Preparation of Tin-Antimony anode modified with carbon nanotubes for electrochemical treatment of coking wastewater

Electrocatalysis degradation of biochemical tail water from coking wastewater using particle electrode with persulphate

Due to the intricate composition and recalcitrant nature of coking wastewater, the biochemical effluent often fails to meet standards. This study explored the preparation of particle electrodes, utilizing activated carbon powder (PAC) loading single-element Fe, Co, and Ni, as well as dual-element Ni-Fe and Co-Fe as catalyst. The particle electrode system was integrated with persulphate (PS) activation to enhance its performance. The effects of potassium persulphate (KPS) dosages, currents, and Ni:Fe ratios were investigated. The results showed that bimetallic particle electrodes outperformed their monometallic particle electrodes. Among the five electrode materials, Ni-Fe/PAC achieved the best degradation efficiency of 84.4% and the lowest energy consumption of 19.73 kW·h·kg-1 COD. When the initial concentrations of TOC and COD were set at 300 and 280 mg L-1, the Ni-Fe/PAC with 5 mmol L-1 KPS achieved removal efficiencies of 61.7 and 84.4%, respectively. The metals on Ni/PAC and Co/PAC existed in the zero-valent state, while Fe on Fe/PAC was present as Fe2O3. Co-Fe/PAC exhibited the formation of CoFe2O4 oxides. Ni-Fe/PAC possessed the lowest hydrogen evolution reaction potential (-0.28 V), and the highest oxygen evolution potential (2.4 V), and reached an electrochemical active surface area (ECSA) of 236.3 cm2. Cyclic voltammetry (CV) curves indicated that the direct redox reactions and indirect oxidation of pollutants occurred concurrently. Both •OH and ⋅ SO 4 - radicals played crucial roles during the degradation processes. The degradation efficiency of organic matter was as follows: benzene compounds (88.4%) >heterocyclic compounds (75.3%) >polycyclic aromatic hydrocarbons (53.9%).

Simultaneous methanogenesis and denitrification coupled with nitrifying biofilm for high-strength wastewater treatment: Performance and microbial mechanisms

A combined system consisting of an upflow blanket filter (UBF) and a moving-bed biofilm reactor (MBBR) was developed for the simultaneous removal of organic matters and ammonia from high-strength wastewater. With a constant COD of approximately 2000 mg/L and ammonium nitrogen in a series of concentrations (e.g., 50, 200 and 400 mg/L in stages I to III) of the influent wastewater, the removal efficiencies of COD, ammonium nitrogen and total nitrogen reached 96.10%-98.19%, 100%, and 79.12%-82.15%, respectively. With the increase of influent ammonia nitrogen concentration, the specific methanogenic activity of the UBF granules decreased significantly, while the specific denitrification rates of the UBF granules and specific nitrification rates of the MBBR biofilms increased significantly. Microbial community analysis showed that Methanobacterium and Methanosaeta were the dominant methanogens in the UBF granules, while Candidatus Competibacter, Thauera and Acinetobacter were identified as dominant denitrifiers. In addition, nitrifiers were enriched in MBBR biofilms at 11.33% and 13.87% of the average abundance of Nitrosomonas and Nitrospira, respectively, at stage III (influent ammonium at 400 mg/L, COD/NH₄⁺-N =  5). The ecological network analysis, including full-networks and sub-networks, indicated that the interactions between methanogens and denitrifiers in the UBF granules were strong when the influent ammonium concentration reached 400 mg/L. No intensive interactions were observed among the functional bacteria in the MBBR biofilms over the entire operation. Overall, this study provides a new strategy for the application and construction of efficient biological processes to achieve simultaneous removal of organic matter and nitrogen for high-strength wastewater treatment.