Copper Recovery from Water by High Gradient Magnetic Separation System

• Main Authors: Wan-I Wu, 吳萬益
• Other Authors: 林正芳
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/98750198816528807039

博士 === 國立臺灣大學 === 環境工程學研究所 === 99 === 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.