松香基阴离子交换树脂的制备及其对己糖碱性降解色素的吸附作用

Rosin-based Anion Exchange Resin: Synthesis and Performance toward Adsorption of Alkaline Degradation Products of Hexoses

摘要:

蔗糖在生产过程中产生的己糖碱性降解色素（Alkaline degradation products of hexoses，HADPs）会导致成品糖色值增加，从而降低成品糖品质。采用悬浮聚合法制备新型松香基阴离子交换树脂（Rosin-based anionic exchange resin，RAER），用于除去糖汁HADPs。采用扫描电子显微镜、氮气吸附-脱附比表面积及孔径分布测试仪、同步热分析仪等对RAER进行表征，结果表明树脂孔隙结构丰富且热稳定性好。研究了RAER对HADPs的吸附性能，在树脂投加量为0.05 g/mL，吸附温度为70 ℃，接触时间为10 h，pH值为7及HADPs浓度为100 mg/L，RAER对HADPs的脱色率可达到100%，再生20次后脱色率仍有92.2%，RAER具有良好的重复使用性能。Zeta电位分析表明，RAER吸附HADPs行为存在静电吸引作用（离子交换）。RAER吸附HADPs动力学符合准二级动力学模型（R2≥0.99），等温线符合Freundlich模型（R2≥0.98），热力学参数ΔH=62.32 kJ/mol，吸附机理是以化学吸附为主的多层吸热过程。

Abstract:

The alkaline degradation products of hexoses (HADPs) produced during the production of sucrose increase the color value of the finished sugar, thereby reducing the quality of the latter. In this study, a novel rosin-based anion-exchange resin (RAER) was prepared by suspension polymerization to remove HADPs from sugar solutions. The RAER was characterized by scanning electron microscopy, Brunauer–Emmett–Teller measurement (with nitrogen), and synchronous thermogravimetric analysis. The results showed that the RAER possesses a highly porous structure and exhibits excellent thermal stability. The performance of the RAER toward HADP adsorption was investigated. The results suggested that the removal rate of HADPs (decolorization) was up to 100% (under the following experimental conditions: concentration of added RAER: 0.05 g/mL; temperature: 343 K; reaction time: 10 h; pH: 7.0; and initial HADP concentration: 100 mg/L). After 20 regeneration cycles, the decolorization rate of HADPs by the RAER was still as high as 92.2%, indicating that the RAER can be effectively reused and exhibits high performance over long-term operation. Zeta potential measurement confirmed the existence of electrostatic attraction (ion exchange) during HADP adsorption by the RAER. Studies on the kinetics, isotherms, and thermodynamics demonstrated that the adsorption of HADPs by the RAER agrees well with the pseudo-second-order kinetic model (R2≥0.99) and the Freundlich isotherm model (R2≥0.98), with ΔH=62.321 kJ/mol. These results indicated that HADP adsorption by the RAER follows a multi-layer endothermic process dominated by chemical adsorption.