Sorption of Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) Compounds by Hectorite Clays Exchanged with Aromatic Organic Cations

Abstract

Abstract--Adsorptive-type organoclays, where hydrocarbons adsorb directly to the siloxane surfaces, were studied to find new organic cations and to determine the parameters that produce effective sorbents. Organoclays were prepared from hectorite by cation exchange with small, aromatic organic cation salt solutions. Trimethylphenylammonium (TMPA) chloride was obtained and iodide salts of commerciallyunavailable aromatic cations were synthesized and used to prepare organoclays. An aqueous mixture of benzene, toluene, ethylbenzene, and xylenes (BTEX) consistent with the composition of unleaded gasoline was used in sorption isotherms to compare the sorptive properties of the organoclays. Only the TMPA, methylphenylpyridinium (MPPyr), and trimethylammonium indan (Indan) organoclays were effective BTEX sorbents. Organoclays prepared from methylpyridinium (MPyr), trimethylammonium biphenyl (Biphenyl), and trimethylammonium fluorene (Fluorene) were poor sorbents. The MPPyr and TMPA organoclays preferentially sorbed ethylbenzene, whereas the Indan organoclay preferentially sorbed benzene and toluene. Langmuir-type sorption isotherms for the TMPA, MPPyr, and Indan organoclays implied surface adsorption, whereas linear isotherms suggested that partitioning was the sorptive mechanism for the MPyr, Biphenyl, and Fluorene organoclays. Water hydrating the small MPyr cation and the larger bulk of the Biphenyl and Fluorene cations may have blocked BTEX access to the interlayer siloxane surfaces. Although the rather bulky MPPyr and Indan cations produced effective organoclays, compact size and low hydration are organic cation properties that typically yield effective adsorptive-type organoclays.

Mild pre-heating of organic cation-exchanged clays enhances their interactions with nitrobenzene in aqueous environment

“…The above understanding of differences in thermal activation between HDTMA-, TEA-and BTMA-clays is interrelated also with the earlier idea (Jaynes and Vance 1999) that organic cations with larger size may block the access of an organic sorbate to the interlayer siloxane surfaces. Compact size and low hydration are organic cation properties that typically yield effective adsorptive-type organoclays (Jaynes and Vance 1999).…”

“…Sheng et al 1996;Jaynes and Vance 1999) and may make a further loss of residual water at 150°C easier; greater fraction of organic cation (i.e. in OC-90 as compared with OC-41) results even in a greater dehydration of a sorbent.…”

“…Both series of sorbents are considered to represent so-called "adsorptive" organoclays (Smith and Galan 1995;Jaynes and Vance 1999;Borisover et al 2001) since they are lacking the long-chain aliphatic fragments. By using these smaller-size organic cations (as compared with HDTMA), we intended to get the better understanding of the role of organic cations in sorptive properties of thermally treated organoclays.…”

Organoclay Sorption of Benzene as a Function of Total Organic Carbon Content

“…Organoclays synthesized with large R groups (with greater than 12 carbons in the chain) tend to sorb nonionic organic contaminants through partitioning, while organoclays synthesized with small R groups or benzyl groups tend to sorb contaminants through adsorption (1,9). In general, organoclays are many times more effective than their unmodified counterparts in the sorption of organic contaminants from water (1,6,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19).…”

Adsorption-Desorption of BTX (Benzene, Toluene and O-xylene) on Fe, Fe-Al Pillared Clay

“…Granular or powdered actived carbon is the most widely used adsorbent [4], but their use is usually limited due to their high cost. Over several decades, many researchers show their interests in searching for low-cost adsorbents with excellent adsorption characteristics, such as zeolites [5], organokaolinite [6], smectite [7], hectorite [8], organosilica [9], and montmorillonite [10] [11]. The pillared interlayer clay (PILC) attracts attention of many researchers, and constitutes one of the most widely studied series among the microporous materials with a wide range of potential applications in adsorption processes.…”