Removal of Reactive Black 5 dye from Aqueous Media using Powdered Activated Carbon – Kinetics and Mechanisms

Abstract

The textile industry is considered one of the major environmental polluters, primarily due to the quantity and composition of wastewater. It is therefore important to examine its different treatment methods. For this purpose, the isothermal adsorption of Reactive Black 5 dye on powdered activated carbon at 25(±)1) °C and 45(±1) °C was carried out to determine the effect of initial dye concentration, contact time and temperature on the adsorption process. In order to investigate the mechanism of adsorption of Reactive Black 5 dye on activated carbon, kinetic studies have also been carried out. Experimental data were analysed using a pseudo-first-order and pseudo-second-order kinetic models, as well as an intraparticle diffusion model. Standard Gibbs free energy values of the adsorption process were also calculated, while the morphological analysis of activated carbon before and after adsorption was performed using a scanning electron microscope. The efficiency of activated carbon as an adsorbent for Reactive Black 5 dye is evidenced by the fact that more than 60% of dye is adsorbed after 30 minutes regardless of initial concentration and temperature. The experimental data also showed that adsorption is kinetically controlled assuming a pseudo-second-order process, and that intraparticle diffusion is not the only process that influences the adsorption rate. Negative values of standard Gibbs free energy indicate that the adsorption reaction is spontaneous, while a higher negative value for temperature of 45 °C compared to 25 °C shows that a higher temperature is more energetically favourable for the adsorption of Reactive Black 5.

Keywords

• adsorption
• activated carbon
• reactive black 5
• kinetics
• intraparticle diffusion