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This study was undertaken to determine the impact of the organic complex concentration on the adsorption of herbicide (acetochlor) at the surface of the organic modified montmorillonite. In this work, natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification. Cation-exchange capacity of this montmorillo...
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... bands at 1681, 1464, and 1373 cm ¡1 in the spectrum of pure Ac were assigned to stretching vibrations of carbonyl group (C D O), phenyl group (1464 cm ¡1 ) and anilidic group (1373 cm ¡1 ) (Fig 8). [21,22] Band assigned to C D O vibration of pure Ac (1681 cm ¡1 ) was shifted on lower (1641 cm ¡1 ) wave numbers in NaMAc (Fig. ...
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... Hectorite is a smectite clay, which has physical and chemical properties relevant to the adsorption processes associated with prebiotic chemistry, such as the propensity to swell in water and other media (e.g., artificial seawater), the capability to disperse in water, the capacity for cation exchange [74][75][76], and the ability to form organic and inorganic interlayer complexes. The inorganic cations on the hectorite surface (e.g., Ca 2+ , Fe 2+ , Mg 2+ ) could be replaced by organic cations through ion exchange, and the clay surface could become organophilic. ...
This study focuses on the radiolysis (up to 36 kGy) of guanine and adenine (nitrogenous bases) adsorbed in hectorite and attapulgite to highlight the potential role of clays as protective agents against ionizing radiation in prebiotic processes. In this framework, the study investigated the nitrogenous bases’ behavior in two types of systems: a) aqueous suspension of adenine–clay systems and b) guanine–clay systems in the solid state. This research utilized spectroscopic and chromatographic techniques for its analytical purposes. Regardless of the reaction medium conditions, the results reveal that nitrogenous bases are stable under ionizing irradiation when adsorbed on both clays.
... In the case of bentonite, the interlayer distance observed was 13.38 Å (1.34 nm). For HDTMA-bentonite, the interlayer distance was increased to 19.62 Å (1.96 nm), similar results have been observed for Na-bentonite modified with 100% CEC equivalent concentration of HDTMA [18,21,22]. According to the literature, the length of the HDTMA + cation is 2.53 nm with 0.43 nm "nail-head" and 2.1 nm "nail-body". ...
... According to the literature, the length of the HDTMA + cation is 2.53 nm with 0.43 nm "nail-head" and 2.1 nm "nail-body". The height of the 'nail-body' is between 0.41 and 0.46 nm and that of the "nail-head" is between 0.51 and 0.67 nm depending on whether a zigzag arrangement of the carbon atoms of HDTMA + is parallel to the plane of the bentonite layer, or perpendicular [21]. Knowing that the thickness of a single bentonite layer is about 0.96 nm [23,24], then the basal spacing of 1.96 nm of HDTAM-bentonite indicates a dimension of the interlayer space around 1 nm. ...
In this study, the main objective is the preparation and the characterization of a modified Algerian bentonite based adsorbent by intercalation with hexadecyltrimethylammonium bromide (HDTMA). Natural and modified bentonites were characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The X-ray results indicated that the geometry of the interlayer space changes by the intercalation of HDTMA cations, resulting in an increase in the basal spacing from 1.34 to 1.96 nm. The adsorption efficiency of natural and HDTMA-bentonite was examined for humic acid (HA) removal by batch adsorption experiments under different operating conditions. The maximum monolayer adsorption capacity qm of HA was found to be 54.80 mg g⁻¹ and 330.34 mg g⁻¹ for natural and HDTMA-bentonite, respectively. The kinetic study indicated that HA adsorption followed the pseudofirst- order model. Both natural and HDTMA-bentonite showed quite good capabilities in removing HA from aqueous solutions.
The H2O resistance of low-temperature NH3-SCR catalysts is a key factor for practical applications. This work aims to strategically enhance the hydrophobicity of catalysts by intercalating surfactants into montmorillonite (M) via its cation exchange capacity. Various thermal pretreatment temperatures and chain lengths of surfactants have been used to enhance the hydrophobicity and interlayer spacing of montmorillonite, respectively. As a result, MnCe-M8-600 (with thermal pretreatment at 600 °C and the chain length of surfactant = 8) exhibits good low-temperature NH3-SCR performance and H2O resistance due to its labile oxygen, hydrophobicity, and structural stability. It is worth noting that the hydrophobicity of MnCe-M8-600 weakens the interaction between –OH and the catalyst, thereby continuously maintaining the redox ability and transferring electrons between Mn4+ and Ce3+. The results of the H2O resistance test showed that the NOX conversion of MnCe-M8-600 decreased by only 6% in the presence of 10% H2O, and its activity was fully recovered after turning off H2O. Hence, MnCe-M8-600 shows high activity and H2O resistance and is a promising catalyst for low-temperature NH3-SCR system applications.
