Study On The Oxidation Of Organic Pollutants By Electrochemistry Integrated With Persulfate

The environmental pollution is serious increasingly,has become a major problem restricting human survival and sustainable development of the society.Organic pollutants are so diverse and complex to biodegrade difficultly,persistent in the environment.It will do harm to environment and human beings through the biological enrichment in the food chain.Advanced oxidation technology based on the strong oxidation of free radical activity can carry on the oxidative degradation of organic pollutants,decomposed into small molecules and CO₂,H2 O.In recent years,advanced oxidation technology based on the sulfate radical is a new depth treatment of organic wastewater,which is concerned by scholars at home and abroad.SO₄^- has the stronger stability and oxidation than ·OH,a wider scope of p H and more ways to activate.So it has more potential in the treatment of refractory organic pollutants.PS is activated by transition metal Fe²⁺ in most of the research currently.But the processing efficiency of SO4-· is not satisfied,because Fe²⁺ can lose activation easily in process.In order to solve the above problems,we use the combination of electrochemistry and persulfate to degrade organic pollutants.Firstly,the advanced oxidation process based on sulfate radical was applied to treat the secondary effluent of papermaking wastewater,which consists of the advanced oxidation tower,ion sedimentation tank,sand filter.SR-AOPs was efficient in deep treatment of the papermaking wastewater?COD of 85-110mg/L?.Under the optimum condition,PS dosage was 1.5mmol/L,Fe²⁺ dosage was 2.25mmol/L,PS/ Fe²⁺ ratio was 2:3,the effluent COD was reduced to 31.2mg/L,the COD removal rate reached 70%,SS was inferior to 5 mg/L,SO₄^2-was 203.5mg/L,the quality of effluent achieved the new standard of papermaking wastewater discharge GB3544-2008,and the cost was about 2.831 yuan each ton.Then,using EC-PS?the combination of electrochemistry and persulfate?to oxidize orange G dye wastewater was studied,in order to improve the efficiency of Fe²⁺/PS.The initial p H had little effect on the decolorization rate of OG;with the increase of the dosage of PS,OG decolorization rate first increased and then decreased.Increasing the current density,OG decolorization rate increased all the way;with the increase of electrode spacing,OG decolorization rate first increased and then decreased.0.2mmol/L OG wastewater was oxidized by EC-PS under the condition OG decolorization rate reached 97.85%,TOC removal rate reached 37.2%.The sequence of every factor for OG decolorization rate was PS dosage,electrode spacing,initial p H,current density.Subsequently,using EC-PS to oxidize papermaking wastewater,the effect of initial p H,PS dosage,current density,electrode spacing on the COD degradation rate and chroma removal rate was investigated.The results showed that EC-PS had good removal efficiency on papermaking wastewater,700 m L papermaking wastewater?COD was 150mg/L,chroma was 200?after secondary biochemical treatment was oxidized by EC-PS under the condition?initial p H=3,PS dosage=2.5mmol/L,current density=30m A/cm²,electrode spacing=6cm?,after 15 minutes reaction time,COD degradation rate reached 62.3%,chroma removal rate reached 97%,EC-PS could improve system ORP and oxidative capacity was significantly enhanced.Finally,the degradation properties and the effect of the anion on EC-PS were analyzed.The results found that the OG degradation effect by EC-PS was significantly higher than the electrochemical,PS alone and Fe²⁺/PS;OG characteristic absorption peak had significant reduction by observing UV-vis Spectrum;there were two strong free radicals,namely sulfate radical and hydroxyl radical through chemical molecular probes in EC-PS system,of which the leading role was sulfate free radical.HCO₃-had certain promoting effect on EC-PS,due to its ability to buffer Fe²⁺ and improve the activation efficiency;Cl-had the obvious inhibitory effect on EC-PS,because reaction with free radicals would reduce the amount of SO₄^- and the processing efficiency;and NO₃^-basically had no impact on EC-PS,because it was relatively stable in aqueous solution.