Carbon-based adsorbents for fluoroquinolone removal from water and wastewater: A critical review.

This review summarizes the adsorptive removal of Fluoroquinolones (FQ) from water and wastewater. The influence of different physicochemical parameters on the adsorptive removal of FQ-based compounds is detailed. Further, the mechanisms involved in the adsorption of FQ-based antibiotics on various adsorbents are succinctly described. As the first of its kind, this paper emphasizes the performance of each adsorbent for FQ-type antibiotic removal based on partition coefficients of the adsorbents that is a more sensitive parameter than adsorption capacity for comparing the performances of adsorbents under various adsorbate concentrations and heterogeneous environmental conditions. It was found that π-π electron donor-acceptor interactions, electrostatic interactions, and pore-filling were the most prominent mechanisms for FQ adsorption by carbon and clay-based adsorbents. Among all the categories of adsorbents reviewed, graphene showed the highest performance for the removal of FQ antibiotics from water and wastewater. Based on the current state of knowledge, this review fills the gap through methodolically understanding the mechanism for further improvement of FQ antibiotics adsorption performance from water and wastewater.

Arrangement Models of Keggin-Al30 and Keggin-Al13 in the Interlayer of Montmorillonite and the Impacts of Pillaring on Surface Acidity: A Comparative Study on Catalytic Oxidation of Toluene.

Acid-base reactivity is a key factor for understanding the interfacial geochemistry of clay minerals. Numerous studies showed the significant role of surface acidity of clay minerals in the geological processes and environmentally related applications. In this work, montmorillonite (Mt) was pillared by polycations of Keggin-Al13 and Keggin-Al30. Arrangement models of Keggin-Al13 and Keggin-Al30 in the interlayer region of Mt were put forward based on the chemical composition analysis, the structural formula calculation of Mt, and the results of powder X-ray diffraction. Ammonia temperature-programmed desorption and diffuse reflectance Fourier transform infrared methods were applied to explore the impacts of pillaring by polycations (Keggin-Al13 and Keggin-Al30) on the surface acidic characteristics of Mt. Results demonstrated that one Keggin-Al30 polycation can affect an area of 9.5 unit cells (from two layers, with 4.7-4.8 unit cells in each layer) in Mt, whereas a Keggin-Al13 polycation controls an area of 7.1 unit cells (from two layers, with 3.5-3.6 unit cells in each layer). Pillaring by polycations could lead to a lot of surface acid sites (1.33 mmol NH3/g) on Mt with the main type of Bronsted acid sites. The increase of surface acid sites on both Keggin-Al13-pillared Mt (Al13-PILM) and Keggin-Al30-pillared Mt (Al30-PILM) is attributed to the high positive charge and high content of aluminum per unit of polycation, which affects the formation of Bronsted acid sites and structural changes of Mt layers. Catalytic oxidation of toluene provided evidence for the high catalytic activity of Al30-PILM under much lower temperature at 78 °C compared with that of Al13-PILM and Mt at 207 and 285 °C, respectively. The basic finding in this study not only reveals the possible sources of abundant micropores and mesopores in the micro/mesoporous materials of Al13-PILM and Al30-PILM but also provides a reasonable mechanism for the formation of abundant Bronsted surface acid sites on these two types of pillared materials. The novel Al30-PILM with an excellent micro/mesoporous structure and extremely high thermal stability also exhibits a potential ability in the application of heterogeneous acid catalysis.

Controlled release herbicide formulation for effective weed control efficacy.

Controlled release formulation (CRF) of herbicide is an effective weed management technique with less eco-toxicity than other available commercial formulations. To maximise the effectiveness of CRFs however, it is crucial to understand the herbicide-releasing behaviour at play, which predominately depends on the interaction mechanisms between active ingredients and carrier materials during adsorption. In this study, we investigated and modelled the adsorption characteristics of model herbicide 2,4-D onto two organo-montmorillonites (octadecylamine- and aminopropyltriethoxysilane-modified) to synthesise polymer-based CRFs. Herbicide-releasing behaviour of the synthesised CRF microbeads was then analysed under various experimental conditions, and weed control efficacy determined under glasshouse conditions. Results revealed that adsorption of 2,4-D onto both organo-montmorillonites follows the pseudo-second-order kinetics model and is predominately controlled by the chemisorption process. However, multi-step mechanisms were detected in the adsorption on both organoclays, hence intra-particle diffusion is not the sole rate-limiting step for the adsorption process. Both organoclays followed the Elovich model, suggesting they have energetically heterogeneous surfaces. Herbicide-releasing behaviours of synthesised beads were investigated at various pH temperatures and ionic strengths under laboratory and glasshouse conditions. Furthermore, weed control efficacy of synthesised beads were investigated using pot studies under glasshouse condition. Desorption studies revealed that both synthesised microbeads have slow releasing behaviour at a wide range of pHs (5-9), temperatures (25-45 °C), and ionic strengths. The results also revealed that synthesised microbeads have excellent weed control efficacy on different broad-leaf weed species under glasshouse conditions.

