The effective adsorption of Ni(II) and nitrate from aquatic systems by superparamagnetic MoS2/γ-Fe2O3 nanocomposites: Optimization through RSM-CCD design

Abstract

In this study, we examined the adsorption capacity (Qe) of superparamagnetic MoS2/γ-Fe2O3 nanocomposite with varying percentages of loaded γ-Fe2O3 nanoparticles (10 %, 20 %, and 30 %) for rapid and effective removal of Ni+2 and NO3- ions from water using response surface methodology combined with the central composite design (RSM-CCD). In essence, the adsorption properties of MoS2 3D ball-flower-like are increased by loaded γ-Fe2O3 nanoparticles by forming nanocomposite. Magnetic nanocomposites were checked under optimum conditions to remove Ni+2 and NO3- ions several times, which showed the material’s ability for regeneration and reuse as adsorptions. In experimental design, in the first step, we attempt to present models for the adsorption capacity (Qe) and removal percent and detect the influence of the parameters of the process using response surface methodology (RSM) by historical data. In the next step, with regard to the detection of impressive variables using obtained results in the previous step, the central composite design (CCD), by consideration of independent variables for the experimental design was done. By interpreting ANOVA and diagnostic plots, the effect of individual and binary effect of variables was discussed. The optimal conditions for maximizing adsorption capacity (Qe) and removal percent were predicted, and the validation of the predicted conditions was experimentally evaluated, which confirmed an agreeable agreement. The optimization of predicted conditions for Ni+2 and NO3- species are reported in the concentration of (0.49 mol.L−1) Ni+2 and (0.50 × 10-4 mol.L−1) NO3- with weight percent of γ-Fe2O3 = 26.72 % and 27.55 %, respectively. Predicted adsorption capacity (Qe) and removal percent of species concentration for Ni+2 and NO3- ions of optimized nanocomposite concluded 0.98, 9.59 × 10-5 (mg/g), 100, and 96 (%), respectively, which was confirmed by experimental research studies. To optimize experimental conditions, the Ni+2 and NO3- concentrations were o.5 and 0.5 × 10-4 mol.L−1, respectively. Furthermore, nanocomposites of MoS2/γ-Fe2O3 with a loaded dose of 26.72 % and 27.55 % γ-Fe2O3 for Ni+2 and NO3- were synthesized, respectively. The experimental of the adsorption capacity (Qe) and removal percent of species concentration for Ni+2 and NO3- ions concluded 0.95, 9.23 × 10-5 (mg/g), 96, and 93 (%) using MoS2/γ-Fe2O3, respectively.