A novel cerium-loaded cellulose nanocomposite bead (CCNB) is synthesized and tested for fluoride adsorption. The optimization of the process under the cooperative influence of different experimental variables was made employing response surface methodology (RSM). It is found from fractional factorial design (FFD) that among the different experimental variables, only adsorbent dose, temperature, and pH are significant. At the optimum condition (adsorbent dose 1 g/L, temperature 313 K, pH 3.0), a maximum fluoride adsorption of 94 % was observed for an initial fluoride concentration of 2.5 mg/L. A quadratic polynomial model equation based on central composite design (CCD) was built to predict the extent of adsorption. The result of the analysis of variance (ANOVA) shows high coefficients of determination (correlation coefficient; R2=0.9772, adjusted R2=0.9545, and adequate precision=18.1045) and low probability value (Prob > F, 0.001) which signifies the validity of the model. The equilibrium adsorption data conformed to the Tempkin isotherm, having higher R2 and lower SE value, among the Langmuir, Freundlich, and Tempkin equations at different temperatures. The adsorption data was found to fit well the second-order rate equation with film diffusion governing the overall rate. The activation energy value was calculated to be 16.74 kJ/mol. Fluoride can be eluted from fluoride-loaded CCNB using alkali. CCNB can be reused at least for five successive operations
Adsorptive removal by far is the most popular technique considering the operational simplicity, applicability in wide range of solution condition, and repetitive use of adsorbent via recycling. However, biopolymer, due to its degradable character and easy availability in nature, becomes a popular choice for preparation of new generation adsorbents. Cellulose being the most abundant one, on modification with transition metal, e.g., cerium, is used for fluoride removal. The bead form of the adsorbent in the present case facilitates its mechanical separation from solution.
Response surface methodology, one of the most popular design tools, is used to design parametric condition and to predict adsorption extent through some quadratic model developed.Dr. Dhiman Santra, Ph.D.
Water Air Soil Pollution
Water Air Soil Pollut (2015) 226:30