Batch-type experiments were carried out to obtain equilibrium isotherms for the adsorption of phenol and m-cresol in aqueous solutions on activated carbon. Single solute systems, at 20 and 40 • C, were tested for Langmuir, Freundlich and Sips adsorption isotherms in the range of concentrations up to 200 mg/L. Equilibrium data were more closely followed by the Freundlich and Sips equations for all cases. Adsorption isotherms for bisolute systems at 20 • C, with two different initial concentrations of phenol and m-cresol, were predicted solely on the basis of single solute equilibrium parameters by using the equations of Butler and Ockrent and the IAS theory. The best agreement with the experimental loading values was afforded with the IAS theory based on Sips isotherm for pure compounds. However, this theory is found to be not able to predict with success the binary isotherms in this work where significant displacement of one solute by the other is observed. Chemical interactions in the adsorbed phase, estimated by a modified Butler-Ockrent model, can be responsible for this lack of success of the conventional IAS theory. The predictions based on the IAS theory are compared with the results of some empirical models.

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Phenolic acids and flavonols of nine leaf and three root samples of Boerhaavia diffusa L., collected at different locations and subjected to several drying procedures, were characterised by reversed-phase HPLC-PAD-ESI/MS for the first time. Ten phenolic compounds were identified: 3,4-dihydroxy-5-methoxycinnamoyl-rhamnoside, quercetin 3-O-rhamnosyl(1-->6)galactoside (quercetin 3-O-robinobioside), quercetin 3-O-(2"-rhamnosyl)-robinobioside, kaempferol 3-O-(2"-rhamnosyl)-robinobioside, 3,5,4'-trihydroxy-6,7-dimethoxyflavone 3-O-galactosyl(1-->2)glucoside [eupalitin 3-O-galactosyl(1-->2)glucoside], caffeoyltartaric acid, kaempferol 3-O-robinobioside, eupalitin 3-O-galactoside, quercetin and kaempferol. Quantification was achieved by HPLC-PAD and two phenolic patterns were found for the leaves, in which quercetin 3-O-robinobioside or quercetin 3-O-(2"-rhamnosyl)-robinobioside was the major compound. Caffeoyltartaric acid was only present in the root material where it represented the main phenolic constituent. The results obtained demonstrated that the geographical origin (particularly the nature of the soil), but not the drying process, influences the phenolic composition.

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Adsorption of D, L-Phenylalanine onto polymeric adsorbents (Amberlite XAD-4 and XAD-16; Sephabeads SP206 and SP207) was studied. Adsorption equilibrium isotherms were measured by batch equilibration at 15 and 40°C showing the possibility of using a parametric pumping technique for aminoacid purification/recovery. Dynamic studies in a laboratory adsorption column Amicon Column (22 x 500 mm) were carried out to further screen adsorbents and obtain mass transfer parameters to be used in the modeling, simulation and operation of the pilot parametric pumping unit. The pilot plant includes a Amicon Columnn (90 x 1000 mm) and is completely automated. A package for the simulation of this cyclic operation was developed. Simulated and experimental results using Sephabeads SP206 (Mitsubishi Kasei Corporation, Japan) are in good agreement. 0 1998 Elsevier Science B.V.