Adsorption of textile dyes on Pine Cone from colored wastewater: Kinetic, equilibrium and thermodynamic studies

In this paper, the adsorption of Acid Black 26 (AB26), Acid Green 25 (AG25) and Acid Blue 7 (AB7) onto Pine Cone (PC) was investigated in aqueous solution. Surface study of PC was investigated using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The effect of operational parameters such as adsorbent dosage, dye concentration, inorganic anion (salt), pH and temperature onto dye removal was studied. The intraparticle diffusion model, the pseudo-first order and the pseudo-second order were used to describe the kinetics data. Equilibrium isotherms were analyzed using Langmuir, Freundlich and Tempkin adsorption models. Thermodynamic parameters of dye adsorption were obtained. The experimental data fitted well to the pseudo-second order kinetics model for dyes. The results indicated that isotherm data of AB26 and AG25 followed Langmuir isotherm and isotherm data of AB7 followed Freundlich isotherm models. The thermodynamic data indicated that the adsorption was endothermic process. Dye desorption studies in aqueous solution at pH 12 showed that maximum desorption of 93%, 97% and 94.5% were achieved for AB26, AG25 and AB7, respectively. It can be concluded that PC could be effectively employed as an effective biosorbent for the removal of dyes.

Research Highlights
► The kinetics data of dye adsorption onto PC fitted well to the pseudo-second order model.
► The AB26, AB7and AG25 followed Langmuir, Freundlich and Langmuir isotherm models, respectively.
► The thermodynamic data indicated that the dye adsorption onto PC was endothermic process.
► Maximum dye desorption for AB26, AG25 and AB7 from PC was 93%, 97% and 94.5%, respectively.
► It can be concluded that Pine Cone could be used as an effective biosorbent to remove anionic dyes.