Peroxymonosulfate activated by amorphous particulate MnO2 for mineralization of benzene gas : redox reaction, weighting analysis, and numerical modelling

Abstract

Amorphous particulate MnO2 (AMO) which features micro-nano hierarchical structure can be viewed as a favorable alternative to crystalline α-MnO2 for Peroxymonosulfate (PMS) activation. The former not only is comparatively simple to obtain but also has similar performance on powerful adsorption and catalytic capability. In this paper, the combined use of AMO and PMS oxidizing system showed the paralleled degradation efficiency of benzene gas with 50.5 ± 3.75%, which was just around 5 percentage points lower than that achieved in the α-MnO2&PMS system. Highly stable catalytic activity of the AMO&PMS system exhibited during an ensuing cyclic experiment, averaging at 63.08% for benzene mineralization. Additionally, a novel method of weighting analysis which evaluates the synergetic effects among operating parameters on benzene removal was firstly explored in the nanosized catalyst-based activation system. Through a novel specific reaction drag model for porous media, specific drag coefficients at various testing conditions, k2, in terms of pressure drop across microporous AMO, were held to establish the correlations between ideal mineralization efficiencies and optimal parameter combinations. A further comparison between laboratory data and model simulations confirmed that, regardless of pH variations, the mineralization rate can be enhanced to around 67.7% at a more higher temperature (45 °C) when the consumed ratio of AMO to PMS leveled off at 0.8, during which time much lower k2 of 0.24 Pa·min·m/mg would present.