Synthesis and Adsorption Performance of Surface-Grafted Co(II)-Imprinted Polymer for Selective Removal of Cobalt

FULL PAPER

* E-mail: [email protected] Received April 10, 2009; revised July 10, 2009; accepted December 22, 2009. Project supported by the National Natural Science Foundation of China (No. 20877036).

548 © 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chin. J. Chem. 2010, 28, 548—554

Synthesis and Adsorption Performance of Surface-Grafted Co(II)-Imprinted Polymer for Selective Removal of Cobalt

Liu, Yan(刘燕) Gao, Jie(高捷) Li, Chunxiang(李春香) Pan, Jianming(潘建明) Yan, Yongsheng*(闫永胜) Xie, jimin(谢吉民)

School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China

The surface-grafting ion-imprinting technology was applied to synthesis of a new Co(II)-imprinted polymer [Co(II)-IP], which could be used for selective removal of Co(II) from aqueous solutions. The prepared polymer was characterized by using the infrared spectra (IR), X-ray diffractometer (XRD), X-ray energy dispersion spectroscopy (EDS) and scanning electron microscopy (SEM). The maximum adsorption capacity values for the Co(II)-imprinted polymer and non-imprinted polymer (NIP) were 22 and 8 mg/g, respectively. The Freundlich equation fitted the adsorption isotherm data well. The applicability of two kinetic models including pseudo-first-order and pseudo-second-order models was estimated on the basis of comparative analysis of the corresponding rate parame-ters, equilibrium capacity, and correlation coefficients. Results suggested that chemical process could be the rate-limiting step in the adsorption process. And the adsorption of Co(II) on the Co(II)-imprinted polymer was en-dothermic. The relative selectivity coefficients of the Co(II)-imprinted polymer for Co(II)/Pb(II), Co(II)/Cu(II), Co(II)/Ni(II), Co(II)/Sr(II) and Co(II)/Cs(I) were respectively 11.5, 6.1, 13.8, 9.4, and 8.1 times greater than that of the non-imprinted polymer. Eventually, the desorption conditions of the adsorbed Co(II) from the Co(II)-imprinted polymer were also studied in batch experiments.

Keywords ion-imprinted, Co(II), chitosan (CTS), adsorption, selective, surface-grafted

Introduction

Cobalt is an essential element not only for life in mammals but also for plants and lower forms of organ-isms. However, the ingestion or inhalation of large doses of this analyte may lead to toxic effects.1 Com-monly, determining heavy metals in environmental samples uses flame atomic absorption spectrometry (FAAS), however, if the concentration of the analyte is too low to be determined directly, FAAS will have in-sufficient sensitivity and matrix interferences. Indeed, cobalt, nickel and copper are metals, which appear to-gether in many real samples.2 The operation of nuclear reactors thus creates a large amount of radioactive waste produced through fission and neutron capture, which is of great concern because of the induced radioactivity of the waste and the existence of some fission products.3 Cobalt, strontium and cesium all belong to the category of low-level radioactive wastes. So, it is very important to separation and enrichment of cobalt at trace.

Ion imprinting polymers (IIP) represent a new class of materials possessing high selectivity and affinity for the target ions. Hence, IIP has outstanding advantages such as predetermined selectivity in addition to simplic-ity and convenience to prepare.4 In the ion-imprinting process, the selectivity of a polymeric adsorbent is

based on the specificity of the ligand, on the coordina-tion geometry and coordination number of the ions, on their charges, and on their sizes.5 Recently, there are some reports on the application of IIP to preconcentra-tion of the heavy metal ions.6,7

Chitosan (CTS) is one of the most abundant bio-polymers in nature, and has remarkable properties such as nontoxicity, high biocompatibility and biodegrada-tion.8 The free amido and hydroxyl function abilities of chitosan give it a better ability to chelate ions of transi-tion metals than other natural compounds. Indeed, ni-trogen atoms hold free electron doublets that can react with metal ions. Amine groups are thus responsible for the uptake of metal ions onto CTS by a chelation mechanism.9 By this aim, CTS was chosen as the monomer to complex Co(II). Usually, the main limita-tions of IIP at present were almost inaccessibility to the sites, time-consuming, insufficient leaching of the im-printing metal ion. In this study, a new surface-grafted ion-imprinted polymer, CTS-Co(II)-potassium titanate whisker (K2O•nTiO2, PTW), has been synthesized using a surface-grafted ion-imprinting technique. Glycidoxy- propyltrimethoxysilane (GPTMS) is an epoxy-siloxane with trimethoxy anchor groups, and on one hand, GPTMS as the cross-linking agents is non-toxic com-pared with glutaraldehyde (GA) and ethylene glycol

