Investigation on water vapor adsorption performance of carbon based composite adsorption material ACF-silica sol-LiCl

The composite adsorption material ACF-silica sol-LiCl (ASL) is prepared by impregnating activated carbon fiber (ACF) with silica sol and LiCl to improve the water vapor adsorption performance. The silica sol provides support to the soft ACF and solidifies it. The silica sol also increases the adhesion area in the ACF for the LiCl. The LiCl can effectively improve the water vapor adsorption performance of the ACF. The adsorption performance of the ASL is optimum when the LiCl impregnation concentration is 430 mg/L. Scanning electron microscope images show that the silica sol and LiCl fill the fibers pores and spaces between the fibers in the ACF after impregnation. And adsorption kinetics of the ASL is characterized using a linear driving force (LDF) model and experiments. Results show that ASL has a high dynamic water absorption rate and adsorption rate coefficient (k). The k of the ASL reaches 1.58 × 10−4−2.05 × 10−4, which is 0.27 × 10−4−0.59 × 10−4 higher than that of the ACF. Meanwhile, the results of water vapor isothermal adsorption tests show that the impregnation of silica sol and LiCl increases the hydrophilicity of the ACF, and thus greatly enhances its water vapor adsorption capacity. The adsorption capacity of the ACF is almost 0 at P/P0 < 0.2 and reaches a maximum of 0.5479 g/g at P/P0 = 0.65. The adsorption capacity of the ASL steadily increases with the relative pressure. When the relative pressure is close to 1, the adsorption capacity of the ASL reaches 2.2876 g/g, which is 2.67 times the maximum for the ACF.