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