Nickel doped Zinc oxide as a potential sorbent for decolorization of specific dyes, methylorange and tartrazine by adsorption process

Abstract Nickel doped zinc oxide (Ni 0.05 Zn 0.95 O) nanoparticles were tested as a possible potential adsorbent for the removal of specific dyes, methylorange and tartrazine, from an aqueous solution. The adsorbent was synthesized by forced hydrolysis conducted in polyol medium and characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, UV–vis spectroscopy and TEM images. Experiments showed that Ni doped ZnO nanoparticles were very efficient for the removal of TA and MO dyes and quasi-equilibrium reached in 30 min. The removal efficiency was found to be dependent on the initial dyes concentration and there is no significant effect of temperature on the adsorption process of dyes. Maximum adsorption capacity of dyes was achieved at pH 4 and 6 respectively for TA and MO. The adsorption capacity decreases proportionately to adsorbent dosage. Both the right match and accurate prediction of q e indicate that the pseudo second-order kinetic model better describes the adsorption of MO and TA dyes on Ni doped zinc oxide. The equilibrium data were analyzed by the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and intra-particle diffusion, mass transfer models, which revealed that Freundlich and Temkin isotherms were more suitable for describing MO and TA dyes adsorption than the other two isotherm models. Thermodynamic study showed that the adsorption was a physisorption, spontaneous and endothermic process.