Investigation of herbicide sorption-desorption using pristine and organoclays to explore the potential carriers for controlled release formulation.

Injudicious application of available commercial herbicide formulations leads to water, air and soil contamination, which adversely affect the environment, ecosystems and living organisms. Controlled release formulation (CRFs) could be an effective way to reduce the problems associated with commercially available herbicides. Organo-montmorillonites are prominent carrier materials for synthesising CRFs of commercial herbicides. Quaternary amine and organosilane functionalised organo-montmorillonite and pristine montmorillonite were used to investigate their potential as suitable carriers for CRFs in herbicide delivery systems. The experiment involved a batch adsorption process with successive dilution method. Results revealed that pristine montmorillonite is not a suitable carrier for CRFs of 2,4-D due to its low adsorption capacity and hydrophilic nature. Conversely, octadecylamine (ODA) and ODA-aminopropyltriethoxysilane (APTES) functionalised montmorillonite has better adsorption capacities. Adsorption of 2,4-D onto both organoclays is higher at pH.3 (232.58% for MMT1 and 161.29% for MMT2) compared to higher pH until pH.7 (49.75% for MMT1 and 68.49% for MMT2). Integrated structural characterisation studies confirmed the presence of 2,4-D on the layered organoclays. The Freundlich adsorption isotherm model fitted best to the experimental data, which revealed an energetically heterogeneous surface of the experimental organoclays, and adsorption which specifically involved chemisorption. The cumulative desorption percentages of adsorbed 2,4-D from MMT1(2,4-D loaded) and MMT2(2,4-D loaded) after seven desorption cycles were 65.53% and 51.45%, respectively. This outcome indicates: firstly, both organoclays are potential carrier materials for CRFs of 2,4-D; secondly, they have the ability to reduce the instantaneous release of 2,4-D immediately after application; and thirdly, eco-toxicity is greatly diminished.

Biomimetic Tremelliform Ultrathin MnO2/CuO Nanosheets on Kaolinite Driving Superior Catalytic Oxidation: An Example of CO.

Highly efficient three-dimensional (3D) kaolinite/MnO2-CuO (KM@CuO-NO3) catalysts were synthesized by a mild biomimetic strategy. Kaolinite flakes were uniformly wrapped by ultrathin tremelliform MnO2 nanosheets with thicknesses of around 1.0-1.5 nm. Si-O and Al-O groups in kaolinite hosted MnO2 nanosheets to generate a robust composite structure. The ultrathin MnO2 lamellar structure exhibited excellent stability even after calcination above 350 °C. Kaolinite/MnO2 exhibited abundant edges, sharp corners, and interconnected diffusion channels, which are superior to the common stacked structure. Open channels guaranteed fast transportation and migration of CO and O2 during CO oxidation. The synthesized KM@CuO-NO3 achieved a 90% CO conversion efficiency at a relatively low temperature (110 °C). Furthermore, the abundant oxygen vacancies on KM@CuO-NO3 assisted the adsorption and activation of oxygen species and thus enhanced the oxygen mobility and reactivity in the catalytic process. The mechanism results suggest that CuO introduced to the catalyst not only acted as CO active sites but also weakened the Mn-O bond, subsequently improved the mobilities of the oxygen species, which was found to contribute to its high activity for CO oxidation. This study provides new conceptual insights into rationally regulating structural assembly between transition metal oxides and natural minerals for high-performance catalysis reactions.

Hydrothermal carbons/ferrihydrite heterogeneous Fenton catalysts with low H2O2 consumption and the effect of graphitization degrees.

