pH对中和沉淀法处理涂装废水效果影响及作用机理

Mechanism and effect of pH on coating wastewater in neutralization and precipitation process

采用中和沉淀法对涂装废水进行处理,研究了pH(4~12)对废水中总磷、COD、浊度、总铁、总镍、总锰等12种主要污染物去除率的影响,并结合絮体粒度分布、Zeta电位、絮体形貌和XRD图谱等表征方式对COD和重金属的去除机理进行了分析。研究结果表明,在综合考虑后续生化处理需要和处理成本的条件下,中和沉淀法处理涂装废水的适宜pH为8,废水经处理后所有重金属离子浓度和总磷浓度均达到《污水排入城镇下水道水质标准》(GB/T 31962-2015)B级标准,COD、浊度和氨氮的去除率分别为30.05%、46.51%和72.49%。无机污染物去除的主要途径包括磷酸盐沉淀形成、氢氧化物沉淀形成和吸附絮凝作用。COD的去除机制随着pH的变化而不同,在pH=2.18~8时,COD的去除主要由于不溶性金属络合物的形成、电性中和与卷扫网捕,在pH=10~12时,主要的作用机制为氢氧化物絮体对其的吸附作用和卷扫网捕。这对中和沉淀法工艺处理实际涂装废水有重要的指导意义。

The neutralization and precipitation process was used for coating wastewater treatment, the effects of pH（4 to 12） on the removal efficiencies of 12 major pollutants such as total phosphorus, COD, turbidity, total iron, total nickel and total manganese were studied and the removal mechanisms of COD and heavy metals were analyzed with the floc size distribution, Zeta potential, the morphology of flocs and XRD patterns. The results showed that suitable pH was 8 for treatment of coating wastewater by neutralization and precipitation process. After the wastewater was treated by the process, the concentration of all heavy metal ions and total phosphorus in the wastewater could meet the class B standard of Wastewater Quality of Standards for Discharge to Municipal Sewers（GB/T 31962-2015）. At pH=8, the removal efficiency of COD, turbidity and ammonium were 30.05%, 46.51% and 72.49%, respectively.Phosphate precipitation formation, hydroxide sinking formation, adsorption flocculation were the main way to remove inorganic pollutants. The removal mechanism of COD varied with pH, at 2.18 to 8 of pH, the removal of COD was mainly due to the formation of insoluble metal complexes, the electrical neutralization and the rewinding of the net,at 10 to 12 of pH, the main mechanism was adsorption of the hydroxide flocs and roll netting. The results can provide theoretical guidance for the application of the neutralization and precipitation process to treat coating wastewater.