Modeling the diffusion of acid dyes on activated carbon

The project was designed to study the removal of color from aqueous solutions using adsorption techniques. The feasibility of activated carbon as an adsorbent for the removal of three acid dyes, namely Acid Blue 80 (AB80), Acid Red 114 (AR114) and Acid Yellow 117 (AY117), from effluents was investigated. The adsorption equilibrium isotherms were characterized and batch kinetic studies were carried out to identify the controlling factors of the mass transfer adsorption rate in three single component systems and three binary component systems.; The Ideal Adsorbed Solution Theory (IAST) with different isotherm equations, namely Langmuir, Freundlich, Redlich-Peterson, Langmuir-Freundlich equations, was applied to predict the binary component equilibrium systems. The IAST model gave a satisfactory prediction of multicomponent competitive adsorption equilibria. Moreover, the accuracy of the multicomponent isotherm prediction using the IAST depended on the quality of the fit of single component parameters.; Several mathematical models were investigated describing kinetic experimental results for the single component batch systems. Two single resistance models, one based on external mass transfer only and another based on intraparticle diffusion only, were analyzed but achieved only limited success. A numerical unreacted shrinking core film-pore diffusion model, based on external mass transfer and pore diffusion was developed to predict the performance of agitated batch adsorbers. Moreover, a further development utilizing solid phase diffusion into the film-pore diffusion model, film-pore-surface diffusion model was developed to improve the correlation of the film pore diffusion model at high activated carbon mass system.; However, the unreacted shrinking core film-pore-surface diffusion model could not provide a good correlation in the low initial dye concentration system. Therefore, another two-resistance model based on the external mass transfer and homogeneous solid phase diffusion (HSDM) was investigated. The HSDM can be used to describe experimental data with a high degree of accuracy for a range of carbon mass and initial dye concentration systems for extended periods of time. Finally, two multicomponent mass transfer adsorption models, multicomponent HSDM, were developed by combining the HSDM with the IAST model and the P-factor model. The models successfully correlated the concentration decay curves of the three binary batch adsorption systems.