sorbing

Sorbing is the process by which a substance is taken up by another substance through sorption, a collective term that includes adsorption and absorption. Adsorption occurs when molecules adhere to a surface, while absorption involves uptake into the sorbent’s interior. Sorption is widely used in chemistry, environmental science, and materials engineering to describe how contaminants, nutrients, or gases interact with solids, liquids, or membranes. Desorption is the reverse process, releasing sorbed species back into the surrounding phase.

Adsorption and absorption have different driving forces and kinetics. Adsorption is driven by surface interactions and is often described by equilibrium isotherms relating sorbed amount to concentration. Absorption involves diffusion into the interior of the sorbent and depends on porosity and internal binding sites. In practice, sorption is an umbrella term for both mechanisms and their combination, while desorption refers to the release of sorbed material.

Quantifying sorbing capacity involves measuring how much a sorbent can hold per unit mass or volume and describing its behavior with isotherms and kinetics. Langmuir and Freundlich models are commonly used for equilibrium, while linear or pseudo-first-order or pseudo-second-order kinetics describe uptake rates. Key factors include surface area and porosity, chemical functionality, temperature, pH, ionic strength, and the presence of competing species.

Applications include water and air purification, soil and groundwater remediation, gas capture, and drug delivery. Sorbents include activated carbon, zeolites, clays, polymers, and inorganic materials that remove contaminants, separate species, or stabilize reactive compounds. The concept of sorption informs the design and assessment of treatment systems, storage strategies, and environmental risk evaluations.