elnaz rezaei-aghdam

In the present study, natural and synthetic adsorbents were used to remove nickel ions through the adsorption process. First, TiO2 nanoparticles (NPs) were prepared through the sol-gel method. The synthesized samples were then characterized using X-ray diffraction spectroscopy (XRD), Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherms (BET). The influences of different operational parameters including adsorbate content, pH, adsorbent concentration, contact time, ionic strength, and stirring speed were also explored. According to the results, the pseudo-second-order kinetic model showed the best performance in evaluating the experimental data when using both adsorbents. The adsorption of nickel cations by the thin film membrane on the surface of TiO2 NPs is a rate-determining step of the removal reaction. The removal rate constants of nickel ions from aqueous solutions by TiO2 NPs and pomegranate peel were evaluated to be 0.013 and 0.018 g mg-1 min-1, respectively. The thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were also determined. Nickel removal processes in all cases were endothermic and spontaneous. The removal mechanism also followed physical adsorption. Equilibrium data were fitted with Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. The results showed that the adsorption of Ni2+ on TiO2 NPs and pomegranate peel followed Freundlich and Temkin isothermal models, respectively. Based on the calculated removal percentage, TiO2 is a better adsorbent for removing Ni2+ from the aqueous medium as compared to pomegranate peel.

This study focuses on the utilization of ZnO (as synthetic) and mango peel (natural adsorbent)  to remove blue 221 dye from aqueous solutions. First, ZnO nanoparticles (NPs) were synthesized and detected using the descriptor-based techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), N2 adsorption/desorption isotherms (BET), and X-ray diffraction (XRD). Various operational parameters including adsorbent concentration, pH, adsorbent dose, contact time, and stirring speed were investigated. The obtained kinetic results demonstrated great compatibility of the pseudo-second-order model with the experimental data. The effects of thermodynamic parameters were calculated to confirm the endothermic, spontaneous and physical nature of adsorption process. Langmuir and Freundlich isotherm models were utilized to fit the obtained equilibrium data. Freundlich model was found sufficient to explain the adsorption of blue 221 dye by ZnO NPs and mango peel. The results indicated that the ZnO NPs performed better in blue 221 dye removal as compared with mango peel. The mean size of ZnO NPs was found to be 22.16 nm. The specific surface area of ZnO NPs was obtained 26.85 m2.g-1 and pore volume and pore-size were 0.0581 cm3.g-1 and 1.22 nm, respectively. The maximum adsorption capacity of blue 221 dye on ZnO NPs and mango peel was estimated as 133.33 and 476.19 mg.g-1, respectively.