title: Capture of metallic copper by high gradient magnetic separation system.
abstract: Valence copper was recovered from wastewater by chemical reduction and use of a high gradient magnetic separation (HGMS) system. Ammonia (NH3) and sodium dithionate (Na2S2O4) at a molar ratio of [Cu]:[NH3]:[Na2S2O4] = 1:4:3 at pH = 9.5 were used first to chemically reduce copper ion to metallic copper; the resultant metal solids were captured in an upflowing reactor space equipped with a permalloy matrix net under a high gradient magnetic field. The captured solids were predominantly 6-20 microm in diameter, with Cu2O and CuO present among the solids. Four treatment configurations with and without the use of magnetic field and metal alloy as the matrix net were tested and their effects evaluated: (1) no magnetic field or matrix, (2) no magnetic field but with matrix, (3) with magnetic field but no matrix, (4) with both magnetic field and matrix. 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 in the presence of magnetic field were 99%, 98%, 95%, and 93%, respectively. The HGMS was critical for a high capture efficiency, whereas a matrix net only marginally enhanced it. Additional tests with a larger reactor confirmed similarly high efficiencies of > 85%. The use of an alloy matrix appeared to be important when high flow rates are most likely to be employed in practical applications.
authors.affiliation: Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Road, Taipei 106, Taiwan.
authors.forename: Wan-I
authors.initials: WI
authors.lastname: Wu
authors.forename: Chung-Hsin
authors.initials: CH
authors.lastname: Wu
authors.forename: P K Andy
authors.initials: PK
authors.lastname: Hong
authors.forename: Cheng-Fang
authors.initials: CF
authors.lastname: Lin
mesh_terms: D003300:Copper / Q000302:isolation & purification* / Q000528:radiation effects; D004574:Electromagnetic Fields; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007220:Industrial Waste / Q000517:prevention & control*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000528:radiation effects; D018508:Water Purification / Q000295:instrumentation*
chemical_list: D007220:Industrial Waste; D014874:Water Pollutants, Chemical; D003300:Copper