Effects of sodium persulfate and hydrogen peroxide on imidazolium ionic liquid degradation by simulated solar light in aqueous ZnO suspension

The degradation of an ionic liquid: hexyl methyl imidazolium chloride (HMImCl) in the systems of simulated solar light/ZnO and simulated solar light/ZnO/oxidant (i.e., H2O2 and S2O82-) were investigated in aqueous solution. The influences of different variables such as catalyst concentration, hydrogen peroxide, and persulfate dosage on HMImCl photocatalytic degradation were determined. It was found that the adsorption of HMImCl on the catalyst surface was insignificant. The photocatalytic degradation of HMImCl followed pseudo first-order kinetics, and the rate constant at natural pH (pH 7.2) was 11.8 x 10(-2) min(-1). The addition of hydrogen peroxide to the process not only does not enhance the degradation rate of HMImCl but also decreases k(app) significantly with [HMImCl] = 3x10(-5) mol L-1, oxidant concentration (in the range of 5 x 10(-5)-10(-1) mol L-1), and catalyst concentration of 1 g L-1. The results elucidated that the use of Na2S2O8 (in the range of 10(-4)-10(-2) mol L-1) strongly enhances the degradation rate of HMImCl compared with photocatalytic process of the catalyst.