The use of activated carbon obtained from pistachio shells in the removal of crystal violet from aqueous solutions

This study investigates the potential of peanut shells, an agricultural waste, to be used as adsorbents in the removal of synthetic dyes from aqueous solutions by transforming them into a high value-added product. In this study, raw peanut shells were carbonized by heat treatment in an ash furnace for 1 hour and then ground into adsorbents. Furthermore, to increase adsorption capacity, the raw material was carbonized after being treated with chemicals such as H2SO4, H3PO4, HCl, and NaOH for 24 hours; however, it was found that acid activations reduced the efficiency by disrupting the adsorbent structure, while basic activation (NaOH) provided only limited improvement. Therefore, experimental studies were focused on carbonized peanut shells without chemical activation. In batch system experiments, the effects of adsorbent dosage, initial dye concentration, and contact time on removal efficiency were investigated. The optimum adsorbent dose was determined as 0.6 g/100 mL, and at this dose, a removal efficiency of 94.07% was achieved at a low pollution load concentration (21.76 mg/L). The obtained equilibrium data were applied to the Freundlich, four types of Langmur isotherms, Temkin, and Dubinin-Radushkevich isotherm models; it was determined that the process best fit the Langmuir Type-1 model (R2≥0.98) and that adsorption occurred as a single layer on a homogeneous surface. The maximum adsorption capacity (qmax) was calculated as approximately 7.20 mg/g. Kinetic studies showed that the adsorption rate followed a Pseudo-Second Order model (R2≥0.98) and that the process was chemically adsorbed. When the performance of the produced carbonized peanut shells was compared with commercial powdered activated carbon, it was observed that commercial carbon provided a yield of 63.26% using a lower dose (0.06 g). However, it was concluded that peanut shell charcoal could be considered an economical and environmentally friendly alternative, especially in the treatment of low-concentration wastewater, given its low cost and waste disposal potential. Keywords: Adsorption, Carbonization, Dye Removal, Equilibrium Isotherm, Chemical Kinetics.