adsorptive

Adsorptive is an adjective relating to adsorption, the process by which molecules or ions accumulate on a surface, forming an adsorbed layer. Not to be confused with absorption, where a substance permeates and distributes within a material. Adsorption is a surface phenomenon driven by interactions between adsorbate and adsorbent.

Mechanisms and factors governing adsorption include physisorption, which involves weak van der Waals forces and is typically reversible and exothermic, and chemisorption, which involves stronger chemical bonds and may be irreversible at ambient temperatures. Both contribute to an adsorptive capacity that depends on surface area, porosity, pore size distribution, and surface chemistry. Temperature and pressure influence adsorption; higher surface area and microporosity increase capacity, and adsorption is often favored at lower temperatures for exothermic processes.

Materials and applications: common adsorbents include activated carbon, zeolites, silica gel, alumina, clays, and metal-organic frameworks. Applications include water purification, air purification, gas separation, catalysis support, desulfurization, and chromatography. In environmental engineering, adsorption is used to remove organic contaminants, dyes, heavy metals, and odors.

Modelling: adsorption data are described by isotherms, such as Langmuir (monolayer on homogeneous sites) and Freundlich (heterogeneous surfaces). Kinetic models like pseudo-first-order and pseudo-second-order describe uptake rates. Fixed-bed and batch processes are used in design. Desorption and regeneration restore adsorbents for reuse.