Vol. 2, Issue 5 (2017)
Central composite design analysis and optimization of cadmium adsorption from synthetic wastewater by avocado seed activated carbon
Author(s): Nkeng Severin Muluh
Abstract: This study examines the adsorptive removal of cadmium from aqueous solutions using chemically modified avocado seed activated carbon (ASAC). The prepared adsorbent was characterized using FTIR, Boehm titration, iodine number, pHpzc, proximate analysis and surface area, respectively. A two-level, four-factor central composite design (CCD) in response surface methodology (RSM) was utilized to optimize the effect of the four process variables namely initial concentration (100-200 mgL-1), adsorbent dosage (0.10-1.0 g), pH (3-8) and contact time (10-180 min) on cadmium removal from aqueous solution. Based on the design, a total of 30 adsorption experiments were performed and a quadratic model was developed linking the process factors to the response. Analysis of variance (ANOVA) was applied to assess the adequacy of the model. From the analysis, the model’s coefficient of determination (R2) of 0.9730 and F-value of 38.55 are indicative that the model is adequate and can be used to navigate the design space. The optimum conditions of initial concentration (200 mgL-1), adsorbent dose (0.1 g), pH (3.37) and contact time (100 min) were obtained from the desirability function. The adsorption equilibrium data were best described by the Jovanovic model. Finally, the pseudo second order kinetic model described the cadmium adsorption process best.