Amine Modification of Silica Aerogels/Xerogels for Removal of Relevant Environmental Pollutants

Abstract

Serious environmental and health problems arise from the everyday release of industrial wastewater effluents. A wide range of pollutants, such as volatile organic compounds, heavy metals or textile dyes, may be efficiently removed by silica materials advanced solutions such as aerogels. This option is related to their exceptional characteristics that favors the adsorption of different contaminants. The aerogels performance can be selectively tuned by an appropriate chemical or physical modification of the aerogel’s surface. Therefore, the introduction of amine groups enhances the affinity between different organic and inorganic contaminants and the silica aerogels. In this work, different case studies are reported to investigate and better understand the role of these functional groups in the adsorption process, since the properties of the synthesized aerogels were significantly affected, regarding their microstructure and surface area. In general, an improvement of the removal efficiency after functionalization of aerogels with amine groups was found, with removal efficiencies higher than 90% for lead and Rubi Levafix CA. To explain the adsorption mechanism, both Langmuir and Freundlich models were applied; chemisorption is most likely the sorption type taking place in the studied cases.

Silica Aerogels/Xerogels Modified with Nitrogen-Containing Groups for Heavy Metal Adsorption

“…This suggests that the surface of the adsorbents can be considered homogeneous and that the adsorption process is due to the interaction at active surface sites—the amine functional groups. This result is expected [ 30 , 31 ] and corroborates the predictions from the hard and soft acids and bases theory. Notable exceptions to this trend are obtained for the systems A_A with nickel and X_3A with copper.…”

“…Each of them is summarized in Table 1 . Formulations A and B were introduced by the authors in an earlier work [ 31 ].…”

“…Organically modified silica aerogels and xerogels were prepared using the procedures previously reported by the authors [ 29 , 30 , 31 ]. In sum, the precursors are mixed in methanol and, then an aqueous oxalic acid solution (1 M) is added to enhance the hydrolysis of precursors.…”

“…Fan [ 28 ] prepared a disulfide bridged silica xerogel for the same application. The authors have also reported silica-based aerogels and xerogels containing those functional groups [ 29 , 30 , 31 ]. Despite having similar modifications, in the aforementioned studies, the adsorption capacity reported differ significantly, due to the importance of the procedure and composition of the silica backbone.…”

Reactive Mesoporous pH-Sensitive Amino-Functionalized Silica Nanoparticles for Efficient Removal of Coomassie Blue Dye

“…Silica is one of the most important inert porous and mesoporous nanomaterials that have large pore sizes and strong chemical stability, besides the presence of terminated silanol groups on their surfaces that facilitate their surface modifications to increase their applicability in the medical and environmental field [9][10][11][12]. The silanol groups can be modified for excellent selectivity toward specific pollutants [13]. The mesoporous silica fulfills most of the criteria to be used as adsorbents for large-molecule organic and inorganic pollutants [14][15][16].…”