HYDROCHLORIC-ACID LEACHING OF SEA NODULES WITH METHANOL AND ETHANOL ADDITION

A study has been made to investigate the effects of methanol and ethanol additions in dilute hydrochloric acid leaching of polymetallic sea nodules. In the absence of additives, the hydrochloric acid solution in an aqueous medium (2.75 kmol/m3) leaches out only copper and iron in considerable amounts and more than 90% recovery of all the metals are achieved only when a very strong concentration of acid (11 kmol/m3) is used. It has been found that metal recoveries can be considerably improved even in 2.75 kmol/m3 hydrochloric acid solution if an appropriate amount of methanol or ethanol is incorporated with it. The addition of 75 vol% of methanol in the 2.75 kmol/m3 hydrochloric acid system has been found to recover more than 90% of each metal. The requirement of ethanol has been found to be 18.5 vol% to achieve the same degree of recovery of metals in dilute hydrochloric acid solution. The effects of other parameters such as period of leaching and acid concentration on the recovery of metals in the alcoholic hydrochloric acid leaching system have also been studied.