Simultaneous oxidative degradation of toxic acid wastewater from production of nitrocellulose and release of Mn2+ from low-grade MnO2 ore as oxidant

Abstract

BACKGROUND To develop low cost and simple treatment process is necessary for the toxic organic effluents. This work investigated the feasibility of the oxidative degradation of toxic nitrocellulose acid wastewater (NAW) using low-grade MnO2 ore as a cheap oxidant and the simultaneous release of Mn2+ for preparation of electrolytic manganese metal (EMM). RESULTS Under optimal conditions of 100 g L−1 MnO2 ore, 200-mesh ore particles, concentrated H2SO4 to NAW ratio of 0.12:1, contact time of 120 min, stirring speed of 160 rpm and temperature of 90 °C, the total organic carbon (TOC) removal of the NAW and Mn release efficiency reached 98% and 97%, respectively. The TOC removal was significantly correlated with the release of Mn. The inert layer model best described the extraction behavior of Mn and apparent activation energy was 54.1 kJ mol −1. Concomitant with TOC removal, the degradation of polysaccharide, phenol, protein and nitrocellulose occurred; meanwhile, the MnO2 totally dissolved owing to reductive extraction of Mn. CONCLUSION A highly significant correlation occurred between TOC removal and Mn2+ release, suggesting a reciprocal causation. The present process was competent to simultaneously realize oxidation degradation of NAW and reductive dissolution of Mn2+ for EMM production, displaying a promising application prospect.