Formation of reactive species during plasma treatment of wastewater from the mining and petroleum industries

Purpose. To investigate the regularities of reactive species formation during the plasma treatment of multicomponent wastewater from the mining and petroleum industries, as well as to assess their role in contaminant transformation and removal efficiency. Methods. Laboratory experiments were carried out using a specially designed plasma-liquid reactor operating under high-frequency electrical discharge conditions (10-25 kV, 10-30 kHz, interelectrode gap 3-7 mm). The study included determination of the initial physicochemical characteristics of wastewater, including pH, electrical conductivity, total dissolved solids, and concentrations of heavy metals (Cu, Zn, Cd). During plasma treatment, the formation of reactive species (•OH, O3, H2O2) was analyzed, and a kinetic model was applied to describe contaminant removal dynamics and treatment efficiency. Findings. It was established that plasma treatment leads to the formation of hydroxyl radicals at a rate of (1-5)·10-6 mol·L-1·s-1, ozone in the concentration range of 10-6-10-4 mol·L-1, and hydrogen peroxide accumulation within 10-80 mg/L, thereby crea-ting a pronounced oxidative environment. Copper concentration decreased from 20 to 0.5 mg/L (97.5%), zinc from 15 to 0.4 mg/L (97.3%), and cadmium from 0.5 to 0.02 mg/L (96.0%). The degree of organic contaminant degradation reached 70-90%. It was shown that the intensity of reactive species formation strongly depends on discharge parameters, while the proposed kinetic model adequately describes the experimentally observed treatment dynamics. Originality. The study provides a comprehensive experimental and model-based analysis of reactive species formation during the plasma treatment of highly mineralized multicomponent wastewater from the mining and petroleum industries. Quantitative relationships were established among discharge parameters, reactive species generation, and contaminant removal efficiency. Practical implications. The obtained results confirm the potential of plasma technologies for the advanced treatment of industrial wastewater with complex composition and high salinity. Practical implementation of the proposed approach may contribute to improved environmental safety, reduced reagent consumption, lower sludge generation, and expanded opportunities for water reuse in mining and petroleum production processes.