The fine fraction of the Tagaran natural clay (TC) from the Kurdistan region of Iraq-Sulaimani was characterized and used to remove Cd ions from industrial swage. Using XRF, XRD, SEM, and FTIR, the dominant clay mineral of the Tagaran clay mineral was identified as saponite, with minor amounts of chlorite. The clay was examined for its efficiency to adsorb and remove (Cd2+) in the presence of other heavy metal contaminants from Sulaimani industrial zone sewage by a batch method. The effect of initial pH, equilibrium time, temperature, clay dosage, and Cd2+ concentration was studied. Results were evaluated using Langmuir, Freundlich, Temkin, and Redlich-Peterson isotherms. The kinetics could be best fitted to pseudo-second-order reaction kinetic model. In addition, the activation energy and the amount of calculated and experimentally determined heavy metal loads were consistent. The thermodynamic studies showed spontaneous endothermic adsorption. The trioctahedral smectite (saponite) showed a good efficiency for the adsorption of Cd2+ from the real sample (up to 100%) which at least partly can be explained by cation exchange. Tagaran clay is a candidate material for the production of an adsorber material for removing Cd2+ from aqueous solutions.
Keywords: Cadmium; Isotherm; Saponite; Sewage; Tagaran natural clay.