Removal of high-molecular-weight hexose alkaline degradation products by rosin-based anion adsorbent: Kinetics, thermodynamics, and mechanisms

The dark pigments of beet juice (mainly high-molecular-weight hexose alkaline degradation products , HHADPs) negatively affect the quality of white sugar and should therefore be removed during processing, e.g., through adsorption. Herein, we developed a rosin-based anion adsorbent (RAA) as an effective, regenerable, and green decolorization agent for the removal of HHADPs from beet juice, achieving an equilibrium HHADP adsorption capacity of 6.50 mg/g and a removal efficiency of 89.36%. The investigations of adsorption kinetics, isotherms, thermodynamics, and mechanisms revealed that the adsorption was a spontaneous endothermic multilayer process and mainly corresponded to chemisorption driven by the interactions between the positively charged protonated tertiary amine groups of RAA and the negatively charged carboxylate groups of HHADPs. Our results pave the way to the development of cost-effective and practical adsorbents for an important industrial process, namely beet sugar production.