No abstract

The solubility of veramoss in n-butyl alcohol, ethanol, isopropanol, ethyl acetate, acetone, tetrahydrofuran, isoamyl alcohol, n-amyl alcohol, n-propyl alcohol, and DMF pure solvents and various {ethanol + water} mixtures at T = 283.15−333.15 K and atmospheric pressure was measured by using the dynamic method. The experiment solubility data showed that the solubility of veramoss increased with increasing temperature in all solvents selected and decreased with the rise of mole fraction of water in the binary solvent mixtures of {ethanol + water}. The modified van't Hoff equation and the Apelblat model were successfully used to correlate the experimental solubility in pure solvents while the modified Apelblat model, the van't Hoff equation, and the CNIBS/R model were applied to correlate the solubility in binary solvent mixtures, and all of the models provided good fitting to the data. Furthermore, the thermodynamic parameters (dissolving enthalpy, dissolving entropy, and Gibbs free energy) of veramoss in different solvents were also calculated based on the Wilson equation and experimental solubility data; the dissolving process of veramoss in all selected pure solvents was observed as an endothermic, nonspontaneous, and entropy-driven process and in the binary solvent mixtures of {ethanol + water} was observed as an endothermic, spontaneous, and entropy-driven process. The data of experimental solubility, correlation equations, and thermodynamic property can be used as essential data for a preliminary study of industrial applications.

The precipitation of calcium carbonate in heat exchanger is a serious problem in seawater desalination which results in significant decrease of heat exchange efficiency and tedious cleaning. Decalcification pretreatment by acidic flue gas provides an efficient and economical solution to this problem, but few literature has been reported about the crystallization mechanism of CaCO3, including the supersaturation ratio, the relationship between the supersaturation ratio of the reaction solution and the crystallization growth rate of CaCO3 in the CO2‐CaCl2‐H2O system. In this study, the crystallization of CaCO3 was studied by combing the dynamic method and the static method to ensure the accuracy in measuring the carbonate ion concentration by chemical titration at pH = 8.0 in the CO2‐CaCl2‐H2O system. It was found that there existed an ion competition between HCO3− and CO2 (aq) in the CO2‐CaCl2‐H2O system, which led to fluctuations of CO2 absorption rate. The supersaturation ratio of the reaction solution still increased when the reaction crystallization rate was reduced. The variations of the concentration of HCO3−, CO32− and Ca2+ ions with time were investigated. The growth process of the vaterite was monitored and described on mesoscale.