Kinetic and thermodynamic studies of the removal of murexide from aqueous solutions on to activated carbon

The objective of this study was to assess the adsorption potential of activated carbon (AC) as an adsorbent for the removal of Murexide (Mu) from aqueous solutions. The influence of variables parameters including pH, amount of adsorbent, sieve size of adsorbent, temperature and contact time on Mu removal was studied. Following optimization of variables, the relation between concentrations of dye remained in aqueous and adsorbent has been evaluated using various adsorption isotherm models like, Langmuir, Freundlich, Tempkin, Harkins-Jura and Dubinin–Radushkevich. Thermodynamic parameters such as enthalpy (ΔH◦), and, entropy (ΔS◦), activation energy (Ea), sticking probability (S*), and Gibb’s free energy changes (ΔG◦) were also calculated. It was found from evaluated different thermodynamic parameters, viz., ΔH◦, ΔS◦ and ΔG◦ that the adsorption of Mu by AC was feasible, spontaneous and endothermic process. The kinetic studies suggest that the all process following pseudo second order kinetics and involvement of intera- particle diffusion mechanism. The results indicated that the intraparticle diffusion also is the rate limiting factor.