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Application of molecularly imprinted polymers to selective removal of clofibric acid from water.

Dai C, Zhang J, Zhang Y, Zhou X, Liu S - PLoS ONE (2013)

Bottom Line: Sorption experimental results showed that the MIP had excellent binding affinity for CA and the adsorption of CA by MIP was well described by pseudo-second-order model.The MIP synthesized was used to remove CA from spiked surface water and exhibited significant binding affinity towards CA in the presence of total dissolved solids (TDS).In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance.

View Article: PubMed Central - PubMed

Affiliation: College of Civil Engineering, Tongji University, Shanghai, China ; State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai, China.

ABSTRACT
A new molecularly imprinted polymer (MIP) adsorbent for clofibric acid (CA) was prepared by a non-covalent protocol. Characterization of the obtained MIP was achieved by scanning electron microscopy (SEM) and nitrogen sorption. Sorption experimental results showed that the MIP had excellent binding affinity for CA and the adsorption of CA by MIP was well described by pseudo-second-order model. Scatchard plot analysis revealed that two classes of binding sites were formed in the MIP with dissociation constants of 7.52 ± 0.46 mg L(-1) and 114 ± 4.2 mg L(-1), respectively. The selectivity of MIP demonstrated higher affinity for CA over competitive compound than that of non-imprinted polymers (NIP). The MIP synthesized was used to remove CA from spiked surface water and exhibited significant binding affinity towards CA in the presence of total dissolved solids (TDS). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance.

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Effect of pH on the adsorption efficiency of CA by MIP (mean ±SD, n = 3).
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pone-0078167-g005: Effect of pH on the adsorption efficiency of CA by MIP (mean ±SD, n = 3).

Mentions: The pH value of water samples as an important parameter plays a vital role in the adsorption studies. Because pH can influence the dissociation status of target compounds as well as MIP. Therefore, it was necessary to study the effect of pH on adsorption. Fig. 5 shows the effect of pH on the adsorption of CA by MIP in deionized water. As shown in Fig. 5, adsorption efficiency of CA by MIP changed very little when the pH value of the solution was below 6. This suggested that the hydrophobic interaction and binding affinity between CA and the selective binding sites play a predominant role in this pH range. However, the adsorption efficiency of CA decreased significantly with the increase of pH when the pH was between 6 and 12. This phenomenon could be explained by the ionization of CA. The pKa value of CA was 3.18. Ionization would occur for CA under strong basic condition. Therefore, CA was negatively charged. On the other hand, the functional monomer of 2-VP (pKa = 4.98) used in the synthesis of MIP could also be negatively charged. It is known that the –COOH groups in the selective binding cavity of MIP play a key role in the rebinding of target compounds [20]. As a result, the electrostatic repulsive interactions between CA and MIP overcome the binding affinity and hydrophobic interactions became the main driving force during the adsorption at basic pH values. Hence, the adsorption efficiency of CA was reduced. This was consistent with the results obtained by Yu et al. [20]. Almost no CA was adsorbed onto the MIP at initial pH 11 and 12, indicating that the adsorption efficiency of CA by MIP was mainly attributed to the electrostatic attraction and the contribution of other interactions such as hydrophobic interaction and hydrogen binding was extremely limited. The experimental results make it clear that pH 6 was the optimum pH through this study.


Application of molecularly imprinted polymers to selective removal of clofibric acid from water.

Dai C, Zhang J, Zhang Y, Zhou X, Liu S - PLoS ONE (2013)

Effect of pH on the adsorption efficiency of CA by MIP (mean ±SD, n = 3).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3814990&req=5

pone-0078167-g005: Effect of pH on the adsorption efficiency of CA by MIP (mean ±SD, n = 3).
Mentions: The pH value of water samples as an important parameter plays a vital role in the adsorption studies. Because pH can influence the dissociation status of target compounds as well as MIP. Therefore, it was necessary to study the effect of pH on adsorption. Fig. 5 shows the effect of pH on the adsorption of CA by MIP in deionized water. As shown in Fig. 5, adsorption efficiency of CA by MIP changed very little when the pH value of the solution was below 6. This suggested that the hydrophobic interaction and binding affinity between CA and the selective binding sites play a predominant role in this pH range. However, the adsorption efficiency of CA decreased significantly with the increase of pH when the pH was between 6 and 12. This phenomenon could be explained by the ionization of CA. The pKa value of CA was 3.18. Ionization would occur for CA under strong basic condition. Therefore, CA was negatively charged. On the other hand, the functional monomer of 2-VP (pKa = 4.98) used in the synthesis of MIP could also be negatively charged. It is known that the –COOH groups in the selective binding cavity of MIP play a key role in the rebinding of target compounds [20]. As a result, the electrostatic repulsive interactions between CA and MIP overcome the binding affinity and hydrophobic interactions became the main driving force during the adsorption at basic pH values. Hence, the adsorption efficiency of CA was reduced. This was consistent with the results obtained by Yu et al. [20]. Almost no CA was adsorbed onto the MIP at initial pH 11 and 12, indicating that the adsorption efficiency of CA by MIP was mainly attributed to the electrostatic attraction and the contribution of other interactions such as hydrophobic interaction and hydrogen binding was extremely limited. The experimental results make it clear that pH 6 was the optimum pH through this study.

Bottom Line: Sorption experimental results showed that the MIP had excellent binding affinity for CA and the adsorption of CA by MIP was well described by pseudo-second-order model.The MIP synthesized was used to remove CA from spiked surface water and exhibited significant binding affinity towards CA in the presence of total dissolved solids (TDS).In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance.

View Article: PubMed Central - PubMed

Affiliation: College of Civil Engineering, Tongji University, Shanghai, China ; State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai, China.

ABSTRACT
A new molecularly imprinted polymer (MIP) adsorbent for clofibric acid (CA) was prepared by a non-covalent protocol. Characterization of the obtained MIP was achieved by scanning electron microscopy (SEM) and nitrogen sorption. Sorption experimental results showed that the MIP had excellent binding affinity for CA and the adsorption of CA by MIP was well described by pseudo-second-order model. Scatchard plot analysis revealed that two classes of binding sites were formed in the MIP with dissociation constants of 7.52 ± 0.46 mg L(-1) and 114 ± 4.2 mg L(-1), respectively. The selectivity of MIP demonstrated higher affinity for CA over competitive compound than that of non-imprinted polymers (NIP). The MIP synthesized was used to remove CA from spiked surface water and exhibited significant binding affinity towards CA in the presence of total dissolved solids (TDS). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance.

Show MeSH
Related in: MedlinePlus