Types Of Organoclays Research Articles

Sorption of organic compounds of varying hydrophobicities from water and industrial wastewater by long- and short-chain organoclays

It is generally assumed that short-chain organoclays are better sorbents for non-ionic organic compounds than are the long-chain organoclays. We believe that the above statement is correct only for relatively hydrophilic or slightly hydrophobic compounds and that the opposite should be true for highly hydrophobic compounds, namely, that long-chain organoclays are expected to be superior to the short-chain analogs for sorption of highly hydrophobic materials. To verify our hypothesis, the sorption of six compounds with a range of log K ow values from 2.5 to 6 was studied on tetramethyltriammonium-(TMA) and octadecyltrimethylammonium-(ODTMA) bentonite, representing short- and long-chain organoclays, respectively. Compounds with low or medium hydrophobicities (log K ow 2.5–3.8) were more strongly sorbed on the short-chain organoclay, whereas the more hydrophobic compounds (log K ow 5.2–6.1) were better sorbed on the long-chain organoclay, in agreement with our hypothesis. The efficacy of organoclays in removing organic pollutants from the effluent of a pesticide producing plant was evaluated. Pesticide sorption from the wastewater was studied on both types of organoclays. It was found that both organoclays were able to remove organic pollutants from industrial wastewater, but solute uptake by short-chain organoclays was strongly depressed by competition, while long-chain organoclays were only slightly affected, if at all, by the presence of competing solutes in the industrial wastewater.

Nanocomposites of poly(trimethylene terephthalate) with various organoclays: morphology, mechanical and thermal properties

Three types of organoclay, 12C-MMT, 18C-MMT, and DK2-MMT, have been used to prepare poly(trimethylene terephthalate)(PTT)/organoclay nanocomposites via melt blending using a co-rotating twin screw extruder. The effect of different types of organoclays on morphology, thermal stability, static and dynamic mechanical properties was examined. The results of wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) suggest that different interaction between the different organoclays and the PTT matrix lead to different morphologies (intercalation or exfoliation) of the three types of nanocomposites. Thermogravimetric analysis (TGA) shows that the nanocomposites are more thermally stable than the neat PTT. Moreover, mechanical properties are improved for all the nanocomposites. Dynamic mechanical analysis (DMA) shows that nano-sized organoclay dispersed in PTT matrix enhances the storage modulus of the material and causes change of the α relaxation of PTT.

Polycarbonate nanocomposites: Part 2. Degradation and color formation

Polycarbonate nanocomposites were prepared using two different twin screw extruders from a series of organoclays based on sodium montmorillonite, with somewhat high iron content, exchanged with various amine surfactants. It seems that a longer residence time and/or broader residence time distribution are more effective for dispersing the organoclay. The effects of organoclay structure on color formation during melt processing were quantified using colorimeter and UV–Vis spectroscopy techniques. Color formation in the PC nanocomposites depends on the type of organoclay and the type of pristine clay employed. Double bonds in the hydrocarbon tail of the surfactants lead to more darkly colored materials than saturated surfactants. The most severe color was observed when using a surfactant containing hydroxy-ethyl groups and a hydrocarbon tail derived from tallow. Molecular weight degradation of the PC matrix during melt processing produces phenolic end groups which were tracked by UV–Vis spectroscopy. Greater dispersion of the clay generally led to higher reduction in molecular weight due to the increased surface area of clay exposed; however, for color, the situation is far more complex. Hydroxy-ethyl groups and tallow unit on the surfactant lead to more degradation. A selected series of organoclays based on synthetic clay Laponite ® and calcium montmorillonite from Texas (TX-MMT) were also prepared to explore the effects of the clay structure. Laponite ® and TX-MMT produce less color formation in PC nanocomposites than montmorillonite probably due to lower content of iron. Dynamic rheological properties support the trends of molecular weight degradation and dispersion of clay.

Poly(lactic acid) nanocomposites with various organoclays. I. Thermomechanical properties, morphology, and gas permeability

AbstractThe thermomechanical properties, morphology, and gas permeability of hybrids prepared with three types of organoclays were compared in detail. Hexadecylamine–montmorillonite (C16–MMT), dodecyltrimethyl ammonium bromide–montmorillonite (DTA‐MMT), and Cloisite 25A were used as organoclays in the preparation of nanocomposites. From morphological studies using transmission electron microscopy, most clay layers were found to be dispersed homogeneously in the matrix polymer, although some clusters or agglomerated particles were also detected. The initial degradation temperature (at a 2% weight loss) of the poly(lactic acid) (PLA) hybrid films with C16–MMT and Cloisite 25A decreased linearly with an increasing amount of organoclay. For hybrid films, the tensile properties initially increased but then decreased with the introduction of more of the inorganic phase. The O2 permeability values for all the hybrids for clay loadings up to 10 wt % were less than half the corresponding values for pure PLA, regardless of the organoclay. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 94–103, 2003

