Construction of the composites of nitrogen and sulfur-doped porous carbon and layered double hydroxides and the synergistic removal of heavy metal pollutants

Abstract

• High dispersion and stable attachment of LDH on nitrogen and sulfur doped porous carbon (NSPC). • The synergistic effect of LDH and NSPC enhances the adsorption of heavy metal ions. • The adsorption mechanism was attributed to surface complexation. Layered double hydroxides (LDHs) composites (NSPC@LDH) were successfully prepared on nitrogen and sulfur-doped porous carbon (NSPC) by a simple co-precipitation method. The synergistic effect between the modified porous carbon and LDH enhanced its adsorption performance. Compared with pure LDH, the composite had a larger specific surface area (188.78 m 2 /g) and pore structure with a smaller crystallite size (4.56 nm). The porous carbon carrier effectively mitigated the aggregation effect of LDH. The maximum adsorption capacities of NSPC@LDH for Zn 2+ (100 ppm) and Cu 2+ (100 ppm) were 125.7 mg/g and 137.5 mg/g, respectively, which were 2.85 and 2.39 times the original LDH. The XRD and XPS studies of the adsorbent after adsorption revealed that surface complexation and physical adsorption played a dominant role in the removal of Zn 2+ and Cu 2+ , and the introduction of N, S heteroatoms provided more active centers for heavy metal ions. Moreover, after five desorption cycles, NSPC@LDH still exhibited high removal efficiency. The results indicated that the synthesized NSPC@LDH composites have great potential for removing Zn 2+ and Cu 2+ from aqueous solutions.