Immobilization of glucose oxidase on montmorillonite clay: hydrophobic and ionic modes of binding

106

Abstract--New pillared clay-based adsorbents have been prepared by incorporating a nonionic surfactant of general formula C~z_~4H25_290(CH2CHzO)sH (commercial name, Tergitol 15S-5), during the synthesis of the aluminum hydroxide pillaring reagent. Different loadings of surfactant have been examined. The presence of the surfactant enhanced the adsorption capacity of the clay toward 3-monochlorophenol from aqueous solution. On the basis of adsorption results for a series of clays with increasing surfactant loadings, the best adsorbent was obtained at a surfactant loading of 255 mg/g of clay. At this loading, the surfactant occupies the micropores, as well as the mesopores and the external surfaces of the pillared clay. Analysis of the adsorption isotherms for 3-monochlorophenol, 3,5-dichlorophenol, 3,4,5-trichlorophenol and pentachlorophenol at different pH shows that the most energetic adsorption sites are the surfactant-occupied micropores between pillars. Additional binding of chlorinated phenols occurs at surfactant sites on external surfaces and mesopores. Upon calcination at 500~ the clay is converted to a conventional aluminapillared clay with a basal spacing near 16 A. This calcined product can be reused as an adsorbent for chlorinated phenols by readsorbing fresh surfactant. The recycled adsorbent exhibits performance properties comparable to the original adsorbent. These results demonstrate the feasibility of utilizing a surfactant-modified pillared clay as a recyclable adsorbent and combustion catalyst for environmental pollutants.

Section: Introductionmentioning

confidence: 99%

Adsorption of Chlorinated Phenols from Aqueous Solution By Surfactant-Modified Pillared Clays

Michot

1991

106

“…Organic cations possessing long-chain alkyl groups are particularly able to impart the hydrophobic quality to the mineral surface (Pashley et al, 1985). Such clay-organic complexes are able to sorb molecules which themselves are hydrophobic by what has been called hydrophobic bonding (McBride et al, 1977;Garwood et al, 1983;Wolfet al, 1986;Mortland, 1985, 1986;Mortland et al, 1986). This process is essentially a non-polar interaction between the organic phase of the clay organic complex and the hydrophobic organic molecule.…”

Section: Introductionmentioning

confidence: 99%

Pentachlorophenol Sorption by Organo-Clays

Boyd

1988

356

180

Abstract--Several clay organic complexes were prepared by placing organic cations on the exchange sites of smectite clays and studied as sorbents for pentachlorophenol (PCP). The organic cations used ranged from very hydrophobic in nature (e.g., dioctadecyldimethyl § (DODMA+) -and hexadecyltrimethyl § (HDTMA+)-ammonium) to those having minimal hydrophobic properties, such as tetramethylammonium § (TMA+). In general, the more hydrophobic the cation on the smectite the greater the uptake of PCP from water. For the very hydrophobic clays (DODMA § and HDTMA+-smectite) the uptake of PCP was via non-polar interactions between the alkyl (e.g., -C18) groups on the organic cation and PCP. In a mechanistic sense, this interaction appeared to be similar to a partitioning process between water and the organic phase of the clay-organic complex. The organic phases of DODMA+-smectite were about 10 times more effective than the organic matter of natural sediments for removing PCP from water. For those organo-clays containing small organic cations (e.g., TMA+), the organic phase consisted of separate small organic moieties, such as the methyl group. This phase did not act as an effective partitioning medium despite a significant carbon content, and very little PCP was taken up. Results from this study suggest the possibility of treating soils and subsurface materials with large hydrophobic organic cations to enhance the sorptive properties of these natural materials.

“…Long-chain alkyl ammonium cations adsorbed on the clay, for example, change the nature of the surface from hydrophilic to hydrophobic. Consequently, whereas enzyme (protein) adsorption on smectite is ordinarily pH dependent (coulombic effects), the enzyme may be strongly bound by clay-organic complexes such as hexadecyltrimethyl-ammonium-smectite (HDTMA+-smectite) by hydrophobic binding which is completely independent of pH (Garwood et al, 1983;Boyd and Mortland, 1985a, 1985b. Such interaction involves hydrophobic portions of the enzyme interacting with the hydrophobic alkyl group on the mineral surface.…”

Section: Introductionmentioning

confidence: 99%

Clay-Organic Complexes as Adsorbents for Phenol and Chlorophenols

Mortland

Sun

Boyd

1986

435

181

Abstract--Several clay-organic complexes were synthesized by placing quaternary ammonium cations on smectite by cation exchange. They were then examined for their ability to adsorb phenol and several of its chlorinated congeners. The organic cations used were: hexadecylpyridinium (HDPY+), hexadecyltrimethyl ammonium (HDTMA+), trimethylphenyl ammonium (TMPA+), and tetramethylammonium (TMA+). The complexes containing long-chain alkyl (hexadecyl) groups were the most hydrophobic and adsorbed the phenols from water in proportion to their hydrophobicities, which increase with chlorine addition (phenol < chlorophenol < dichloropohenol < trichlorophenol). With n-hexane as the solvent, different adsorption was found which depended on the type and degree of solvent interactions with the compound and the clay-organic complex. Thus, the amount of adsorption of these phenols on clay-organic complexes was dependent on the relative energies of adsorbent-adsorbate and adsorbate-solvent interactions.