1 Clays and Clay Minerals, Vol. 33, No. 4, 301-311, 1985. INTERACTION OF ALIPHATIC AMINES with . montmorillonite TO enhance adsorption OF. ORGANIC POLLUTANTS. TIMOTHY A. WOLFE, l TURGUT DEMIREL, AND E. ROBERT BAUMANN. Department of Civil Engineering, Engineering Research Institute Iowa State University, Ames, Iowa 50011. Abstract--X-ray powder diffraction studies were performed with propyl-, dodecyl-, and dodecyldiam- monium bentonites saturated with aqueous mixtures of eleven organic pollutants at concentrations of to 100%. The alkylammonium salt treatment separated the montmorillonite unit layers, which increased the interlamellar volume and exposed the interlamellar surfaces for adsorption of the organic pollutants.
2 Washing the salt-treated clays with distilled water removed excess, physically adsorbed al- kylammonium ions that could interfere with adsorption of the organic pollutants. adsorption isotherms conducted at organic pollutant concentrations of 100 and I000 rag/liter indicated the three alkylam- monium montmorillonites, especially propylammonium montmorillonite ,were effective adsorbents from aqueous solution, but to a lesser extent than adsorbents currently used in the water and wastewater fields. Key Words-- adsorption , Amine, Bentonite, montmorillonite , Pollutant, X-ray powder diffraction. INTRODUCTION Stul et al. (1979) were able to adsorb 9 to 330 milli- Organic chemicals in surface and ground-water sup- grams of hexanol and 40 to 530 milligrams ofoctanol plies have become a major environmental problem.
3 Per gram of d o d e c y l a m m o n i u m montmorillonite in adsorption by activated carbon is widely used to re- studies conducted over a wide range of alcohol con- c e n t r a t i o n s . These o b s e r v a t i o n s for d o d e c y l - move these pollutants from drinking water. Although clays have been recognized as adsorbents of such or- a m m o n i u m montmorillonite and suggestions by Weiss (1963) that dodecyldiammonium ions form pillars when ganic compounds, few studies have been conducted to adsorbed in the interlamellar space of montmorillon- determine whether certain clays could serve as prac- ite, led to the selection of these two a l k y l a m m o n i u m tical adsorbents in the treatment of water and waste- ions for exchange with montmorillonite in the present water.
4 Study. Furthermore, Barter and Millington (1967) re- Bentonite has had limited use as a coagulant in the ported relatively large free interlamellar volumes for purification of both water and wastewater (Olin and p r o p y l a m m o n i u m montmorillonite . Therefore, pro- Peterson, 1937; Olin et al., 1937; Olin et al., 1942). p y l a m m o n i u m montmorillonite was also used to de- Some clays have been investigated specifically to ad- termine the effect of amine chain length on the capa- sorb organic compounds from water supplies (E1-Dib bility of a l k y l a m m o n i u m montmorillonites to adsorb et aL, 1978; McBride et aL, 1977) and from waste- organic contaminants from an aqueous solution.
5 Water (Williamson et aL, 1964). Except for the study A major concern of the present study were the in- by McBride et al. (1977), these studies have not at- teractions between a l k y l a m m o n i u m clays and repre- tempted to alter the adsorption characteristics of clays sentative organic compounds included in the En- prior to their use. The literature dealing with interactions between al- vironmental Protection Agency's list of 129 priority k y l a m m o n i u m montmorillonites and organic com- pollutants (Keith and Telliard, 1979). Jordan et al. pounds suggests that modified montmorillonites may (1950) noted that a bentonite exhibiting high swelling be potentially effective adsorbents to improve water properties in water showed an aversion to water and a tendency to swell in various organic liquids after quality.
6 Cowan and White (1963) showed dodecylam- m o n i u m bentonite, in a series of ethyl- to octadecyl- reaction with appropriate organic a m m o n i u m salts. a m m o n i u m bentonites, to be the most active adsorbent Barrer and MacLeod (1955) found that exchange of tetramethyl- and tetraethylammonium ions opened up for mono- and dihydric phenols. Slabaugh and Carter (1968) reported adsorption of ~ 31 milligrams of meth- the laminae of the clay, and caused profound changes anol per gram o f d o d e c y l a m m o n i u m montmorillonite . in the sorption and the intercalation of organic mole- cules. In contrast to their reaction with untreated ma- terials, paraffins and aromatic hydrocarbons were free- Present address: Department of Civil Engineering, Cleve- ly adsorbed between the laminae of the organic-treated land State University, Cleveland, Ohio 44115.
7 Montmorillonites. Barter and Reay (1957) showed that Copyright 9 1985,The ClayMineralsSociety 301. 302 Wolfe, Demirel, and Baumann Clays and Clay Minerals sorbates having critical dimensions less than the initial analyses before and after removing excess, physically intersheet separation were intercalated in substantial adsorbed a m m o n i u m ions with a distilled water wash- amounts and that sorbates with larger critical dimen- ing. The amine content o f the centrifugate and wash- sions could also be i m b i b e d by expanding the clay water was determined using a Beckman carbon ana- structure further. lyzer, Model 915-A.
8 The intent o f the present investigation was threefold. First, montmorillonite separated from W y o m i n g ben- adsorption of organic molecules on tonite was interacted with propyl-, dodecyl-, and do- alkylammonium-treated bentonites d e c y l d i a m m o n i u m salt solutions to see how the al- adsorption isotherms were determined for aqueous k y l a m m o n i u m ions became attached and oriented solutions o f eleven organic pollutants and the alkyl- within the interlamellar space o f a pure smectite. Sec- a m m o n i u m - t r e a t e d montmorillonites; the results are ond, X-ray powder diffraction (XRD) experiments were reported elsewhere (Wolfe, 1981).
9 The organic pollu- conducted with three a l k y l a m m o n i u m bentonites sat- tants included butanol, hexanol, octanol, benzene, tol- urated with aqueous mixtures o f eleven different or- uene, nitrobenzene, phenol, chloroform, dimethyl- ganic pollutants to study the extent to which these phthalate, acetaldehyde, and acetone. The present organic molecules were intercalated and how the mol- investigation entailed X R D studies conducted i m m e - ecules became oriented in the interlameUar space. Third, diately after interacting aqueous mixtures of the or- the pure a l k y l a m m o n i u m montmorillonites from the ganic pollutants with a l k y l a m m o n i u m - t r e a t e d benton- first part were used to determine individual adsorption ires.
10 The a l k y l a m m o n i u m - t r e a t e d bentonites were isotherms with the eleven organic pollutants to predict prepared in large batch operations using the procedures whether the treated clays would be useful in removing described above for adsorption o f the amine salts on the pollutants from dilute aqueous solutions (Wolfe, montmoriUonite. 1981). The eleven organic pollutants were mixed with dis- EXPERIMENTAL PROCEDURES tilled water at concentrations o f , , , , , , , and 100% (by weight). Some o f the The clay used in this investigation was a W y o m i n g organic pollutant concentrations exceeded their solu- bentonite (Volclay-SPV) commercially available from bilities in water, but the wide range o f concentrations the American Colloid Company.