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The transition metals and PFRs mainly participated in the single-electron pathway via activating PMS to generate a large amount of ROS, while the graphitic N -containing carbon matrix with π-π* shake up and C O groups acted as the electron mediator to favor the two-electron transfer and directly oxidized the BHA through the ternary activated outer-sphere complexes. [Display omitted] • The introducing of carbon source changed the surface electrification. • Both single-electron and two-electron pathway involved in the oxidation process. • PFRs and transition metals could activate PMS to produce abundant ROS. • N -containing carbon with prone to act as electron mediator and sacrifier. In this study, a novel carbon-wrapped-iron hierarchical porous catalyst (Fe/C-Mn 800) was prepared from electrolytic manganese residue (EMR) and sewage sludge (SS), which showed outstanding degradation ability toward benzohydroxamic acid (BHA, nearly 90 % was removed within 60 min) with low metal leaching rate. Mechanism exploration found transition metal ions (Fe and Mn) can serve as electron acceptors and facilitate the generation of persistent free radicals (PFRs). These transition metal ions and PFRs mainly participated in the single-electron pathway via activating PMS to generate a large amount of reactive oxygen species (ROS). While the electron negative graphitic N and C O groups not only improve the electronegatively of catalyst, but also acted as the electron sacrificers to favor the electron transfer and directly oxidized the absorbed BHA through the ternary activated outer-sphere complexes. Eley–Rideal (E-R) and Langmuir–Hinshelwood (L-H) analysis further demonstrated the crucial role of pre-adsorption during the degradation process. This work provided a deep insight into the degradation mechanism of metal/carbon composite and promising opportunity widened the horizon of the high-value utilization of EMR and SS. [ABSTRACT FROM AUTHOR]

The contamination of organoarsenic is becoming increasingly prominent while SR-AOPs were confirmed to be valid for their remediation. This study has found that the novel metal/carbon catalyst (Fe/C–Mn) prepared by solid waste with hierarchical pores could simultaneously degrade roxarsone (ROX) and remove As(V). A total of 95.6% of ROX (20 mg/L) could be removed at the concentration of 1.0 g/L of catalyst and 0.4 g/L of oxidant in the Fe/C–Mn/PMS system within 90 min. The scavenging experiment and electrochemical test revealed that both single-electron and two-electron pathways contributed to the ROX decomposition. Spectroscopic analysis suggested the ROX has been successfully mineralized while As(V) was fixed with the surface Fe and Mn. Density functional theory (DFT) calculation and chromatographic analysis indicated that the As7, N8, O9 and O10 sites of ROX molecule were vulnerable to being attacked by nucleophilic, electrophilic and radical, resulting in the formation of several intermediates such as phenolic compounds. Additionally, the low metal leaching concentration during recycling and high anti-interference ability in various water matrices manifested the practicability of Fe/C–Mn/PMS system. • The acidic condition was beneficial for the ROX degradation. • ROX has been mineralized while As(V) was fixed with the surface Fe. • Both single-electron and direct-electron ways contributed to the degradation. • The Fe/C–Mn could simultaneously degrade ROX and remove/fix As(V). [ABSTRACT FROM AUTHOR]

• The replacement of Mn to Fe in FeOOH could form O V -rich (Fe 0.67 Mn 0.33)OOH. • The surface metal−OH facilitated the production of •OH. • FeIII could be served as Lewis sites to facilitate the formation of (FeIII−PMS)−OH−. A novel ternary composite catalyst (FeOOH/Fe 2 O 3 /(Fe 0.67 Mn 0.33)OOH) directly prepared from electrolytic manganese residue was applied for terpineol degradation in this study. The reaction system could remove 76.8% of chemical oxygen demand (COD) from simulated water containing terpineol (100 mg/L), while the degradation process could be accelerated under alkaline condition (84.6% at pH 9.0). The degradation performances of Fe 2 O 3 , FeOOH and (Fe 0.67 Mn 0.33)OOH indicated that the in-situ formed (Fe 0.67 Mn 0.33)OOH riched in oxygen vacancies (O V) could promote the PMS activation activity of catalyst mainly ascribed by enhancing interfacial electron transfer. The · OH was the primary active radical, the production of which was favored by the metal−OH. This ternary composite catalyst had anti-jamming ability toward most common ions. Further, this system also displayed an outstanding degradation ability for actual mineral processing wastewater (93.2% COD removal). The developed system expanded the horizon for the high-value utilization of metallurgical slag and the treatment of refractory organic pollutants in mineral processing wastewater. [ABSTRACT FROM AUTHOR]

