To improve the performance of the nanoscale zero-valent iron (nZVI)-based advanced oxidation process (AOPs), a sulfidation pre-modification endowed nZVI with stable reduction nature mechanism was proposed, and a coupled system of activating PMS with sulfidized nanoscale zero-valent iron supported by biochar(S-nZVI/BC@PMS) was constructed in this study. It could be found that sulfidation state and formation, largely dependent on the sulfidized modification method, had a great impact on the enhancement for nZVI/BC in activating PMS for Acid Red 73 degradation. Compared with original nZVI/BC, the formed FeS shell blocked the external air to protect the internal Fe 0 , and S-nZVI/BC became relatively hydrophobic, which could slow down the material corrosion by water and dissolved oxygen to enhance the reaction durability. Appropriate sulfidation reduced the electrochemical impedance and enhanced the electrical conductivity of the catalyst, which facilitated the electron transfer in the system, and the participation of reducing sulfur species enabled the reaction to form a positive cycle and ensure a prolonged duration. Excessive sulfidation caused the material to become unstable and thus susceptible to air erosion, reducing the efficiency of contaminant removal. Due to the FeS protective shell, hydrophobicity of S-nZVI/BC and the promoted electron transfer in the system, S-nZVI/BC@PMS system secured more free radicals and had longer reaction time under the same conditions. In addition, S-nZVI/BC had good antioxidant properties, universality, and reusability for practical applications. These findings not only elucidated the superiority of S-nZVI/BC@PMS system but also provided new insights into cost-saving and efficient advanced oxidation processes.
A novel antimony-doped tin oxide nanoparticles electrode (Ti/ATONPs) was fabricated by screen printing method, which was applied in wastewater treatment area for the first time. In contrast with traditional Ti/SnO 2 -Sb electrode prepared by electrodeposition , Ti/ATONPs electrode possessed smaller grains and crystallite size, remarkable porous structure with 39.9 m 2 g −1 surface area and 3.0 nm average pore size as seen by Scanning electron microscopy (SEM), X-ray diffraction (XRD) Brunauer-Emmett-Teller (BET). Electrochemical measurements including linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronocoulometry (CC) were employed to investigate the electrochemical activity, compared with Ti/SnO 2 -Sb, Ti/ATONPs owned a higher oxygen evolution potential (2.18 V versus 2.08 V), a lower charge transfer resistance (0.47 Ω versus 13.24 Ω), a larger electrochemically effective surface area (38.97 cm 2 cm −2 versus 3.03 cm 2 cm −2 ) and the voltammetric charge analysis indicated that Ti/ATONPs could create more reaction active sites to enhance the electrocatalytic efficiency. To further explore the electrocatalytic oxidation performance, AR 73 was used as target pollutant to monitor the concentration changes with time through UV/vis spectroscopy, the removal of AR 73 degradation and corresponding kinetic constant of Ti/ATONPs electrode was 83.9%, 0.62 h −1 while that of Ti/SnO 2 -Sb was 65.8%, 0.40 h −1 respectively. These results show that Ti/ATONPs electrode prepared by screen printing method may become a promising electrode in treating wastewater.
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