Oxidized Multiwalled Carbon Nanotubes as Adsorbents for Kinetic and Equilibrium Study of Removal of 5-(4-Dimethyl Amino Benzylidene)Rhodanine

The oxidized multiwalled carbon nanotube was used as efficient adsorbent for the adsorption of 5-(4-dimethyl benzylidene amino) rhodanine (DMBAR) from aqueous solutions. The effect of solution pH, initial dye concentration contact time, temperature and sorption time on DMBAR removal ability was studied. The equilibrium sorption isotherms have been analyzed using different model such as Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich models. The experimental data well fitted with Freundlich and Langmuir isotherms with correlation coefficients more than 0.97 and adsorption capacity of 15.52 mg/g. The apparent calculated thermodynamic parameters (Delta H (0) = 24.592, 24.285, 15.954 Kj/mol, Delta S (0) = 118.581, 109.081, 80.005 j/k mol and Ea = 23.936, 23.744, 15.464 Kj/mol) support the conclusion that the DMBAR molecules are adsorbed by entropy-driven endothermic process. Among different conventional kinetic methods such as pseudo-first order, pseudo-second and intraparticle diffusion-order kinetic models, the adsorption process follows a second-order equation while the intraparticle diffusion is one of the rate-limiting factor.