Facile synthesis of sulfhydryl modified covalent organic frameworks for high efficient Hg(II) removal from water

In present study, we fabricated sulfhydryl modified covalent organic frameworks (COF--SH) through one-step reaction for the removal of Hg(II) from water. Different techniques were employed to characterize the fabricated COFs. We find that COF--SH exhibits great adsorption capacity (1283 mg/g) towards Hg(II), which is over 25 times higher than that of COF-1 without --SH (53.1 mg/g). COF-SH has fast adsorption kinetics with the removal of 95% of 1000 mu g/L Hg(II) within 30 min and over 99% after 2 h. Under a wide pH range (from 4 to 9), COF--SH exhibits high removal efficiencies (>99%). Moreover, COF-SH can selectively adsorb Hg(II) in the presence of other metal cations up to 1000 mu g/L. X-ray photoelectron spectroscopy analysis reveals the presence of high affinity between thiol-S atom and Hg(II), which is also responsible for the high selectivity towards Hg(II) compared with other cations. Because of the transfer from enol form to keto form during synthesis, COF-SH exhibit remarkable stability during 10-cycle regeneration and reuse test. During utilization in wastewater extracted from Hg contaminated sludge, COF--SH displays high Hg(II) removal efficiency (>95%) under multiple coexisting ions conditions. The results suggest that COF--SH have great potential for Hg(II) removal from water under complex conditions.

Automated summary

In this study, sulfhydryl modified covalent organic frameworks (COF--SH) were fabricated for efficient removal of Hg(II) from water. The COF--SH showed high adsorption capacity, fast adsorption kinetics, high selectivity and stability, as well as high Hg(II) removal efficiency under multiple coexisting ions conditions. The results suggest great potential for COF--SH in Hg(II) removal from water under complex conditions.