ANS:A - Higbie

T he Higbie penetration theory, developed by Albert Higbie in 1935, is a fundamental concept in the field of mass transfer, particularly in the context of diffusion and absorption processes occurring at a gas-liquid interface. The theory describes the rate at which a solute or gas diffuses through a stagnant liquid film to reach the interface where it can be absorbed or react with the liquid. This concept is crucial in various engineering applications such as chemical reactions, gas absorption, and liquid extraction. Higbie's theory assumes that the concentration gradient of the solute or gas across the liquid film is the driving force for mass transfer. It considers the liquid phase to be stagnant, meaning that there is no bulk motion of the liquid within the film. The theory also assumes that the concentration of the solute or gas in the bulk of the liquid remains constant, and any change in concentration occurs only within the thin film adjacent to the gas-liquid interface. Mathematically, the Higbie penetration theory can be expressed using Fick's law of diffusion, which relates the flux of a solute or gas through a medium to the concentration gradient: 𝐽=−𝐷𝑑𝐶𝑑𝑥J=−DdxdC​ Where:

• 𝐽J is the flux of the solute or gas,
• 𝐷D is the diffusion coefficient of the solute or gas in the liquid,
• 𝐶C is the concentration of the solute or gas at a given distance from the interface,
• 𝑥x is the distance from the interface.

Higbie's theory provides a valuable framework for analyzing and designing mass transfer processes involving gas-liquid interfaces. However, it's important to note that in many real-world situations, the assumptions made by the theory may not hold true, and more complex models may be necessary for accurate predictions.