Study of low‐cost and high‐performance biomass activated carbon for phenol removal from wastewater: Kinetics, isotherms, and thermodynamics

Abstract

AbstractIn this study, biomass activated carbon (AC) has been prepared by CO2 activation from pine sawdust, and its ability to extract a model compound (phenol) from solutions was studied to estimate its purifying capacity on wastewater. Ninety minutes and 800 °C were selected as the proper conditions on account of both good pore distribution and feasible yield. Thermogravimetric analysis, N2 adsorption/desorption, scanning electron microscope (SEM), and X‐ray diffractometer analyses were used to characterize the surface and textural properties. The contributions of CO2 activation to the evolution of porous structures, especially to the formation of micropores, were originated from the reaction of CO2–C at above 800 °C and the oxidizing effect on the residual volatiles after carbonization to reopen the blocked pores. The best fitted pseudo‐second‐order kinetic model, Langmuir and Temkin isotherm models, suggested that chemisorption might be the rate‐limiting step of the homogeneous and monolayer adsorption process. The diffusion of phenol into PS‐800‐90 was mainly controlled by film diffusion and intraparticle diffusion. The maximum monolayer capacity (qm) of PS‐800‐90 obtained by Langmuir model was 161.03 mg/g at 298 K. Spontaneous (ΔGo < 0) and exothermic (ΔHo < 0) nature of the adsorption process was obtained through thermodynamic study, indicating that the increase of temperature was unfavorable to adsorption. The Fourier transform infrared spectroscopy analysis of the fresh and spent AC coupled with pH experiments revealed that the main adsorption could be originated from H‐bonding and π–π stacking interactions between AC and phenol. The adherence of phenol on the surface of AC was also proved by SEM‐Energy Dispersive Spectrometer (EDS) results.