Synthesis and Adsorption Performance of Surface-Grafted Co(II)-Imprinted Polymer

Chin. J. Chem. 2010, 28, 548—554 © 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cjc.wiley-vch.de 549

diglycidy1 ether (EGCE),10 while on the other hand, GPTMS as the silane coupling agent can graft CTS-Co(II) onto PTW. Thus, the preparation method-ology, its main characteristic features and application to selective sorption of Co(II) from aqueous solution are described and discussed in detail in this paper.

Experimental

Chemicals

CTS, degree of deacetylation more than 90% (Guoyao Chemical Reagents Corp, AG, China), and GPTMS (Nanjing Shuguang Chemical Corp, China) were used in our work. Potassium titanate whiskers (PTW) (Shanghai Composite Manufacturing of Whisker, China), to activate the surface of PTW, was treated with hydrochloric acid (3 mol/L) for 24 h, followed by washing with doubly distilled water (DDW) and heated up at 110 for 2 h drying. Standard stock solution of ℃

Co(II) (1.0 g/L) was prepared by dissolving Co(NO3)2• 6H2O, and further diluted prior to use, and also the same for other metal ions. All the chemicals used were of analytical grade. DDW was used for all dilutions.

Apparatus and work condition

Infrared spectra were recorded by a Nicolet Nexus 470 FT-IR spectrometer (Thermoelectric, USA) using KBr as background. A D-5005 powder X-ray diffracto-meter (XRD, Siemens, Germany) was used with Cu Kα radiation (λ＝0.1541 nm). An S-4800 scanning electron microscope (SEM, Hitachi High, Japan) was used after gold plating at 15 kV on a field emission scanning elec-tron microscope. X-ray energy dispersion spectroscopy of un-leached and leached Co(II)-IP was conducted with a putong GENENIS 4000 energy dispersive X-ray mi-cro analyzer (EDS, USA). pH-values were measured with a pHS-3C meter (Lida Instrument, China) in the aqueous phase. A TAS-986 flame atomic absorption spectrophotometer (FAAS, Putong, China) was used, and all measurements were carried out in an air/acetylene flame with the instrumental parameters being as follows: Co(II), 1800 (flow mL/min), 8 (high nm), 5 (location mm). Pb(II), 1000 (flow mL/min), 5 (high nm), 2 (location mm). Cu(II), 1500 (flow mL/min), 5 (high nm), 4 (location mm). Ni(II), 1200 (flow mL/min), 5 (high nm), 2 (location mm). Sr(II), 2000 (flow mL/min), 10 (high nm), 4 (location mm). Cs(I), 1100 (flow mL/min), 1 (high nm), 1 (location mm).

Preparation of Co(II)-imprinted polymer

The following preparation procedures were modified according to the literature.11 CTS (4.0 g) and Co(NO3)2•6H2O (0.4 g) were dissolved in HOAc (0.1 mol/L) aqueous solution and stirred constantly for 1 h. Then, GPTMS as both a crosslink and a silane coupling agent was added into the transparent solution. The mix-ture was stirred for 4 h and then bathed in an ultrasonic bath for 20 min before the potassium titanate whiskers

(PTW) were added. While the dry product was ground and treated with 3.0 mol/L HNO3 to completely leach the coordinated and non-coordinated Co(II). The con-sequent polymer was soaked in an ammonia solution (0.85 mol/L) at 60 for 4 h to recover some amino ℃

groups lost in cross-linking step12 and ensure the neu-tralization of hydrogen ion. The polymer was then fil-tered, dried at 50 under vacuum, ground and sifted ℃

with 100 meshes, resulting in the desired Co(II)-imprinted polymer. By comparison, the non-imprinted polymer (NIP) was also prepared as a blank in parallel but without the addition of Co(NO3)2•6H2O.

