A biological-based adsorbent for a non-biodegradable pollutant: Modeling and optimization of Pb (II) remediation using GO-CS-Fe3O4-EDTA nanocomposite

Abstract

A new graphene oxide (GO)-derivative nanocomposite containing biological polymer (i.e. chitosan) was successfully fabricated and investigated for Pb (II) adsorption from aqueous solutions. The nanocomposite (NC) performance was evaluated under different conditions of adsorbent dose (1–18.51 mg), Pb (II) initial concentration (0.35–33.65 mg/L), pH (1.24–10.76), temperature (~ 28–52 °C), and time (~ 2.5–23 min). The process was modeled by the methods of CCD, ANFIS, and GRNN and optimized by the approaches of Derringer's desirability function (DF) and genetic algorithm (GA). Although all models indicated good predictions, ANFIS showed the best function (with R2 0.9998, RMSE 0.0026, MAE 0.0016, and AAD 0.0023) in modeling of Pb (II) adsorption by GO-Fe3O4-CS-EDTA NC. Moreover, GA resulted the following optimum conditions: adsorbent dose 9.50 mg, initial Pb (II) concentration 24.00 mg/L, pH 8.00, tempreature 49.32°C, and time 22.20 min in which 93.98% Pb (II) predicted to be removed. And a maximum adsorption capacity of 666.66 mg/g was calculated by the Langmuir model (R2 = 0.937) that was much higher than that of stated by using the recently developed adsorbents for Pb (II). The enthalpy changes (ΔH°) of −21.62 to −26.65, Gibbs free energy (ΔG°) of 15.90, and entropy changes (ΔS°) of 0.1259 revealed an endothermic and spontaneous nature of the process. The elimination of Pb (II) followed a pseudo second-order kinetic model (R2 = 0. 9437). The influence of co-existing ions on the adsorption of Pb (II) showed a negative significant effect (of 93% to 75%) only at high mixture concentration (> 10 mg/L).All in all, the high removal efficiency and adsorption capacity, selectivity, reusability (six times without significant breakthrough), and working in a normal pH value, make GO-Fe3O4-CS-EDTA NC as a potential adsorbent for in situ treatment of lead ions-containing aqueous solutions.