Comparative sorption capacity of Pb(II) and Cd(II) by natural zeolite in phosphoric acid medium

Zeolite, a well-known inorganic compound, was used for Pb(II) and Cd(II) sorption. For this purpose, the model system composed with H3PO4-Pb2+-Cd2+ medium was selected and applied with various amounts of both heavy metal salts. The results revealed that sorption capacity of the sorbent was higher for Pb2+ cation than in the diluted phosphoric acid (20% H3PO4) for all periods. The absorption of toxic metal ions was measured by atomic absorption spectroscopy. Different physical and chemical analysis techniques such as Fourier Transform infrared, scanning electron microscope, DTA, and XRD showed that natural state of zeolite in a diluted phosphoric acid (20% H3PO4) system underwent protonation and hydroxylation to produce additional OH- groups that are active in the sorption process and no destruction was observed in the structure.