Mechanistic investigation of levofloxacin adsorption on Fe (III)-tartaric acid/xanthan gum/graphene oxide/polyacrylamide hydrogel: Box-Behnken design and Taguchi method for optimization

[Display omitted] •FXM was well-designed for levofloxacin removal from water.•Box-Behnken design and Taguchi method were used to optimize the adsorption process.•The maximum removal efficiency of 98.00% recorded in a short equilibrium time (∼2 min).•Adsorption mechanism was discussed based on fractal-like kinetic model and XPS analysis. Fe (III)-tartaric acid/xanthan gum/graphene oxide/polyacrylamide (FXM) hydrogel was synthesized and probed its effectiveness in removing levofloxacin from water. The hydrogel (FXM) was characterized by instrumental techniques. Brunauer-Emmett-Teller (BET) analysis showed a surface area of 161.85 m2/g and Barrett-Joyner-Halenda (BJH) analysis provided pore size of 3.41 nm, indicating mesoporous nature. The adsorption experiments (batch mode) showed the adsorption capacity of 154.83 mg/g in a short equilibrium time (∼2 min). The controllable factors (adsorbent dose, pH and initial concentration of levofloxacin) were optimized by response surface methodology (RSM) and Taguchi technique. Various isotherm models were employed to correlate the equilibrium data; Freundlich isotherm model fitted well with equilibrium data as compared to other models based on high R2 values (0.9975–0.9980) and low values of χ2 (0.004–0.005) for non-linear analysis. Classical kinetic and fractal-like kinetic equations were applied to fit the experimental data. The experimental data best fit with fractal-like pseudo first order equation and heterogeneity parameter was 0.531. Mechanism of adsorption of levofloxacin on FXM was discussed based on XPS analysis and ΔG° values. Reusability experiments were executed in five adsorption–desorption cycles and percent removal varied from 98.00 to 82.25%, demonstrating high potential of FXM for re-use.