As the heterogeneous Fenton reactions are always restricted by the unsatisfied reduction efficiency of Fe(III) and ineffective consumption of H2O2, many strategies have been developed. In this work, we prepared hydrothermal carbons (HTC) with different graphitization degrees using glucose under different hydrothermal times, and then they were combined with ferrihydrite (Fh). Interestingly, although 30%HTC/Fh has much better BPA degradation efficiency than Fh (26 times larger of calculated degradation rate constants), the decomposition rate of H2O2 in the former system is lower. The generated Fe(II) of HTC/Fh is much higher than that of Fh during the heterogeneous Fenton reactions, and the degradation of BPA is almost unaffected by p-benzoquinone (scavenger of superoxide radicals (O2•-)) while greatly inhibited by isopropanol (scavenger of hydroxyl radicals (HO•)). These results indicate that HTC act as electron donors due to the abundant carbon-centered persistent free radicals (PFRs) to directly reduce Fe(III) to Fe(II) and therefore decrease the H2O2 consumption by Fe(III), which subsequently inhibits the generation of less active O2•- and promote the utilization efficiency of H2O2. HTC with a low graphitization degree contain more PFRs for Fe(III) reducing, significantly enhancing the Fenton catalytic activity of Fh.

Complete chloroplast genome characterization and phylogenetic analysis of Clematis mandshurica (Ranunculaceae).

The complete chloroplast genome sequence of Clematis mandshurica Ruprecht (1867), a specie of the Ranunculaceae family, and its phylogenetic relationships with other species have been reported in this study. The complete chloroplast genome of C. mandshurica is 159,563 bp in length, including a large single-copy (LSC) region of 79,360 bp, a small single-copy (SSC) region of 18,121 bp, and a pair of identical inverted repeat regions (IRs) of 31,041 bp. The genome encodes a total of 132 genes, including 90 protein-coding genes, 34 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. The phylogenetic analysis reveals that C. mandshurica was found to be closest to Clematis taeguensis. The complete chloroplast genome of C. mandshurica contributes to a better understanding of phylogenetic relationships among Clematis species.

Development of novel multifunctional adsorbent by effectively hosting both zwitterionic surfactant and hydrated ferric oxides in montmorillonite.

Intercalating various functional species into the interlayer space is an effective strategy to multi-functionalize 2D materials (e.g., montmorillonite, Mnt), but general limitations have emerged therefrom: (1) various intercalated species compete for the limited interlayer space, and (2) the neighboring intercalated species probably inhibit each other's reactivity. Herein, we have synthesized a novel Mnt-based multifunctional adsorbent (HFO-AZ16Mnt) via intercalation of zwitterionic surfactant (Z16), acid activation by chloric acid, and introduction of hydrated ferric oxides (HFOs). The acid activation can lead to formation of porous nanosilica, which serves as the new active sites for supporting HFO nanoparticles. Employing tetrachloroferrate (FeCl4-) as an anionic precursor of HFOs can help preserve the sulfonyl group (SO3-) of Z16 from being electrostatically occupied during the HFO introduction. As a result, HFO-AZ16Mnt can separately and effectively host Z16 and HFOs. The unique structure endows HFO-AZ16Mnt with the efficiency on simultaneous removal of hydrophobic organic contaminants, oxyanions, and heavy metal cations (nitrobenzene, phosphate, and Cd(II), respectively in this study) from water. Particularly, HFO-AZ16Mnt exhibits impressive capacity towards Cd(II) in both the single- (26.1 mg/g) and the multi-contaminant system (30.6 mg/g). This work has demonstrated a new strategy to multi-functionalize Mnt, and provided a promising novel Mnt-based multifunctional adsorbent for simultaneous and effective removal of organic and inorganic contaminants from water.

Organoclay-derived lamellar silicon carbide/carbon composite as an ideal support for Pt nanoparticles: facile synthesis and toluene oxidation performance.

A lamellar SiC/C composite was synthesized from organoclay via pyrolysis followed by salt-assisted magnesiothermic reduction. The in situ-formed carbon sheet within the restricted interlayer space of clay served as the carbon source and nanotemplate for forming SiC/C. With a large specific surface area, hierarchical porosity, available anchoring sites, good hydrophobicity, and thermal stability, SiC/C proved to be a promising support for Pt. The resulting Pt loaded SiC/C exhibited an excellent toluene oxidation performance.

