A greener one-pot synthesis of nanostructured SiO2 for the efficient emerging contaminant removal from simulated textile wastewater

Abstract

Emerging contaminants are a group of chemicals that havethe potential to enter the environment and cause potentially adverse effects onthe ecosystems and their components. Currently, the interest in achieving theremoval of emerging contaminants from water bodies and wastewater has grownconsiderably, which is reflected in several publications on the synthesis of nanomaterialscapable of adsorbing them. Among emerging pollutants,methylene blue (MB) is a widely used model dye for the study of adsorptionprocesses on nanomaterials. In this work, we report a facileand greener one-pot synthesis of SiO2 nanoparticles (SiO2NPs) than the classical Stöber method,involving a cheaper Si source than TEOS, only water as solvent, and shorterreaction times under neutral conditions at room temperature, i.e. a new sol-gelstrategy with favorable greenness attributes. A multi-technical characterization of SiO2NPs (XRD,FTIR, UV-vis DR, TEM, SEM, EDS, Z-potential, and N2 adsorption-desorption isotherms at 77 K)confirmed the formation of spherical NPs, with amorphous and polydispersenature, negatively charged surface, and mesoporous structure. Several batch adsorptionexperiments of MB were performed by varying pH, contact time, model dyeconcentration, and SiO2NPs dosage, and the kinetic and thermodynamic behavior ofthe removal reaction was elucidated. It was determined that the adsorptionprocess followed a pseudo-second-order kinetic model and a Langmuir isothermmodel. SiO2NPs showed high efficiencytowards MB removal after 30 min of contact time (maximum adsorption capacity =165.6 mg g-1) and high reusability for up to seven cycles withoutappreciable loss of adsorption efficiency. In addition, this work reports thefirst successful application of SiO2NPs as acationic dye nanoadsorbent under simulated conditions of real textilewastewater (high pH, very high concentration of MB and dissolved salts, and high COD), proving that NPsare suitable for conditioning water resources contaminated with industrial dyes.