Insight into preparation of activated carbon towards defluoridation of waste water: Optimization, kinetics, equilibrium, and cost estimation

The present investigation highlights the optimization of preparation conditions of activated carbon developed from Cocos nucifera towards fluoride removal from wastewater. Activated carbon was prepared through chemical activation using phosphoric acid (H3PO4). Central composite design (CCD) was used to examine the effect of three variables: H3PO4 concentration, carbonization temperature and time on the three responses: surface area, micropore volume and fluoride adsorption capacity. Activated carbon prepared under optimized conditions possessed a surface area of 941.45 m2 g−1 and micropore volume of 0.401 cm3 g−1. It was characterized by FTIR and SEM. The fluoride removal process was further investigated by studying the effect of pH, temperature, initial fluoride concentration, time, adsorbent dose and agitation speed. The maximum removal of fluoride was found to be 94.4%. The adsorption equilibrium data well fitted into Langmuir isotherm in comparison to Freundlich isotherm. Kinetic study revealed that the surface adsorption as well as intraparticle diffusion is the rate limiting step for fluoride sorption onto adsorbent. The low cost incurred in its production signifies its commercial exploitation as adsorbent. Therefore, the activated carbon prepared statistically from Cocus nucifera could be employed as an effective tool for fluoride adsorption from wastewater.