Diatomite-Metal-Organic Framework Composite with Hierarchical Pore Structures for Adsorption/Desorption of Hydrogen, Carbon Dioxide and Water Vapor.

Distinctive Cr-MOF@Da composites have been constructed using chromium-based metal-organic frameworks (MOFs) and diatomite (Da). The new materials have hierarchical pore structures containing micropores, mesopores and macropores. We have synthesized various morphologies of the MOF compound Cr-MIL-101 to combine with Da in a one-pot reaction step. These distinctive hierarchical pore networks within Cr-MIL-101@Da enable exceptional adsorptive performance for a range of molecules, including hydrogen (H2), carbon dioxide (CO2) and water (H2O) vapor. Selectivity for H2 or CO2 can be moderated by the morphology and composition of the Cr-MIL-101 included in the Cr-MOF@Da composite. The encapsulation and growth of Cr-MIL-101 within and on Da have resulted in excellent water retention as well as high thermal and hydrolytic stability. In some cases, Cr-MIL-101@Da composite materials have demonstrated increased thermal stability compared with that of Cr-MIL-101; for example, decomposition temperatures >340 ℃ can be achieved. Furthermore, these Cr-MIL-101@Da composites retain structural and morphological integrity after 60 cycles of repeated hydration/dehydration, and after storage for more than one year. These characteristics are difficult to achieve with many MOF materials, and thus suggest that MOF-mineral composites show high potential for practical gas storage and water vapor capture.

Simultaneous detoxification of polar aflatoxin B1 and weak polar zearalenone from simulated gastrointestinal tract by zwitterionic montmorillonites.

The current research focuses on the development of novel mycotoxins adsorbents using zwitterionic surfactants modified montmorillonites (ZMts) for simultaneous removal of highly health-hazardous polar aflatoxin B1 (AFB1) and low polar zearalenone (ZER). Two types of ZMts including dodecyl dimethyl betaine (BS-12) and lauramidopropyl betaine (LAB-35) modified montmorillonites (BS-12/Mts and LAB-35/Mts) were fabricated, and the structural, interfacial and textural features of which were explored by different techniques. It is indicated that ZMts have different structural configurations based on the surfactant type and loadings, convert from hydrophilic to hydrophobic property, with a mesoporous network inherited from Mt. The resultant adsorbents show significant improvements on the detoxification efficiency of both AFB1 and ZER. pH has little effect on the adsorption of ZMts, suggesting no desorption happens. The adsorption mechanisms of raw Mt, BS-12/Mts and LAB-35/Mts to AFB1 and ZER were proposed based on the characterizations and adsorption isotherms. This study demonstrates that ZMts possess simultaneous detoxification functions to mycotoxins with different polarities, and provides new insights into development of versatile mycotoxins adsorbents.

Speciation of metal-EDTA complexes by flow injection analysis with electrospray ionization mass spectrometry and ion chromatography with inductively coupled plasma mass spectrometry.

Flow injection analysis (FIA) with ESI-MS and ion chromatography (IC) with inductively coupled plasma-MS (ICP-MS) as the complementary technique have been explored for the determination of metal ions as their metal-EDTA complexes. ESI-MS enabled the identification of metal-EDTA complexes such as [Mn(EDTA)](2-), [Co(EDTA)](2-), [Ni(EDTA)](2-), [Cu(EDTA)](2-), [Zn(EDTA)](2-), [Pb(EDTA)](2-), and [Fe(EDTA)](1-) and their MS spectral showed that these metal-EDTA complexes were present in solution. Based on the ESI-MS, ion chromatographic separation and ICP-MS detection of these complexes are possible because IC-ICP-MS requires stable metal-EDTA complex during the chromatographic separation. The separation of these metal-EDTA complexes was achieved on an anion-exchange column with a mobile phase containing 30 mM NH(4)(HPO(4))(2) at pH 7.5 within 7 min with ICP-MS providing element specific detection. The ICP-MS LODs for the metal-EDTA were in the range of 0.1-0.5 microg/L with the exception of Fe (15 microg/L). The proposed method was a simple procedure for sample processing, using direct injection of sample without removal of sample matrix and was successfully applied to the determination of metal-EDTA complexes in real samples.

