Electrowinning of metals using buffered sodium-chloride electrolyte during electrochlorination of sea nodules

Abstract

The effect of the addition of acetic acid and formic acid to sodium chloride electrolyte has been studied for the electrowinning of metals from sea nodules using the electrochlorination technique. Polarization results obtained in different electrolytes suggest that the direct electrowinning of metals at the cathode is possible with the sodium chloride electrolyte by addition of acetic acid or formic acid. Electrochlorination of sea nodules in a diaphragm cell using a sodium chloride-acetic acid/formic acid electrolyte has confirmed the cathodic deposition of metals. Further studies with differing amounts of formic acid in the electrolyte revealed that the optimum addition of formic acid in the 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 electrochlorination. Deposition of metals at the cathode increases with the period of electrochlorination. The cathodic recoveries of copper, nickel and cobalt at the end of 8 h electrochlorination are about 52%, 58% and 36%, respectively. Only 5% iron and 1% manganese are deposited.