Ammonia oxidation by in-situ chloride electrolysis in etching wastewater of semiconductor manufacturing using RuSnOx/Ti electrode: Effect of plating mode and metal ratio.

The indirect chloride-mediated ammonia oxidation encounters challenges in maintaining the effectiveness of metal oxide anodes when treating wastewaters with complex compositions. This study aims to develop a highly stable anode with RuO2-SnO2 coatings for treating an etching effluent from semiconductor manufacturing, which majorly contains NH3 and organic compounds. The RuSnOx/Ti electrode was synthesized using wet impregnation and calcination processes. The metal oxide configuration on Ti plate substrate was tuned by varying the step-dipping process in RuCl3 and SnCl4 baths. A 10-day continuous-flow electrolysis was conducted for studying the ammonia removal and chlorine yield under variable conditions, including detention, pH, current density, and initial ammonia and chloride concentrations. In the RuSnOx coatings, the configuration comprising RuO2 nanorods as the surface layer and an intermediate layer of SnO2 crystallites (by plating Ru3+ for three times to cover one Sn4+ layer, denoted as the Ru3Sn/Ti electrode) exhibited the best durability for acid washing, along with relatively high Faradaic efficiency and low energy consumption. To further improve the treatability of real wastewater (NH3-N = 634 mg L-1, chemical oxygen demand (COD) = 6700 mg L-1, Cl- = 2000 mg L-1, pH 11), the duel-cell electrolyzers were constructed in series under a current density of 30 mA cm-2 and 45 min detention. Ultimately, removals of NH3 and COD reached 95.8% and 76.3%, respectively, with successful limitation of chloramine formation.

Electrochemical enhancement of high-efficiency wet removal of mercury from flue gas.

Electrochemical wet absorption composite system has an excellent potential to remove Hg0 from flue gas. In this study, ruthenium iridium titanium platinum quaternary composite electrode is used as an anode and titanium electrode is used as the cathode, and KI/I2 absorption solution is introduced into the electrocatalysis system as an electrolyte to form KI/I2 electrochemical catalytic oxidation system. The removal rate of Hg0 in flue gas can be increased to 92.3%. The effects of electrolytic voltage, current, Pt content, I2 concentration, and the ratio of KI/I2 on the removal of Hg0 were discussed. The possible free radicals in the electrochemical cathode, anode, and solution were characterized and tested by XRD, SEM, UV-Vis (detection of H2O2, ·OH, O3), and FTIR (detection of IO3-). Combined with experimental data and theoretical derivation, the mechanism of Hg0 removal from flue gas by electrochemical catalytic oxidation alloy formation wet absorption combined process was studied. The results show that the combined process, which is a promising technology can not only improve the removal efficiency of Hg0, but also realize the resource recovery of Hg0 and I2, and provide a feasibility study for the subsequent regeneration of KI/I2 absorption solution.

Application of Ti/IrO2 electrode in the electrochemical oxidation of the TNT red water.

Via the thermal sintering, a nanocrystalline IrO2 coating was formed on the Ti substrate to successfully prepare a Ti/IrO2 electrode. Based on the electrochemical analysis, the prepared Ti/IrO2 electrode was found to have powerful oxidation effect on the organics in the TNT red water, where the nitro compound was oxidized through an irreversible electrochemical process at 0.6 V vs. SCE. According to the analysis of the nitro compound content, the UV-vis spectra, and the FTIR spectra of 2,4,6-trinitrotoluene (TNT) red water with electrolytic periods, the degradation mechanism of the dinitrotoluene sulfonate (DNTS) was developed. And the intermediates were characterized by UPLC-HRMS. The DNTS mainly occurred one electron transfer reaction on the Ti/IrO2 electrode. At the early stage of the electrolysis, the polymerization of DNTS was mainly dominated. The generated polymer did not form a polymer film on the electrode surface, but instead it promoted a further reduction. After electrolyzing for 30 h, all NO2 function group in the TNT red water was degraded completely.

Study on Electrochemical Degradation of Nicosulfuron by IrO2-Based DSA Electrodes: Performance, Kinetics, and Degradation Mechanism.

The widely used sulfonylurea herbicides have caused negative effects on the environment and human beings. Electrochemical degradation has attracted much attention in the treatment of refractory organic compounds due to its advantage of producing no secondary pollution. Three kinds of IrO2-based dimensionally stable anodes (DSAs) were used to degrade nicosulfuron by a batch electrochemical process. The results showed that a well-distributed crack network was formed on the Ti/Ta2O5-IrO2 electrode and Ti/Ta2O5-SnO2-IrO2 electrode due to the different coefficients of thermal expansion between the Ti substrate and oxide coatings. The oxygen evolution potential (OEP) increased according to the order of Ti/RuO2-IrO2 < Ti/Ta2O5-SnO2-IrO2 < Ti/Ta2O5-IrO2. Among the three electrodes, the Ti/Ta2O5-IrO2 electrode showed the highest efficiency and was chosen as the experimental electrode. Single factor experiments were carried out to obtain the optimum electrolysis condition, shown as follows: currency intensity 0.8 A; electrode spacing 3 cm, electrolyte pH 3. Under the optimum conditions, the degradation of nicosulfuron followed first-order kinetics and was mainly due to indirect electrochemical oxidation. It was a typical diffusion-controlled electrochemical process. On the basis of the intermediate identified by high performance liquid chromatograph-mass spectrometry (HPLC-MS), two possible degradation routes were proposed.