Application of waste peanut shells to form activated carbon and its utilization for the removal of Acid Yellow 36 from wastewater

A low cost activated carbon was prepared from agricultural waste, peanut shells (PnsAC), using H3PO4 followed by pyrolysis at 650 degrees C under nitrogen environment and used as a precursor to remove Acid Yellow 36 (AY-36) dye from wastewater. Batch experiments were conducted to study the effects of pH (2-11), adsorbent dose (2-6 g L-1), and initial AY-36 concentration (100-250 mg L-1). Equilibrium adsorption isotherms, kinetics, and thermodynamics were investigated. The experimental data were analyzed using isotherm models Langmuir, Freundlich, Redlich - Peterson, Sip, and Toth. The kinetics of dye adsorptive removal was studied with pseudo-first-order, pseudo-second-order, and intra-particle diffusion model. Equilibrium study revealed that Freundlich isotherm model described best the experimental data. The kinetics of dye adsorption was found to conform to the pseudo-second-order kinetics with a correlation coefficient value of 0.999. Thermodynamic study revealed that the adsorption process was endothermic and spontaneous. Overall, results obtained indicated that the chemisorption likely dominated the adsorption of AY-36 on PnsAC.