Adsorption performances of nickel oxide nanoparticles (NiO NPs) towards bromophenol blue dye (BB)

In this research, the microwave-assisted method was used for the synthesis of nickel oxide nanoparticles (NiO NPs). The synthesized NiO NPs were characterized using Brunauer–Emmett–Teller surface analyzer, transmission electron microscopy, X-ray diffraction and pHZPC. We found that the specific surface area, total pore volume, average pore diameter and pHZPC of the prepared NiO NPs were 78.37 m2/g, 0.068 cm3/g, 34.92 Å and 8.1. Also, we examined the adsorption of Bromophenol blue (BB) using NiO NPs at different temperatures (303, 318 and 333 K). Further, we evaluated the impacts of adsorbate concentration, agitation time, temperature and pH. Indeed, the adsorbate concentration of 300 mg/L, temperature of 333 K and pH of 12 at 24 h were observed to be the ideal experimental conditions. Isotherm models of Freundlich and Langmuir were employed and the obtained results revealed that the equilibrium data were described well by Langmuir equation. The highest monolayer capacities of this adsorption were found to be 58.48, 79.37 and 93.46 mg/g at 303, 318 and 333 K. Kinetic models of first order, second order and intra-particle diffusion were used to examine the kinetic experimental data. Thermodynamic factors were determined and the values obtained designate that the adsorption of BB on NiO NPs is endothermic and non-spontaneous processes.