Adsorption experiments

Co(II) adsorption batch experiments Adsorption of Co(II) from aqueous solutions was investigated in a batch experiment. 0.2 g of Co-IP was added into a 50 mL colorimetric tube containing an amount of Co(II) at a pH 6.0 (adjusted with 0.1 mol/L HCI and 0.1 mol/L NaOH). Then the mixture was shaken vigorously for 10 min, and the adsorption was maintained for a moment. After centrifugation, the concentration of the Co(II) in the residual solution was determined by FAAS. The experiment steps could be modulated according to the actual situation. The adsorption rate (E in %) and ab-sorption capacity (Q in mg/g) were calculated by Eqs. 1 and 2.

0

0

100%C C

EC

－＝ × (1)

0( )C C VQ

W

－

＝ (2)

where C0 (mg/L) and C (mg/L) are initial and equili-brated concentrations of Co(II), respectively. V (L) and W (g) are solution volume and the mass of Co(II)-imprinted polymer, respectively.

Selectivity study In order to measure the selectiv-ity of the imprinted polymer, competitive adsorption of Co(II)/Pb(II), Co(II)/Cu(II), Co(II)/Ni(II), Co(II)/Sr(II) and Co(II)/Cs(I) from their binary mixtures were inves-tigated by using Co(II)-IP and NIP. The distribution coefficient Kd (mL/g)，selectivity coefficient k, and the relative selectivity coefficient k′13 were given in Eqs. 3—5.

i fd

f

( )C C VK

C W

－

＝ (3)

d(Co)

d(M)

Kk

K＝ (4)

IP

NIP

'k

kk

＝ (5)

where Ci and Cf represent the initial and equilibrated concentrations of the given metal ions in solution, re-

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spectively; Kd(Co), Kd(M) represent the distribution coeffi-cients of Co(II) and M [M＝Pb(II), Cu(II), Ni(II), Sr(II), Cs(I)], respectively; kIP, kNIP represent the selectivity coefficient of Co(II)-IP and NIP, respectively.

Results and discussion

Preparation

The synthesis route designed for Co(II)-IP was schemed in Figure 1. In the ion-imprinting process, tem-plate Co(II) is firstly coordinated to —NH2 and —OH from the functional monomer CTS. Then, GPTMS attend polymeric reaction, forming a cross-linked polymer network CTS-Co(II). Next step is the self- condensation and co-condensation of —OH between silanols from siloxane and PTW surface, then the product is grafted on the surface of PTW. Finally, Co(II) is leached from the surface of polymer leaving behind some specific binding sites with functional groups in a predetermined orientation and cavities with special size of templates. On the one hand, GPTMS is reacted onto chitosan chains through the acid-catalyzed amino- oxirane addition reaction in the acidic aqueous solution.14 On the other hand, PTW is a solid substrate with hydroxyl groups on its surface, which is allowed to react with silanetriol groups in GPTMS to form cova-lently-bound surface monolayers of the metal alkox-ide.15 Thus, the GPTMS will not only put effect on crosslinking chitosan but also on alkoxysilane-modified PTW, as indicated in Figure 2.

Figure 1 Scheme of the Co(II)-IP preparation.

IR results As indicated in Figure 3b, the characteristic broad absorption band at 3450 cm－1 repre-sented multi-overlapped absorption peaks of hydroxyl groups (O—H) and amido groups (N—H) for stretching vibration, which might be related to the strong inter- and intramolecular hydrogen bonding.16 But these charac-teristic broad absorption bands shifted and obviously became narrower in Figure 3d and 3e due to —NH2 and —OH complexation with Co(II), which declined the capacity of hydroxyl groups (O—H) and amido groups (N—H) in forming hydrogen bonding. Comparing Fig-ure 3b and 3e, the characteristic peaks of δs(N—H) at

Figure 2 Scheme representation of CTS-GPTMS-PTW.

1595 cm－1 and νas(C—N) at 1380 cm－1 were shifted to 1640 and 1430 cm－1, respectively. The absorption peak of C—OH decreased from 1030 to 1019 cm－1. More-over, a new peak at 500 cm－1 assigned to the Co(II)—O appeared in Figure 3e. This fact can lead to a conclusion that the —NH2 and —OH groups in CTS coordinate simultaneously with Co(II) from the observed excursion of peaks.

Figure 3 Infrared spectra: (a) GPTMS; (b) CTS; (c) PTW; (d) Co(II)-IP; (e) CTS-Co(II).

