Study on the efficacy and mechanism of treatment of manganese-containing wastewater by pulse-alternating current coagulation

Abstract

ABSTRACT To assess the effectiveness and underlying mechanism of pulse-alternating current coagulation (PACC) for treating manganese-laden wastewater, we examined the influence of various parameters. Specifically, we investigated the impact of current density, initial pH, initial Mn2+ concentration, electrolyte concentration, and alternating current frequency on the removal efficacy. The removal mechanism was meticulously examined using an adsorption kinetics analysis, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectrum (FTIR), and X-ray Photoelectron Spectroscopy (XPS). The findings indicated that the concentration of Re (Mn2+) was 99.09% under the specified conditions: j = 2.5 A·m−2, pH0 = 7, c 0(Mn2+) = 50 mg·dm−3, f = 500 Hz, c 0(NaCl) = 500 mg·dm−3 and t = 40 min. When Re (Mn2+) = 98%, the energy consumption (EEC) was significantly lower for PACC at 1.23 kWh·m−3, compared to 1.52 kWh·m−3 for direct current condensation (DCC). This indicated a reduction in EEC by 19.1% when using PACC over DCC. The adsorption process of Mn2+ by the iron sol adheres to the principles of pseudo-second order kinetics. The primary component of flocs generated in the PACC process is α-FeOOH. The mechanism of Mn2+ removal in the PACC process involved the synthesis of Mn oxides, the formation of metal hydroxide precipitates and adsorption by nano-iron sol. This study provides a theoretical basis and technical support for the application of PACC technology in the field of manganese-containing wastewater treatment.