Kinetic and equilibrium modelling of adsorption of cadmium on nano crystalline zirconia using response surface methodology

• A novel nanoadsorbent, nano zirconia was synthesized and characterized.
• The process parameters were optimized by response surface methodology(RSM).
• Removal of Cd by nanoadsorbent was significant.
• The nanoadsorbent could be regenerated and reused several times to cut the cost of treatment.
• Process could be used for other metallic contaminants.

Nano zirconia has been employed for adsorption of cadmium from aqueous solution. Adsorption parameters were optimized using Box-Behnken design. Adsorption parameters Initial concentration, adsorbent dose and temperature were optimized. Optimized conditions were found out at initial concentration = 1 ppm, adsorbent dose = 4 g/l and pH = 7. The best-fit equations of linear and non-linear forms of kinetics and isotherm models were compared among themselves. Results exhibit that chi-square reduction method in Microcal origin curve fitting tool is better than Error analysis method of solver add in for determination of isotherm parameters. However, linear model explains the system best fit on the basis of R2adj in isotherm analysis. Experimental qe values were slightly closer to theoretical qe values in linear pseudo-second order model as compared to pseudo-first order non linear model. The system follows Langmuir isotherm model and pseudo-second order model. Thermodynamic parameter by partition and Langmuir constant method suggests that the system is spontaneous in nature.