Modified cation exchange resin applied to demineralisation of a liquid industrial waste. Comparison to a classical treatment and electrodialysis

An experimental study has been made on the separation and recovery of some metals from an effluent waste. Three methods (i.e. classical neutralisation, electrodialysis and ion exchange) were used and compared. Purification efficiency was determined in all cases of treatment. It was found that classical treatment causes formation of a large amount of sludge constituted principally of Al(OH)(3), Fe(OH)(3) and CaSO4. Ten grams of solid were formed using 1 L of effluent treated. The electrodialysis process was efficient for removal of monovalent anions such as Cl- and NO3- from effluent using a monovalent selective anion exchange membrane. Increase of current density causes an increase of efficiency. Finally, a cation exchange resin modified by adsorption of tetrabutylammonium or polyethyleneimine on its surface was used and compared to unmodified resin and the two methods of treatment cited above. Modification of the resin surface allowed separation of species according to their valencies and hydration, Cations with high valencies were fixed on the resin modified by tetrabutylammonium, while transition metals were retained by chelate bonding with polyethyleneimme fixed on resin modified by this polyelectrolyte. (C) 2002 Elsevier Science B.V. All rights reserved.