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

BACKGROUND: The development of a low cost and simple treatment process is necessary for 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 120 min, stirring speed 160 rpm and temperature 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.