Self-formed MnCO3/FeS2@SiO2 in modified electrolytic manganese residues as an enhanced peroxymonosulfate activator for ammonium dibutyl dithiophosphate removal

In this study, a peroxymonosulfate (PMS) activator named NMN95 using electrolytic manganese residues (EMR) as raw material was successfully synthesized. The NMN95 consisting of MnCO3, FeS2 and SiO2 showed excellent degradation ability for ammonium dibutyl dithiophosphate (ADD) attributed to the synergistic effects of Fe, Mn and reducing S species. Under the optimum conditions, the NMN95/PMS system could effectively degrade 95.8% of ADD (100 mg/L) within 30 min. The degradation system could produce a large number of free radicals including sulfate radical (SO4•−), hydroxyl radical (•OH) and superoxide radical (O2•−), as well as the non-radical singlet oxygen (1O2), in which O2•− and 1O2 played the crucial role in decomposing the ADD molecule. Spectroscopic analysis and density functional theory (DFT) demonstrated that the adsorption and activation of PMS are more favorable on MnCO3 than FeS2, where S sites in FeS2 acted as the electron donor to accelerate the transformation between high and low valance of Mn and Fe. Additionally, P1, S2, S5 and N14 on ADD molecules were in sensitive positions attacked by reactive species. Cyclic and metal ions leaching experiments showed that NMN95 has excellent reusability and stability within seven cycles. This study has sought a new high-value utilization approach for EMR and provided an efficient degradation system for the remediation of organic contaminants in beneficiation wastewater.