污酸中有价成份的综合利用及有害元素As的去除工艺试验研究

Experimental research on the comprehensive utilization of valuable components and centralized removal of harmful elements in waste acid

  • 摘要: 目前我国大型冶炼企业产生的污酸均被当做一种高浓度重金属废水来处理,不仅需要高额的废水处理费用,而且还会产生大量的废水处理渣。结合污酸及氧化锌烟灰的主要成份,采用循环浸出工艺,利用污酸对氧化锌烟灰进行浸出,浸出完全后,综合回收浸出液中的Cu、Zn、As。实验研究了终点pH、浸出温度、浸出时间对污酸一次浸出和二次循环浸出的影响,以及双氧水加入量、温度、时间对一次除As的影响和硫化钠加入量、温度、时间对二次除As的影响。实验表明:最佳一次浸出条件为终点pH值为1.5、反应温度为85 ℃、反应时间为5 h;最佳二次循环浸出条件为终点pH值为4、反应温度为85 ℃;最佳一次除As条件为每毫升二次循环浸出液添加0.067 mL双氧水、反应温度为40 ℃、反应时间为1.5 h;最佳二次除As条件为每毫升一次除As后液添加0.02 g硫化钠、反应温度为35 ℃、反应时间为2 h。污酸综合利用后, 原来的高浓度重金属废水变成了中性废水,其中的重金属(As、Cu、Zn)质量浓度分别降至3.26、2.63和50.63 mg·L−1,稍加处理即可达到污水综合排放标准。此工艺既综合回收了污酸和氧化锌烟灰中的有价成份,又集中处理了有害元素As,消减了危险废物的产生量,达到了节能减排的目的。

     

    Abstract: Currently in China, the waste acid generated from large-scale smelting plants is treated as “wastewater with high concentration of heavy metals”, which leads to high cost and many wastewater treatment residues (hazardous wastes). In this paper, based on the main components of waste acid and zinc oxide dust, the adoption of a cyclic leaching process was proposed, in which zinc oxide dust is leached by waste acid, thus enabling the recovery of copper (Cu) and zinc (Zn) from the circulating leaching solution and the central treatment of arsenic (As). The main factors affecting the first and second cyclic leaching processes were investigated, including the final pH, leaching temperature, and leaching time. After leaching was completed, several factors in the first and second As removal processes were investigated, including the H2O2 dosage, Na2S dosage, removal temperature, and removal time. The following optimal conditions were identified: the optimal final pH, leaching temperature, and leaching time for the first leaching are 1.5, 85 ℃, and 5 h, respectively. The optimal final pH and leaching temperature for the second leaching are 4 and 85 ℃, respectively. The optimal H2O2 dosage, removal temperature, and removal time for the first As removal are 0.067 mL per 1 mL of the secondary circulation leaching solution, 40 ℃, and 1.5 h, respectively. The optimal Na2S dosage for the second arsenic removal is 0.02 mL per 1 mL of the second circulation leaching solution, and the removal temperature and removal time were determined to be 35 ℃ and 2 h, respectively. Under these conditions, the concentrations of As, Cu, and Zn can be reduced to 3.26, 2.63, and 50.63 mg·L−1, respectively. The pH of the wastewater after processing was neutral, which meets the integrated wastewater discharge standard with minor treatment. In this way, valuable components in the waste acid can be comprehensively recovered, and the harmful element As centrally treated, thus reducing the production of hazardous wastes, saving energy, and reducing emissions.

     

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