Ozonation of Reactive Orange 4 dye aqueous solution using mesoporous Cu/SBA-15 catalytic material

Abstract

The catalytic ozonation using mesoporous SBA-15 supported copper catalyst (Cu/SBA-15) was employed for the degradation of reactive orange 4 (RO4) azo dye in aqueous solution. The catalyst was synthesized and characterized using BET, SEM, TEM and EDX techniques. The characteristic results revealed highly ordered mesoporous structure, uniform pore sizes, parallel arranged channels and large surface area for the catalyst. The effects of copper loading on SBA-15, initial solution pH and ozone dose on the degradation of RO4 dye were studied. The complete colour removal from RO4 azo dye aqueous solution was obtained after 21 min of ozonation. The maximum TOC removal efficiency of 86% was obtained at optimum operational conditions of 2% copper loadings, initial solution pH 9 and ozone dose of 5 g/m3 after 60 min reaction time. The degradation pathway of catalytic ozonation reaction was studied by adding t-butanol as radical scavenger and it was found that the presence of radical scavenger had no effect on colour removal efficiency suggesting direct ozone molecular type mechanism. However, TOC removal efficiency was significantly reduced with the addition of t-butanol, thereby, indicating a hydroxyl radical based mechanism. The catalytic ozonation reaction followed pseudo-first order kinetics with respect to RO4 dye concentration. The reusability study for the catalyst suggested a negligible loss in the degradation efficiency after five runs of experiments. The stability of the catalyst was studied by performing leaching experiments which suggested that the catalyst has the potential to be utilized for the degradation of aqueous dye solution.