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Continuous development of new technologies leads to increasing pollution of water, thus creating the need for new materials that could be used in the processes of its purification. Therefore, adsorbents prepared from agricultural waste, resins, silica gels, zeolites, clays, flying ash, aluminosilicates and other materials are being investigated as potential sorbents. Recently, research has focused on improving the adsorption capacity by modifying the material by binding or impregnating inorganic and organic molecules on the surface. In this paper, the kaolinite modification with amino acids, histidine and cysteine, was performed to improve the efficiency of adsorption of cadmium ion. Cation exchange capacity (CEC) of raw and modified kaolinite was determined by titration with methylene blue. The influence of operating parameters, such as adsorption time, pH value of the solution, initial metal concentration and temperature, on the capacity and adsorption efficiency were examined. Better agreement of experimental results with Freundlich's adsorption isotherm and the pseudo-second order kinetics model suggest that the adsorption of cadmium ions on the investigated adsorbents takes place by chemisorption mechanism. The change of Gibbs free energy has a negative value for both adsorbents, which shows that the adsorption process is spontaneous. The efficacy of cadmium removal from the aqueous solution onto histidine-modified kaolinite increased from 78.6% to 91.8%.

Za uklanjanje jona kadmijuma iz otpadnih voda korišćeni su alumosilikatni polimeri (geopolimeri) na bazi metakaolina kao prekursora i alkalni aktivator različitih koncentracija (2M, 4M, 6M i 8M NaOH/ Na2SiO3). Eksperimenti su vršeni u šaržnom procesu na sobnoj temperaturi (23±1 °C) pri različitim radnim parametrima: vreme adsorpcije, pH vrednost rastvora, početna koncentracija metala i masa adsorbenata. Utvrđeno je da je optimalna pH vrednost za sve adsorbente iznad 6,0. Efikasnost adsorpcije raste sa porastom pH vrednosti rastvora. Sa povećanjem početne koncentracije kadmijuma raste adsorpcioni kapacitet i dostiže vrednost preko 200,0 mg/g. Ekperimentalni rezultati su pokazali dobro slaganje sa Freundlich-ovom adsorpcionom izotermom i modelom pseudo-drugog reda. Karakterizacija geopolimera urađena je pomoću rendgenske difrakcije (XRD), skenirajuće elektronske mikroskopije (SEM) i infracrvene spektroskopije sa Furijeovom transformacijom (FTIR).