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.
Yao Xiao,Hai-Qin Lu,Chang-Rong Shi,Fu-Hou Lei,Darryn Rackemann,Kai Li,Wen Li,William O.S. Doherty
The decolorization of remelt syrup is the most critical step in the sugar refining process as it directly affects the quality of refined sugar. Adsorption is a useful method that can be applied to decolorize the syrup. A quaternary ammonium-functionalized chitosan/graphene oxide composite aerogel (GO-QACSA) was developed as an effective adsorbent for the removal of high-molecular-weight reducing sugar alkaline degradation products (HRSADPs), the main class of colorants in remelt syrup. The advantages of GO-QACSA to remove HRSADPs can be attributed to its well-connected 3-D network-like porous structure, nontoxicity, high hydrophilicity, and the richness of quaternary ammonium groups. The equilibrium adsorption capacity of GO-QACSA for HRSADPs reached 364.09 mg/g and the removal rate was > 90%. GO-QACSA exhibited an ultra-fast adsorption rate. Recycling experiments indicated that GO-QACSA exhibited good renewability and reusability. The interaction mechanism for the adsorption of HRSADP on GO-QACSA was studied, and the results revealed that two layers of HRSADPs adhered to the surface of GO-QACSA via electrovalent bonds formed between the quaternary ammonium and carboxylate groups. On average, 2–3 carboxylate ions in one HRSADP molecule bonded with the quaternary ammonium cations of GO-QACSA. Four phenomenological mathematical models, namely, External mass transfer resistance (EMTR), Internal mass transfer resistance (IMTR), combined EMTR–IMTR, and Adsorption on active sites (AAS), were presented based on the best-fit equilibrium isotherms. These models could be used to provide new insights into the adsorption mass transfer behaviors of the system.
危险品化学品经营许可证（带存储）