Insights into degradation of pharmaceutical pollutant atenolol via electrochemical advanced oxidation processes with modified Ti4O7 electrode: Efficiency, stability and mechanism

Preparation and Electrochemical Applications of Magnéli Phase Titanium Suboxides: A Review

Magnéli phase titanium suboxides (M-TSOs) belong to a type of sub-stoichiometric titanium oxides based on the crystal structure of rutile TiO2. They possess a unique shear structure, granting them exceptional electrical conductivity and corrosion resistance. These two advantages are crucial for electrode materials in electrochemistry, hence the significant interest from numerous researchers. However, the preparation of M-TSOs is uneconomic due to high temperature reduction and other complex synthesis process, thus limiting their practical application in electrochemical fields. This review delves into the crystal structure, properties, and synthesis methods of M-TSOs, and touches on their applications as electrocatalysts in wastewater treatment and electrochemical water splitting. Furthermore, it highlights the research challenges and potential future research directions in M-TSOs.

Integrated electrochemical-adsorption for simultaneous removal of pharmaceuticals from water: Process optimization and synergistic insights

Water contamination with pharmaceuticals has become an evident environmental challenge. Treatment processes such as electrochemical oxidation (EO) and adsorption have limitations in the simultaneous removal of pharmaceuticals from water. Therefore, this study examined the potential of coupled process (EO followed by adsorption) in binary pharmaceuticals (acetaminophen (ACM) + ciprofloxacin (CIP)) removal from water, with an emphasis on coupled process optimization. Consequently, optimized coupled process conditions including current density (22 mA/cm2), pH (5.5), EO time (40 min), adsorbent dose (0.1 g/L) and adsorption time (60 min) were obtained. Under optimal conditions, removal efficiencies of 94.6% (ACM)+92% (CIP), 94.07% (ACM)+91.15% (CIP), and > 99.8% (ACM + CIP) were recorded for 20 mg/L (ACM + CIP) removal in EO, adsorption and EO + adsorption, respectively. Further, the coupled process was employed in multiple pharmaceuticals (20 mg/L of ACM + CIP + ATN (atenolol) + AMX (amoxicillin)) removal from water and removal of > 97.56% (ACM + CIP + ATN + AMX) was achieved. Removal efficiencies of ACM (83.35%) + CIP (73.1%) + ATN (68.52%) + AMX (63.05%) and ACM (80.37%) + CIP (66.5%) + ATN (73.07%) + AMX (60.5%) were obtained in EO and adsorption, respectively. The noted lower removal efficiencies in EO and adsorption are associated with the diverse nature of the pharmaceuticals, limited adsorbent active sites, and the shared utilization of reactive oxygen species (ROS) among the pharmaceuticals in EO. The total organic carbon (TOC) removal of 40.24%, and 99% and chemical oxygen demand (COD) removal of 72.45%, and 99.6% were obtained under optimal conditions of EO, and coupled process, respectively. These findings indicate that the pharmaceuticals are only partially mineralized in EO and the subsequent adsorption effectively eliminated the remaining target pharmaceuticals, and degradation by-products from water. Additionally, integrating EO with adsorption reduced the electrical energy consumption of the EO process from 31.6 kWh/m³ to 6 kWh/m³ under optimal conditions. Overall, coupling EO with adsorption offers the utmost advantages when removing multiple pharmaceuticals from complex water matrices.

The effect of crystal structure of MnO2 electrode on DMAC removal: degradation performance, mechanism, and application evaluation

The crystal structure has a significant impact on the electrochemical properties of electrode material, and thus influences the electrocatalytic activity of the electrode. In this work, α-, β-, and γ-MnO2 electrodes were fabricated and applied for investigating the effect of crystal structure on electro-oxidation treatment of N,N-dimethylacetamide (DMAC) containing wastewater. The prepared MnO2 electrodes were characterized by scanning electron microscopy and X-ray diffraction, suggesting that different crystal structures of MnO2 electrodes with the same morphology of stacking-needle structure were successfully prepared. The electrochemical performances, including removal efficiencies of DMAC, chemical oxygen demand (COD) and total nitrogen (TN), and energy consumption, were compared between different MnO2 electrodes. Results indicated that β-MnO2 electrode presented the excellent electrochemical activity, and could remove 93% DMAC, 62% COD, and 78.9% TN, which was much higher than that of α- and γ-MnO2; moreover, energy consumptions of 11.3, 9.7, and 10.5 kWh/m3 were calculated for α-, β-, and γ-MnO2, respectively. Additionally, the oxidation mechanism of the MnO2 electrodes was presented, indicating that DMAC was mainly oxidized by hydroxyl radical through reactions of hydroxylation, demethylation, and deamination, and electrode characteristics of specific surface area, oxygen evolution potential, and hydroxyl radical production were the key factors for degrading DMAC on MnO2 electrodes. Finally, an actual DMAC containing wastewater was applied for testing the electrochemical performance of the three electrodes, and β-MnO2 electrode was verified as the suitable electrode for potential application which achieved removal efficiencies of 100%, 64.5%, and 73% for DMAC, COD, and TN, respectively, after system optimization.

Highly efficient activation of periodate by a manganese-modified biochar to rapidly degrade methylene blue

In this study, the manganese oxide/biochar composites (Mn@BC) were synthesized from Phytolacca acinosa Roxb. The Mn@BC was analyzed via techniques of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD). The results show that MnOx is successfully loaded on the surface of BC, and the load of MnOx can increase the number of surface functional groups of BC. X-ray photoelectron spectroscopy (XPS) shows that MnOx loaded on BC mainly exists in three valence forms: Mn(Ⅱ), Mn(Ⅲ), and Mn(Ⅳ). The ability of Mn@BC to activate periodate (PI) was studied by simulating the degradation of methylene blue (MB) dye. The degradation experiment results showed that the MB removal rate by the Mn@BC/PI system reached 97.4% within 30 min. The quenching experiment and electron paramagnetic resonance (EPR) analysis confirmed that Mn@BC can activate PI to produce iodate (IO3•), singlet oxygen (1O2), and hydroxyl radical (•OH), which can degrade MB during the reaction. Response surface methodology (RSM) based on Box-Behnken Design (BBD) was used to determine the interaction between pH, Mn@BC and PI concentration in the Mn@BC/PI system, and the optimum technological parameters were determined. When pH = 5.4, Mn@BC concentration 0.56 mg/L, PI concentration 1.1 mmol/L, MB removal rate can reach 98.05%. The cyclic experiments show that Mn@BC can be reused. After four consecutive runs, the removal rate of MB by the Mn@BC/PI system is still 82%, and the Mn@BC/PI system also shows high performance in treating MB in actual water bodies and degrading other pollutants. This study provides a practical method for degrading dyes in natural sewage.