Application And Progress Of Organic Bentonite In Wastewater Treatment(6)

- Jan 15, 2018 -

Organic Bentonite removal of organic matter in water performance, mechanism, law and influencing factors

 

As early as 1949, Jorda n et al. [45] synthesized organobentonites first and organic bentonites were used to adsorb organics in water and wastewater after the 1960s [11-13]. After the organic bentonite adsorption of organic matter in water performance mechanism and influencing factors research reports gradually increased, laying the foundation for the application of organic bentonite in wastewater treatment.

 

Woel et al [56] modified the montmorillonite with fatty ammonium salt to enhance its ability to adsorb organic pollutants. It was found that the bentonite modified with different carbon chain quaternary ammonium salts showed better interlayer spacing, pore volume and inner surface than the original soil Increase, thereby improving the performance of bentonite adsorption of organic matter in water. Wo lfe et al [57] also studied the organic montmorillonite adsorption of organic pollutants, respectively, with eicosyl ammonium salt, dodecyl diammonium salt, propyl ammonium salt modified montmorillonite, a comparative study of Adsorption Properties of Acetone, Benzene, Butanol, Trichloromethane, Dimethyl Phthalate, Hexanoic Acid, Nitrobenzene, Octanol, Phenol and Toluene in Three Organic Montmorillonites and Na-montmorillonite , The adsorption isotherms of 11 organic compounds were plotted. The results showed that the adsorption properties of natural montmorillonite could be as good as that of activated carbon with appropriate modification. Xiangyang et al. [58] obtained CTM AB-montmorillonite, CPB-montmorillonite and CTM AB by montmorillonite with cetyltrimethylammonium bromide (CTM AB) and cetylpyridinium bromide (CPB) The adsorption capacity of CTM AB-montmorillonite and CPB-montmorillonite to water-soluble benzene, toluene and ethylbenzene was found to be one to two orders of magnitude higher than that of the original soil. The adsorption was characterized by the non-polar fatty chain end extraction Organic and inorganic contaminants in the water enter the montmorillonite layer that is splayed by the cationic organic ammonium.

 

In the past five years, Zhu Li has made a systematic and in-depth study on the properties, mechanism and influencing factors of organobentonites in the removal of organobentonites [51-54, 59-63], using DTM AB ), Cetyltrimethylammonium bromide (CTM AB), cetylpyridinium bromide (CPB) and octadecyltrimethylammonium bromide (OTM AB) modified bentonite to prepare a series of organic bentonite; research The performance, mechanism and influencing factors of benzene, toluene, ethylbenzene, aniline, nitrobenzene, phenol, p - nitrophenol, α - naphthylamine, β - naphthylamine and α - naphthol in water were studied. The results show that the organic bentonite removal of organic matter in water is far higher than the native soil; organic bentonite removal of organic matter in water and the saturation adsorption capacity of the quaternary ammonium cationic surfactants used in the modification of species, carbon chain length and concentration , But also with the nature of the organic matter itself (polarity, octanol-water partition coefficient, etc.) and its interaction with organic bentonite.

 

Our research shows that: (1) the interlayer spacing of organic bentonite and the removal rate of organic compounds increase with the increase of the carbon chain of the surfactants used in the modification; for example, organic bentonite modified with the same concentration of surfactants can remove water The capacity of the organics is as follows: O TM AB-bentonite> CTM AB-bentonite> D TM AB The spacing of bentonite beds and the removal of organics in water generally increases with the amount of surfactant added during the modification, When the amount of cationic surfactant exceeds the cation exchange capacity of the original soil, the removal rate and interlayer spacing no longer increase with the amount of surfactant added; for example, the interlayer spacing of a series of C TM AB-bentonites and the removal of organics in the water Bentonite> 80CTM AB-bentonite> 60CTM AB-bentonite> 40C AB AB-bentonite> 20C AB AB-bentonite [54]; (3) the same organic bentonite removal of organic matter in water is also related to For example, the removal rates of five organic compounds in the same CTM AB-bentonite are in the order of α-naphthylamine ~ β-naphthylamine ~ α-naphthylamine → nitrobenzene> aniline [53]. a-naphthylamine> p-nitrophenol> nitrobenzene-phenol> aniline [54]. In addition, the organic solubility or octanol-water partition coefficient (Kow) is also an important factor affecting the organobentonite adsorption of organic matter. Under normal circumstances, the greater the organic Kow, that is, the poorer the water solubility, the greater the removal rate of organic bentonite.

