Application of plasma technology in the removal of volatile organic compounds (BTX) using manganese oxide nano-catalysts synthesized from spent batteries

Abstract

In this paper, the powder of manganese oxide was recovered from spent alkaline batteries and the effect of calcination temperature on the physiochemical properties of resultant powder was studied. Synthesized manganese oxide was impregnated at different percentages on alumina and the resultant material was used as catalyst for oxidation of benzene, toluene, and xylene (BTX) in a hybrid plasma-catalytic process. Manganese oxide/alumina (MnAl) catalysts were analyzed by FTIR, XRD, FESEM, EDX, BET, TEM, and TPR-H2 and the results indicated that high crystalline big cubes of manganese oxide are in good connection with highly dispersed ultra-fine nanoparticles of alumina. Enhancing the Mn content increased the agglomeration of alumina particles probably around the cubes of manganese oxide. Nitrogen adsorption measurements (BET) showed that the specific surface area of these catalysts was high but reduced with increasing Mn percent. TPR-H2 showed that using alumina had a good impact on the redox ability of the catalyst. Oxidation of BTX using synthesized MnAl catalysts was carried out in the presence of plasma. While MnAl catalysts showed similar results in benzene and toluene oxidation percent (97–98%), the oxidation of xylene was difficult and depended on the Mn percent so that the catalyst with 10% wt. of manganese oxide indicated 74% of xylene oxidation while higher or lower Mn contents exhibited lower oxidation percent. In order to evaluate the experimental parameters, the influence of plasma input voltage, catalyst location in the plasma reactor, BTX flow rate, and the catalyst loadings were investigated. Results showed that benzene and toluene were oxidized almost completely regardless of input plasma voltage but the amount of xylene oxidation soared with increasing the voltage. Moreover, the catalyst location in the reactor had no significant influence on the conversion of BTX whereas increasing the flow rate led to a decline in BTX removal efficiency.