Preparation and preliminary assessment of polymersupported zirconium phosphate for selective lead removal from contaminated water

In the present study, polymer-supported zirconium phosphate (ZrP-CP) was prepared for selective removal of lead from the contaminated water. ZrP-CP was characterized using nitrogen adsorption technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lead sorption on ZrP-CP was found to be pH dependent due to the ion-exchange mechanism. Also, ZrP-CP was proved to be more selective than the polystyrene strong-acid cation exchanger D-001 to remove lead ion from water, where other competing cations such as Na+, Ca2+, and Mg2+ ions coexist at high concentrations. Generally, lead sorption isotherms on ZrP-CP can be divided into two distinct regions at different load levels, and isotherms at both regions can be well elucidated by Langmuir model. The distribution coefficients (K-d) and binding constants (B-L) obtained experimentally indicated that stronger sorption affinity of ZrP-CP towards the lead ion occurs at a relatively lower load level. Also, lead sorption onto ZrP-CP was found to be an endothermic and entropy-driven process. High selectivity of ZrP-CP towards the lead ion was possibly attributed to the crystal state of zirconium phosphate and a specific interaction between orthophosphate and lead ion. Fixed-bed column runs showed that lead sorption on ZrP-CP could result in a conspicuous decrease of this toxic metal from 0.5 mg/L to below 0.01 mg/L, which is recommended as the standard of drinking water by WHO (the treatment technique standard set by US EPA is 0.015 mg/L). Also, the spent sorbent can be readily regenerated for reuse by dilute HNO3 or HCl solution. (c) 2006 Elsevier Ltd. All rights reserved.