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

Abstract

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. • Rosin-based anion adsorbent (RAA) for beet juice decolorization was developed. • High-molecular-weight hexose alkaline degradation products were used as pigment model. • Equilibrium adsorption capacity of 6.50 mg/g (removal degree = 89.36%) was achieved. • Several adsorption parameters were optimized to improve adsorption performance. • Adsorption was spontaneous and endothermic, mainly corresponding to chemisorption.