电絮凝-过硫酸盐氧化协同工艺处理页岩气压裂返排废水

采用电絮凝-过硫酸盐氧化协同工艺处理页岩气压裂返排废水,通过电解过程产生的Fe2+活化过硫酸盐产生强氧化性的硫酸根自由基氧化废水中的有机物,同时Fe2+被氧化成Fe3+进而水解起到絮凝作用。实验结果表明,在电解时间25 min、电流密度41.7 m A/cm~2、电极间距4 cm、搅拌转速100 r/min、废水pH 7.0、过硫酸盐添加量0.006 mol/L的条件下,COD去除率达94.5%,出水BOD_5/COD从0.13增至0.56,电导率从104 mS/m降至71 mS/m,矿化度从16 704 mg/L降至4 065 mg/L,不可滤残渣含量从554 mg/L降至59 mg/L。电絮凝-过硫酸盐氧化协同处理的效果明显优于单独电絮凝和硫酸亚铁活化过硫酸盐氧化工艺,循环伏安测试结果表明其原因是硫酸根自由基的产生,同时溶液的导电性增强,强化了絮凝效果。

Treatment of shale gas fracturing flow-back wastewater by electrocoagulation-persulfate oxidation synergetic process

The shale gas fracturing flow-back wastewater was treated by electrocoagulation-persulfate oxidation synergetic process. The Fe²⁺ produced by the electrolysis process activated persulfate and produced strong oxidizing sulfate radical to degrade the organic compounds in wastewater,when the Fe²⁺ was oxidized to Fe³⁺ and then hydrolyzed to form flocculation. The experimental result showed that under the conditions of electrolysis time 25 min,current density 41.7 mA/cm²,electrode gap 4 cm,stirring rate 100 r/min,wastewater pH 7.0 and persulfate amount 0.006 mol/L,the removal rate of COD reached 94.5%,the BOD₅/COD value increased from 0.13 to 0.56,the conductivity decreased from 104 mS/m to 71 mS/m,the salinity decreased from 16 704 mg/L to 4 065 mg/L and the residue content reduced from 554 mg/L to 59 mg/L. The treatment effect of the electrocoagulation-persulfate oxidation synergistic process was significantly better than that of the single electrocoagulation process and the ferrous sulfate-activated persulfate oxidation process. The reason（as indicated by cyclic voltammetry test）was that the flocculation effect was enhanced with the production of sulfate radical and the increase of solution conductivity.