高梯度磁化分離系統回收水中銅離子

Copper Recovery from Water by High Gradient Magnetic Separation System

吳萬益(Wan-I Wu)

指導教授 ： 林正芳

共同指導教授 ： 馬鴻文 ； 童心欣

國立臺灣大學/工學院/環境工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.01211

摘要

中文摘要
人類自古至今與銅金屬的關係即密不可分，尤其近年來，隨著光電業的日新月異以及新興國家的崛起，生活水準提高之後無論是在銅消費量或消費速度都不斷的再增加，而且增幅量非常驚人，再以專家的說法銅資源將在大約30年內耗盡；而目前的問題不但資源不足，事業廢水甚至經常不當處理，導致地面水體的重金屬銅污染程度亮出警訊，為因應此環境衝擊必須研究一個能兼顧環保及回收的處理系統，以解決目前一般所使用的處理程序如化學混凝沉澱處理或電鍍處理以及鋁置換回收之方法所帶來耗能及二次污染的種種問題。
本研究是利用高梯度磁化分離系統(High Gradient Magnetic Separation System, HGMS)回收水中銅離子，首先以還原劑(Na2S2O3)將高濃度銅廢液之銅離子還原為0.4-20 μm之零價銅，並添加順磁性物質(MnCl2)增加溶液的導磁性，以及在反應槽內加入高導磁性金屬波莫合金(permalloy)做為基體絲籠(matrix)，最後在反應槽外部利用較高的外加磁場(10000 Gauss = 1 Tesla)，使水中銅金屬顆粒流經金屬絲籠表面而產生非常高的磁場梯度，同時使得銅金屬在Matrix附近產生磁化作用，而磁吸在金屬絲籠上以及在金屬絲籠周圍產生出一種效應，我稱它為磁凝絮作用(Magnetic Flocculation)，使銅金屬明顯懸浮且緊密的磁吸在一起而達到分離的效果，這穩定且均勻分佈的「磁凝絮懸浮金屬團」不但有磁吸的作用，還能兼俱過濾的效果，使得反應不但不會因金屬絲籠的吸附表面積而受限，還能處理更大的流量，同時因過濾作用能使顆粒更容易產生碰撞、攔截等效應使捕獲率提高。
當銅溶液（銅離子濃度為3.9或16 mM）加入於過量的聯二亞硫酸鈉（莫耳比為1:3）及氨（莫耳比為4）和定量的氯化錳（2.5克/ L）再混合通過一個上流式反應槽後，強大的外加磁場（1 TG）可使銅在反應器中超過95％的捕獲量。化學還原反應對氯化錳的存在並沒有影響。而銅的回收效率，特別是在銅離子濃度較高時（16 mM），因氯化錳的添加量不同（0、20、和32 mM）則有顯著不同。此法可提供從銅廢污水資源回收銅金屬的良好方法。
固體被捕獲的主要成分為Cu2O和CuO，且直徑在4 ~ 20微米。四項實驗配置為：投入、不投入外加磁場，以及有、沒有使用波莫合金絲籠的影響，進行了測試和評估。在沒有磁場且流量分別為 40，60，80和100 cm3/min時，其捕獲金屬銅的效率分別為 87％，86％，63％和39％；但投入外加磁場後其捕獲金屬銅的效率則分別提高至 99％，98％，95％和93％。HGMS是捕獲效率提高的關鍵因子，而波莫合金絲籠的使用亦可使捕獲效率略微增加。同樣的實驗證實在較大的反應槽中，亦有> 85％的高捕獲效率。在高流速的狀況下可看出使用波莫合金絲籠的捕獲效率相對顯著，此Matrix在實際應用時則扮演相當重要的角色。

關鍵字

高梯度磁化分離系統 ； 銅分離 ； 化學還原 ； 廢水 ； 回收

並列摘要

Abstract
Copper plays an important role in human history since ancient times. In recent years, with the ever-changing optical industry and the rise of emerging countries, and the raising of living standards, copper consumption rate are increasing significantly. According to experts in the field,it is possible that copper resources would be exhausted within 30 years,The current problems are not only the lack of copper resources, but also the frequent inappropriate treatment of industrial wastewater that lead to copper pollution of the surface water supply. In response to the environmental impact,an environment-friendly recycle system should be established in order to address the issue of energywaste and secondary pollution problems caused by the current use of chemical coagulation and sedimentation processes or electroplating and aluminum replacement processes.
Copper recovery from water by high gradient magnetic separation system (HGMS) was investigated in this study.High concentration of copper waste effluents was reduced by the reduction agent(Na2S2O3)to zero-valent copper with diameter ranged 0.4 to 20 micrometer, Paramagnetic substance(MnCl2) was added to increase the magnetic susceptibility the solution.Then high magnetic susceptibility metal (Permalloy) was added into the reaction tank as wire mesh (Matrix), and high external magnetic field (1000 Gauss = 1 Tesla) was applied to the reactor in order to drive copper particles within the solution to flow through the high magnetic susceptibility matrix and resulted in a high magnetic gradient on the Matrix surface. At the same time, magnetic flocculation was observed around the metal mesh that suspended and aggregated copper particles closely attached together to achieve the copper separation. Magnetic flocculated suspended metal aggregation was stable and uniformly distributed in the solution, and not only consists of magnetic attraction ability but also could act as a filtration so that the reaction would not be limited to the surface area of metal mesh and larger capacity could be handled. At the meantime, filtration could enhance particles collision and interception to elevate the recovery rate.
High gradient magnetic separation (HGMS) is seen as a viable method. We tested the capture of valence copper from aqueous cupric ion by HGMS in combination with a reduction process. When a cupric solution (3.9 or 16 mM) was exposed to excess of dithionite (mole ratio of 1:3) in the presence of ammonia (mole ratio of 4) and amended with MnCl2 (2.5 g/L) and the mixture passed through a flow reactor under a high magnetic field (1 T), We have demonstrated the captured of valence copper in the reactor with well over 95% yields. The chemical reduction reactions were unaffected by the presence of MnCl2 while the amount of MnCl2 (0, 20 and 32 mM) has significantly varied the copper recovery efficiency especially in the case of high initial cupric ion concentration (16 mM). Formation of MnO2 flocs was found to have detrimental effect on copper removal efficiency. The HGMS method offers a tool of resource recovery for copper from waste effluents.
Sizes of the captured particulate were predominantly of 4-20 μm in diameter, with Cu2O and CuO present among the solids. Four treatment configurations with and without the uses of magnetic field and metal alloy as matrix net were tested and their effects evaluated. At flow rates of 40, 60, 80, and 100 cm3/min , capture efficiencies for metallic copper in the absence of magnetic field were 87%, 86%, 63%, and 39%, respectively, and demonstrated an enhance mat to 99%, 98%, 95%, and 93%, respectively in the presence of msgnetic field. HGMS was critical to high capture efficiency, while a matrix net marginally enhanced it. Additional tests with a larger reactor confirmed similarly high efficiencies of > 85%. The use of alloy matrix appeared important when high flow rates would most likely be employed in practical applications.

並列關鍵字

High gradient magnetic separation ； metallic copper separation ； chemical reduction ； magnetic field ； wastewater ； recovery

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