Synthesis of MgCl2/vermiculite and its water vapor adsorption-desorption performance

In atmospheric water harvesting (AWH), the development of new adsorbents can increase the water harvesting capacity of AWH. In this article, a new composite adsorbent MgCl2/vermiculite was synthesized. Scanning electron microscopy (SEM) test, N-2 adsorption test, adsorption performance test, desorption performance test, cyclic adsorption test, and adsorption characteristic curve fitting were carried out on this new type of composite adsorbent. The composite adsorbent MgCl2/vermiculite was compared with the traditional adsorbent 13X and MgCl2/13X. The conclusion is as follows: The adsorption performance of MgCl2/vermiculite prepared with a salt solution with a salt content of 31.03% is the best. The equilibrium adsorption capacity of MgCl2/vermiculite is sensitive to changes in humidity. As the humidity increased from 50% to 80%, its equilibrium adsorption capacity increased by 2.5 times. When MgCl2/vermiculite is adsorbed for 200 minutes, the adsorbent adsorption can reach 80% of the equilibrium adsorption capacity, and the adsorption efficiency is the highest at this time. At 160 degrees C, the desorption time of MgCl2/vermiculite is short, and the desorption capacity reaches 96.75% at 45 minutes. The adsorption cycle of MgCl2/vermiculite was performed 10 times, the average adsorption value was 0.3275 g/g, the fluctuation range was 0.3275 +/- 0.038 g/g, and the adsorption cycle performance was good. Based on the Polanyi adsorption potential theory, the adsorption characteristic curve of the composite adsorbent was fitted, and the D-A equation was obtained. Under 40-90% humidity and normal temperature conditions, the error between the predicted value of the equation and the actual value is less than 10%. Compared with the traditional adsorbent 13X, MgCl2/vermiculite has the advantages that MgCl2/vermiculite has high water vapor adsorption performance, hard texture, and not easy to break. In summary, MgCl2/vermiculite is a more excellent water vapor adsorption material, which is expected to be used in large-scale AWH.