Sevugan Palaniappan

Adsorption of soy oil free fatty acids by rice hull ash

Studies demonstrated that free fatty acids can be adsorbed from a soybean oil/hexane miscella by inorganic rice hull ash. A 1% dose was effective in diminishing free fatty acid concentrations but acid activation reduced the adsorption. Binding of free fatty acids followed a Freundlich isotherm with smaller doses of ash adsorbing more efficiently. Addition of isopropanol to the miscella promoted the adsorption, while water deactivation of the ash had no effect, possibly because water occupied sites not accessible to free fatty acids. Impaired adsorption behavior of ash heated above 700°C could have been due to disruption of the crystal form. The adsorption behavior of rice hull ash may be more fully understood with a better knowledge of adsorbent structure.

Soy Oil Lutein Adsorption by Rice Hull Ash

Rice hull material was converted to an adsorbent of the soy oil pigment, lutein, by a combination of ashing and acid activation. Pigment was adsorbed from a 20% (v/v) soy oil/hexane miscella. The most effective ashing temperature was 500°C. Five percent acid activation significantly promoted adsorption of the ash, but greater acid activation did not increase adsorption capacity very much. In the system studied, the performance of activated ash was comparable to that of activated bleaching earth. Nonactivated ash also had an ability to bind lutein but was less effective than activated adsorbent. The absorbance spectrum of the residual lutein was not altered by rice hull ash, but was changed when exposed to bleaching clay.

Competitive adsorption of lutein from soy oil onto rice hull ash

Adsorption of lutein from crude soybean oil onto acid ash prepared from rice hulls displayed Freundlich-type isotherms. Different isotherms were obtained depending on the amount of adsorbent used. Addition of isopropanol to the miscella and water deactivation of the adsorbents decreased lutein adsorption. These observations suggested competitive adsorption based on polarity. Triglycerides were adsorbed to a greater extent than lutein, probably due to their larger concentrations. These findings parallel the adsorption behavior of silicic acid.

Phospholipid adsorption onto rice hull ash from soy oil miscellas

Phospholipid was adsorbed from soy oil miscellas by rice hull ash, with small doses of adsorbent binding most efficiently. Adsorption increased with residual phosphorus, suggesting that less accessible adsorption sites were being used as residual values increased, probably due to the heterogeneous nature of the ash. Binding of phospholipid was enhanced by isopropanol, as has been found for adsorption on silicic acid.

Evaluation of Soy Oil Lutein Isotherms Obtained with Selected Adsorbents in Hexane Miscellas

Bleaching of soy oil hexane/miscellas by adsorption of the lutein was examined. Quantitative differences in the adsorption behavior between a bleaching clay, alkaline rice hull ash and acid rice hull ash were measured by comparing the constants,K andn, of Freundlich isotherms. All the isotherms were dose-dependent withK being inversely related andn directly related, to adsorbent mass. Overall, the bleaching clay performed better than the ashes. Alkaline ash had a largerK value than acid ash, but then value of acid ash was greater.Equations of lutein adsorption were derived based on initial concentrations on lutein and the amount adsorbed per gram. Logarithmic plots produced constants,Ki and ni which were the intercept and slope, respectively. As adsorbent dose increased,Ki decreased andni increased for each adsorbent studied. These findings may have applications in the processing of dilute miscellas where low temperature, low viscosity oil refining is desired.

Desorption of soy oil lutein from rice hull cristobalite with polar solvents

The effectiveness of sequential isopropanol/hexane washes of increasing polarity for desorbing soy oil pigment (lutein) from alkaline and acid rice hull ash was studied. Increasing the polarity promoted desorption of pigment. However, the amount of pigment desorbed with each extraction decreased after washing with 2% isopropanol. More lutein was desorbed as the amount of adsorbed lutein increased. Desorption from acid ash was greater than that from alkaline ash, which may be due to the absence of potassium from acid ash. The data suggest that the adsorption sites, occupied by lutein, are not all equally accessible to isopropanol, probably because of the irregular structure of the ash.