Treatment of halogenated hydrocarbons from the wastewater of vinylidene chloride synthesis using H2O2/UV technology

摘要

The wastewater from vinylidene chloride (VDC) synthesis contains high concentration of sodium chloride and halogenated hydrocarbons which are all volatile organic chemicals (VOCs). Based on the wastewater characteristics, an air-stripping process was applied for pretreatment to remove most of the halogenated hydrocarbons in the wastewater, and then the H2O2/UV advanced oxidation process (AOP) was used for polishing treatment so that the treated wastewater could be reused for making chlorine and sodium hydroxide through electrolyzing. And the polishing testing results of the air-stripping unit's effluent were reported in this paper. The experimental results showed that halogenated hydrocarbons almost could not be degraded if H2O2 was used alone, and limited efficiency was observed when UV used alone, but when the H2O2 was used with UV together, their oxidation efficiency was significantly improved, this indicated that cooperative effect happened when H2O2 and UV were used simultaneously. The degradation rate of halogenated hydrocarbons was increased with H2O2 concentration increasing, but when H2O2 concentration was up to 15mmol/L, the degradation rate of halogenated hydrocarbons almost didn't increase with H2O2 concentration increasing again. The residual concentration of halogenated hydrocarbons was decreased linearly with UV radiation time prolongation at a given H2O2 dosage; this indicated that the reaction kinetics belonged to pseudo-zero-order formulation. Additionally, the experimental result also showed that the high concentration sodium chloride in wastewater had a negative effect on H2O2/UV oxidation process.