Adsorptive separation of cadmium from aqueous solutions and wastewaters by riverbed sand

Application of riverbed sand for the adsorptive separation of cadmium(II) from aqueous solutions has been investigated. Removal increased from 26.8 to 56.4% by decreasing the initial concentration of cadmium from 7.5 × 10−5 to 1.0 × 10−5 M at pH 6.5, 25 °C temperature, agitation speed of 100 rpm, 100 μm particle size and 1.0 × 10−2 NaClO4 ionic strength. Process of separation is governed by first order rate kinetics. The value of rate constant of adsorption, kad, was found to be 2.30 × 10−2 per min at 25 °C. Values of coefficient of mass transfer, βL, were calculated and its value at 25 °C was found to be 1.92 × 10−2 cm/s. Values of Langmuir constant were calculated. Values of thermodynamic parameters ΔG0, ΔH0 and ΔS0 were also calculated and were recorded as −0.81 kcal/mol, −9.31 kcal/mol and −28.10 cal/mol at 25 °C. pH has been found to affect the removal of cadmium significantly and maximum removal, 58.4%, has been found at pH 8.5. Process can be used for treatment of cadmium(II) rich wastewaters.