The characterization of terpene-based eutectic solvent systems is performed to describe their solid–liquid phase transitions. Physical properties are measured experimentally and compared to computed correlations for deep eutectic solvents (DES) and the percentage relative error er for the density, surface tension, and refractive index is obtained. The thermodynamic parameters, including the degradation, glass transition and crystallization temperatures, are measured using DSC and TGA. Based on these data, the solid–liquid equilibrium phase diagrams are calculated for the ideal case and predictions are made using the semi-predictive UNIFAC and the predictive COSMO RS models, the latter with two different parametrization levels. For each system, the ideal, experimental, and predicted eutectic points are obtained. The deviation from ideality is observed experimentally and using the thermodynamic models for Thymol:Borneol and Thymol:Camphor. In contrast, a negative deviation is observed only experimentally for Menthol:Borneol and Menthol:Camphor. Moreover, the chemical interactions are analyzed using FTIR and 1H-NMR to study the intermolecular hydrogen bonding in the systems.
Spent mushroom compost biochar (SMCB) was prepared by carbonization and tested for the removal of heavy metals (Zn(II), Cu(II), and Pb(II)) by adsorption. The sorption of heavy metals was evaluated by studying several factors, such as the initial solution pH, contact time, temperature, and individual and competitive adsorption. Kinetic and equilibrium studies were carried out to determine the mechanism involved during adsorption. The Weber−Morris model demonstrated the significance of intraparticle diffusion on the adsorption process. In addition, thermodynamic studies showed that the process is endothermic and favorable, with good affinity of metals to the biochar. At last, SMCB was used as the adsorbent in a continuous fixed-bed column. The breakthrough curve was obtained for each heavy metal, and Thomas and Clark models were fitted. When all three metals coexisted in solution, competitive adsorption took place in both batch and continuous systems, showing that Pb has higher affinity to SMCB than Cu and Zn.
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