What is GAB model?

The GAB (Guggenheim–Anderson–de Boer) and BET (Brunauer–Emmett–Teller) are the most common models used for the determination of the sorption isotherms for different materials. The GAB model is represented by constant C and K. Constant C is a positive value that represents the total heat of the first layer of sorption.

What is food moisture sorption isotherm?

The food sorption isotherm describes the thermodynamic relationship between water activity and the equilibrium of the moisture content of a food product at constant temperature and pressure. The typical shape of an isotherm reflects the way in which the water binds the system.

How do you draw an isotherm sorption curve?

The classic way to create an isotherm is to put the sample in a desiccator with a salt solution of known water activity until the sample’s weight stops changing. Then, the sample is weighed to determine water content. Each sample produces one point on the isotherm curve.

What are the types of adsorption isotherms?

Type I is characteristic of microporous solids with a relatively small proportion of the outer surface. Type II refers to polymolecular adsorption in nonporous or macroporous adsorbents. Type III is characteristic of non-porous sorbents with low energy of adsorbent-adsorbate interaction.

What is Type 2 adsorption isotherm?

The reversible Type II isotherm is the normal form of isotherm obtained with a non-porous or macroporous adsorbent. It forms because lateral interactions between adsorbed molecules are strong in comparison to interactions between the adsorbent surface and adsorbate.

What do adsorption isotherms show?

An adsorption isotherm is a graph that represents the variation in the amount of adsorbate(x) adsorbed on the surface of the adsorbent with the change in pressure at a constant temperature.

What are isotherm models?

Classification and physical meanings of the isotherm models. Isotherm refers to the relationship between the equilibrium adsorbate concentrations in the liquid-phase and the equilibrium adsorption amount on the solid-phase at a certain temperature.

What is Type 3 adsorption isotherm?

Type III isotherm is obtained when the amount of gas adsorbed increases without limit as its relative saturation approaches unity. This type of isotherm is obtained when bromine is adsorbed on silica gel at 20 oC.

What is the benefits to have mesoporous isotherm?

Mesoporous materials are ideal in diagnostics applications due to their increased image contrast and chemical stability. Moreover, functional moieties that can be conjugated within the pores enables new possibilities for multiple measurements and detection.

What is C in isotherm?

A type I isotherm is obtained when P/Po < 1 and c > 1 in the BET equation, where P/Po is the partial pressure value and c is the BET constant, which is related to the adsorption energy of the first monolayer and varies from solid to solid.