Preparation, flocculation and application in sugar refining of eco-friendly dextran-polylysine complex flocculant

Polysaccharides have been widely used in many fields. In the field of food water treatment, polysaccharide-based flocculants have attracted extensive attention. Based on the enzymatic preparation of high molecular weight dextran, two safe, sustainable and eco-friendly dextran based high molecular flocculants were developed by introducing flocculating active groups into the molecular chain of dextran through cross-linking (DEPL) and esterification (Dex-PL). The prepared product was characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy (FESEM). Because amino group is the main active group of flocculation, more amino groups are retained in esterification reaction. In the flocculation experiment of kaolin suspension, the efficiency of the two flocculants is very excellent, both of which are greater than 96%. The results of the study on the flocculation mechanism showed that charge neutralization, adsorption bridging and sweeping flocculation mechanisms occurred in the flocculation process. Dex-PL was applied to the clarification of sugarcane juice in sugar industry. At the dosage of 118 mg/L, the clarification efficiency reached 91.4%. The results of biodegradation experiment showed that the product can be biodegraded by enzymatic hydrolysis. This study provides experience for the development and application of new polysaccharide based flocculants, and provides safe and effective flocculants for sugar refining.