Benzene, Toluene, m-Xylene Adsorption on Silica-Based Adsorbents

Abstract

It was proposed that incorporation of nitrogen groups on mesoporous silica pores would enhance its surface polarity and improve adsorption of gaseous BTX (benzene, toluene, and m-xylene). Among the popular list of mesoporous silica adsorbents, KIT-6 and SBA-15 were selected as a result of their superior textural properties, as well as because they are being widely reported in literature. After preliminary screening using toluene test, KIT-6 was chosen to have better affinity and therefore selected for Aptes (3-aminopropyl triethoxysilane) surface modification. Aptes modification was performed through the grafting method utilizing factorial design of experimental techniques to identify the effective process variable covering the parameters: Aptes concentration, reaction temperature, and reaction duration. The results of a statistical design of experiments using Minitab-15 showed that Aptes concentration was the only significant factor which affects the silica adsorbent BET surface area. Benzene adsorption was found to be highest on KIT-6 adsorbent, while m-xylene and toluene had their highest values on 0.006% Aptes adsorbent (KIT-6 modified with 0.006% v/v Aptes) relative to other adsorbents. m-Xylene had the highest adsorption relative to toluene and benzene on all modified silica adsorbents (0.006% Aptes, 0.33% Aptes, and 0.66% Aptes) except for 8% Aptes adsorbent. 0.006% Aptes adsorbent was selected as the best adsorbent for BTX adsorption.

Toluene Adsorption by Mesoporous Silicas with Different Textural Properties: A Model Study for VOCs Retention and Water Remediation

“…In addition, in the most recent literature, studies concerning the use of mesoporous ordered silicas for VOC adsorption were published, mainly focusing on silica surface functionalization with organic groups to improve VOC adsorption capacity [ 15 , 16 ]. For example, Zhou et al studied amino-functionalized spherical mesoporous silicas as potential toluene adsorbent materials.…”

Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel

“…The results display that a large amount of toluene was adsorbed at any given time and, at the simulated equilibrium condition, compared with methane, which may be caused by the different surface interactions. The silica gel adsorbent-toluene interaction is dominated by the hydrogen bond between the hydrogen atom bonds to the Si-OH and the aromatic delocalized pi electrons [25], which hold a much higher adsorption force than the Van der Waals force. Although the silanol groups can also interact with methane, the silica gel adsorption-methane interaction is so weak that the bands for adsorbed methane completely disappear when the temperature is over 213 K. This phenomenon was confirmed by Chen et al [26].…”

Silica Gel Impregnated by Deep Eutectic Solvents for Adsorptive Removal of BTEX from Gas Streams

“…They are commonly found in many waste streams, i.e., industrial wastewater [1] or waste gases [2]. They also occur on a large scale in natural gas [3] and biogas [4], from which they have to be removed before further processing due to their toxic nature and carcinogen character-shortening the lifetime of the catalysts, and having potential emission to the atmosphere during combustion processes [5,6].…”

“…Among the available technologies, one of the most popular is adsorption, due to its high efficiency without use of toxic chemicals, with the possibility of adsorbents regeneration. In the industrial process, silica gel [5], activated carbon [7], carbon molecular sieves, zeolites [8], activated carbon impregnated with polymers, and polymeric adsorbents are the main adsorbents used for the removal of BTEX from the industrial gas streams [2]. Ideal adsorbents should be characterized by high selectivity and sorption capacity for BTEX as well as high stability after many adsorption-desorption cycles.…”