Process Optimization Study of Zn2+ Adsorption on Biochar-Alginate Composite Adsorbent by Response Surface Methodology (RSM)

Abstract

A novel biochar alginate composite adsorbent was synthesized and applied for removal of Zn²⁺ ions from aqueous solution. Kinetics, equilibrium and thermodynamic studies showed the suitability of the adsorbent. From a Langmuir isotherm study, the maximum monolayer adsorption capacity of the composite adsorbent was found to be 120 mg/g. To investigate the effect of process variables like initial Zn²⁺ concentration (25–100 mg/L), adsorbent dose (0.4–8 g/L) and temperature (298–318 K) on Zn²⁺ adsorption, response surface methodology (RSM) based on a three independent variables central composite design of experiments was employed. A quadratic model equation was developed to predict the relationship between the independent variables and response for maximum Zn²⁺ removal. The optimization study reveals that the initial Zn²⁺ concentration and adsorbent dose were the most effective parameters for removal of Zn²⁺ due to higher magnitude of F-statistic value which effects to a large extent of Zn²⁺ removal. The optimum physicochemical condition for maximum removal of Zn²⁺ was determined from the RSM study. The optimum conditions are 43.18 mg/L initial metal ion concentration, 0.062 g adsorbent dose and a system temperature of 313.5 K. At this particular condition, the removal efficiency of Zn²⁺ was obtained as 85%.