Adsorption of organochlorine pesticides on modified porous Al30/bentonite: Kinetic and thermodynamic studies (original) (raw)
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Water Practice and Technology, 2020
Bentonite samples collected from M'Zila of Mostaganem (Algeria) were treated in first protocol with sulfuric acid at concentrations 1, 3 and 6N. The second protocol concerns the acid attack of bentonite combined with thermal treatment at temperatures of 100 and 200 °C. The obtained adsorbents were characterized by different analyses techniques such as chemical composition, X-ray diffraction (XRD), specific surface area and pHPZC. The modified bentonites were used for removal of Chlorothalonil (Chl) from aqueous solution. The adsorption behavior of the pesticide was studied under different experimental conditions of pH, contact time, concentration of Chl and temperature of solution. The adsorption of Chl followed pseudo-second order kinetics and was described by the Freundlich equation. Thermodynamic study revealed that Chl adsorption was endothermic and physical in nature.
Adsorption of herbicide 2,4-D from aqueous solution using organo-modified bentonite clay
Environmental Science and Pollution Research, 2019
This study analyzed the performance of organophilic clays obtained from the chemical modification of sodium bentonite clay when applied to the adsorption of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Kinetic curves and equilibrium isotherms were obtained in order to determine time and adsorption capacity of the material, as well as understand the mechanisms involved in this phenomenon. The results showed that the most predictive kinetic model for experimental data was of pseudo-second order (R 2 > 0.98), and that external mass transfer is the dominant factor in the time of operation. Isotherms were obtained at temperatures of 298, 308, and 318 K, under which the Dubinin-Radushkevich model was shown to have a good fit to data (R 2 > 0.96), according to mathematical adjustments. The maximum adsorption capacity obtained experimentally was 50.36 mg g −1 , found at a temperature of 298 K, being higher or compatible with other materials reported in the literature. With help of the thermodynamic studies on the process, it was observed that the adsorption of 2,4-D in organophilic clays refers to a spontaneous (ΔG°a ds < 0), exothermal (ΔH°a ds = − 9.99 kJ mol −1) process of physical nature. Lastly, it was observed that the adsorbent can be easily regenerated when subjected to eluents such as mixtures containing fractions of ethanol/water (desorption = 95%).
Minerals
Natural and modified clay minerals have been extensively used for the adsorption/desorption of organic substances, especially pesticides, from waters and wastewater, aiming at pollution control and more efficient use of the herbicides through controlled release. While natural clay minerals efficiently remove organic cations such as paraquat and diquat, the adsorption of anionic or neutral species demands surface chemical modification with, for instance, quaternary ammonium salts containing long alkyl chains. Basic pesticides, on the other hand, are better absorbed in clay minerals modified with polycations. Kinetic studies and adsorption/desorption isotherms provide the parameters needed to evaluate the clay mineral’s adsorptive performance towards the pollutant target. However, the direct comparison of these parameters is complicated because the experimental conditions, the analytical techniques, the kinetic and isotherm models, and the numerical fitting method differ among the var...
Removal of Pesticide Residues from Water by Organo-Bentonites
Contamination of water resources with pesticides residues becomes a pressing problem in Gaza due to the frequent application of pesticides in the intensive agricultural system. This study tests the potential of using organo-bentonite as a porous material to remove bromoxynil residues from contaminated water. Bentonite surfaces were activated for removal of bromoxynil residues from water by simple ion exchange reaction using Hexadecyl tributyl phosphonium (HDTBP + ) or N-cetylperidinium (NCP) salts. HPLC results showed that raw bentonite is a poor material for removing bromoxynil residues, whereas NCP + -/HDTBP + -bentonite are powerful materials for removing bromoxynil residues due to changing bentonite surfaces from hydrophilic to hydrophobic. Reducing the temperature or the pH of the solution further enhanced the removal process. These results suggest that NCP + -/HDTBP + -Bentonite are promising porous material for removing bromoxynil residues from water. The application of these materials in water filter may be a promising and economically feasible technology for water purification.
Removal of Chlorothalonil from water by a bentonite treated chemically
Journal of Materials and Environmental Sciences, 2017
The adsorption of Chlorothalonil fungicide from aqueous solution onto raw and activated bentonite samples was investigated as a function of parameters such as pH, contact time, and temperature. The acid activation of natural bentonite was performed by treatment with hydrochloric solution of different concentrations. The high adsorption capacity of chlorothalonil was obtained by activated bentonite at 323 K in the range of pH 3-4 for 60 min of contact time. It was be 32.01 and 42.88 mg/g for raw and bentonite activated by 1N hydrochloric acid, respectively. The Langmuir and Freundlich adsorption models were applied to describe the related isotherms. Freundlich equation has shown the best fitting with the experimental data. The pseudo-first order and pseudo-second order kinetic models were used to describe the kinetic data. The changes of enthalpy, entropy and Gibbs free energy of adsorption process were determined. The results indicated that the adsorption of chlorothalonil occurs spontaneously as an endothermic process.