Adsorption of 4-Nitrophenol onto Iron Oxide Bentonite Nanocomposite: Process Optimization, Kinetics, Isotherms and Mechanism

Despite its importance in chemical industry, 4-Nitrophenol (4-NP) is a persistent organic pollutant that has serious effects on the ecosystem. In the present study, Box–Behnken design in response surface methodology was used to optimize the adsorption process parameters for the maximum 4-NP removal at 30 ℃ using Fe 3 O 4 /Bt NC. The regression model results suggested that the optimum adsorbent dosage, initial concentration, pH and contact time were 0.3182 g, 85 mg/L, 11 and 137.2 min, respectively. The regression model showed an optimum removal of 100%, while 99.5% removal was obtained from batch experiments at the optimum conditions suggested by the regression model, which confirm the model validity. The adsorption data best fitted to Freundlich isotherm model and Pseudo second-order kinetic model suggesting the existence of physical and chemical interaction between the fabricated composite and 4-NP. FTIR analysis suggested that the adsorption mechanism included an electrostatic attraction and the formation of new chemical bonds. Obtained results suggest that Fe 3 O 4 /Bt NC can be an effective adsorbent for complete 4-NP removal at the indicated optimum conditions. Graphical Abstract