The spectrum of GPTMS (Figure 3a) showed the Si—O—Si peak at about 1100 cm－1, which also could be found in Figure 3e. The peaks at 2940 and 2880 cm－1



were attributed to the stretching vibrations of —CH3 in GPTMS, which hardly changed but the intensity of the peaks was weakening in Figure 3e. The peak at 750 cm－1 was assigned to epoxy group in GPTMS, which disappeared in Figure 3e, concluding that the GPTMS reacted with the amino group on chitosan chains through its oxirane ring. Besides, the absorption peak around 3420 cm－1 was due to hydroxyl groups on sur-face of PTW, which was allowed to react with si-lanetriol groups in GPTMS to form covalently bound surface monolayers of the metal alkoxide. Thus, the overlapped absorption band of Si—O—Si from cross- linking reaction and condensation was obtained in Fig-ure 3d.

XRD patterns The prepared Co(II)-IP (Figure 4b) appeared to show different diffraction patterns with those of two pure components (Figure 4a and 4c). There was a distinct crystalline peak around 20° in the XRD patterns of the CTS. It is probably because plenty of —NH2 and —OH groups exist in the CTS structure, which can form stronger intermolecular and in-tramolecular hydrogen bonds. However, comparing CTS with Co(II)-IP, the distinct crystalline peak around 20° disappeared. This could be considered as that Co(II) was introduced into CTS main chains, which would de-struct the intermolecular and intramolecular hydrogen bonds and certain regularity of CTS.17 The peaks from PTW could be seen from the XRD of Co(II)-IP but the intensity decreased greatly, which indicated that the synthesis process did not result in the phase change of PTW, and Co-CTS was grafted just on the surface of PTW via GPTMS (Figure 2). The results were in agreement with the results of IR. This work has synthe-sized the surface-grafted Co(II)-imprinted polymer suc-cessfully.

Figure 4 X-ray spectra. (a) CTS; (b) Co(II)-IP; (c) PTW.

Morphological structure and EDS The Co(II)-IP surface (Figure 5) was smoothless and had some tiny cavities and interspace structures so that to the metal in the solution could be adsorbed easily by Co(II)-IP.

The results of microanalysis studies of un-leached and leached Co(II)-IP were illustrated in Figure 6. The species and percentage of each element on the

Figure 5 SEM of Co(II)-IP.

Figure 6 X-ray energy dispersion spectroscopy of unleached (a) and leached (b) Co(II)-IP.

un-leached and leached Co(II)-IP changed steadily, meaning that 3.0 mol/L HNO3 was intact to leached Co(II)-IP and sufficient to leach Co(II) from un-leached Co(II)-IP frequently.

Adsorption experiments

Effect of pH on the adsorption Solution acidity is an important parameter on Co(II)-IP adsorption from Co(II) solution because it affects the complexing reac-tion between Co(II) and CTS. The influence of pH on adsorption of Co(II) was studied in the range of pH 1.0—9.0 (Figure 7). The adsorption capacity for Co(II) increased with the pH, and Co(II)-IP exhibited a low affinity in acidic conditions (pH＜4.0), while a some-what higher affinity at pH＞5.0. In fact, it is known that at low pH, the —NH2 from CTS can be protonated and can not bind the Co(II) in the solution, because an ex-cess of hydrogen ions can compete effectively with Co(II) for —NH2. Noteworthily, the condition (pH＜4.0) may be utilized for desorption Co(II) from the polymer. In consideration of hydrolysis, pH above 8.0 was not chosen for this experiment, so the following experi-ments used pH 6.0 as optimal acidity.

Adsorption isotherm The adsorption capacity for Co(II) onto Co(II)-IP and NIP was investigated by static adsorption methods (Figure 8). To the Co(II)-IP, the amount of Co(II) adsorbed per unit mass of Co(II)-IP increased with the initial concentration of Co(II). In or-der to reach the saturation, the initial Co(II) concentra-tions were increased till 400 mg/L, which represents



Figure 7 Effect of pH value on adsorption of Co(II) onto Co(II)-IP.

Figure 8 Adsorption isotherms.

saturation of the active binding cavities onto the Co(II)-IP. The maximum adsorption capacity was 22 mg/g. To the NIP, the amount of Co(II) adsorbed per unit mass of NIP was lower obviously than that of Co(II)-IP, which may be due to the fact there were no active binding cavities onto the NIP. The maximum ad-sorption capacity for Co(II) onto NIP was only 8 mg/g.

