The Preparation Of Glucose Acid By Desalination

Glucose acid is an important food additive widely used in chemical, food, medicine, and light industry; which was mainly produced from sodium gluconate(a fermentation product) by cation exchange chromatography.This technology has a long production cycle, and need to regenerate resin, and produces a large amount of waste water.In order to reduce the industrial waste water, three alternative desalting technologies were investigated for preparation of glucose acid. The main results were as follows:(1)Desalt by ethanol precipitationEffects of sodium gluconate to hydrochloric acid ratio, volume fraction of ethanol and incubation time on the yield of gluconic acid and desalinization ratio were investigated under Single factor test.The optimal technology of ethanol precipitation was obtained by the orthogonal test and variance analysis. The results showed that it yielded 66.15% of gluconic acid and removed 80.44% of salt under the following optimal condition: one part of sodium gluconate was reacted with 2 volume of HCl(in equimolar ratio), and then ethanol was added to 75%(final concentration) and incubated at room temperature for 24 h.(2)Desalt by nanofiltrationEffects of pressure,temperature and concentration time on the retention rate of gluconic acid and permeate flux were investigated under Single factor test.The optimal technology ofnanofiltration was obtained by the orthogonal test and variance analysis. The optimal nanofiltration(150 D molecular cut-off) technology was: 10.0 L of solution, in which sodium gluconate(1g) was neutralized using HCl,was nanofiltrated at 0.3 MPa and 30 ℃ for 110 min. Under this condition, membrane flux reached 10.01L/m2 h, 85.99% of gluconic acid was and 78.66% of salt was removed after nanofiltrated for four cycles.(3)Preparation of glucose acid using calcium gluconateEffects of calcium gluconate to sulfuric acid molar ratio,temperature and time on the yield of gluconic acid and the weight of calcium sulfate were investigated under Single factor test.The optimal technology of ethanol precipitation was obtained by the orthogonal test and variance analysis. The results showed that it yielded 85.11% of gluconic acid and 0.3758 g calcium gluconate of calcium sulfate was obtained under the following optimal condition: one part of calcium gluconate was reacted with 7 volume of H2SO4(in equimolar ratio), and then kept at 50℃for 1h. On the basis of a comprehensive score of yield of glucose acid and the weight of calcium sulfate, themost influential factor was the mola ratio of calcium gluconate to H2SO4, the least influential factor was the precipitation timecomprehensive score of.