Preparation of sulfur self-doped coal-based adsorbent and its adsorption performance for Cu²

The limited application of high-sulfur coal (HSC) and the increasing severity of copper pollution in solution are two pressing issues. To alleviate such issues, a sulfur self-doped coal-based adsorbent (HSC@ZnCl₂) was obtained by pyrolysis (850 °C, 60 min holding time) of HSC and ZnCl₂ with a mass ratio of 1:0.5. The results adsorption experiment revealed that the endothermic and spontaneous adsorption process was consistent with the Sips isothermal model (R² = 0.992) and pseudo-second-order kinetic (R² = 0.994), and that the adsorption process with a maximum adsorption capacity of 11.97 mg/g. Meanwhile, the adsorption of Cu²⁺ onto HSC@ZnCl₂ was a result of the synergistic effects of various interactions, such as the complexation by oxygen-containing functional groups, electrostatic attraction and surface precipitation by ZnS on the adsorbent surface, and the process also included redox reaction. The findings of this work indicate that the preparation of sulfur self-doped coal-based adsorbent prepared from high-sulfur coal is a promising method for its large-scale utilization.