Abstract
Highly porous hydrophilic silica aerogels (SAs) are potential excellent adsorbents in aqueous media, which are generally synthesized via a standard sol–gel method followed by the relatively complex and dangerous supercritical fluid drying process. Herein, a facile and novel synthetic method applying ambient pressure drying technology for the rapid preparation of hydrophilic SAs is reported, which are soaked by metal cations without the need of traditional surface modification and supercritical fluid drying process. Chemical and physical properties of the hydrophilic SAs were characterized and compared with a trimethylchlorosilane (TMCS) modified hydrophobic silica aerogel. Besides the integrity and low shrinkage of the as-prepared products, Fourier transform infrared (FTIR) spectra and integrated thermal analyzer (ITA) results revealed the presence of hydroxyl groups as well as the absence of multitudinous hydrophobic groups on the silica surface after soaking. Field emission scanning electron microscope (FE-SEM) and Brunauer–Emmett–Teller (BET) measurements confirmed the mesopores inside the aerogel skeleton. Among the tested metal cations, the Mg2+ soaked SAs demonstrated the best pore properties (pore diameter 9.35 nm and pore volume 1.09 cc/g) while the Fe3+ soaked ones got the biggest surface area (855.62 m2/g) in contrast to other metal cations. Rhodamine B and Methylene blue solutions are used to check the absorption ability of the SAs in aqueous media, where the best adsorption capacity for Rhodamine B and Methylene blue reached 2.8 mg/g and 40.4 mg/g, respectively, showing a potential application in aqueous pollutant removal.
Highlights
Organic dyes, which are widely used in the textile, paper, and cosmetics industries, have been considered as one of the major pollutants in wastewater (Cheng et al, 2014; Yu et al, 2015)
The synthesis routes of different metal cation–soaked silica aerogelsSilica Aerogels for Dye Removal (SAs) and TMCS-modified SA are shown in Scheme 1
For the TMCSmodified SA, 24 h is needed for the solvent exchange and another 24 h for the surface modification, and the metal cation–soaked SAs only need 24 h altogether, which significantly decreases the preparation time
Summary
Organic dyes, which are widely used in the textile, paper, and cosmetics industries, have been considered as one of the major pollutants in wastewater (Cheng et al, 2014; Yu et al, 2015). We report a facile surface hydroxyl modification method for the synthesis of hydrophilic silica aerogel monoliths by applying metal cations as the soak solutions followed by a modified APD technology This method could exempt the utilization of organosilane reagents as well as the hydrophobic modification course, and shorten the modifying time from 2 days to 1 day. Oxidation of the organic groups (-CH3) on the silica surface was characterized by means of thermogravimetric analyses (TGA) (STA 409 PC, NETZSCH, Germany) with a heating rate of 10◦C/min under an air flow from 25◦C up to 800◦C The values of their specific surface area, pore volume, N2 gas adsorption–desorption isotherm, and pore size distribution of the hydrophobic and hydrophilic SAs were determined by a Brunauer–Emmett–Teller (BET) N2 gas adsorption/desorption apparatus (TriStar II plus, Micromeritics, USA) via weighing about 100 mg of powder at 77 K in liquid nitrogen. The theoretical values of the adsorption capacity were calculated from the slopes and intercepts of the plots of ln(qe − qt) vs. t, t/qt vs. t, and qt vs. t0.5 (Huang X. et al, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
