Mercury Adsorption on Thiol-Modified Porous Boron Nitride: A Combined Experimental and Theoretical Investigation

Abstract

Heavy metal pollutants from industrial wastewater pose a great threat to public health and ecosystem safety. In this paper, a thiol-modified porous boron nitride (pBN–SH) adsorbent synthesized by a facile acid-etching method was studied for the highly selective adsorption of Hg(II) in a complex environment. pBN–SH was characterized by X-ray diffraction, thermogravimetric, elemental analysis, Brunauer–Emmett–Teller analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. The effect of adsorption dosage, pH, contact time, and temperature on Hg(II) adsorption was comprehensively investigated. Characterized results show that thiol groups are loaded on the surface of pBN through oxygen-containing groups and π–π bond. Due to the abundant structural defects and surface modification of functional groups, pBN–SH can effectively capture Hg(II) from water. Compared with the pristine pBN, the adsorption capacity of pBN–SH increases significantly by nearly 2.1 times, which suggests broad application prospects of pBN–SH in removing the Hg(II) aspect. Experimental results corresponding to the pseudo-second-order kinetic, the intra-particle diffusion model, and the Langmuir isotherm demonstrate that pBN–SH holds a high potential in environmental remediation. In addition, the recovered pBN–SH loaded with Hg(II) waste can be available for a valid catalyst for the conversion of phenylacetylene to acetophenone, providing a new way for the reuse of Hg(II)-adsorbed materials. Density functional theory calculations revealed that multitudinous defects and thiol functional groups on the pBN–SH surface, electrostatic attraction, and ligand exchange are responsible for the excellent Hg(II)-selective adsorption capability discovered in the experiment.