D. Petruzzelli et al., CR(III) AL(III)/FE(III) ION-BINDING ON MIXED BED ION-EXCHANGERS - SYNERGISTIC EFFECTS OF THE RESINS BEHAVIOR/, Reactive & functional polymers, 31(2), 1996, pp. 179-185
Ion exchange, as a conservative technology, allows for removal and rec
ycling of metals from liquid effluents. Chelating exchangers may be us
ed to the purpose due to their specificity toward metal species. The s
pecificity, related to the metal-functional group affinity and thus th
e high stability of the complexes formed, is paid in terms of regenera
tion levels necessary to reverse the exchange reaction by mass action.
Moreover, the liquid-phase speciation of the metals with organic and
inorganic ligands, commonly present in industrial effluents, determine
s the active metal concentrations at the binding sites and thus the re
moval efficiency of the chelating resins which is, in general, more af
fected by stereochemical factors during the interaction of the active
species at the functional groups. In this context, we investigated the
behaviour of a mixed bed weak electrolyte anion (amino) and cation (c
arboxylate) conventional ion-exchangers as an alternative to chelating
resins. The synergistic effects of the two functional groups to selec
tively remove, separate and recover Cr(III), Al(III), Fe(III) from seg
regated industrial effluents are discussed. The exhaustion behaviour o
f the carboxylate resin toward chromic and aluminum species is synergi
zed by the cooperative presence of the anion resin, this latter being
able to selectively retain ferric species. Difficult regeneration beha
viour of the metal-form carboxylate resin is also favored by the prese
nce of the weak base amino functional groups in the free base form.