Adsorption of Gas Phase Organic Compounds by Swellable Organically Modified Silica

Abstract

Swellable organically modified silica (SOMS) is a sol–gel derived material that spontaneously expands >2.5× upon contact with organic liquids, absorbing 7.8 mL/g. Adsorption of gas-phase volatile organic compounds by SOMS was measured to examine how the capability to swell affects capacity and rate of organic vapor absorption. Static adsorption capacities of SOMS for organic vapors at saturated vapor pressure ranged from 0.7 to 1.05 g/g, which was higher than values for other sorbents (powdered activated carbon, Amberlite XAD-4, Tenax TA, OptiPore, and organophilic zeolite). Rates of adsorption by SOMS were similar to those of XAD-4, a porous polymer with similar surface chemistry, and slower than that of activated carbon. Sequential coadsorption of multiple compounds by SOMS was measured, yielding enhanced adsorption capacity attributed to adsorption-induced pore expansion. The sequential adsorption of phenol and acetone vapor (p = p 0) led to a total capacity of 5.7 g/g. Adsorption of organic vapors was not selective and fully reversible in all cases. The hydrophobicity of SOMS strongly excludes water and water vapor. Fluorescence recovery after photobleaching was used to measure in-particle diffusion constants of fluorescein before and after adsorption for vapor and liquid.

A Review of Volatile Organic Compound Contamination in Post-Industrial Urban Centers: Reproductive Health Implications Using a Detroit Lens

“…An active area of research is the development and characterization of new sorbent materials that address shortcomings of traditional sorbents (e.g., humidity effects, performance goals above ppb ranges). One example is swellable organically modified silica, which has been used in applications ranging from sorbing dissolved aqueous species [ 126 ] to concentrating organic ligands for engineered resins [ 127 , 128 ] and has also been investigated as a potential air purifier sorbent [ 129 , 130 ]. Soil vapor extraction has also been used extensively [ 131 ].…”

Effect of High Temperature on Swellable Organically Modified Silica (SOMS) and Its Application for Preferential CO Oxidation in H2 Rich Environment

“…[43][44][45] The peak observed at 50 ppm corresponds to the presence of Si-OCH 3 groups resulting from the precursor used (BTEB). These observations can be supported by the fact that the 29 Si NMR spectra also confirmed the presence of distinct species with Si-CH 3 and Si-OCH 3 groups. Furthermore, the peaks at 15 and 29 ppm can be assigned to the α-CH 2 and β-CH 2 species respectively, of the aryl group of BTEB, the precursor used to synthesize SOMS.…”

“…This is a hydrophobic, mesoporous, absorptive material which can "swell" while selectively absorbing organics dissolved in water or air. [29] It belongs to a class of materials known as bridged polysilsesquioxanes. [30] The surface area and pore volume of SOMS in its swollen state is very high.…”

“…C and 29 Si MAS NMR spectra are reported in Figure 2. Note that, in the following sections, heat treated SOMS is denoted as HSOMS-X where X is the temperature of heat-treatment.…”

“…Note that, in the following sections, heat treated SOMS is denoted as HSOMS-X where X is the temperature of heat-treatment. For example, HSOMS-100 refers to SOMS heat-treated at 100 o C. In the 29 Si NMR spectra (Figure 2a), three distinct chemical shifts (∂) were obtained at 9 ppm, -59 ppm and -67 ppm. These peaks were found to remain intact up to 400 o C, however, at 500 o C, the features at 9 ppm and -59 ppm seemed to have disappeared whereas, a broad peak at -67ppm remained.…”