Removal of reactive red dye 198 by modified apricot kernel shell derived-activated carbon bio-composite: kinetics, equilibrium, and thermodynamics

Nowadays, due to the reduction of fresh water resources and the increase in demand in the world, the removal of various pollutants, such as dyes, from industrial wastewaters to reuse them has received much attention. In this research, activated carbon (AC) was synthesized by the chemical activation of apricot kernel shell, and then, this adsorbent was modified by iron-containing functional groups (Fe-AC) and used as an adsorbent to remove reactive red dye 198 from the aqueous medium. The properties of these adsorbents were identified using BET, EDX-SEM, and FT-IR analyses. The results of equilibrium data showed that the adsorption process is single-layer and the maximum adsorption capacity of AC and Fe-AC absorbents is equal to 192.6 mg/g and 277 mg/g, respectively. The increase in adsorption capacity after modification is due to the positive adsorption sites of iron (O-Fe+) on the surface of the modified adsorbent, which adsorb the reactive dye red 198 by electrostatic mechanism. Also, the physical adsorption due to the porous structure of the adsorbent is effective in the adsorption of reactive red dye on the Fe-AC adsorbent. The analysis of kinetic data with different kinetic models showed that the pseudo-second-order kinetic model is consistent with the experimental result. The spontaneity and exothermic nature of the adsorption process were determined by determining the thermodynamic parameters. The successive cycles of adsorption and desorption indicate the ability to regenerate and reuse the synthesized adsorbent, which can be a suitable option for use in industrial dimensions.