An infrared study of adsorption of para-nitrophenol on mono-, di- and tri-alkyl surfactant intercalated organoclays.

Infrared spectroscopy has been used to study the adsorption of para-nitrophenol on mono-, di- and tri-alkyl surfactant intercalated montmorillonite. Organoclays were obtained by the cationic exchange of mono-, di- and tri-alkyl chain surfactants for sodium ions [hexadecyltrimethylammonium bromide (HDTMAB), dimethyldioctadecylammonium bromide (DDOAB), methyltrioctadecylammonium bromide (MTOAB)] in an aqueous solution with Na-montmorillonite. Upon formation of the organoclay, the properties change from strongly hydrophilic to strongly hydrophobic. This change in surface properties is observed by a decrease in intensity of the OH stretching vibrations assigned to water in the cation hydration sphere of the montmorillonite. As the cation is replaced by the surfactant molecules, the para-nitrophenol replaces the surfactant molecules in the clay interlayer. Bands attributed to CH stretching and bending vibrations change for the surfactant intercalated montmorillonite. Strong changes occur in the HCH deformation modes of the methyl groups of the surfactant. These changes are attributed to the methyl groups locking into the siloxane surface of the montmorillonite. Such a concept is supported by changes in the SiO stretching bands of the montmorillonite siloxane surface. This study demonstrates that para-nitrophenol will penetrate into the untreated clay interlayer and replace the intercalated surfactant in surfactant modified clay, resulting in the change of the arrangement of the intercalated surfactant.

Application of near infrared spectroscopy for the determination of adsorbed p-nitrophenol on HDTMA organoclay--implications for the removal of organic pollutants from water.

NIR spectroscopy has been used to measure the adsorption of p-nitrophenol on untreated montmorillonite and surfactant exchanged montmorillonite. p-Nitrophenol is characterised by an intense NIR band at 8890 cm(-1) which shifts to 8840 cm(-1) upon adsorption on organoclay. The band was not observed for p-nitrophenol adsorbed on untreated montmorillonite. Both the montmorillonite and the surfactant modified montmorillonite are characterised by NIR bands at 7061 and 6791 cm(-1). The organoclay is characterised by two prominent bands at 5871 and 5667 cm(-1) assigned to the fundamental overtones of the mid-IR bands at 2916 and 2850 cm(-1). A band at 6017 cm(-1) is attributed to the p-nitrophenol adsorbed on the organoclay. The band is not observed for the montmorillonite with adsorbed p-nitrophenol. It is concluded that p-nitrophenol is adsorbed to significantly greater amounts on the organoclay compared with the untreated montmorillonite. The implication is that organoclays are most useful for removing organic molecules from water through adsorption.

A nanoclay-induced defective g-C3N4 photocatalyst for highly efficient catalytic reactions.

A nanoclay-induced defective graphitic carbon nitride (g-C3N4) catalyst was successfully synthesized through intercalation and in situ calcination. The degradation time for Orange II dye using the as-synthesized g-C3N4/kaolinite (g-C3N4/Kaol) catalyst was only 10 min under visible light irradiation, which could be attributed to their special structures and synergistic effects.

Evaluation of nonionic surfactant modified montmorillonite as mycotoxins adsorbent for aflatoxin B1 and zearalenone.

This work aims at exploring the potential of nonionic surfactant octylphenol polyoxyethylene ether (OP-10) modified montmorillonites (NMts) as mycotoxins adsorbent. The resulting NMts has different structural configurations, organic carbon contents, surface hydrophobicity and textural properties at different surfactant loadings. The prepared NMts were used for adsorption of polar aflatoxin B1 (AFB1) and weak polar zearalenone (ZER) in both single and binary-contaminate systems by simulating conditions of gastrointestinal tract. The adsorption capacities of NMts to AFB1 and ZER increased up to 2.78 and 8.54 mg/g respectively from 0.51 and 0.00 mg/g of raw montmorillonite (Mt). High adsorption capacities of NMts to AFB1 and ZER could be reached at low surfactant loadings. There was little decrease from pH of 3.5 to 6.5 but became negligible with increasing the surfactant loadings. In binary-contaminate adsorption system, the adsorption of ZER was obviously affected by the existence of AFB1, while ZER had little effect on the adsorption process of AFB1 due to different adsorption mechanism. This study demonstrates that NMts could be a promising adsorbent for simultaneous detoxification of polar and non-polar mycotoxins.

