Adsorption of toluene into commercial organoclay in liquid phase: Kinetics, equilibrium and thermodynamics

Optimized isolation and purification of Shaoyao Gancao decoction using macroporous resin

In this study, high-performance liquid chromatography was used to determine four components of Shaoyao Gancao Decoction (SGD), and the effect of purification was evaluated using fingerprints, similarity analysis and cell experiments. An effective method for isolation and purification of SGD was established. The adsorption/desorption properties of SGD were evaluated using resin screening, isothermal analysis, adsorption kinetics, and dynamic adsorption-desorption experiments. It was shown that the Langmuir equation fitted the isotherm data well and that a pseudo-second-order model accurately described kinetic adsorption on AB-8 resin. Analysis of thermodynamic parameters showed that the adsorption process was exothermic. Under the optimal process conditions, the concentrations of albiflorin, paeoniflorin, liquiritin and ammonium glycyrrhizinate in the product were 73.05, 134.04, 45.04 and 75.00 mg/g, respectively. The yields of the four components were 71.89 %-86.19 %. Cell experiments showed that the purified SGD retained anti-inflammatory activity. This research lays the foundation for the separation and purification of SGD and subsequent preparation research.

Adsorption of cefazolin on organoclay: experimental design, characterization, and a complete batch study

Cefazolin (CFZ) is a ubiquitous antibiotic in hospital settings and has been recognized as an emerging contaminant due to its ecotoxicity. Despite the growing concern around this compound, the literature addressing feasible advanced techniques for CFZ uptake from aqueous matrices is still scarce. Thus, the objective of this work was to evaluate the adsorption of cefazolin on Spectrogel® organoclay in a batch system as an efficient remediation method. The optimization of experimental conditions was determined by a central composite rotational design. A pH study, as well as equilibrium, kinetic, and thermodynamic assays, was performed to assess the adsorption of CFZ on Spectrogel®. The kinetic and equilibrium models that best described the system were the external mass transfer resistance and Sips models, respectively. A removal efficiency above 80% was achieved, and the maximum adsorption capacity at 25 °C was 398.6 mg g^-1. The post-process contaminated organoclay was thermally regenerated. The outcomes of this work indicate that Spectrogel® is an environmentally friendly adsorbent for the removal of cefazolin from wastewater.

Adsorption of antibiotic cefazolin in organoclay fixed-bed column: characterization, mathematical modeling, and DFT-based calculations

Cefazolin (CFZ) is an antibiotic widely used in veterinary and human medicine that has been detected in high residual levels in the environment and is therefore considered an emerging contaminant. This work evaluated the adsorption of this contaminant by Spectrogel® type C organoclay, in continuous mode using a fixed-bed column. The fluid dynamics and the effect of the CFZ concentration were evaluated. In addition, prior and post-process organoclay were characterized. The continuous system under the conditions of C₀ = 0.3 mmol/L and Q = 0.1 mL/min presented lower values of mass transfer zone (5.88 cm), whereas the system with C₀ = 0.5 mmol/L and Q = 0.1 mL/min achieved higher CFZ adsorption capacity (20 µmol/g). Phenomenological and mass-transfer models were applied to the experimental data. The dual-site diffusion (DualSD) model better described the breakthrough (BTC) data. Furthermore, density functional theory (DFT) calculation was performed at the molecular level to provide a better comprehension of CFZ adsorption.

Adsorption of Diuron from aqueous solution onto commercial organophilic clay: kinetic, equilibrium and thermodynamic study

Due to their abundance in nature, clays have been frequently studied in the adsorption of different emergent contaminants, since they have good efficiency and low cost. Therefore, the present study aimed to evaluate the performance of commercial organoclays as an adsorbent in the environmental remediation of wastewater containing the herbicide Diuron. The clay was characterized by the techniques of N₂ physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and point of zero charge. In the batch adsorption experiments it was verified that the adsorption kinetics is ruled by the pseudo-second-order model (R² > 0.97), and the adsorption equilibrium study at different temperatures (298, 302 and 308 K) showed that the non-linear models of Langmuir (R² > 0.99) and Freundlich (R² > 0.98) were those that present better adjustments to the experimental data. In addition, the adsorption capacity in monolayer (q_max) was 44.24 mg g^-1, being higher or comparable to several works reported in the literature. As for the thermodynamic adsorption study, it was possible to infer that the process is spontaneous (ΔG°_ads < 0) and endothermic (ΔH°_ads = 71.58 kJ mol^-1) in the temperature range studied. As far as the regeneration study was concerned, the maximum desorption capacity, 26.59 mg g^-1, was obtained from the use of ethanol as eluent at 298 K.

Technological applications of organo-montmorillonites in the removal of pyrimethanil from water: adsorption/desorption and flocculation studies

Pyrimethanil (2-aniline-4, 6-dimethylpyrimidine, PRM) is used in fruit packing plants to control fungal infections and diseases. The effluents greatly polluted with this fungicide, as a point source contamination, need to be technologically treated for their regeneration before they reach water bodies. This work evaluates the use of organo-montmorillonites, synthetized in our laboratory, for their application in adsorption and coagulation/flocculation processes for the removal of PRM from water. The adsorption-desorption performance of PRM in a raw montmorillonite (Mt) and several organo-montmorillonites (organo-Mt) obtained by different amounts and types of exchanged surfactants (octadecyltrimethylammonium (ODTMA) and didodecyldimethylammonium (DDAB) bromides and benzyltrimethylammonium chloride (BTMA)) was studied. The PRM adsorption on raw Mt was assigned mainly to an interlayer occupancy, while hydrophobic interactions between PRM and the surfactants in the exchanged samples increased PRM adsorption, which was correlated with the surfactant loading. PRM desorption showed irreversible behavior in raw Mt, which changed to reversible for organo-Mt samples, and was also correlated with the increase of surfactant loading.Two of the organo-Mt with high surfactant loading (twice the CEC) were assayed for the removal of commercial PRM in coagulation/flocculation tests, and their performance was compared to that of the native clay (Mt). The use of the organo-Mt produced flocculation at a very low ratio (0.5 g L^-1), whereas no flocculation was observed with Mt. These results proved the feasibility of the use of organo-Mt for the treatment of wastewater contaminated with PRM using a low organo-Mt/liquid ratio.