Paper Title
Statistical Optimisation of Defluoridation using Calcium Impregnated Activated Sludge as an Adsorbent: Batch Study and Mathematical Modeling

In this investigation, the de-fluoridation in water was investigated by using calcium impregnated activated sludge .Here activated sludge was the precursor for the preparation calcium impregnated activated sludge. The effect of chemically modified Ca-Activated Sludge(Ca-AS) as an adsorbent was carried out in de-fluoridation study. The different process parameters such as dose of adsorbent, contact time, temperature are optimized by applying two level three factor(23) CCD(Central Composite Design) with the help of Design Expert Software in Response Surface Methodology(RSM).Three important process parameters : adsorbent dose (1.0-2.0 g L-1) temperature (35-60 0C ), and contact time(40 -120 min) were selected as the independent variables, while the fluoride adsorption capacities were specified as dependent variables. The higher correlation coefficient(R2) 0.9762 implies the fitness to the response surface quadratic model.The optimum condition for fluoride adsorption onto Ca-AS was experimented and it was observed respectively 1.0 gL-1, 120 minutes and 600C.In this optimized condition the removal efficiency is achieved as 99.31%. Keywords - Fluoride; Adsorption; Calcium impregnated activated sludge; Response surface methodology; Desirability function