Adsorption isotherms describe how adsorbates in-teract with adsorbents and so are critical in optimizing the use of adsorbents. Thus, the correlation of equilib-rium data by either theoretical or empirical equations is essential to the practical design and operation of adsorp-tion systems.18 Langmuir and Freundlich isotherms are the most frequently used models for describing the rela-tionship between the adsorbed on solids and the re-maining in solutions.

The Langmuir equation is

e e

e max L max

1 C C Q Q K Q

＝＋ (6)

where Ce (mg/L) is the different initial concentration of Co(II), Qe (mg/g) the adsorption capacity at the different initial concentration of Co(II) and KL (L/mg) the ad-

sorption-desorption equilibrium constant related to the binding energy.

The Freundlich equation is

1lg lg lgQ K Cn＝＋ (7)

where K and 1/n are Freundlich constants related to ad-sorption capacity and intensity of adsorption.

The data of the uptake of Co(II) have been processed in accordance with the Langmuir and Freundlich iso-therm equations, respectively in Table 1. The R2 values (0.1976 and 0.9482) for the adsorption of Co(II) ions showed that the Freundlich equation gave a good fit to the adsorption isotherm. And the calculated value of Qmax 22.5 mg/g from Freundlich equation was very close to the experimental values. The Freundlich iso-therm was derived by assuming an exponential decay energy distribution function instead in the Langmuir equation. It describes reversible adsorption and is not restricted to the formation of the monolayer.19

Table 1 Langmuir, Freundlich isotherm constants

Langmuir

KL/(L•mg－1) 0.0013

R2 0.1976

Qmax/(mg•g－1) 54.1

Freundlich

K/(L•mg－1) 0.1159

n 1.2024

R2 0.9482

Qmax/(mg•g－1) 22.5

Adsorption kinetics Kinetic adsorption experi-ments were carried out as a function of contact time under initial concentrations of 10 mg/L at three tem-perature settings 25, 35, and 45 (Figure 9). The ℃

curves at different temperatures all suggested that the adsorption rate was increased sharply in initial time, and a complete equilibrium was established after 300 min. There were abundant binding sites, which were tailored

Figure 9 Curve of kinetic adsorption.



to Co(II) in shape, size, and coordination geometry in initial adsorption step. Over a period of time, the bind-ing sites were filled with Co(II), and the adsorption be-havior reached the adsorption equilibration.

In order to examine the controlling mechanism of adsorption process such as mass transfer and chemical reaction, kinetic models were used to test experimental data. We used the kinetic data to fit the Lagergren pseudo-first-order kinetic model20 and pseudo-second- order kinetic model.21

The pseudo-first-order Lagergren equation is

1max max lg( ) lg

2.303t

K tQ Q Q －＝－ (8)

The pseudo-second-order Lagergren equation is

2e2 maxt

t 1 t

Q QK Q＝＋ (9)

where Qmax (mg/g) is the adsorption capacity at equilib-rium, Qt (mg/g) is the adsorption capacity at time t (min), K1 (min－1), K2 (mg•min•g－1) are pseudo-first- order and pseudo-second-order rate constants of adsorp-tion, respectively. The pseudo-first-order model is ren-dered the rate of occupation of the adsorption sites to be proportional to the number of unoccupied sites; the pseudo-second-order kinetic model assumes the chemi-cal reaction mechanisms,22 and that the adsorption rate is controlled by chemical adsorption through sharing or exchange of electrons between the adsorbent and ad-sorbate.23 The correlation coefficients for the pseudo- second-order model were higher than those of the pseudo-first-order one (Table 2). The theoretical Qmax value estimated from the pseudo-second-order kinetic model is very close to the experimental value. Therefore, the adsorption behavior of Co(II) onto Co(II)-IP be-longed to the second-order kinetic model and the ad-sorption process was a chemical one, which could be the rate-limiting step in the adsorption process.

Effect of temperature The relationship between temperature and adsorption amount was observed at 25, 35, and 45 (Figure 9), adsorption amount of Co(II) ℃

increased simultaneously with increasing temperature. The adsorption amount at 45 was larger by about ℃

33.4% than that at 25 . The adsorption process of ℃

Co(II) on Co(II)-IP was endothermic in nature. In this experiment, temperature 25 was chosen for easy co℃ n-trol.

