Adsorptive Separation of Oils

Abstract

Vegetable oil refining processes, specifically, silica refining and bleaching, require a working understanding of adsorption or more specifically the physico‐chemical interaction between sorbent, substrate and contaminants. An understanding of adsorption theory and the factors affecting adsorption is useful in controlling these processes. Isotherms have been used as mathematical models to describe the relationship between adsorbed and non‐adsorbed molecules. The Langmuir isotherm theoretically describes oil pigment binding as reversible, monolayer chemisorption, where all adsorption sites are energetically equal. However, many systems conform to a Langmuir isotherm without these suppositions necessarily holding true. Langmuir behavior may provide useful practical information on the variables affecting the adsorption, but it does not provide proof of the adsorption mechanism. The Freundlich isotherm is supposed to describe reversible adsorption of a single solute at equilibrium at a fixed temperature. It also has been successfully used to describe pigment adsorption from vegetable oil and, likewise, has empirical value in describing the effect of processing variables on adsorption performance. In reality, pigment binding onto adsorbent clays is irreversible and there will be more than one oil solute competing for adsorption sites. Adsorptive binding of solute to adsorbent involves a number of forces, including chemisorption and physisorption, all of which affect bleaching efficiency. Adsorbent dosage, acidity, moisture in the system, temperature and pressure, all key factors that can be used to control the adsorption process.

Optimisation of soya bean oil bleaching by ultrasonic processing and investigate the physico‐chemical properties of bleached soya bean oil

“…The optimal temperature for the adsorption of polar compounds such as soap, phospholipids, trace metals and peroxides is around 60–80 °C. This temperature for colour adsorption (chlorophyll and carotenoid) is 100–120 °C, 100 °C for splitting of soap and free fatty acid and peroxide breakdown and aldehyde and ketone occur at 110–120 °C (Proctor & Brooks, ). Ultrasonic processing decreased the optimal temperatureto 65 °C, which is about a 35% energy saving.…”

“…The optimal temperature range for oil bleaching is 85-120°C depending on oil type and clay activity (i.e. residual and surface acidity) (Proctor & Brooks, 2005).…”

Accelerating Bleaching of Soybean Oil by Ultrasonic Horn and Bath Under Sparge of Helium, Air, Argon and Nitrogen Gas

“…(2) Unstable cavitation results in the growth of bubbles to the maximum size and their violent collapse. This phenomenon occurs at low frequencies and high intensities of irradiation leading to the chemical processing (Proctor and Brooks ; Kulkarni and Rathod ).…”