This review deals with modification of montmorillonite and other clay-minerals and clays by interacting them with organic cations, for producing slow release formulations of herbicides, and efficient removal of pollutants from water by filtration. Elaboration is on incorporating initially the organic cations in micelles and liposomes, then producing complexes denoted micelle- or liposome-clay nano-particles. The material characteristics (XRD, Freeze-fracture electron microscopy, adsorption) of the micelle– or liposome–clay complexes are different from those of a complex of the same composition (organo-clay), which is formed by interaction of monomers of the surfactant with the clay-mineral, or clay. The resulting complexes have a large surface area per weight; they include large hydrophobic parts and (in many cases) have excess of a positive charge. The organo-clays formed by preadsorbing organic cations with long alkyl chains were also addressed for adsorption and slow release of herbicides. Another examined approach includes “adsorptive” clays modified by small quaternary cations, in which the adsorbed organic cation may open the clay layers, and consequently yield a high exposure of the siloxane surface for adsorption of organic compounds. Small scale and field experiments demonstrated that slow release formulations of herbicides prepared by the new complexes enabled reduced contamination of ground water due to leaching, and exhibited enhanced herbicidal activity. Pollutants removed efficiently from water by the new complexes include (i) hydrophobic and anionic organic molecules, such as herbicides, dissolved organic matter; pharmaceuticals, such as antibiotics and non-steroidal drugs; (ii) inorganic anions, e.g., perchlorate and (iii) microorganisms, such as bacteria, including cyanobacteria (and their toxins). Model calculations of adsorption and kinetics of filtration, and estimation of capacities accompany the survey of results and their discussion.
Dynamic and equilibrium research on the adsorption of phenol and monochlorophenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol) on modified halloysite with the use of HDTMA (hexadecyltrimethylammonium) bromide was conducted at three temperatures: 293, 303, and 313 K. The interpretation of experimental data was based on the Temkin, the Dubinin-Radushkevich, the Freundlich, and the Langmuir equations to establish the appropriate adsorption models and to define the characteristic parameters describing the process. We determined that the Freundlich isotherm perfectly described experimental data as regards the adsorption equation concerning phenol; however, 2-chlorophenol, 3-chlorophenol, and 4-chlorophenol sorption took place in compliance with the Langmuir model. The adsorption of the studied compounds on the HDTMA-modified halloysite increased in the following order: phenol <4-chlorophenol <2-chlorophenol <3-chlorophenol. Thermodynamic parameters of the processes indicated the physical as well as exothermal adsorption character. The adsorption kinetics of phenol and monochlorophenols was discussed based on the following models: pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, and film-diffusion model. The rate of the sorption process was described with the pseudo-second-order model. The global electrophilicity indices of phenol and the monochlorophenols were applied to demonstrate the difference through the interaction of these adsorbates with a molecule of surfactant (HDTMA) and, as a result, the different properties of the studied compounds.
This paper discussed the recent advances in the removal of herbicides and pesticides (H & P) from polluted waters using various adsorbents. It was observed that montmorillonite and activated carbon (AC) cloth showed the highest adsorption capacity (q) of 1067 and 421.58 mg/g for 2,4-D herbicide and aldicarb, respectively. Atrazine and aldrin (the most researched H & P, respectively) were captured most efficiently removed using eucalyptus bark-derived biosorbent (936.1 mg/g) and acid-treated patellidae shells (208.33 mg/g), respectively. Two new adsorption attributes were derived: effective surface area (eSBET) and preferential adsorption (qp). The eSBET correlates more strongly with the reported q than the conventional SBET because the former accounts for the effect of surface chemistry. Likewise, qp is more reliable than q because the former considers the chemical properties and solubility of the adsorbent and adsorbate. The correlation between the eSBET and qp was strongest for 2,4-D (95%) and AC (62.25%). Future research could use spent, heavy metal-laden adsorbents, adsorption with photo-degradation, and competitive adsorption processes for H & P control. Conclusively, adsorption is an excellent technique for mitigating H & P pollution, and the technique is available for performance optimisation based on the novel adsorption attributes.
The results presented in this paper show an impact of the concentration of the aromatic organic cation on the adsorption of acetochlor on the surface of the organic-modified montmorillonite. Natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification in this experiment. Cation exchange capacity of this montmorillonite (86 mmol 100 g⁻¹ of clay) was determined using the methylene blue method. In pretreatment, montmorillonite was modified with NaCl. For the purpose of organic modification, three different concentrations of phenyltrimethylammonium chloride (PTMA) have been selected, based on calculated CEC value: 43 mmol 100 g⁻¹ of clay (0.5 CEC), 86 mmol 100 g⁻¹ of clay (1 CEC) and 129 mmol 100 g⁻¹ of clay (1.5 CEC). The changes in the properties of the inorganic and organic modified montmorillonite were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and batch equilibrium method. Freundlich coefficients show higher uptake of the herbicide by montmorillonite modified with PTMA, compared to inorganic-modified montmorillonite. The results also indicate the influence of the organic cation concentration on the adsorption of the selected herbicide.
