Adsorption of Direct Yellow 4 Dye on the Silica Prepared from Locally Available Sodium Silicate

Abstract

In this study the ability of removing direct yellow 4 dye (DY4) from aqueous solutions using silica as adsorbent was examined. The silica was prepared from locally available sodium silicate. The effect of various experimental parameters contact time, amount of silica used, pH, ionic strength and temperature were investigated in a batch adsorption technique. The obtained experimental data shows that, the adsorption of direct yellow 4 dye was increased directly with increasing concentration, amount of silica, added sodium chloride and temperature in optimum pH (7) and equilibrium time of 45 min. The kinetic data were analyzed through pseudo first-order, pseudo second-order and intraparticle diffusion models. The pseudo second-order model best represented adsorption kinetics. Additionally, this study used the Langmuir, Freundlich and Temkin isotherms to describe equilibrium adsorption and calculating thermodynamic values. The equilibrium adsorption of direct yellow 4 on silica is best fitted in the Langmuir isotherm (R2 =0.981).