Polyferric sulfate-derived ceramsite for Sb(V) removal from acid mine drainage: performance and immobilization mechanism.

Antimony (Sb) contamination, especially as Sb(V), is a significant environmental concern in acid mine drainage (AMD). Iron-based materials are effective for Sb(V) removal but often face limitations from iron speciation and coexisting ion interference. This study developed a novel approach for Sb(V) removal using PFS-derived ceramsite, synthesized by immobilizing polyferric sulfate (PFS) onto a ceramic matrix using bentonite as a binder and corn straw as a pore-forming agent. The effects of sintering temperature and atmosphere on performance were investigated, with results showing that lower sintering temperatures and an oxidizing atmosphere enhanced Sb(V) removal efficiency. The ceramsite exhibited a high Sb(V) removal rate of 97.9%, with pseudo-second-order kinetics and Freundlich isotherm fitting, indicating multilayer adsorption on a heterogeneous surface. While phosphate and silicate pose competitive adsorption, the ceramsite maintained effective Sb(V) removal in the presence of common coexisting ions and real AMD water, and exhibited good regeneration performance of 86% Sb(V) removal during repeated acid-base washing cycles. The removal of Sb(V) is primarily driven by inner-sphere complexation between Sb(OH)6- and Fe-OH sites on the ceramsite surface, along with Fe-Sb coprecipitation. These findings highlight the potential of PFS-derived ceramsite as an effective and cost-efficient material for Sb(V) removal from AMD.