Fabrication of MnOx heterogeneous catalysts from wet sludge for degradation of azo dyes by activated peroxymonosulfate

Abstract

For dewatering and resource utilization of sewage sludge, catalyst preparation paralleled with sewage sludge dewatering, was explored. In order to obtain a better understanding of this strategy, an anaerobic sludge based MnO_x catalyst (MnO_x/HCAS) was characterized, and tested in activation of Oxone for dye degradation in aqueous solution. The multi-valence oxidation states of manganese were formed in MnO_x/HCAS. The catalyst exhibits high catalytic activity towards Oxone for the degradation of dyes in aqueous solution. The kinetic data followed first order kinetics with an activation energy of 21.87 kJ mol⁻¹. The evaluation of the reusability of MnO_x/HCAS showed that MnO_x/HCAS exhibited high stability in recycled tests without losing its activity. The removal of a variety of anionic dyes also demonstrates an excellent catalytic performance of MnO_x/HCAS. To investigate stabilization of heavy metals in the catalyst, a leaching test was conducted, and the result showed that heavy metals can be solidified to prevent their leaching into solution. The effect of different kinds of wet sludge was investigated. And all these sludge based MnO_x catalysts exhibit good catalytic performance with azo dyes with degradation rates more than 98%, which decides its unquestionable possibility for fabrication of MnO_x heterogeneous catalysts from wet sludge and its practical applications.