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

Abstract

ABSTRACT 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%).