以電解提煉法回收污泥中銅之研究

Abstract

表面處理業、電鍍業及電路板製造業等工業之廢水處理方法，大多目前仍然採取傳統的化學混凝沉澱法，其產生的污泥，數量龐大且含有大量的銅、鎳、鋅等重金屬。本研究目的在於利用酸對重金屬污泥之萃取特性，以其萃取液作為電解液，用電解法將其中的銅提煉出來，進而探討結合廢酸之利用，以廢酸萃取含銅重金屬污泥，及電解提煉法回收銅的可行性。 根據污泥的物化特性，及污泥重金屬含量分析顯示，DY廠污泥中銅金屬含量平均為32.8％，遠高於其他廠汚泥中之銅含量，且此含銅量甚至高於銅礦開採之含銅量，因此DY廠污泥中銅金屬深具有回收再利用的價值與潛力。 本試驗所使用之各種化學萃取劑，主要萃取的對象以銅為主，對銅的萃取效果，依序為濃硫酸>氟硼酸>EDTA>金屬捕集劑 Epoflocl-1，其中以濃硫酸及氟硼酸萃取效果最好，而濃硫酸萃取效果略高於氟硼酸。批次電解提鍊試驗結果發現，以氟硼酸為萃取劑可獲得97％左右純度的電解銅;而以濃硫酸為萃取劑的電解產品，銅的純度為94∼99％。 本試驗在25A、3V的電解條件下，以濃硫酸萃取後之電解液，進行流體化床電解反應，由陰極板所收集到的銅金屬產品，純度介於88∼99％之間。由陰極電解效率分析得知，為避免電能的浪費，在流體化床電解銅操作中，其電解液銅離子濃度需維持在2000mg/L以上。 電解後之電解液再以不同固液比進行污泥中重金屬萃取試驗，研究顯示在相同之固液比1:3時，或固液比1:10時，電解後之廢液對重金屬污泥中Cu的萃取效率皆優於未經電解廢酸之萃取效率。

Nowadays, the process of wastewater treatment performed by metallic surface, electro-plating, and printed circuit board manufacturing industries mostly produces large amounts of sludge that contains copper, nickel, and zinc. The purpose of this research is to use the acid agent to work on leaching copper out from the sludge for realizing the characteristics of heavy metals extracted. The extracted solution works as the electrolyte, from which copper can be recovered by electrolysis. The next one to be explored is the utility of combining the waste acid and the sludge. That is, it is worthwhile to investigate the possibility of the recovery of copper through the electro-winning processes by using the acid agent to extract copper from heavy metal sludge. According to the result of analysis data experimented with a variety of sludge samples, we find that approximately 32.8% copper is contained in the dried sludge from DY plant, which reveals that there is high potential for the recovery and reuse of copper. When it comes to the effect of chemical agents on copper extraction, sulfuric acid and fluoroboric acid are better than EDTA and metal captured agent. And strong sulfuric acid is a little better than fluoroboric acid. The purity of copper produced in batch electro-winning processes is approximately 97% and 94-99%, obtained from the sludge extracted solution with fluoroboric acid and sulfuric acid, respectively. After electro-winning processes, the residual solution can be used for the heavy-metal extraction test of sludge. The study has shown that when the same ratio of solid to liquid is one to three or one to ten, the copper-extracted efficiency in the residual solution which has been electro-winned is better than that in the original waste acid.