Главная – Журналы – Химия в интересах устойчивого развития 2010 номер 6

A technique was developed to remove and immobilize the cadmium ions from simulated industrial effluents. The cadmium ions were removed from industrial effluents by applying most economical method of sorption under certain physicochemical conditions. Removal of cadmium ions from industrial effluents using silica sand (originated from Ravi River) was studied to optimize the physicochemical conditions for maximum removal. The range of pH and temperature was optimized to get maximum removal of metal ions. Maximum removal (94-98 %) of cadmium was achieved with pH 10 and at temperature 25 ^oC. Under optimized conditions with temperature range of 298-318 K, ΔH, ΔS and ΔG₂₉₈ for 200 mg/L solution were -71.10±3.8 kJ/mol, -220.2±11.5 J/(mol · K) and -6.70±0.4 kJ/mol, respectively, and for 250 mg/L solution thermodynamic entities were ΔH = -108.7±5.7 kJ/mol, ΔS = -335.7±17.5 J/(mol · K) and ΔG₂₉₈ = -9.64±0.4 kJ/mol. This removal required certain physicochemical conditions; therefore, there were chances of desorption of the adsorbed metal ions under changed physicochemical conditions in final disposal. It was necessary to stabilize/immobilize sorbed metals ions by converting this "secondary waste" in a stable vitreous material having high resistance to leachibility. Such stabilization/immobilization of sorbed metal ions was obtained by converting the silica sand along with the sorbed cadmium ions into the glass matrix to prevent leaching/mobilization in final disposal under natural conditions. Stability of sorbed metals ions in final matrix was tested by desorption attempts in acidic and basic media and in ground water as well.