Degradation of dimethyl phthalate using a liquid phase plasma process with TiO₂ photocatalysts

The liquid phase plasma (LPP) method with a TiO₂ photocatalyst and hydrogen peroxide was used to decompose dimethyl phthalate (DMP). As the applied voltage, pulse width, and frequency were increased, the rate of decomposition was increased and the decomposition rate was 63% for 180 min under plasma optimum conditions. The addition of TiO₂ photocatalyst and hydrogen peroxide increased the DMP decomposition reaction rate, but an excess cause a decrease in decomposition rate due to a decrease in conductivity, blocking of ultraviolet light, and scavenger effect. When the TiO₂ photocatalyst and hydrogen peroxide were used together, the decomposition reaction rate of DMP was greatly improved by using LPP single process alone. Also, when all the processes were used at the same time, the decomposition reaction rate was improved to about 2.8 times. DMP undergoes bond cleavage and ultimately decomposes into CO₂ and H₂O via dimethyl 4-hydroxyphthalate and methyl salicylates due to hydroxyl radicals and various active species generated by the LPP reaction.