Removal of trivalent chromium ions by adsorption on hydrogels

The aim of this work is to study the performance of a hydrogel prepared by swelling a sodium polyacrylate-based polymer in excess distilled water for the removal of the inorganic pollutant chromium (III) in synthetic aqueous solution. Physicochemical characterization of the adsorbent by IR, XRD, SEM and EDAX showed that PANa gel is an amorphous, porous material rich in carboxylate groups. Swelling of PANa in water showed that the hydrogel has a fairly high swelling rate. Adsorption experiments showed that good Cr(III) extraction efficiency was obtained after 120 min stirring of the metal solution in a pH range varying between 4.5 and 6, for a concentration of 20 ppm at room temperature (25 2 C). The maximum adsorption capacity is around 108 mg Cr per g PANa. Total purification of the polluted solution is achieved by a very small amount of dry polymer. The thermodynamic study showed that the metal cation retention process is spontaneous and endothermic. The good adsorption performance can be attributed to the ionic exchange of carboxylate groups.