It is very important to understand the characteristics, mechanism and rules of organic bentonite adsorbing organic matter in water to the application of organic bentonite in water treatment and environmental remediation. The results show that organic bentonite sorption to organic matter in water is related to the type and nature of the cationic surfactant used in the modification and the nature of the organics themselves.

 

In general, bentonites modified with short carbon chain cations exhibit non-linear adsorption and strong solute absorption of nonpolar organic compounds, which is the result of organic bentonite adsorption on organic surfaces. However, Cation-modified bentonites linearly adsorb nonpolar organic compounds and weak solute absorption, that is, adsorption (Sorptio n), is the result of Partitio n partitioning of organics in a long carbon chain organobentonite hydrophobic medium. Smith et al. [64] modified bentonites with quaternary ammonium cations of ten different carbon chains and investigated the adsorption of CCl4 on these organobentonites. The results showed that the organic bentonite modified with tetramethyl-, trimethylbenzyl-, or triethylbenzylammonium adsorbed strongly solute CCl4 and the isothermal adsorption curve was nonlinear. However, Alkyl dimethyl-, dodecyl trimethyl-, tetradecyl trimethyl-, hexadecyl trimethyl-, hexadecyl dimethyl benzyl-modified organobentonites to CCl 4 The adsorption shows weak solute absorption, noncompetitive adsorption, isothermal adsorption curve is linear. Smith et al [65] modified bentonite with dodecyltrimethylammonium bromide (DTM A) and decyltrimethylammonium (DTM DA) to produce DTM A-bentonite And DTM DA-bentonite (double cationic organic bentonite). DTM A-bentonite was found to be noncompetitive and weak solute absorption of CCl4. The adsorption isotherm was linear, while that of DTM DA-bentonite was competitive adsorption and solute absorption for CCl4. Isothermal adsorption curve was nonlinear. Smith et al. [66] also studied the adsorption of non-ionic organic pollutants on bentonites modified with either one or two quaternary ammonium salt cations. One or two quaternary ammonium salts were cation exchanged into bentonite to study the adsorption of CCl 4, trichloroethane and benzene by biquarterly ammonium organobentonites. The first organic cation is a tetramethylammonium, methylethylammonium and trimethylbenzylammonium with a short carbon chain. The second organic cation has a (C H3) 3 -N + -R structure and R is a C 12 -C 18 alkyl . Sorbitan adsorbed on the organic bentonite modified with the first organic cation is mainly caused by Adsorption. When the bentonite is modified by the second organic cation at the same time, the amount of exchange Is 20%, 40%, 60% of the CEC of bentonite, the long chain alkyl has two effects; one long chain alkyl interferes with the short carbon chain quaternary ammonium salt modified bentonite surface of non-ionic solute Surface adsorption; the other is long carbon chain alkyl adsorption (Sorptio n) of non-ionic solute created a distribution medium. Thus, the double quaternary ammonium organobentonites prepared by cationic modification of long carbon chains and short carbon chains have the property of a distribution medium with strong adsorbents.

Organic bentonite adsorption of organic matter in water is also related to the nature of the organic matter itself. A study by Julie et al. [67] showed that the adsorption isotherms of CTM AB-bentonite for benzene, toluene, and ethylbenzene were linear, as the distribution of organics between the water-organic phase (long carbon chain quaternary ammonium salt) n). The removal of phenol and nitrophenol is mainly Adsorption and the isotherm adsorption curve is non-linear. The distribution and adsorption of polar organic compounds such as aniline and nitrobenzene can be simultaneously Occurs, the isothermal adsorption curve is linear.


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