Study On Removal Of Carbon Tetrachloride Based On Ultraviolet Activated Formic Acid Technology

Carbon tetrachloride is a chlorinated hydrocarbon that is very harmful to the ecological environment and human health.Because of its simple operation,fast reaction speed,photocatalytic reduction technology has been widely concerned.In this study,three systems?UV/formic acid,UV/nitrate/formic acid,UV/persulfate/formic acid?were constructed to degrade carbon tetrachloride,the effects of solute concentration,solution pH,and several anions on the experiment were also discussed.?1?UV/HCOOH can degrade CCl₄ almost completely,and the dechlorination effect is 38.8%.The order of the initial pH degradation rate of CCl₄ is:pH 6>pH 9>pH 3>pH12,the removal rate increases with the increase of formic acid concentration,and the removal rate decreases with the increase of CCl₄ concentration.Cl^-and HCO₃^-inhibit the degradation of CCl₄,low concentrations of NO₃^-?1 mM?inhibit the degradation of CCl₄,and high concentrations of NO₃^-?10 and 100 mM?promote the degradation of CCl₄.The addition of?methyl viologen?MV²⁺as a free radical quencher indicates that CO₂·^-is the main active species for CCl₄ degradation.?2?UV/NO₃^-/HCOOH can degrade CCl₄ almost completely,and the dechlorination effect is 41.2%.The initial pH degradation rate of CCl₄ is in the order of pH 9>pH 6>pH 3>pH 12,and the removal rate of CCl₄ increases with the increase of formic acid concentration from 5mM to 40mM.When formic acid is greater than40mM?40-80mM?,the system CCl₄ degradation is slightly inhibited,and the removal rate decreases as the CCl₄ concentration increases in the range of 2-15 mg/L.Cl^-and HCO₃^-inhibit the degradation of CCl₄,while SO₄^2-has no effect on the degradation of CCl₄.?3?UV/S₂O₈^2-/HCOOH can degrade CCl₄ almost completely,and the dechlorination effect is 76%.The order of the initial pH degradation rate of CCl₄ is pH 9>pH 6>pH 3>pH 12.The removal rate of CCl₄ increases with the increase of persulfate concentration,increases with the increase of formic acid concentration,and decreases with the increase of CCl₄ concentration.Cl^-,NO₃^-and high-concentration HCO₃^-inhibit the degradation of CCl₄,and high-concentration HCO₃^-and SO₄^2-promote the degradation of CCl₄.