Polymerization compounding: Epoxy‐montmorillonite nanocomposites

AbstractA strategy to design intercalated montmorillonite nanocomposites has been explored. A commercial organoclay, 1.34 TCN (Nanocor Inc.), with bis(2‐hydroxylethy1) methy1 tallow ammonium, was modified by tolylene 2,4‐diisocyanate (TDI) and bisphenol A (BA). Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) results of unmodified and modified 1.34 TCN (1.34‐TDI‐BA) indicate that TDI and BA have reacted with hydroxy1 groups on the surface of 1.34 TCN and hydroxy1 groups in the interlayer of 1.34 TCN. Using a classical two‐stage cure process with diamine as curing agent, intercalated epoxy nanocomposites were prepared for both types of organoclays. XRD and TEM results showed that the basal spacing of clay in nanocomposites was 3.68 and 4.42 nm for 1.34 TCN and 1.34‐TDI‐BA, respectively. Dynamic mechanical analysis (DMA) was performed on both modified and unmodified organoclay composites. Modified organoclay composites were found to have enhanced storage moduli, particularly at temperatures higher than the glass transition, Tg, of the matrix. Glass transition temperatures extracted from linear viscoelastic data are found to be slightly higher for modified organoclay nanocomposites, indicating enhanced interactions between the modified organoclay and the epoxy matrix. These results were also confirmed by independent measurements of Tg using differential scanning calorimetry (DSC).

Cone Calorimeter Combustion and Gasification Studies of Polymer Layered Silicate Nanocomposites

Polymer composites based on organically modified phyllosilicates (organoclay) and poly(ethylene-co-vinyl acetate) (EVA) were prepared by melt processing to study their combustion behavior. Their degrees of dispersion and intercalation spacings as determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD) were typical of either a microcomposite or an exfoliated nanocomposite, depending on the type of organoclay. Combustion experiments showed that the microcomposite burns in the same way as pure EVA, whereas the heat release is reduced by 70−80% when nanocomposites with low silicate loadings (2−5%) are burned, because a protective charred ceramic surface layer is formed as a result of reassembly of the clay layers and catalyzed charring of the polymer. A chemical mechanism for this charring is proposed.

Organoclays for controlled release of the herbicide fenuron.

Organoclays were assayed as matrices in which to associate herbicides, with the aim of decreasing product losses that could give rise to water contamination from agricultural activities. Fenuron was selected as model of a very mobile and highly water-soluble herbicide. Two different organoclays of high (A-HDT) and low (H-C18) reversible fenuron sorption were selected. Herbicide-organoclay complexes were prepared from the two organoclays and with two different fenuron contents (20 and 40 g AI kg-1) and two different mixing times, so as to form a series of weak and strong complexes. The release of fenuron from those complexes into water and water/soil suspensions gave values of T50 (time to release 50% of the fenuron content) ranging from 0.3 min to 2400 h. The total fenuron released in these closed systems ranged from 48 to 80% of the fenuron in the complex. The organoclay type (high or low sorptivity) had the greatest influence on fenuron release, followed by the strong or weak complex, suggesting that herbicide-organoclay interactions are the main factors controlling release. Soil column leaching experiments showed fenuron-organoclay complexes to be effective in reducing the peak herbicide concentration in the leachate to a half (6 microns) or a quarter (3 microns) of that obtained from the free technical compound (12 microns). Herbicide lost through leaching was reduced from 78% for the free technical fenuron to 50-30%, depending on the organoclay used as carrier and the strength of the complex. Bioassay with ryegrass showed that the weak fenuron/H-C18 complex (40 g AI kg-1) gave the same herbicidal activity as technical fenuron. The potential suitability of low-sorptive organoclays for conferring slow-release properties on the fenuron complex has been demonstrated.

Use of Inorgano-Organo-Clays in the Removal of Priority Pollutants from Industrial Wastewaters: Adsorption of Benzo(a)Pyrene and Chlorophenols from Aqueous Solutions

AbstractBenzo(a)pyrene (B(a)P), and chlorophenols were sorbed from their respective aqueous solutions onto inorgano-organo-clays (IOCs). Cetyl pyridinium hydroxy-Al montmorillonite (CPC-hydroxy-Al montmorillonite), an IOC, containing only 11–12% surface organic carbon by weight, bound pentachlorophenol strongly, with an observed monolayer capacity of 0.08 mmole/g. The comparable value for granulated activated carbon (GAC) was found to be 0.12 mmole/g. On the other hand, cetyl pyridinium cation-exchanged montmorillonite (CPC-montmorillonite), containing 19.2% surface organic carbon by weight, did not bind pentachlorophenol as efficiently as did IOCs. For benzo(a)pyrene, CPC-hydroxy-Al montmorillonite was found to be a better adsorbent than GAC and CPC-montmorillonite. The significant difference in the sorption potential of the two types of surfactant-laden clays for pentachlorophenol and benzo(a)pyrene was probably due to the surface orientation of the adsorbed organic carbon. For 3,5-dichlorophenol, however, both types of organo-clays exhibited weak binding, which was probably due to the greater aqueous solubility of the dichlorophenol.

HPLC analysis of commercial alkyl and aryl quaternary ammonium compounds used in organoclay type rheological additives.

Mixtures of aliphatic and aromatic "quats" can be qualitatively identified in a one step chromatographic run. After separation on a strong cation exchange column, the eluted components are detected using a UV and RI detector system in series. The quaternaries present in organoclays (e.g., BENTONE type products) can also be identified by prior destruction of the silicate with hydrofluoric acid followed by chromatography of the residual quat fluorides.