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

• Ni doped zinc oxide nanoparticles was synthesized by forced hydrolysis in polyol media.
• The as-prepared Ni doped zinc oxide adsorbent was very efficient for the removal of TA and MO dyes.
• Rapid decolorization of TA and MO dyes occurred in the initial stage of adsorption process.
• Freundlich and Temkin isotherms fitted data well and were best to describe adsorption of dyes on Ni doped ZnO adsorbent.
• Pseudo-second-order is the predominant kinetic process in adsorption of TA and MO dyes.

Nickel doped zinc oxide (Ni0.05Zn0.95O) 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 qe 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.

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