Application of a novel bi-functional nanoadsorbent for the simultaneous removal of inorganic and organic compounds: Equilibrium, kinetic and thermodynamic studies

The notion of hazardous pollutants removal in environmental water resources has gained widespread attention in the recent years. Generally, the pollutants have irreparable effects on aquatic ecosystems, organisms and human beings. Considering that, within the current study, a bi-functional nanoadsorbent Fe3O4@SiO2@NH2@SH was successfully synthesized for the simultaneous adsorption of two types of well-known contaminates namely heavy metals and pesticides. The physical and surface properties of the synthesized nanoparticles were characterized by XRD, FT-IR, SEM, TEM, BET and EDX analytical techniques. To evaluate the efficiency of the as-prepared adsorbent, influential parameters such as pH, adsorbate concentration, nanoadsorbent dosage and contact time were also investigated and optimized. Following on, the nanoadsorbent was then implemented for the simultaneous removal of Pb(II) and 2,4�dichlorophenoxyacetic acid (2,4�D) from the synthetic wastewater. The structural analysis revealed that Fe3O4@SiO2@NH2@SH nanoparticles have a core-shell spherical structure modified by both amine and thiol functional groups. The kinetic and isotherm studies underlined that the process of adsorption follows the second-order kinetic (R2 > 0.99) and Langmuir isotherm (R2 > 0.97) model. It was also found out that pH plays a key role in the adsorption system whose optimum value was determined to be 6. The thermodynamic studies showed that the adsorption process is of endothermic and spontaneous nature. Additionally, the results regarding the desorption process revealed that the nanoadsorbent could be used several times with almost no decline in the removal efficiency. Finally, it was concluded that bi-functional adsorbent could be potentially applied for the simultaneous removal of further inorganic and organic chemicals from various aqueous solutions. © 2018 Elsevier B.V