Cathodic reductive dissolution and surface adsorption behavior of ocean manganese nodules.pdf

Cathodic reductive dissolution and surface adsorption behavior of ocean manganese nodules Abha Kumari, K.A. Natarajan* Department of Metallurgy, Indian Institute of Science, Bangalore 560012, India Received 26 September 2001; received in revised form 15 April 2002; accepted 18 April 2002 Abstract Cathodic slurry reductive dissolution of ocean manganese nodules in 1 M H2SO4 at 600 and 1000 mA resulted in significant dissolution of copper and nickel, while the dissolved copper was simultaneously deposited at the cathode. Dissolved manganese could be anodically converted to MnO2. Ocean manganese nodules exhibited good adsorption capacities for copper and nickel from acidic solutions. Adsorption behavior and mechanisms for uptake of various metal ions such as copper, nickel, cobalt and iron are discussed. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Ocean manganese nodules; Cathodic reductive leaching; Adsorption; Desorption 1. Introduction The discovery of large quantities of manganese nodules on the floor of the ocean holds promise as a source of copper, nickel and cobalt. Electroleaching of base metal sulphides has been reported by Natarajan et al. (1985) and Natarajan (1992). A study of the electro- leaching of manganese ore has been reported by Elsherief (2000). Electrochlorination of sea nodules to recover copper, nickel and cobalt has been studied by Jana et al. (1993). Electroleaching of ocean manganese nodules to extract copper, nickel and cobalt has been recently reported (Kumari and Natarajan, 2001). Attempts at the simultaneous electrodeposition of zinc andmanganese dioxide have beenmade by several workers (French and French, 1917) during the 1920s. The simultaneous electrowinning of zinc at the cathode and gamma phase of MnO2 at the anode from the leach liquor was studied (French and French, 1917). Electro- lytic manganese dioxide from chloride electrolyte has been reported by Rethinaraj et al. (1993). An inves- tigation of manganese electrow