Sulfuric acid leaching of ocean manganese nodules using phenols as reducing agents

Pacific Ocean manganese nodule samples were leached with dilute sulfuric ac id in the presence of phenol type aromatic reducing agents. Six phenols, in cluding hydroxybenzene, o-dihydroxybenzene, m-dihydroxybenzene, p-dihydroxy benzene, o-trihydroxybenzene and m-trihydroxybenzene. were rested. The resu lts indicated that all the rested phenols were effective reducing agents th at significantly increased the extraction of Mn, Cu, Ni, Co from the nodule s. At a dosage of 0.25 similar to 0.4 grams of the reducing agents and 0.92 5 grams of H2SO4 per gram of nodules, over or nearly 95% of the Mn, Cu, Ni and Co could be extracted in IO similar to 20 minutes from art aqueous slur ry containing about 20% manganese nodule, under ambient temperature and pre ssure. In the absence of the reducing agents, the extraction of Cu was abou t 65% and that of Mn, Ni and Co was below 20%. ESCA, TLC and UV/VIS spectro scopic analyses indicated that the Mn in the nodules was reduced in the pre sence of phenols in the acid medium, while the phenols could be oxidized to p-benzoquinone. (C) 2001 Published by Elsevier Science Ltd. All rights res erved.