Process optimization studies on solvent extraction with naphthalene-2-boronic acid ion-pairing with trioctylmethylammonium chloride in sugar purification using design of experiments

The extraction of xylose and glucose from aqueous solution with naphthalene-2-boronic acid (N2B) in diluents of n-hexane:1-octanol (85:15 v/v) was investigated. The influence of pH, N2B concentration and phase ratio (O/W) (organic phase volume to aqueous phase volume) were investigated for an optimized condition of xylose and glucose extraction from the aqueous solution. The optimization process was analyzed using Central Composite Face-Centered Experimental Design by Design Expert Version 6.0.6 (Stat-Ease, USA). The optimum pH for extraction, N2B concentration and phase ratio (O/W) are at 11, 0.083 mol/L and 1.5, respectively. The extraction percentage of xylose and glucose under these conditions are found to be 92.7 and 98%, respectively. Additionally, the sugar-loaded extractants were regenerated by dilute hydrochloric acid in the stripping process. With sufficient amount of acid available in the strip solution, the sugars are completely recovered in the aqueous phase.