Enhanced methyl orange degradation by natural manganese sand-catalyzed in-situ electro-generated active chlorine

Abstract

The application of electro-oxidation (EO) technology in organic dyes is restricted by the drawbacks, such as the expensive electrode materials, high energy consumption, and narrow pH applied range. Herein, a natural manganese sand (NMS)-catalyzed in situ electro-generated active chlorine (e.g., HClO) system was proposed to remove methyl orange (MO). The results show that MO can be efficiently removed by the NMS/EO system over a wide pH range (pH 3–12). Radicals (e.g., HO^•, Cl^•) and non-radical active species (e.g., ¹O₂, Mn⁴⁺) are involved in the removal of MO by the NMS/EO system. The effects of important parameters, including the initial solution pH, NMS dosage, current density, electrolyte type, and electrode space, on MO degradation by the NMS/EO system were investigated. The kinetic model of MO removal confirmed that the degradation rate of MO was mainly affected by the dosage of NMS compared with the NaCl concentration. Moreover, the NMS/EO system exhibited a significant reduction in energy consumption for MO removal. This work provides new insights into the degradation of organic dyes by NMS-catalyzed in situ electrogenerated active chlorine.