Catalytic degradation of Orange II in aqueous solution using diatomite-supported bimetallic Fe/Ni nanoparticles.

A functional diatomite-supported Fe/Ni nanocomposite successfully remediated Orange II contaminant in aqueous solution. The hypothesis was that diatomite-supported Fe/Ni would not only be more effective than Fe/Ni but also require less metallic loading to effect the catalytic reaction. Batch experiments indicate that 99.00% of Orange II was removed using diatomite-supported Fe/Ni, while only 86.64 and 3.59% of Orange II were removed using bimetallic Fe/Ni nanoparticles and diatomite, after 6 h of reaction, respectively. Characterisation by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) indicates that the use of diatomite as a support material reduced the aggregation of bimetallic Fe/Ni nanoparticles, thereby resulting in an enhancement in the reactivity. A synergistic mechanism for the removal of Orange II by diatomite-supported Fe/Ni was proposed which involves adsorption, followed by catalytic reduction. This study has demonstrated that diatomite may be a suitable support material for stabilizing and dispersing bimetallic Fe/Ni nanoparticles and the resulting diatomite-supported Fe/Ni composite could be a promising catalyst for the remediation of dye-contaminated wastewater.

Modification of the surfaces of Wyoming montmorillonite by the cationic surfactants alkyl trimethyl, dialkyl dimethyl, and trialkyl methyl ammonium bromides.

Surfaces of a Wyoming SWy-2 sodium montmorillonite were modified using microwave radiation through intercalation with the cationic surfactants octadecyl-trimethyl ammonium bromide, dimethyldioctadecylammonium bromide, and methyl-tri-octadecyl ammonium bromide by an ion exchange mechanism. Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG) and infrared (IR) spectroscopy. Different configurations of surfactants within montmorillonite interlayer are proposed based on d(001) basal spacings. A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition. IR spectroscopy using a smart endurance single bounce diamond attenuated total reflection (ATR) cell has been used to study the changes in the spectra of CH asymmetric and symmetric stretching modes of the surfactants to provide more information of the surfactant molecular configurations.

Thermal stability of octadecyltrimethylammonium bromide modified montmorillonite organoclay.

Organoclays are significant for providing a mechanism for the adsorption of organic molecules from potable water. As such their thermal stability is important. A combination of thermogravimetric analysis and infrared emission spectroscopy was used to determine this stability. Infrared emission spectroscopy (IES) was used to investigate the changes in the structure and surface characteristics of water and surfactant molecules in montmorillonite, octadecyltrimethylammonium bromide and organoclays prepared with the surfactant octadecyltrimethylammonium bromide with different surfactant loadings. These spectra collected at different temperatures give support to the results obtained from the thermal analysis and also provide additional evidence for the dehydration which is difficult to obtain by normal thermoanalytical techniques. The spectra provide information on the conformation of the surfactant molecules in the clay layers and the thermal decomposition of the organoclays. Infrared emission spectroscopy proved to be a useful tool for the study of the thermal stability of the organoclays.

Changes in the surfaces of adsorbed p-nitrophenol on methyltrioctadecylammonium bromide organoclay--an XRD, TG, and infrared spectroscopic study.

Water purification is of extreme importance worldwide. p-Nitrophenol was used as a test chemical to design and test an organoclay for the removal of p-nitrophenol from an aqueous solution. Synthesis of the organoclay with methyltrioctadecylammonium bromide [CH(3)(CH(2))(17)](3)NBr(CH(3)) labeled as MTOAB results in multiple expansions of the montmorillonite clay from 1.24 nm to a maximum of 5.20 nm as is evidenced by the XRD patterns. Thermal analysis shows strong bonding of the surfactant to the clay siloxane layers and the interaction of the p-nitrophenol with the clay surfaces. It is proposed that the p-nitrophenol penetrates the siloxane layer of the clay and bonds through the ditrigonal space of the siloxane hexagonal units to the inner OH units. Such a concept is supported by the observation of an additional infrared band at 3652 cm(-1) for the organoclay. Shifts in the p-nitrophenol OH stretching vibrations mean a strong interaction of the p-nitrophenol molecule. Significant changes in the siloxane stretching bands are also observed.