Equilibrium and kinetic studies on the adsorption debittering process of ponkan (Citrus reticulata Blanco) juice using macroporous resins

• The bitter component of ponkan juice was limonin, and not narigin.
• Adsorption isotherm models of two macroporous resins were established in debittering ponkan juice.
• Adsorption kinetics of two macroporous resins were estimated in debittering ponkan juice.
• EXA-45 had better adsorption capacity and removal of limonin than LX-900 resin.

Limonin was found be the main cause of bitterness in ponkan juice. Adsorption debittering of ponkan juice was carried out with macroporous adsorbent resins of EXA-45 and LX-900. Effects of adsorbent dosage, initial limonin concentration, and adsorption time on debittering efficiency were investigated. Data on equilibrium were fitted with Langmuir, Freundlich, and Temkin models. It was observed that the Temkin equation was the best fit for limonin adsorption by EXA-45 (R2 = 0.9641), while the Freundlich equation was the best fit by LX-900 (R2 = 0.9930). EXA-45 presented higher adsorption capacity and faster adsorption rate than LX-900. The kinetic equations were examined and the results showed that the adsorptions of limonin on EXA-45 and LX-900 were fitted to pseudo second-order kinetic model with R2 of 0.9936 and 0.9922, respectively. This study indicated that EXA-45 and LX-900 exhibited potential application for removal of limonin from ponkan juice, and the former resin may be better.