Decolorization is critical in sugar refining, where reducing sugar alkaline degradation products (RSADPs) constitute major colorants. Conventional decolorants face limitations including non-renewability, high cost, and narrow applicability. This study developed quaternary ammonium-functionalized chitosan adsorbents (QA) as high-performance and cost-effective alternatives. QA was synthesized via (3-chloro-2-hydroxypropyl) trimethylammonium chloride modification, followed by chemical cross-linking with glutaraldehyde and freeze-drying. QA displayed a more intricate surface morphology with rougher pore walls, while increasing quaternary ammonium-functionalized chitosan (QACS) content contributed to the preservation of the porous framework. Additionally, QA exhibited a stable positive charge (pH 3–11) and industrial-grade thermal stability. Compared to the unmodified chitosan adsorbent, QA exhibited superior adsorption performance and maintained pH-independent functionality, with adsorption capacity increasing with rising QACS content. QA 5 (with 5 wt.% quaternary ammonium-functionalized chitosan) performed optimally, achieving 95.9% RSADPs removal with 172.6 mg/g equilibrium capacity (theoretical max of 287.7 mg/g) and > 15% higher efficiency than unmodified adsorbent. The adsorption kinetics followed the pseudo-second-order model (chemisorption-dominated), and the isotherms fitted the Freundlich model, indicating multilayer heterogeneous adsorption. The QA thus provides an efficient, eco-friendly solution with broad pH tolerance for industrial sugar decolorization.
Xia et al. (Thu,) studied this question.
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