this initial experiment, all the following experiments

on adsorption of Zn (II) from aqueous solution were carried out by maintaining the solution pH 4.0 for both

lemon peel and banana peel. Zinc metal uptake for L-peel and B-peel were 4.375 and 4.55 mg/g at pH 4

respectively.

Figure 4.4 Effect of pH on removal of zinc (a) Effect on percentage removal

(b) Effect on zinc uptake



4.2.2 Effect of adsorbent dosage on zinc removal

The effect of adsorbent dosage on percentage removal and specific uptake of zinc from aqueous

solution are shown in Figure 4.5 (a) and (b), respectively. It is evident from Figure 4.5 (a) that initially the

percentage removal of zinc increased rapidly with an increase in adsorbent dosage, but after certain adsorbent

dosage the removal efficiency did not increase. Increasing the adsorbent dosage increases the available binding

sites. Thus more surface area is available for adsorption, thereby increasing the zinc percentage removal from

the solution (Hawari et al., 2009). Figure 4.5 (b) shows that the specific uptake decreased with increasing

adsorbent dosage. This is due to the interference between the binding sites and insufficiency of metal ions in the

solution with respect to the available binding sites (Hawari et al., 2009). This can also be explained on the basis

of the definition of specific uptake (q) as given in equation:

q = (Co .V.P)/M (Hawari et al., 2009)

Where C0 is the initial metal concentration in mg/L and P is the percentage removal of zinc; V is the volume of

the solution in liter; and M is the mass of the sorbent used in gm.

Maximum percentage removal of Zn (II) was found to be 83.5 % and 90.50 % respectively for both lemon peel

and banana peel adsorbent at an adsorbent dosage of 10 g/L. Similarly, the specific uptakes for adsorption of

zinc were 4.175 and 4.525 mg/g respectively for both lemon peel and banana peel adsorbent at an adsorbent

dosage of 10 g/L. Similar trend was reported for the biosorption of zinc by sugar beet pulp (Pehlivan et al.,

2006). It was concluded that with increase in sugar beet pulp dose from 0.1 to 1.0 g, the percentage removal

increased from 60 to 70%.

Figure 4.5 Effect of adsorbent dosage on removal of zinc (a) Effect on percentage removal

(b) Effect on zinc uptake



4.2.3 Effect of temperature on zinc removal With the increase in temperature percentage removal of zinc decreased. For lemon peel Figure 4.6 (a)

and (b), zinc removal decreases from 82.68 % to 71.76 % due to the increase in temperature from 30 to 500C for

initial zinc concentration of 50 mg/l. For banana peel Figure 4.6 (a) and (b), zinc removal decreases from 86.8 %

to 76.4 % due to the increase in temperature from 30 to 500C for initial zinc concentration of 50 mg/l. The

percentage removal is decreased with increase of temperature, so it was concluded that the adsorption reactions

are exothermic. Biosorption capacity also increased with decrease in temperature. The decrease of biosorption

capacity at higher temperature may be due to the damage of active binding sites in the biomass.

Figure 4.6 Effect of temperature on removal of zinc (a) Effect on

Percentage removal (b) Effect on zinc uptake

4.2.4 Effect of contact time on zinc removal The effect of contact time on batch adsorption of 50 mg/L Zn (II) at 30

0C and at pH 4.0 by banana peel

and lemon peel is shown in figure 4.7 (a) and (b) respectively. During the experiment contact time was varied

from 0 to 360 min. The results showed that the percentage removal of metal ion by both the adsorbents

increased by increasing contact time. The rate of increase in the percentage removal of zinc with increase in

contact time is appreciably fast at the initial stage. At the beginning of the experiment the number of available



active sites of adsorbents as well as the concentration of zinc in the solution is maximum. Thus, the driving

force for adsorption of zinc on the adsorbent surface is maximum. Further, agitation provides the energy

required to bring the zinc from the bulk of the solution to the active sites of the adsorbent by reducing the

resistance to mass transfer between bulk phase and adsorbent. In fact, all the above three effects promote

adsorption. Hence, at the initial stage, percentage removal of zinc increases very fast with the increase in

agitation period. Time needed to reach equilibrium for adsorption of zinc from aqueous solution was 260 min

both for banana peel and lemon peel adsorbents.

Figure 4.7 Effect of contact time on removal of zinc (a) Effect on percentage

removal (b) Effect on zinc uptake

4.2.5 Effect of initial zinc concentration on zinc removal

The effect of initial Zn (II) concentration on percentage removal and specific uptake by both adsorbents

are shown in Figure 4.8 (a) and (b), respectively. Percentage removal of Zn (II) from aqueous solution decreased

as concentration increased from 50 to 300 mg/L at constant pH. With increase in the concentration, the

percentage removal of the metal ion from solution decreases because at higher concentration, metal ions diffuse

to the adsorbent surface by intraparticle diffusion and the hydrolyzed ions diffuse at a slower rate, thus

decreasing the percentage removal (Arshad et al., 2008). Also at higher metal ion concentration to adsorbent

ratio, higher energy sites get saturated and adsorption starts on lower energy sites, resulting in lower percentage



removal of metal ions (Bhattacharya et al., 2006). Figure 4.8 (b) indicates that the adsorption capacity increased

with increase in initial Zn (II) concentration. Similar trend was reported for the biosorption of Zn (II) on T.

grandis L.f. leaves biomass (Kumar et al., 2006), when, with increase in the Zn (II) concentration, zinc uptake

increased from 4.3868–12.9702

mg /g and the percentage removal of zinc decreased from 73.11% to 43.23%.

