Hydrometallurgy, 25 (1990) 61-83 61 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands Physico-chemical nature and leaching behaviour of goethites containing Ni, Co and Cu in the sorption and coprecipitation mode Rakesh Kumar, R.K. Ray and A.K. Biswas* Department of Metallurgical Engineering, Indian Institute of Technology, Kanpur- 208016 (India) (Received April 14, 1989; revised and accepted October 22, 1989 ) ABSTRACT Kumar, R., Ray, R.K. and Biswas, A.K., 1990. Physico-chemical nature and leaching behaviour of goethites containing Ni, Co and Cu in the sorption and coprecipitation mode. 14ydrometallurgy, 24: 61-83. Goethite (c¢-FeOOH) samples containing Ni, Co and Cu in coprecipitation and sorption mode were synthesized and characterized in terms of chemical composition, surface area, phase constitu- ents, crystallinity and structural disorder (by XRD) and crystal size and morphology (by TEM). Dissolution behaviour of Fe in Ni-, Co- and Cu-bearing goethite samples in sulfuric and sulfurous acid leaching systems have been compared with the behaviour of a pure goethite sample and corre- lated with the physical characteristics of the samples. Minor elements interfere with the dissolution of iron in sulfurous acid leaching. Elements in the sorption mode are easily leachable compared to the coprecipitation mode. In the latter case these may be present as a part of the goethite structure or as occluded oxyhydroxide. The implications of these results are discussed for acid leaching of manganese nodules. INTRODUCTION Goethite is the most frequently observed iron-bearing mineral present in manganese nodules [1-4]. Generally observed elemental correlations in manganese nodules have indicated that Ni and Cu correlate positively with manganese, and Co with either manganese or iron [ 3,4 ]. Thijssen et al. [ 5 ] have noted that Ni, Co and Cu are positively correlated with Fe in Peru Basin nodules. No separate phase of Ni, Co or Cu has been recorded in nodules. The minor elements are thoroughly disseminated in the nodule internal struc- ture. The precise mode of incorporation (e.g. coprecipitation, sorption etc. ) of minor elements and its implications in nodule processing are poorly under- stood [ 6 ]. It appears from the literature that there has been very little effort *To whom all communications should be addressed. 0304-386X/90/$03.50 © 1990 Elsevier Science Publishers B.V.