Adsorptionbased

Adsorption-based technologies rely on adsorption, the adhesion of molecules from a gas or liquid onto a solid surface. The adsorbent provides sites where target species concentrate, enabling separation, purification, storage, or energy-related functions. Adsorption is distinct from absorption, in which substances diffuse into a material's interior.

Adsorption can be physisorption, driven by weak van der Waals forces, or chemisorption, involving stronger chemical bonds. Physisorption is typically reversible with modest energy input, while chemisorption is more selective and often irreversible under mild conditions.

Common adsorbents include activated carbon, silica gel, alumina, and zeolites, as well as magnetically treated materials. More recently, metal-organic frameworks and covalent organic frameworks offer high surface area and tunable pore structures, enabling selective uptake of water, CO2, hydrocarbons, or organic contaminants.

Prominent processes are pressure swing adsorption (PSA), temperature swing adsorption (TSA), and vacuum swing adsorption (VSA). These cycles involve adsorbent beds that capture the target species at one condition and release it upon depressurization or heating, enabling gas separation, purification, and dehydration.

Applications span gas purification, natural gas dehydration, carbon dioxide capture, hydrogen separation, air separation, and moisture control in ventilation. In thermal management, adsorption chillers and heat storage systems use adsorbents to exchange heat with a sorbate, offering quiet, low-maintenance operation.

Advantages include energy-efficient operation at moderate temperatures, simple hardware, and adaptability to variable energy sources. Limitations involve finite adsorption capacity that depends on humidity and contaminants, sorbent degradation, regeneration energy requirements, and higher capital costs for some materials.

Research focuses on developing robust, high-capacity sorbents with selective affinities, such as advanced MOFs and zeolites, as well as composites and coatings to enhance stability and ease of regeneration.