Water Vapor Adsorption/Desorption Behaviors on Activated Carbon Particles and Fixed Beds: Isotherms, Kinetics, and Axial Temperature
Chao Zheng, Yongxiang Niu, Kai Kang, Yucong Xie, Hao Han, Hua Song, Jian Hu, Shupei Bai
Abstract
Relative humidity and moisture content are the key factors affecting the adsorption abilities of activated carbons (ACs) against these physisorption-type volatile organic compounds and industrial toxic chemicals due to competitive adsorption. Water vapor adsorption/desorption behaviors on AC particles and fixed beds are of great interest in materials science, the chemical industry, and military chemistry. This work selected two typical ACs (AC and ASZM-T) used in chemical protection. Water vapor adsorption equilibrium, adsorption kinetics, dynamic adsorption/desorption curves, and axial temperature during the adsorption/desorption process were systemically investigated. Results show that water vapor adsorption–desorption isotherms belong to the “S” type with obvious triangular hysteresis loops. Adsorption curves at different temperatures almost overlap, proving the temperature-independence. Dynamic adsorption–desorption curves on the fixed beds could be divided into different stages. The duration of each stage and adsorption/desorption rate are mainly determined by the relative humidity and moisture content. The heat effect induced by water vapor adsorption/desorption could cause the fixed bed to be in a nonisothermal state, indicating that the heat transfer inside the fixed bed was mainly controlled by the water vapor mass transfer. It provides a theoretical basis for temperature-induced low-concentration multicomponent competitive adsorption under relative humidity and moisture content levels.