Selective Removal Of Estrogenic Compounds From Aqueous Solution Using Novel Adsorbent-Molecularly Imprinted Polymer.

ZHANG ZHONGBO

Publication

Selective Removal Of Estrogenic Compounds From Aqueous Solution Using Novel Adsorbent-Molecularly Imprinted Polymer.

ZHANG ZHONGBO

Abstract

The objective of this research was to synthesize a kind of qualified MIP and to study whether MIP could be effectively used to remove estrogenic compounds from aqueous solution and what factors influenced the removal of these compounds. A molecular imprinted polymer (MIP) was successfully synthesized in this study and used for selective removal of estrogenic compounds, estrone (E1), 17ß-estradiol (E2), 17a-ethinylestradiol (EE2) and Bisphenol A (BPA) from aqueous solution. The mass balance results of template molecule showed further that 2.172 mg of E2 extracted out from 125 mg MIP. The adsorption isotherms of E1, E2, EE2 and BPA were studied at the concentration ranging from 1 ppb to 1 ppm. MIP was able to attain adsorption capacities of 111.7, 106.5, 121.5 and 59.4 µmole/g polymer for E1, E2, EE2 and BPA, respectively. According to the adsorption isotherms for E1, E2, EE2 and BPA, a physical adsorption model containing three types of binding sites, namely, specific binding site, semi-specific binding site and non-specific binding site was proposed to interpret the adsorption performance of MIP. The adsorption mechanisms were interpreted by a physical adsorption model in terms of binding affinity. The adsorption mechanisms were further confirmed by desorption isotherms of E1, E2, EE2 and BPA obtained from static gradient desorption. The kinetics of MIP adsorption was also studied. According to the adsorption isotherms and the template molecule¿s mass balance, an experimental concept, selective adsorption ratio (SAR), was proposed to assess how many template molecules extracted out of MIP could create selective binding sites in MIP. The SAR of the MIP used in this study was 16.9, 74.3, 26.8 and 14.2% for E1, E2, EE2 and BPA, respectively. In this study, the effects of environmental factors, including humic acid (HA), pH, ionic strength and the coexistence of competing estrogenic compounds, on the adsorption of four typical estrogenic compounds, estrone (E1), 17-ßestradiol (E2), 17a-ethinylestradiol (EE2) and Bisphenol A (BPA), were studied by molecularly imprinted polymer (MIP). The results implied that no significant effect could be found with the increasing HA concentrations. Ionic strength did not exert a considerable influence on the adsorption capacities of MIP and NIP for E1, E2 and BPA except for EE2 due to the increased hydrophobic interactions. The study demonstrated that there was no significant effect of pH on the adsorption capacity of both MIP and NIP from pH 3.1 to 9 and that no considerable effect of pH on selective adsorption capacity of MIP could be established. However, at the pH 11, the adsorption capacity and selective adsorption capacity were influenced significantly due to the ionization of target compounds. The immobilization of MIP and NIP was performed with PVA-boric acid in order to carry out the regeneration of MIP. The results showed the MIP can be effectively regenerated with thee batches of regeneration and, the MIP can be used at least 6 times without losing removal efficiency after regeneration.