Defluoridation using pinecone-based activated carbon: Adsorption isotherm, kinetics, regeneration, and co-ions effect investigation

In this work, cheap and locally available pinecones of Pinus kiseya were used as a precursor to prepare activated carbon using single-step KOH activation for the removal of fluoride from water. The prepared activated carbon?s BET surface area, and total pore volume, were determined as 972.13 m2 g-1 and 0.469 cm3 g-1, respectively. Batch adsorption studies were evaluated at different contact times, solution pH, adsorbent dose and concentration to obtain the optimum conditions for maximum adsorption. The adsorption data were fitted with the isotherm models (Langmuir, Freundlich ad Temkin isotherm model) and the adsorption kinetic models. The experimental data were found to best fit using the Langmuir isotherm which confirmed the formation of a monolayer coverage with a maximum adsorption capacity of 2.845 m2 g-1. The adsorption kinetics was well described by the pseudo-second-order model. A study on the effects of co-existing ions showed that fluoride adsorption capacity was observed to decrease in the order: CO3 2- > SO4 2- > NO3 - > Cl-. The regeneration studies were investigated to determine the reusability of the spent adsorbent. In summary, these findings demonstrated substantial evidence that the activated carbon can be prepared from P. kiseya cones as an eco-friendly adsorbent for the removal of ions such as fluoride from water.