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污酸中有價成份的綜合利用及有害元素As的去除工藝試驗研究

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

  • 摘要: 目前我國大型冶煉企業產生的污酸均被當做一種高濃度重金屬廢水來處理,不僅需要高額的廢水處理費用,而且還會產生大量的廢水處理渣。結合污酸及氧化鋅煙灰的主要成份,采用循環浸出工藝,利用污酸對氧化鋅煙灰進行浸出,浸出完全后,綜合回收浸出液中的Cu、Zn、As。實驗研究了終點pH、浸出溫度、浸出時間對污酸一次浸出和二次循環浸出的影響,以及雙氧水加入量、溫度、時間對一次除As的影響和硫化鈉加入量、溫度、時間對二次除As的影響。實驗表明:最佳一次浸出條件為終點pH值為1.5、反應溫度為85 ℃、反應時間為5 h;最佳二次循環浸出條件為終點pH值為4、反應溫度為85 ℃;最佳一次除As條件為每毫升二次循環浸出液添加0.067 mL雙氧水、反應溫度為40 ℃、反應時間為1.5 h;最佳二次除As條件為每毫升一次除As后液添加0.02 g硫化鈉、反應溫度為35 ℃、反應時間為2 h。污酸綜合利用后, 原來的高濃度重金屬廢水變成了中性廢水,其中的重金屬(As、Cu、Zn)質量濃度分別降至3.26、2.63和50.63 mg·L?1,稍加處理即可達到污水綜合排放標準。此工藝既綜合回收了污酸和氧化鋅煙灰中的有價成份,又集中處理了有害元素As,消減了危險廢物的產生量,達到了節能減排的目的。

     

    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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