Adsorption behavior of selected monosaccharides onto an alumina interface.

The adsorption of glucose and fructose from their aqueous solutions onto an alumina interface has been carried out spectrophotometrically at room temperature. The adsorption isotherms are characterized as typical L-type and an adsorption mechanism on the basis of dipolar interactions has been suggested. In addition to this, a partial role of metal-saccharide interactions as found in organometallic complexes (OMCs) for the observed adsorption cannot be ruled out. Various kinetic and thermodynamic parameters of the adsorption process have been evaluated. The effects of variation in experimental conditions of the system have also been investigated. The adsorption exhibited a typical response to the pH effect and maximum adsorption was found near the isoelectric point of alumina (pH 9.0). The anionic addition to the suspension affects the adsorbed amount and Cl(-), SO(4)(2-), and PO(4)(3-) affect the adsorption quantitatively. The addition of similar concentration of cations was found to reduce the adsorbed amount. The presence of cationic and anionic detergents was found to influence both the adsorbed amount and the adsorption rate. The temperature was found to have an inverse effect on adsorption. Adsorptive kinetic parameters have revealed that fructose tends to be a better adsorbate than glucose. This is found to be consistent with the chelation behaviour of monosaccharides as found in the OMC of monosaccharides. The thermodynamics of the adsorption model indicates its spontaneous and exothermic nature. The negative values of entropy are an indication of the probability of a favorable nature of adsorption.