The Application Of Multiple Oxidation/Electro-fenton Technology In PCB/Pharmacy Industrial Wastewater Treatment

With the rapid development of industrialization,the industrial wastewater is growing rapidly and this phenomenon also result in serious environmental problems.If the industrial wastewater discharged into the environment without any treatment,it can do harm to the ecosystem and human health.This paper studied the COD removal rate of two different industrial wastewater（printed circuit board and pharmacy wastewater）and recovered copper in the PCB wastewater.The main content of this paper includes:1 In the study of PCB wastewater treatment,we compared the COD removal rate and the electrical energy per order（EE/O）of nine different oxidation processes on PCB wastewater.These processes include UV/H₂O₂,UV/Na₂S₂O₈,KMnO₄,UV/H₂O₂/Fe²⁺,UV/Na₂S₂O₈/H₂O₂,UV/Na₂S₂O₈/H₂O₂,Na₂S₂O₈/H₂O₂/KMnO₄,UV/Na₂S₂O₈/H₂O₂/KMnO₄ and PEC/Na₂S₂O₈/H₂O₂/KMnO₄.The result show that the effectiveness of multiple-oxidation process is better than single-process.At last we choose UV/Na₂S₂O₈/H₂O₂/KMnO₄ process as base for the subsequent experiments by comparison.We also discussed the effect of different mole ratios of Na₂S₂O₈/H₂O₂and dosage on the residual COD.The results indicated that the optimal KMnO₄ dosage is3mM,the optimal mole ratio of Na₂S₂O₈/H₂O₂ is 1:1,the optimal oxidant dosage is31mM.In the end,the COD of PCB wastewater reduced from 32800mg/L to 1680mg/L,the removal rate was reached 94.8%.Copper recovery experiments show that the recovery rate of copper arrive at 99%.This process can bring￥1639200 of net income.2 To further verify the degradation mechanism of the main organics in single-oxidation,double-oxidation and triple-oxidation processes,we investigated the mainintermediatesgeneratedduringKMnO₄,UV/Na₂S₂O₈/KMnO₄,UV/Na₂S₂O₈/H₂O₂/KMnO₄ processes.From the mass spectrum we can reasonably infer the fragmentation of these intermediates and the change law of their functional groups.UV-Vis spectra show the degradation effect of benzotriazole by KMnO₄ process is better than 2-aminothiazole,but free radical oxidant process produce opposite effects.The results of mass spectrum analysis confirmed that different oxidant processes have different degradation mechanism,KMnO₄ process is more likely to generate carboxylic acid compounds,but free radical oxidant process is more likely to generate phenolics.In addition,the synergy of the two ways can generate intermediates with smaller molecule weight which is easier to be degraded.3 We choose electro-Fenton process as the preprocessing step for pharmacy wastewater treatment by compared the COD removal rate of different oxidant process.we studied the different influent factors on COD removal rate.The results show that the best pH is 3,the optimal mole ratio of Fe²⁺/H₂O₂ is 1:5,the optimal current is 240mA for electro-Fenton process.During the course of the experiment,we find the effectiveness of four times dosage process is better than one-time dosage process.In the best condition,the COD of pharmacy wastewater reduced from 34600mg/L to1250mg/L,the removal rate was reached 96.4%.After electro-Fenton process,the biochemical treatability is improved,which accelerates subsequent process.