• CNTs could accelerate the transformation of metals in EMR with partial mass loss. • Surface activated-complex contributed to the directly ROX oxidization. • The k obs of catalytic reaction was increased by 10.1 times after combination. • The M-O-C (M =Fe or Mn) bonds in CNT/EMR making the catalyst more stable than EMR. • Amorphous FeAsO 4 •H 2 O was formed after degradation. A novel catalyst (MT/EMR) used for SR-AOPs with high removal efficiency toward roxarsone (ROX) (90.96% within 60 min) was prepared for the first time by ball milling multi-walled carbon nanotubes (MWCNTs) with electrolytic manganese residue (EMR). The incorporation of MWCNTs could improve the adsorption capacity and accelerate the transformation of metals in EMR with partial mass loss to facilitate the PDS activation. Additionally, pH test, quenching experiment and electrochemical test verified a two-electron pathway involving surface activated-complex contributed to the directly ROX oxidization. Benefit from the introduction of MWCNTs, the degradation rate (k obs) of catalytic reaction was increased by 10.1 times compared with that of single-EMR. Additionally, the M-O-C (M =Fe or Mn) bonds in MT/EMR making the catalyst more stable than EMR. This work provided a novel and effective strategy to establish waste solid-based catalysts for green preparation and expanded the adsorption-oxidation technology to solve the problem of organoarsenic pollution. [ABSTRACT FROM AUTHOR]

The recycling of solid wastes is obligable as it can reduce the environmental pollution and prevent the diffusion of secondary pollution. In this study, a novel cheap adsorbent was prepared by modifying electrolytic manganese residue (EMR) with EDTA. The maximum adsorption capacity of adsorbents for diethyl dithiocarbamate (DDTC) was 133.46 mg/g under initial pH of 7.32 at room temperature. Adsorption kinetics study revealed the DDTC adsorption on EDTA-EMR is mainly controlled by chemisorption and isotherm studies implied the adsorption is a monolayer process. Mechanism exploration found that the DDTC molecules could enter into the holes of EDTA-EMR, and the transition metal-based sorption sites were crucial for the target molecule immobilization and chelation. High pH value (> 10) was found to have inhibited the adsorption capacity of adsorbent, which should be due to the fact that the decreasing of functional groups on adsorbents surface and the competition between DDTC and OH–. The ionic strength has negligible effect on the adsorption and the as-synthesized adsorbents showed excellent performance after five cycles. The overall results reveal that EDTA-EMR is a promising adsorbent ascribed by its low cost, good recyclability and excellent adsorption capacity. [Display omitted] • The adsorption is a monolayer and spontaneous process. • EDTA could remove the impurities of EMR and retain transition metals. • DDTC could coordinated with the Fe/Mn containing active sites by chelation. [ABSTRACT FROM AUTHOR]

• This study developed a short-cut method for preparation of AOPs catalyst. • Phase transformation and active sites exposure facilitated the removal capacities. • Pre-adsorption was one of key steps to facilitate catalytic reaction. • Radical pathway played a dominant major role in LVF molecules decomposition. Preparations of catalysts for sulfate radicals-based advanced oxidation (SR-AOPs) are usually time-consuming and costly. This study developed a short-cut method for preparation of AOPs catalyst (MS-N3H) directly from electrolytic manganese slag. MS-N3H/PMS could effectively remove levofloxacin (LVF) from solution. Phase transformation and active sites exposure after modifications facilitated the adsorption and catalysis capacities. Both radical and non-radical pathway contributed to the degradation of LVF, in which abundant Mn and Fe on MS-N3H surface contributed to the generation of SO 4 −, OH and O 2 − radicals, and lattice oxygen played a crucial role in non-radical 1O 2 production. The MS-N3H/PMS was stable for the degradation of LVF in different water matrixes and kept high recyclability even after four recycles. This study brought underlying insights to develop novel high-efficient and easy-preparing catalysts for the degradation of recalcitrant organic pollutes. [ABSTRACT FROM AUTHOR]

• Alkali modification of EMR could prepare MnCO 3 /FeS 2 @SiO 2 composites. • O 2 •− and 1O 2 played the crucial role in decomposing the ADD molecule. • Fe, Mn and reducing S species have synergistic effects. In this study, a peroxymonosulfate (PMS) activator named NMN 95 using electrolytic manganese residues (EMR) as raw material was successfully synthesized. The NMN 95 consisting of MnCO 3 , FeS 2 and SiO 2 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 NMN 95 /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 (SO 4 •−), hydroxyl radical (•OH) and superoxide radical (O 2 •−), as well as the non-radical singlet oxygen (1O 2), in which O 2 •− and 1O 2 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 MnCO 3 than FeS 2 , where S sites in FeS 2 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 NMN 95 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. [ABSTRACT FROM AUTHOR]