Recyclable Organic Acid Catalyst-Mediated Fractionation and Purification of Pectin from Orange Peel Waste

Pectin, a complex polysaccharide with extensive applications in the food, pharmaceutical, and cosmetic industries, is present as a potential component of citrus processing residues such as orange peel waste. In this study, an integrated approach was followed for the efficient fractionation, isolation, and purification of pectin using para-toluenesulphonic acid (p-TsOH), a recyclable solid organic acid catalyst. Various organic and mineral acids were also tested for pectin fractionation, and performance was compared with p-TsOH. Still, the use of p-TsOH offers key advantages such as high yield (>21%) and conversion (>58%). Moreover, a process optimization study is conducted to check the influence of operating parameters such as catalyst concentration, temperature, reaction time, slurry concentration, agitation speed, and particle size. The optimized process provides >33% pectin yield at 95 °C in 180 min in batch mode. Downstream processing was conducted by integrating adsorptive chromatography using ICT-HC-1 adsorbent and an ultrafiltration membrane to remove impurities and recover the catalyst, respectively. The final product was dried using spray drying, eliminating the need for conventional alcohol-based precipitation methods. The integration of membrane separation provides efficient separation and recovery of both pectin and catalyst. A catalyst recycle study for five consecutive runs showed consistency in biomass conversion (58%) and pectin yield (21%). The present study outlines a practical approach for valorizing orange peel waste with efficient catalyst recyclability and avoiding conventional alcohol precipitation techniques. Thus, the present protocol achieves a dual goal of valorizing orange peel waste and developing an industrially feasible process for pectin fractionation.