Entropy and MTOPSIS assisted central composite design for preparing activated carbon toward adsorptive defluoridation of wastewater

Abstract Activated carbon-based adsorption has been hailed as one of the most promising processes for treating fluorine-contaminated water. Numerous techniques have been espoused previously for modeling and optimizing the activated carbon preparation process for adsorptive defluoridation of wastewater. This chapter demonstrates a new framework in this series based on the amalgamation of the multi-criteria decision-making method and response surface methodology. The multi-criteria decision-making and the response surface methodology design considered were modified techniques for order preference by similarity to ideal solution (MTOPSIS) and central composite design, respectively. A literature case of activated carbon prepared from coconut shell has been taken as a representative optimization problem in this study. Here, Brunauer–Emmett–Teller (BET) surface area, micropore volume, and fluoride removal by activated carbon were converted to an MTOPSIS score. Later, the MTOPSIS score (single output variable) was modeled in terms of H3PO4 concentration, carbonization time, and carbonization temperature (three input variables). The entropy concept was used to calculate the objective weights of activated carbon preparation criteria. The empirical model obtained within this scheme was statistically validated and put under optimization by the desirability approach. The optimum condition of H3PO4 concentration, carbonization time, carbonization temperature, and MTOPSIS score was estimated to be 4.51 mol/L, 4.15 hours, 49.26oC, and 0.9479, respectively, with overall desirability 1. This hybrid method resulted in 2.15% higher desirability and advocated 9.48% lower H3PO4 consumption as well as 43.8 min less carbonization time as compared to the optimum values previously reported. Such beneficial findings evidence that the suggested strategy can efficiently model and optimize the chemical activation-based activated carbon production process for adsorptive defluoridation of wastewater.