Dimethyl phthalate elimination from micro-polluted source water by surface discharge plasma: Performance, active...

Plasticizer pollution brought huge risks to ecological environment and human health. Surface discharge plasma (SDP) was employed to eliminate plasticizer in natural water, with dimethyl phthalate (DMP) as a typical plasticizer. Experimental results showed that DMP degradation efficiency reached 82.8% within 60 min's SDP treatment, and the elimination process fitted well the first-order kinetic model. Low initial DMP concentration, alkaline condition, and low natural organic matter content were all conducive for DMP degradation. The contributions of OH radical and O₂^- to DMP elimination were 91.9% and 78.1%, respectively. Total organic carbon (TOC), UV-vis spectroscopy, and atomic force microscopy analysis demonstrated that DMP molecular structure was destroyed after the SDP treatment, and some small molecular fractions were generated. Approximately 47.8% of TOC and 73.5% of COD were eliminated after 60 min's SDP treatment. Phthalic acid monomethyl ester, phthalic acid, o-phthalic anhydride, acetic acid, formic acid, and oxalic acid were detected as the byproducts. Carbon balance analysis among these intermediates showed that total carbon content was approximately 4.64 × 10^-2 mmol before treatment, and it was 4.578 × 10^-2 mmol after treatment, suggesting that some C-containing intermediates still existed but not detected. DMP degradation pathways in the SDP system were proposed.