There are several factors affecting the adsorption of gases on solid surfaces. Some of the main factors include:1. Nature of the adsorbent: The chemical composition and structure of the adsorbent play a crucial role in adsorption. Porous materials like activated carbon, zeolites, and metal-organic frameworks have high surface areas and are excellent adsorbents.2. Surface area of the adsorbent: The larger the surface area of the adsorbent, the more adsorption sites are available for gas molecules to interact with, leading to higher adsorption capacity.3. Nature of the adsorbate: The chemical nature of the gas molecules adsorbate affects their interaction with the adsorbent. Polar molecules are more likely to be adsorbed on polar surfaces, while non-polar molecules prefer non-polar surfaces.4. Temperature: Adsorption is an exothermic process, meaning it releases heat. As temperature increases, the adsorption capacity generally decreases because the adsorbate molecules gain more kinetic energy and are less likely to be retained on the surface.5. Pressure: At low pressures, adsorption increases with increasing pressure as more gas molecules are available to interact with the adsorbent. However, at high pressures, the adsorption capacity may level off or even decrease due to saturation of the adsorption sites.6. Presence of other gases or impurities: The presence of other gases or impurities can affect the adsorption process by competing for adsorption sites or by modifying the adsorbent surface properties.To experimentally determine the surface area of adsorbents like activated carbon, the most common method used is the Brunauer-Emmett-Teller BET method. This method involves the adsorption of a gas, typically nitrogen, onto the surface of the adsorbent at a constant temperature usually 77 K, the boiling point of liquid nitrogen . The amount of gas adsorbed is measured at different relative pressures, and the data is used to construct an adsorption isotherm. The BET equation is then applied to the isotherm data to calculate the specific surface area of the adsorbent.The BET method is based on the assumption that gas molecules form a monolayer on the adsorbent surface, and the surface area is calculated by considering the area occupied by each adsorbed gas molecule. This method is widely used for characterizing porous materials and provides a reliable estimation of the surface area of adsorbents like activated carbon.