Abstract
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Waste effluents of textiles and leather industries are seriously causing numerous health problems. Organic dyes are one of the major contaminants of industrial wastewater. Adsorption techniques can be used effectively to remove organic dyes and treat water for human consumption. In this work, we reported a rational multistep synthesis of mesoporous silica nanoparticles (MSNs) with selectively generated active inner/external surfaces. The functional groups were incorporated into the silica surface using a combination of co-condensation and post-grafting procedures. Both amine and sulfonic acid functional groups were used to produce a total coffer of MSNs inner/outer surface by amino or sulfonic moiety denoted as [N-MSNs]-N and [S-MSNs]-S, respectively. Furthermore, bifunctional groups were also synthesised by coffering the MSNs outer surface by sulfonic acid functional groups and the inner surface with amino functional groups or vice-versa denoted as [N-MSNs]-S and [S-MSNs]-N, respectively. The efficiency of the multiple grafting strategies was evaluated for the removal of cationic dye (methylene blue (MB)) from contaminated water samples using batch method mode. The physical adsorption parameters such as pH, initial concentrations of MB, exposure time and the effect of salt concentration was examined. Moreover, the adsorption kinetic models: pseudo first order, pseudo second order and interparticle diffusion were also applied for the collected data. The highest adsorption performance was accomplished by [N-MSNs]-S sorbent with 98% extraction efficiency, whereas the lowest adsorption efficiency was observed for [N-MSNs]-N sorbent. Increasing the electrolyte concentration had led to an increase in the adsorption efficiency of all nanomaterials containing sulfonic acid. An excellent extraction efficiency was obtained when the materials were applied to spiked real water samples. These adsorbents are promising for the removal of MB from wastewater on account of their high adsorption capacity and for their resistance to the presence of other unavoidable anions in the wastewater.