Desalination Of Sugar Cane Molasses By Electrodialysis

Molasses, which is mainly consisted of sucrose, reducing-sugars, colorants, collides, inorganic ash, is one of the by–products in sugar industry. It has great potential exploitation value in chemical industry, food industry, medicine and building materials industry due to its low price and simple processing. This paper introduced the desalination process of molasses by electrodialysis, besides, the desalted molasses could be served as the resource material for special sugars, and the wastewater produced by electrodialysis could be used as inorganic fertilizer.First, primary compositions in molasses were measured, and the results showed as follows: the average content of sucrose was 528.75mg/mL tested by colorimetric method; the average content of reducing-sugars were 220.95mg/mL measured by DNS assay; the average content of potassium ion was 114.9mg/mL, which revealed that molasses was rich in potassium ion, and thus this component could be collected and be used for multipurpose.Then, molasses was desalted to find out the influence factors of the desalination process. Desalination ratio and depotassication ratio were adopted as the quantitative indicators, operation voltage, material flux and concentration of molasses were employed as variable elements. Box-Behnken model of response surface in Design Expert software was used to analyze the experiment data. The model of desalination (Y1) and depotassication (Y2) were:The optimal process conditions were given as follows: operation voltage was 33.70V, material flux was 66.00L/h, concentration of molasses was 10.00°Bx, and the ratio of desalination and depotassication were 87.06% and 87.42%, respectively. The results of verification experiments were 85.67% and 84.81%, which proved that this model was reliable and practicable.Meanwhile, the limited current had a great effect on electrodialysis; hence energy consumption should be taken into account as a critical factor during the industrialized production. Limited current of electrodialysis processing was determined, and some abnormal phenomena such as concentration polarization during the molasses desalination process were analyzed as well. When the flux of fresh and concentrated water section reached to 60L/h, the maximum limited current was 0.520A, and the corresponding voltage was nearly 1.11V,that meant the applied voltage was about 33.30V.Under the optimal operation conditions of electrodialysis. The antioxidant activity of crude molasses and sample molasses desalted by electrodialysis process was measured by DPPH method. IC50 value (the value of molasses concentration for scavenging half of DPPH radical) of them was 0.2887 mg/mL and 0.3669 mg/mL, respectively. The results showed that electrodialysis process had a little effect on antioxidant activity of molasses. Meanwhile, under the optimal operation conditions of electrodialysis, electric current ratio was 52.65%, and electricity consumption was 3.56 KW·h when the molasses desalination ratio achieved 87.08%.