Cadmium removal from diluted aqueous solutions by electrowinning in a flow-by cell

Mineral processing and metal finishing industries produce lar ge amounts of effluents containing a host of heavy metals - cadmium, lead, nickel and ch romium - with cadmium as a heavy hazard, since, even in mild concentrations , it may give rise to serious environmental problems. Effluents from electr oplating industries and from zinc ore hydrometallurgical processing may con tain this metal in the range of 15 to 100 ppm. Cadmium harm to all living s ystems is aggravated bq, its strong cumulative effect because of the long n umber of years required for its elimination The electrolytic waste treatmen t has shown advantages over the classical chemical precipitations by alkali s or carbonates, because it does not produce bulky sludges, which require l and for its accumulation, and which may have a retarded pollution effect, d ue to the redissolution by rain, a great advantage comes from the possibili ty of the metal recovery in a commercially pure form. In this paper; a labo ratory scale electrolytic flow-by cell with a reticulated vitreous carbon ( RVC) cathode, developed in our laboratory is described, which permitted the purification of aqueous solutions containing cadmium ion on the usual orde r of concentration of metallurgical industries effluents, with this cell, o perating in a mass transport regime, it has been possible to decrease cadmi um concentration of solutions of 2 liters volume from 200 to 0.1 ppm, with current efficiencies up to 40%, in a matter of 85 minutes. (C) 2000 Publish ed by Elsevier Science Ltd. All rights reserved.