Na2S与高聚复配絮凝剂处理酸性高As废水

摘要

An efficient and low-cost technology was developed for high concentration arsenic wastewater recycling by combining the advantages of sulfuration and polymer composite flocculants.In the experiment,the high-arsenic wastewater from a smelter was chosen as the treatment object.The arsenic was recycled using Na2S·9H2O for sedimentation.The Na2S·9H2O dosage,dosing manner,initial pH,reaction time were optimized before the experiments.The arsenic dregs were characterized by X-ray diffraction (XRD) and X-Ray Fluorescence (XRF).The results showed more than 98％ of arsenic was recovered under the optimal condition with Na2S· 9H2O dosage of 55 g/L,a charging style of twice dosing,an initial pH of 2.0 and a reaction time of 5 minutes.The arsenic content in the treated wastewater was 0.61 g/L,and contents of arsenic and sulfur in arsenic dregs reached as the percentages of 49.15％ and 40.98％ with other heavy metallic ions.The wastewater from sulfuration process was consequently treated with a polymer composite flocculants.The parameters such as optimal proportioning,dosage,pH and flocculants were investigated first.The results showed that:under the condition of Fe:Si =5:1,flocculant dosage of 7 mL/L and pH of 8,arsenic can be deeply removed,and the remaining arsenic concentration was lower than 0.3 mg/L.These results demonstrated that this method is superior to the common flocculants under the same conditions.Based on above findings,expanded multi-batch experiments using combination technique (sulfuration with a polymer composite flocculants) were conducted as well.And the results showed that:the average recovery rate of arsenic was higher than 98％,and average residual arsenic content was less than 0.3 mg/L.The experimental results proved that the combined technique can achieve the reclamation of high-arsenic wastewater,with promising application on the engineering and commercial uses.%以酸性高As废水为处理对象,利用硫化法去除并回收As,研究了Na2S·9H2O投加量、反应初始pH、反应时间、Na2S·9H2O投加方式对As去除效果的影响,并通过XRD(X射线衍射)、XRF(X射线荧光光谱分析)对回收的As渣进行分析；对处理后的含As废水,利用高聚复配絮凝剂深度脱As,研究了絮凝剂优化条件、絮凝剂投加量、反应pH对深度脱As的影响并与常见絮凝剂进行对比.结果表明,Na2S·9H2O投加量为55 g/L、两段投加、反应时间为5 min、初始pH为2.0的条件下可达最佳除As效果,处理后As回收率达98％以上,出水ρ(As)为0.61 g/L,As渣中w(As)、w(S)分别达49.15％、40.98％,其他重金属元素几乎未检出.在絮凝剂n(Fe)∶n(Si) =5∶1、投加量为7 mL/L、pH为8的条件下可得最优深度脱As效果,出水ρ(As)低于0.3 mg/L,同等条件下优于常规絮凝剂处理效果.多批次扩大试验结果表明,组合技术处理废水水质稳定,As回收率平均可达98％以上,出水ρ(As)低于0.3 mg/L.