Principal Investigator: Valentine A. Nzengung (Georgia Institute of Technology)
Principal Investigator: Evangelos A. Voudrias (Georgia Institute of Technology)
Principal Investigator: J. M. Wampler (Georgia Institute of Technology)
Principal Investigator: Charles E. Weaver (Georgia Institute of Technology)
Sponsor: GWRI
Start Date: 1993-04-01; Completion Date: 1994-03-31;
Keywords: Organoclays, Quaternary ammonium ions, Clay minerals, Montmorillonite, Sorption, Sorption kinetics, Adsorption and exchange, Aromatic hydrocarbons, Organic wastes, Wastewater treatment
Description:
The second year of a two-year research project was used to complete a series of experiments on the sorptive properties of organoclays prepared from Wyoming montmorillonite by replacing the natural exchange ions of the clay by the quaternary ammonium ions TMA (tetramethylammonium), TMPA (trimethylphenylammonium), HDTMA (hexadecyltrimethylammonium), and BDTDA (benzyldimethyltetradecylammonium). Experiments on the kinetics of sorption of naphthalene and diuron by two of the organoclays show that equilibrium is attained quickly, in most cases within one or two hours. Of the organoclays studied, TMP A-montmorillonite has the greatest sorptive ability for naphthalene and is followed in order of decreasing sorptive ability by BDTDA-, HDTMA-, and TMA-montmorillonite. Naphthalene molecules are too large to penetrate the interlayers of TMA-montmorillonite. TMA-montmorillonite is much more effective as a sorbent for benzene than it is for naphthalene. For benzene sorption, TMP A-montmorillonite is most effective, followed in order by TMA-, BDTDA- and HDTMA-montmorillonite. Diuron molecules are too large to penetrate the interlayers of TMA- and TMPA-montmorillonite, so sorption of diuron by the organoclays is increasingly effective in the order TMA-, TMPA-, HDTMA-, and BDTDA-montmorillonite, the same as the order of increasing organic carbon content of the organoclays. The presence of methanol as a cosolvent reduces the sorption coefficients roughly in the manner predicted by the solvophobic theory of Rao et al. (1985), that is, the sorption coefficients decrease approximately in log-linear fashion as the methanol content increases, but there are irregularities in some of these relationships owing to swelling of the organoclays in the presence of the cosolvent. The swelling of these organoclays in methanolwater mixtures has been quantified by x-ray diffraction analysis of samples equilibrated with the solvent mixtures. Differences in the apparent value of the empirical constant, a, for different sorbate-sorbent pairs point to other interactions not accounted for by the solvophobic theory. Experiments with radiolabelled HDTMA-montmorillonite indicate that organoclays are stable in methanol-water mixtures and that appreciable loss of organic ions by exchange with inorganic cations is appreciable only if the concentration of inorganic cations is relatively large (~1 N).