Adsorption isotherms and thermodynamics of microbial inhibitors generated by the acid-catalyzed hydrolysis of hemicellulose were investigated using activated carbon as the adsorbent. Parameters of temperature (25-65 degrees C) and pH (1.0-10.0) were employed to study the adsorption isotherms of phenol, acetic acid, and furfural. The results based on the Langmuir model indicated that a higher efficiency of adsorption could be achieved at a lower pH and lower temperature for phenol and acetic acid. Furfural removal from the aqueous solution was only dependent on temperature, with a higher performance at 25 degrees C. Negative values obtained for the heat of adsorption (Delta H), entropy (Delta S), and free energy (Delta G) indicated that the adsorption of all three components is exothermic (physisorption) in nature, with a mechanism based on the affinity of the solute toward the adsorbent and non-spontaneous. The adsorptive removal of the main inhibitors (8.7 g/L phenols and 4.2 g/L acetic acid) from the concentrated hydrolysate of oat hull hemicellulose was dependent on the activated carbon dosage, temperature, and pH. Under operational conditions of pH 1.0 and 25 degrees C with an incremental carbon dosage of 1.25- 5% in the hydrolysate, the removal of phenols was 64-95.4% and that of acetic acid was 6-13.2%, respectively. The xylitol fermentation process indicated that oat hull hemicellulosic hydrolysate is low in toxicity to Candida guilliermondii. Meanwhile, a mild adsorptive detoxification using activated carbon resulted in over 10% increase in xylitol yield (approximate to 0.8 g/g) and productivity (0.5 g/L/h).