Exploitation of Bentonite for Wastewater Treatment

Bentonite is a clay with interesting surface properties (affinity for water, adsorption capacity for electro-positive compounds….). The characteristics and clarifying properties of bentonite from various companies are the subject of numerous studies. The present work focuses on the study of the efficiency of bentonite and modified bentonite to purify aqueous solutions containing organic pollutants such as phenol. First, before starting the adsorption study, a physical–chemical characterization of the clay by FTIR, BET and XRD techniques was undertaken. The specific surface of the bentonite is calculated by BET. Then, the study of isotherms and kinetics of phenol adsorption on commercial BTC showed that this pollutant can be removed from liquid effluents with a significant percentage. Langmuir and Freundlich models were applied. Finally, the kinetic study performed by UV–Visible was reproduced by FTIR spectroscopy

Assessment of Untreated Coffee Wastes for the Removal of Chromium (VI) from Aqueous Medium

Industrial discharges loaded with heavy metals present several problems for aquatic ecosystems and human health. In this context, the present study aims to evaluate the potential of raw spent coffee grounds to remove chromium from an aqueous medium. A structural and textural study of coffee grounds was carried out by FTIR, XRD, and TGA analysis. The optimum conditions for the removal of Cr(VI), for a solution with an initial concentration of 100 mg/l, were adsorbent dose 2.5 g/l, pH 4.0, and contact time 90 min. The adsorption equilibrium results show that the Langmuir isotherm best describes the process with an adsorption capacity of 42.9 mg/g and that the adsorption kinetics follows the pseudosecond-order model. The calculated thermodynamic parameters showed that the adsorption is exothermic and spontaneous. The activation energy value (Ea) indicated that the retention is physisorptive in nature. The regeneration of the adsorbent was carried out by three eluents, among which HCl was the best. Finally, a brief cost estimation showed the great potential of coffee grounds as a low-cost adsorbent

Adsorption of Crystal Violet onto an Agricultural Waste Residue: Kinetics, Isotherm, Thermodynamics, and Mechanism of Adsorption

Agricultural waste can be exploited for the adsorption of dyes, due to their low cost, availability, cost-effectiveness, and efficiency. In this study, we were interested in the elimination of crystal violet dye, from aqueous solutions, by adsorption on almond shell-based material, as a low-cost and ecofriendly adsorbent. The almond shells were first analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction; then, the influence of adsorbent dose, initial dye concentration time, and pH were studied to assess adsorption capacity under optimal experimental conditions. Experimental results indicate that almond shell adsorbent removes about 83% of the dye from the solutions at room temperature and in batch mode; the kinetic study showed that the equilibrium time is about 90 min, and the model of pseudo-second order could very well describe adsorption kinetics. The modulation of adsorption isotherms showed that retention follows the Langmuir model. The thermodynamic study has shown that the adsorption is endothermic (ΔH° > 0) and spontaneous (ΔG° < 0)

Comparative Study on Adsorption of Crystal Violet and Chromium (VI) by Activated Carbon Derived from Spent Coffee Grounds

In the context of the circular economy, used coffee grounds were transformed into powdered activated carbon by chemical activation using potassium hydroxide. Its characterisation was conducted in comparison with that of a commercial activated carbon by scanning electron microscopy (SEM) coupled with energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Boehm titration, and point zero charge (pHPZC) and by determination of the methylene blue number (MBN) and the iodine number (IN). Performance of the prepared activated carbon was tested in the adsorption of the cationic dye crystal violet (CV) and hexavalent chromium. Batch adsorption tests were carried out and the effects of operating parameters were studied. The results collected on the adsorption kinetics show that the adsorption followed pseudo-second order kinetics and that the Langmuir isotherm best fits the equilibrium data for crystal violet and hexavalent chromium. The thermodynamic study showed that the adsorption of both adsorbates is spontaneous and exothermic and leads to a decrease in disorder at the solid–liquid interfaces. These results indicate that this activated carbon can be used as an alternative adsorbent to remove cationic dyes and heavy metals from aqueous solutions