The retention of metal species by different solid sorbents. Mechanisms for heavy metal speciation by sequential three column uptake

An apparatus consisting of three columns packed with different substrates, namely an anion exchange resin, a reversed phase sorbent and a chelating ion exchange resin, was developed. The retention of cadmium, copper and lead onto the substrates at different pH conditions was investigated, first by considering each column separately, then by connecting them in series. The aim of the study is to distinguish among species with different charge or chemical behaviour. Experiments were performed with the free metal ions, their anionic complexes with EDTA and 8-hydroxyquinoline-5-sulphonic acid, and their neutral complexes with 8-hydroxyquinoline. The results obtained were compared with those computed according to the theoretical species distribution of all species as a function of pH. The applicability of the technique to seawater was demonstrated.