Cationic polyacrylamide aerogel intercalated molybdenum disulfide for enhanced removal of Cr(VI) and organic contaminants

Abstract

The removal of heavy metal ions from industrial effluents by molybdenum disulphide (MoS2) has attracted considerable attention, but developing the removal capacity of MoS2 toward hexavalent chromium ions (Cr(VI)) in wastewater treatment is still a challenge. Herein, a cationic polyacrylamide aerogel (CPAMA) containing -N+(CH3)3 was creatively introduced as a precursor to synthesize the CPAMA intercalated MoS2 (MoS2@CPAMA). The addition of CPAMA as carrier greatly improved the dispersion and the exposure of active sites of MoS2, and even the -N+(CH3)3 effectively increased the surface potential of MoS2, which facilitated the adsorption and reduction for Cr(VI). Notably, MoS2@CPAMA removed 95% of Cr(VI) within 50 min and the maximum Cr(VI) removal capacity reached 800.0 mg g−1 at 400 mg L−1, which was significantly higher than that of MoS2 (237.1 mg g−1) and almost all reported MoS2-based materials. The results of ICP-OES and UV–vis spectrophotometer revealed that both reduction and adsorption pathway were participated during the Cr(VI) removal process, while the reduction was obviously dominated. The results of XPS showed that the -N+(CH3)3 and amide groups played a significant role in adsorbing Cr(VI) onto the MoS2@CPAMA surface, and the Mo was oxidized from Mo4+ to Mo6+ and the S2− was oxidized into S6+ subsequently during the reduction of Cr(VI). Interestingly, MoS2@CPAMA could also be used as a co-catalyst in the Fe2+/PMS system, and the TOC removal rate of 67% in 60 min and the retention rate of 80% for Fe2+ were achieved. Notably, MoS2@CPAMA possessed high durability in the co-existing cations and anions, and the 4-CP removal rate was still as high as 94% after four consecutive cycles, indicating the splendid reusability of MoS2@CPAMA. This study offers new insights into the development of multifunctional MoS2-based materials for wastewater treatment.