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

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.

Automated summary

In this study, a novel magnetic mesoporous silica/chitosan (MMS/CS) composite was synthesized using the thiol-ene click reaction strategy for selective capture and reuse of toxic Hg(II) from aqueous media. The obtained materials exhibited high Hg(II) uptake capacity and rate, and could be utilized as efficient catalysts for organic transformations. This work provides a new and facile method for preparing chitosan-based functional materials with promising application potentials in environmental and catalytic fields.