Thiol-ene click chemistry synthesis of a novel magnetic mesoporous silica/chitosan composite for selective Hg(II) capture and high catalytic activity of spent Hg(II) adsorbent

Abstract

Development of multifunctional bioadsorbents by a simple method for selective capture of the toxic Hg(II) from aqueous media, and subsequent reuse of the spent Hg(II) adsorbents as efficient heterogeneous catalysts are of great interest but remains a great challenge. Hence, in this work, a novel magnetic mesoporous silica/chitosan (MMS/CS) composite was facilely synthesized via the thiol-ene click reaction strategy to overcome the drawbacks of conventional cross-linking methods. The obtained materials were characterized by FTIR, XRD, SEM, XPS analyses. The uptake of Hg(II) by MMS/CS was systematically investigated under different parameters. Kinetic studies indicate that the sorption equilibrium can be reached within 20 min and sorption process fits well to the pseudo-second-order model. Sorption isotherm is well described by Langmuir model with the maximum sorption capacity of 478.47 mg/g at 298 K. Which represent a better Hg(II) uptake capacity and rate than the concerned materials previously reported. Besides, the coexisting ions exhibit little competition effluence on Hg(II) uptake. What’s more, the Hg(II) loaded MMS/CS can be used as an efficient catalyst to transform the phenylacetylene into acetophenone with yield of 98.3%. Therefore, this work not only demonstrates thiol-ene click reaction is a new and facile method for preparing chitosan-based functional materials with promising uptake capacity for Hg(II), but also provides a new approach for reusing of Hg(II) adsorbed material for catalytic application, thus expand the application of chitosan and magnetic mesoporous silica in diverse scientific fields.