Mercury removal by porous sulfur copolymers: Adsorption isotherm and kinetics studies

Abstract

Mercury is one of the most toxic, harmful element present in water that severely affects human health. Many traditional as well as advanced technologies were developed to remove mercury from wastewater. In this study, sulfur copolymers containing micro and macro porous structure were prepared via inverse vulcanization technique and used to capture the mercury ions from wastewater. Initially, porogens with varying particle size were added to the sulfur and cross-linker mixture, later the obtained solid copolymers was treated with water to generate porous structure with different porosicity. Structure of the prepared sulfur copolymer was confirmed by FTIR, NMR spectroscopy and the surface morphology studied by SEM indicate the presence porous structure relating to the size of the porogen. Thermal properties analyzed by DSC and TGA supports the stability of the copolymer. Obtained sulfur foams were used to capture mercury ions from water and studied the adsorption behaviour using different isotherm and kinetics models. The adsorption kinetics showed a pseudo-second-order rate equation and the metal ion diffusion was found to be a combination of both intraparticle and liquid film diffusion mechanisms. The adsorption capacity improved with the increasing porosity in the sulfur foam and the adsorption isotherm suggested that the mercury ions were captured via both physical and chemical adsorption mechanism. Modification in the sulfur foam porosity can significantly influence the mercury ion adsorption capacity. The main advantage of this technique is the use of surplus sulfur and one step preparation method which can be scalable and cost effective.