ELECTROWINNING OF METALS USING BUFFERED SODIUM-CHLORIDE ELECTROLYTE DURING ELECTROCHLORINATION OF SEA NODULES

The effect of the addition of acetic acid and formic acid to sodium ch loride electrolyte has been studied for the electrowinning of metals f rom sea nodules using the electrochlorination technique. Polarization results obtained in different electrolytes suggest that the direct ele ctrowinning of metals at the cathode is possible with the sodium chlor ide electrolyte by addition of acetic acid or formic acid. Electrochlo rination of sea nodules in a diaphragm cell using a sodium chloride-ac etic acid/formic acid electrolyte has confirmed the cathodic depositio n of metals. Further studies with differing amounts of formic acid in the electrolyte revealed that the optimum addition of formic acid in t he electrolyte was 7.5 vol.%. With this acid concentration, about 98% each of copper, nickel and cobalt are dissolved and about 19% Cu, 29% Ni and 17% Co are deposited at the cathode during 4 h electrochlorinat ion. Deposition of metals at the cathode increases with the period of electrochlorination. The cathodic recoveries of copper, nickel and cob alt at the end of 8 h electrochlorination are about 52%, 58% and 36%, respectively. Only 5% iron and 1% manganese are deposited.