Adsorption study of bisphenol-A and chlorpyrifos onto nanobentonite intercalated with magnetite and sodium alginate: kinetics and isotherm models

Despite the fact that a great number of researches have been dedicated to the adsorptive removal of hazardous contaminates such as organic micropulltants, it is still highly desirable to develop novel nanosorbents/nanocomposites with high adsorption uptake capacities. In the present work, a novel nanocomposite (N-Bent-NFe3O4-Sod.Alg) was designed and assembled from magnetic Fe3O4 nanoparticles (NFe3O4), nanobentonite (N-Bent) and sodium alginate (Sod.Alg) to apply as an effective nanosorbent for the removal of two selected organic pollutants, namely Bisphenol-A (BPA) and Chlorpyrifos (CPS), from contaminated water samples. The characteristics of this newly developed nanocomposite were explored using the following techniques, Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area determination and high-resolution transmission electron microscopy (HR-TEM). This work also explored the parameters influencing adsorption process, including the pH of solution, contact time, initial concentration of pollutant in the sample, as well as the nanocomposite mass dosage. Maximum removal efficiency values (R% = 92.21% and 88.33 for BPA and CPS, respectively) were achieved at pH 7.0, using 20.0 mg L−1 initial concentration of BPA and CPS at 20 °C and 80.0 min contact time. The data from kinetic studies fitted well to the pseudo-second-order kinetic model with R2 = 0.990 and 0.992 for BPA and CPS, respectively. Among the investigated isotherm models, Langmuir showed the best fit with the adsorption process and demonstrated a monolayer adsorption pattern of the selected organic pollutants. In the case of BPA and CPS adsorption from water samples, and according to the Langmuir model, the characterized values of qmax were 28.94 and 29.17 mg/g, respectively. The newly developed (N-Bent-NFe3O4-Sod.Alg) nanocomposite can be listed out as an efficient and environmentally friendly alternative for the removal of organic pollutants from aqueous media.