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Separation Science and Technology, Vol.40, No.9, 1761-1780, 2005
Separation of fructose and glucose from cashew apple juice by SMB chromatography
The simulated moving bed (SMB) technology has been applied to a number of carbohydrate separations. The cashew apple is the pseudo-fruit of the cashew tree; it contains approximately equal amounts of fructose and glucose and is presently an agricultural waste largely found in Northeastern Brazil. This work shows experimental results for the separation of fructose from glucose, found in cashew apple juice, using a conventional four-section SMB. The two sugars were successfully separated with product purities around 90%. The operating conditions were chosen from the equilibrium theory applied to a multicomponent system with linear uncoupled isotherms. The performance at cyclic steady state was well predicted with both TMB- (true moving bed) and SMB-based models. However, during startup, there was a buildup of sugar concentration in the unit, which was not observed for synthetic mixtures. Fixed-bed adsorption and desorption runs were performed with dilute cashew apple juice. They provided experimental evidence that high molecular weight molecules might have been adsorbed onto the resin, which could be a probable explanation for the anomalous behavior previously observed. Clarified cashew apple juice (free of tannins) was also used as the SMB feed and no anomalous transient behavior was observed. On the contrary, process performance perfectly matched that obtained from simulation assuming a synthetic glucose-fructose mixture. The results presented herein are the first record of sugar separation in SMB from cashew apple juice and should provide scientific support for economic alternatives to the industrial processing of the cashew crop.