Chemical behavior of organic compounds in the interface of water/dual-cation organobentonite

The sorption behavior of polar or ionizable organic compounds, such as p nitrophenol, phenol and aniline, in the water/organobentonite systems is investigated. Both adsorption and partition occur to the sorption of organic compounds to dual cation organobentonites. The separate contributions of adsorption and partition to the total sorption of organic compounds to dual cation organobentonites are analyzed mathematically in the first time. The factors to the contributions are also discussed. The results indicated that the contribution of adsorption and partition is related to the composition and ratio of dual cation surfactants exchanging onto the bentonite. The sorption of organic compounds to dual cation organobentonite is dominated by adsorption at low concentrations and by partition at high concentrations, making the organobentonites powerful sorbents for organic contaminants over wide range of concentrations.

Organobentonites as adsorbents for some organic pollutants and its application in wastewater treatment

Two organobentonites were synthesized by placing quaternary ammonium cationscetyltrimethylammonium bromide (CTMAB) and cetylpyridinium chloride (CPC) on bentonite bycation exchange. Their ability to adsorb phenol, aniline. nitrobenzene and p-nitrophenol were examined.The optimal conditions for organobentonites to remove the organic pollutants from waterwere studied. The removal rates for organobentonites to treat the organic compounds in water werefound to be over 8 times for the original mineral (untreated bentonite).The removal rates of organic pollutants and COD of wastewater were further improved by organobentonites in the presence of aluminum sulfate. The structure of organobentonites and the mechanism for their adsorption were investigated by X-ray diffraction (XRD) analysis, infrared spectra and BET surface area.

Partition of polycyclic aromatic hydrocarbons on organoben-tonites from water

A series of organobentonites synthesized by exchanging organic ration such as dodecyltri-methylammonium ( DTMA), benzyldimethyltetradecylammonium (BDTDA), cetyltrimethyl-ammonium (CTMA), octodeyltrimethylammonium (OTMA) on bentonite The optimal condition, properties and mechanisms for the organobentonites to sorb phenanthrene, anthracene, naphthalene, acenaphthene in water were investigated in detail. The partition behavior was determined for four polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, phenanthrene, anthracene and acenaphthene, from water to a series of organobentortites. The interlayer spacings and organic carbon contents of organobentonites, removal rate and sorption capacities for organobentonites to treat phenanthrene, anthracene, naphthalene, acenaphthene were correlated to the length of alkyl chains and the amounts of ration surfactant exchanged on the bentonite. Phenanthrene, anthracene, naphthalene, and acenaphthene sorption to organobentonites were characterized by linear isotherms, indicating solute partition between water and the organic phase composed of the large alkyl functional groups of quaternary ammonium rations. PAHs distribution coefficients (K-d) between organobentonites and water were proportional to the organic carbon contents of organobentonites. However, the partition coefficients ( K-oc) were nearly constants for PAHs in the system of organobentonite-water. The K-ocx of phenanthrene, anthracene, naphthalene, acenaphthene were 2.621 x 10(5), 2.106 x 10(5), 2.247 x 10(4), 5.085 x 10(4), respectively. The means K-oc values on the organobentonites are about ten to twenty times larger than the values on the soils/sediments, what is significant prerequisite for organobentonite to apply to remediation of pollution soil and groundwater. The sorption mechanism was also evaluated from octanol-water partition coefficients and aqueous solubility of PAHs. The correlations between 1gK(oc) and 1gK(ow), 1gK(oc) and 1gS for PAHs in the system of water/organobenotonites are also discussed.

Sorption of BTEX mixtures to organobenonites

Organobentonites synthesized by replacing the metal ions in bentonite with cetyltrimethylammonium(CTMA) or tetramethylammonium cation(TMA) were investigated for their behaviors to sorb benzene, toluene, p-xylene from water. The results served to distinguish the sorption mechanisms(adsorption or partition) of the two types of organobentonites. Bentonites modified with short-chain alkyl functional groups(e.g., TMA) sorb organic contaminants primarily by an adsorption process, in which the sorbed amount decreases with increasing steric hindrance of the organic compound and the process exhibits a competitive effect because of steric hindrance in multi-solute systems. In contrast, the sorption of contaminants to organobentonites modified with long-chain alkyl groups(e.g., CTMA) occurs by partition process without exhibiting a competitive effect, and the additional organic compounds may induce a cosorptive effect. In the latter case, the measured distribution coefficients of organic compounds between organobentonites and water(logK d) are positively correlated with the octanol-water partition coefficients of the compounds(logK ow ) and the sorption process exhibits no competitive effect in multi-solute systems.