In the current study, amorphous titanium phosphate (TiP) was prepared as an adsorbent for heavy metals from waters. Uptake of Pb2+, Zn2+, and Cd2+ onto TiP was assayed by batch tests; a polystyrene -sulfonic acid exchanger D-001 was selected for comparison and Ca2+ was chosen as a competing cation due to its ubiquitous occurrence in waters. The pH-titration curve of TiP implied that uptake of heavy metals onto TiP is essentially an ion-exchange process. Compared to D-001, TiP exhibits more preferable adsorption toward Pb2+ over Zn2+ and Cd2+ even in the presence of Ca2+ at different levels. FT-IR analysis of the TiP samples laden with heavy metals indicated that the uptake of Zn2+ and Cd2+ ions onto TiP is mainly driven by electrostatic interaction, while that of Pb2+ ions is possibly dependent upon inner-sphere complex formation, except for the electrostatic interaction. Moreover, uptake of heavy metals onto TiP approaches equilibrium quickly and the exhausted TiP particles could be readily regenerated by HCl solution.

Aminated polystyrene resins (NDA-101 and NDA-103) were synthesized, and their adsorption performances for phenol in aqueous solutionwere investigated and compared with the commercial polystyrene resin (Amberlite XAD-4) andweakly basic polystyrene resin (Amberlite IRA-96). All the associated adsorption isotherms are well described by Freundlich and Langmuir equations. The results indicated that all the four resins spontaneously adsorb phenol driven mainly by enthalpy change, and their adsorption capacities, free energy changes, enthalpy changes, and entropy changes for phenol followed the same order as: NDA-101>NDA-103>XAD-4>IRA-96. Surface energy heterogeneity analysis by Do's model also suggested that the surfaces of XAD-4 and IRA-96 were more homogeneous, and the better adsorption capacity and affinity of the aminated resins (NDA-101 and NDA-103) are probably due to their multiple hydrogen bonding and-stacking interactions with phenol molecule.

The present study reported synthesis of a new inorganic exchanger, i.e., zirconium hydrogen monothiophosphate [Zr(HPO3S)2, denoted ZrPS] and its selective sorption toward Pb(II), Cd(II) and Zn(II) ions. ZrPS sorption toward all the three metals is dependent upon solution pH due to the ion-exchange nature. As compared to another inorganic exchanger zirconium phosphate [Zr(HPO4)2, denoted ZrP], ZrPS exhibits highly selective sorption toward these toxic metals from the background of calcium ions at great levels. Such sorption preference is mainly attributed to the presence of-SH group in ZrPS, as further demonstrated by FT-IR analysis and XPS study. Moreover, ZrPS particles preloaded with heavy metals could be efficiently regenerated with 6M HCl for multiple use without any noticeable capacity loss. All the experimental results indicated that ZrPS is a promising sorbent for enhanced heavy metals removal from contaminated water.

In the present study, a novel hybrid sorbent ZrP-001 was prepared by loading zirconium phosphate (ZrP) onto a strongly acidic cation exchanger D-001. Sorption behavior of Pb2+, Zn2+, and Cd2+ onto ZrP-001 was experimentally examined by comparing with the host exchanger D-001. ZrP-001 was characterized by scanning electron micrograph (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), pH-titration and pore size distribution analysis. Sorption of the heavy metals onto ZrP-001 was found to be pH-dependent due to the ion exchange mechanism. Compared to D-001, a smaller pore size of ZrP-001 due to the ZrP dispersion consequently resulted in a lower sorption rate. Competitive effect of Ca2+ on sorption of heavy metals onto ZrP-001 and D-001 was compared to elucidate sorption preference of the hybrid sorbent towards heavy metals. More favorable sorption of ZrP-001 than D-001 was observed for all the three metals and their sorption preference onto ZrP-001 followed the order Pb2+> >Zn2+ ≈Cd2+. Fixed-bed sorption results and its efficient regeneration property further demonstrated that ZrP-001 is a potential candidate for removing heavy metals from contaminated water.

Sorption of aromatic sulfonates onto two aminated polystyrene sorbents with different pore structures (M-101 and D-301) was investigated for optimization of their potential application in chemical wastewater treatment. Sodium benzenesulfonate (BS), sodium 2-naphthalene sulfonate (2-NS) and disodium 2,6-naphthalene disulfonate (2,6-NDS) were selected as reference solutes and sodium sulfate was as a competitive inorganic salt. Sorption selectivity of both sorbents is dependent upon the concentration levels of aromatic sulfonates in solution coexisting with sodium sulfate at a high level. However, both sorbents exhibit different characters. D-301 presents more favorable sorption for the solutes at relatively high levels (e.g., higher than 5 mM for BS, 0.7mM for 2-NS and 0.05mM for 2,6-NS), while M-101 removes aromatic sulfonates more completely when the solute concentration kept at relatively low levels. Based on the experimental results, we proposed an integral process of sorption onto D-301 followed by secondary-sorption onto M-101 to remove aromatic sulfonates from industrial wastewater completely and economically. Furthermore, the satisfactory performance revealed from large-scale application further demonstrated the feasibility of extending this process to dispose of other associated chemical wastewaters.