Figure 4.8 Effect of initial metal ion concentration on removal of zinc (a) Effect on percentage removal (b)

Effect on zinc uptake

V. CONCLUSIONS In general, the present study shows that lemon peel and banana peel are effective biosorbents for

removal of zinc ions from water under suitable experimental conditions. Specifically, the following conclusions

can be drawn from the results of this study:

Zinc adsorption on these biosorbents is highly dependent upon solution pH. The optimum pH for lemon

peel and banana peel is found to be 4 with removal efficiencies of 87.5% and 90.5% respectively.

The maximum removal of zinc occurs at an adsorbent dosage of 1g/100ml for both the biosorbents, so this

can be considered as an optimum dosage under specific conditions.



The percentage removal of zinc and adsorption capacity was found to decrease with increasing temperature,

indicating the exothermic nature of the process.

The optimum contact time is found to be 260 min for lemon peel and banana peel.

With an increase in initial Zn (II) ion concentration, adsorption capacity of Zn (II) ions by

both biosorbents is found to increase and the % removal of Zn (II) ions is found to decrease.

VI. SCOPE OF FURTHER WORK Based on the results of the present study, the following recommendations are suggested for further

investigations.

The results of this study can also be used in designing column reactor for removal of

Zinc from water.

Study can also be performed on industrial waste water of various other industries like paints and pigments,

battery, ground wood pulp production, pulp and paper industries etc.

Thermodynamics study can be performed by using both adsorbents (lemon peel and banana peel) for further

investigation.

VII. ACKNOWLEDGEMENTS

I would like to express the deepest gratitude to my project advisor and mentor Mrs. Balpreet Kaur for

her supervision, advice, and guidance from the very early stage of this thesis work. She continually and

convincingly conveyed a spirit of adventure regard to research. She provided me unflinching encouragement

and support in various ways. Without her guidance and persistent help, this dissertation would not have been

possible.

I am highly grateful to Associate Professor Dr. Rajeev Kumar Garg, Head, Department of Chemical

Engineering, (SBSSTC Ferozepur) for providing necessary facilities and encouragement during the course of

the work. I express my sincere thanks to all faculty members of the Department of Chemical Engineering

SBSSTC, Ferozepur, for their help during the course of work.

I am thankful to Dr. Neelkanth Grover, Associate Professor, Head, Department of Mechanical Engineering,

(SBSSTC Ferozepur) for his invaluable help and encouragement throughout my post graduation.

I am heartily thankful to all Faculty Member, Department of Chemical Engineering, Doon College of

Engineering and Technology, Dehradun, who helped me time to time regarding my project.

I must record my heartfelt appreciation for my wife, Mrs. Garima Rajoriya, who never complained and kept

my spirits high. She not only managed the kid’s studies and family problems but also spared me with a pleasing

smile from most homely chores to accomplish this project. My heart also owes out naturally in appreciation of

my caring daughter Saumya who never complained even if she felt lack of attention from me on account of this

project. Above all, I render my gratitude to the Almighty who bestowed self confidence, ability, strength and

path for accomplishing this work.

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[12] Elinder, C. G., Friberg, L., Nordberg, G. F, Vouk, V. B., Handbook on the toxicology of metals, Elsevier Science Publishers, Amsterdam, (1986) 664-679.

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[15] Fuerhacker M Haile TM, Kogelnig D, Stojanovic A, Keppler B, Application of ionic a. liquids for the removal of heavy metals from wastewater and activated sludge. 65, (2012)1765-73.

[16] G. O. El-Sayed1, H. A. Dessouki and S. S. Ibrahiem, Removal of Zn (II), Cd (II) and Mn(II) from aqueous Solutions by Adsorption

on maize stalks. The Malaysian Journal of Analytical Sciences, Vol. 15 No 1 (2011): 8 – 21. [17] Gupta, N., Amritphale, S., Chandra, N., Removal of Zn (II) from aqueous solution by using hybrid precursor of silicon and carbon,

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[19] J. O. Akaninwor, M. O. Wegwu and I. U. Iba, Removal of iron, zinc and magnesium from polluted water samples using thioglycolic

modified oil-palm fiber, African Journal of Biochemistry Research July (2007)Vol. 1 (2), pp. 011-013. [20] Juang, R. S., Shiau, R. C., Metal removal from aqueous solutions using chitosanenhanced membrane filtration, J. Member Sci. 165,

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APPENDIX

Calibration curve are shown as below:

Graph -1 Calibration curve of std. zinc (II)

http://www.ncbi.nlm.nih.gov/pubmed?term=Fuerhacker%20M%5BAuthor%5D&cauthor=true&cauthor_uid=22546790

http://www.ncbi.nlm.nih.gov/pubmed?term=Haile%20TM%5BAuthor%5D&cauthor=true&cauthor_uid=22546790

http://www.ncbi.nlm.nih.gov/pubmed?term=Kogelnig%20D%5BAuthor%5D&cauthor=true&cauthor_uid=22546790

http://www.ncbi.nlm.nih.gov/pubmed?term=Stojanovic%20A%5BAuthor%5D&cauthor=true&cauthor_uid=22546790

http://www.ncbi.nlm.nih.gov/pubmed?term=Keppler%20B%5BAuthor%5D&cauthor=true&cauthor_uid=22546790



Graph -2 Calibration curve of Effect of pH (a) lemon peel (b) banana peel



Graph -3 Calibration curve of Effect of adsorbent dosage (a) lemon peel (b) banana peel

Graph -4 Calibration curve of Effect of temperature (a) lemon peel (b) banana peel



Graph -5 Calibration curve of Effect of contact time (a) lemon peel (b) banana peel



Graph -6 Calibration curve of Effect of Initial concentration (a) lemon peel

(b) banana peel

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Adsorptive Removal of Zinc from Waste Water by Natural …ijesi.org/papers/Vol(3)6/Version-3/K0363060080.pdf · · 2014-06-26the removal of zinc from ... Table1.2 Typical concentration