Selectivity study Pb(II), Cu(II), and Ni(II) were chosen as competitive metal ions because of their simi-lar ionic radii and the same charge with Co(II), addi-tionally Sr(II), Cs(I), and Co(II) belong to mid-low ra-dionuclide. The competitive adsorption capacity of Co(II)-IP for Co(II) was higher than those for other metal ions and adsorption capacity of non-imprinted polymer for Co(II) was evidently lower than that of Co(II)-IP (Table 3). The higher complex formation re-sulting from the imprinting is caused by the energy benefit due to formation of non-distorted complexes in comparison with non-imprinted samples.24

Desorption From the effect of pH on adsorption, this work could desorb Co(II) in acidity solution, there-fore HNO3 was used as elution solvent. Desorption of Co(II) from the Co(II)-IP was investigated in batch ex-periments including the concentration and volume of HNO3, and quiescent time (Table 4). Lower concentra-tion of HNO3 might be not enough to protonate the —NH2 and —OH, but the high acid concentration would have an influence on determination step. In order to make desorption completely and integrate actual con-ditions, we should select the optimal desorption condi-tions as follows: 15 mL of 1 mol/L HNO3 and quiescent time of 120 min.

Conclusion

The Co-(II) imprinted polymer was synthesized though a simple and convenient method. Chitosan (CTS) was chosen as the complexing monomer. In the first step, Co(II) was complexed with CTS and CTS-Co(II) was grafted onto potassium titanate whiskers (PTW) by glycidoxypropyltrimethoxysilane (GPTMS). After that, the template ions Co(II) were removed using HNO3 (3.0 mol/L) solution. The optimal pH for quantitative ad-sorption was pH 6.0. The maximum adsorption capacity of Co(II) on Co(II)-IP was about 22 mg/g, and the ad-sorption isotherm was described by the Freundlich model, which describes reversible adsorption and is not restricted to the formation of the monolayer. The sec-ond-order kinetic model could be used to illustrate the adsorption process and chemisorption processes could be the rate-limiting step in the adsorption process. Competitive adsorption studies showed that Co(II)-IP offered the advantages of selectivity toward targeted Co(II) even in the presence of the category of low-level radioactive metals and Pb(II), Cu(II), Ni(II). The pre-

Table 2 Kinetic paraments of the Lagergren pseudo-first-order and pseudo-second-order kinetic models

Pseudo-first-order Pseudo-second-order Temperatue/℃

Experimental Qmax/(mg•g－1) K1/min－1 R2 Qmax K2/(mg•g－1•min－1) R2 Qmax

25 0.9100 4.6×10－3 0.8956 0.4022 2.0×10－2 0.9770 0.9272

35 1.1900 3.2×10－3 0.9490 0.4956 2.3×10－2 0.9789 1.1930

45 1.3550 8.8×10－3 0.9592 0.8652 1.9×10－2 0.9948 1.4450



Table 3 Competitive sorption of Co(II), Pb(II), Cu(II) Ni(II), Sr(II) and Cs(II) by Co(II)-IP and NIP sorbent at pH 6.0 (temperature 25 )℃

Imprinted polymer Non-imprinted polymer Metal type

kd/(mL•g－1) k kd/(mL•g－1) k k'

Co(II) 235.8 47.8

Pb(II) 79.3 3 183.4 0.26 11.5

Cu(II) 63.5 4 72.1 0.66 6.1

Ni(II) 31.1 26 25.3 1.89 13.8

Sr(II) 34.0 8 56.3 0.85 9.4

Cs(I) 87.6 3 127.5 0.37 8.1

Table 4 Effects of HNO3 concentration, volume and quiescent time on the desorption of Co(II)

Concentration/(mol•L－1) Recovery/% Volume/mL Recovery/% Quiescent time/min Recovery/%

0.1 49.1 5 80.5 30 80.5

0.5 78.3 10 88.9 60 87.9

1 89.7 15 92.4 90 90.5

2 95.4 20 98.1 120 93.1

pared Co(II)-imprinted polymer was shown to be a promising low-cost, stable, environmental sorbent for the preconcentration of trace Co(II) from real samples.

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Documents

Synthesis and Adsorption Performance of Surface-Grafted Co(II)-Imprinted Polymer for Selective Removal of Cobalt