Wastewater contains a variety of pollutants that are basically classified into organic such as dyes and inorganic substances. The contamination of surface and groundwater with synthetic dyes is a serious environmental problem and is a threat to human beings. These dyes could be cationic, anionic, or neutral. For instance, many industries use pigments to color their products such as textiles, plastics, paper, and so forth. The discharge of the produced wastewater effluents into the environment is worrying for toxicological and aesthetical reasons. Therefore, their removal from wastewater is of great interest. All processes for removing such pollutants from wastewater have their own limitations. However, the adsorption process is recognized to be an effective and economic process for cleaning wastewater. In addition, adsorptive remediation of wastewater on metal-oxide-based nanoparticles has been reported in the literature extensively. Recent studies showed significant awareness of metal oxides as nanoadsorbents and nanocatalysts (nanosorbcats) for cleaning wastewater, due to their individual chemical and physical properties, which make them ascendant to the conventional adsorbent/catalysts.
Herein, in this study, the employment of in-house prepared nickel oxide silica-based (SBN)s and commercial nickel oxide (NiO) nanoparticles as nanosorbcats for cleaning up synthetic wastewater was investigated. Different model molecule pollutants; mainly methylene blue (MB) and bromocresol green (BCG) exemplifying cationic and anionic pollutants, respectively, were removed from synthetic wastewater samples by SBNs and NiO nanoparticles. Batch isotherm adsorption studies in addition to kinetics and thermodynamics were performed for the removal of both dyes from wastewater. The experimental adsorption data has been modeled using the Sips adsorption isotherm model to understand the adsorption behavior of these molecules. Fast adsorption kinetics of both nanoparticles have been observed; NiO nanoparticles took 60 minutes to reach saturation of BCG while SBNs took only 2 minutes for the case of MB. Moreover, both nanoparticles have shown high uptakes of about 99% and 96% at low concentrations of MB and BCG. Furthermore, thermodynamic parameters like the changes in free Gibbs energy (ΔG), enthalpy (ΔH), and entropy (ΔS) of the system were calculated. The catalytic activity behavior of spent nanoparticles was investigated via thermogravimetric Analysis (TGA), to check out the applicability of the nanosorbcats concept.
Consequently, the regeneration, uptake saturation capacities and the performances of spent SBNs and commercial NiO nanoparticles after each adsorption cycle were studied and compared with the virgin ones. The detailed findings of this study will be discussed further during the poster presentation.