两段石灰中和-洗涤-絮凝沉淀法脱除污酸中砷的研究

以高砷铜冶炼污酸废水为原料,采用两段石灰中和-洗涤-絮凝沉淀法处理,研究了该工艺除砷原理、影响因素、及效果,讨论了不同终了pH时溶液及渣中砷含量变化情况,洗涤对渣中砷含量变化的影响和絮凝剂PFSS对溶液深度除砷效果的影响。结果表明：一段中和后溶液中砷含量由13.69g/L降到12.90g/L,除砷率仅为5.77%,渣中砷含量为2.80%。用蒸馏水洗涤一段中和渣,液固比为10:1,洗涤5次后,渣中砷含量降至0.06%；用0.1mol/L的Na2CO3溶液洗涤一段中和渣,液固比为10:1,洗涤4次后,渣中砷含量降至0.05%。两者均可使中和渣由固体危废变为普通固废,减少危废排放量25%以上。当溶液pH中和到12.04时,砷的残留量仅为3.6mg/L,除砷率达99.97%,PFSS的滴加可使溶液中砷含量低于0.5mg/L,甚至低于0.01mg/L,出水砷含量满足排放标准。

Study of the removal of arsenic by the process of two-stage lime-neutralizationin combination with washing and flocculation

This paper studies the technology of the removal of arsenic by the two-stage lime-neutralization-washing-flocculation precipitation of acid treatment process. The raw materials for experiments is copper smelter acid in which arsenic is of high content. The principle, influence factors, and effect of the removal of arsenic are studied. Experiments study the influence ofarsenic removal rate in wastewater and the change of the arsenic content in slag of different pH at the end, the changes of arsenic content in slags with different washing times and the depth of arsenic removal effect by flocculant.The results show that arsenic content in the solution drop to 12.90g/L from 13.69g/L,namely,The arsenic removal rate is only 5.77% when the solution pH is 3.14.And the arsenic content in slags is 2.80%.Washing the slags in the first stage with distilled water of liquid-solid ratio 10:1. Arsenic content in slag drop to 0.06% after washing 5 times. Washing he slags in the first stage with Na₂CO₃ solution of liquid-solid ratio 10:1. Arsenic content in slag drop to 0.05% after washing 4 times. They can both reduce the quantity of hazardous solid waste more than 25% by turning the slag into ordinary solid waste from hazardous solid waste. The residues of arsenic is only 3.6 mg/L when the solution pH is 12.04, the arsenic removal rate is 99.97%. The arsenic content in the solution can drop to 0.5mg/L even 0.01 mg/L by adding PFSS. And the arsenic content of effluent meet the emission standards.