Removal of Cd2+ from wastewater to form a three-dimensional fiber network using Si-Mg doped industrial lignin-based carbon materials

Abstract

In this study, SiMg doped industrial lignin-based carbon materials (SLCs) were prepared by water bath silicification and MgCl₂ activation to remove Cd²⁺ from aqueous solutions. What's more, the doping of SiMg jointly promoted the excellent physicochemical properties of the material, e.g., high specific surface area, good pore volume, and numerous oxygen-containing groups. The Cd²⁺ batch adsorption experiments proved that SLCs have good Cd²⁺ removal capacity within pH 3-7, and the adsorption model demonstrated the adsorption process as a physicochemically complex process. The maximum adsorption of Cd²⁺ in the SLC was 665.35 mg/g, and the contributing factors to the removal of Cd²⁺ were as follows: ion exchange (59.36 %) > Cd²⁺ precipitation (24.93 %) > oxygen-containing functional group complexation (14.79 %) > Cd²⁺-π interactions (0.92 %). In addition, the complexation of SiO, MgO, and Cd precipitates allowed the formation of a three-dimensional fiber mesh structure. The application of SLCs has the potential to eliminate Cd²⁺ pollution in water bodies, and its preparation is simple and environmentally friendly. Finally, this study provides a theoretical basis for an in-depth understanding of the mechanism of heavy metal adsorption by inorganic nonmetals in combination with metal oxides.

Keywords: Cadmium removal; Carbon material; Industrial lignin.