Preparation and characterization of photocured thiol-ene hydrogel: Adsorption of Au(III) ions from aqueous solutions

Role of surface functional groups of hydrogels in metal adsorption: From performance to mechanism

Hydrogels have been studied quite intensively in recent decades regarding whether their metal adsorption abilities may be modified or even enhanced via functionalization (i.e., functionalizing the surfaces of hydrogels with specific functional groups). Studies have found that functionalizing hydrogels can in fact give them higher adsorptive power. This enhanced adsorptive performance is articulated in this paper through critically reviewing more than 120 research articles in such terms as the various techniques of synthesizing functionalized hydrogels, the roles that specific functional groups play on adsorption performance, selectivity, reusability, as well as on adsorption mechanism. Moreover, this critical review offers insight into future designs of functionalized hydrogels with specific metal adsorption capabilities.

Fast and effective recovery of Au(III) from aqueous solution by a N-containing polymer

In this work, a N-containing polymer was successfully synthesized by one-step treatment with 3-amine-1,2,4-triazole ligands and Zn(II) using the thermal solvent method, and employed to recover Au(III) from water. The adsorption kinetics was comprehensively studied through kinetics models including pseudo-first-order model, pseudo-second-order model, moving boundary model and Weber-Morris model. It is found that the overall adsorption rate was determined by chemical adsorption, and the rate-limiting step of diffusion steps is film diffusion. Rising temperature can improve the adsorption rate significantly, making the adsorption equilibrium time be reduced from 6 h at 298 K to 2 h at 318 K. The adsorption isotherm can be described well by Sips model, indicating it is a heterogeneous adsorption. The material shows high adsorption capacity towards Au(III) up to 1073 mg/g. It shows strong affinity towards Au(III) in the mixture solutions containing Au(III), Cu(II), Zn(II), Co(II), Cd(II), Pb(II) and Ni(II) ions. The material can be easily and completely desorbed by thiourea solution and still maintains its adsorption performance only with a slight decrease after three cycles. Combined with studies on pH influence, adsorption kinetics, adsorption isotherm and XPS analysis, it can be concluded that the adsorption mechanism could be attributed to electrostatic interaction, the coordination of the Zn-OH and -C-N/-CN- with Au(III), and partial reduction of Au(III) to Au(I) by -NH group on the polymer. The N-containing polymer is an excellent candidate for Au(III) recovery efficiently and selectively from aqueous solution.

Thiol–ene “click” reactions and recent applications in polymer and materials synthesis: a first update

This contribution serves as an update to a previous review (Polym. Chem.2010,1, 17–36) and highlights recent applications of thiol–ene ‘click’ chemistry as an efficient tool for both polymer/materials synthesis as well as modification.