Characterization of Water Vapor Sorption Performance and Heat Storage of MIL-101 (Cr) Complex MgCl2, LiCl/LaCl3 System for Adsorptive Thermal Conversion

Adsorption heat conversion systems can provide heating and cooling across time and space in a more environmentally friendly way. Porous materials are potential candidates for water-based adsorption thermal conversion, in which a metal-organic framework (MOF) has a larger specific surface area and porosity than other porous matrices. However, many MOFs with high saturated adsorption capacity have great deficiencies in performance at low water vapor partial pressure, which hinder their application in adsorption thermal conversion. To improve the water vapor adsorption performance of MIL-101 (Cr), different contents of magnesium chloride, lithium chloride, and lanthanum chloride are mixed into MIL-101 (Cr) by an impregnation method. The properties and structures of the materials are characterized by XRD, SEM, nitrogen adsorption tests, water vapor adsorption tests, TG, FTIR, and so on. The results show that the saturated water vapor adsorption capacity of the sample impregnated with salt increases by 1.5-2.3 times, up to 2.24 g/g, compared with that of the unimpregnated sample. When the partial pressure of water vapor is 0.3, the adsorption capacity increases by 5.3-7.5 times and reaches 0.68 g/g at most. The maximum heat storage density of impregnated samples can be increased by 866 J/g. Impregnated MgCl2 can greatly improve the adsorption and thermal conversion performance of MOF, and impregnated MgCl2 and the proper amount of LiCl can further improve the performance of the material system. Our experiments show that the composite impregnation of magnesium chloride and the proper amount of lithium chloride can improve the application performance of the MOF materials in the adsorption thermal conversion process.

Efficient Cationization of Cotton for Salt-Free Dyeing by Adjusting Fiber Crystallinity through Alcohol-Water-NaOH Pretreatment

Cationization of cotton is considered to be an effective way to realize salt-free dyeing of reactive dyes. However, applying cotton modified with glycidyltrimethylammonium chloride (GTA) suffers from large consumption of the cationic reagent. One of the reasons is that high crystallinity of cotton fibers hinders the penetration of the reagents into the cellulose interior and limits the reaction between them. This paper designed to use alcohol-water-NaOH system to pretreat the fibers before cationization. With this method, crystallinity of the cotton fibers is decreased and more reactive -OH is exposed, resulting in much higher fiber-reagent reactivity and increased GTA utilization. Influence of alcohol type, alcohol-to-water ratio, and quantity of NaOH on fiber crystallinity and GTA dosage for cationization are all examined. It is found that for achieving 96.0% fixation of C.I. Reactive Black 5 in the absence of salt, GTA dosage can be reduced by half when the fibers are pretreated by alcohol-water-NaOH. Compared with ethanol, n-propanol and isopropanol, tert-butyl alcohol incorporated system shows better performance in increasing fiber reactivity due to their weaker ability to dissolve ions. In this study, XRD and FT-IR are used to demonstrate changes in crystallinity of the fibers after pretreatment. The alteration in micromorphology and hydrophilicity of the pretreated fibers is observed by SEM and water contact angle test, respectively. Furthermore, the alcohol-water-NaOH system can be recycled to show very good repeatability. Notably, all dyed samples pretreated with the system present high color saturation and satisfactory color fastness, especially that the wet rub fastness reaches 4-5 grade, which is one grade higher than that obtained from the conventional dyeing with salt. The above findings prove that alcohol-water-NaOH pretreatment is effective in enhancing reactivity of the cotton fibers and penetrability of the agent, and it shows promising prospects in real application.