Concentration of Phenolic Compounds from Ultrafiltered Mandarin Wastewater by Novel Membrane Technologies: Forward Osmosis and Membrane Distillation

Abstract Mandarin wastewater is largely generated during the production of canned mandarin segments. Phenolic compounds are high added value bioactive compounds due to their antioxidant properties, making them particularly important in the pharmaceutical and cosmetic industries. Given the significant content of polyphenols in mandarin wastewater, maximizing their concentration is a key objective. Polyphenols concentration from mandarin wastewater by novel membrane technologies has not been previously explored. First, a previous ultrafiltration pretreatment must be performed to reduce the pectin and total solids content, minimizing membrane fouling during the concentration process. Subsequently, concentration experiments were conducted using two emerging membrane processes, forward osmosis and membrane distillation, until a volume reduction factor of 2 was attained. In the forward osmosis experiments 50 g·L −1 NaCl was used as draw solution. Polyphenols reached a concentration factor of 2.02 ± 0.04 over a period of 96 h, although the reverse salt flux has to be considered. Regarding membrane distillation, the conditions selected for concentrating polyphenols were a feed temperature of 47.6 °C with a 0.2 μm pore size membrane. The membrane distillation test lasted 20.7 h, obtaining a phenolic compounds concentration factor of 1.98 ± 0.01. Membrane distillation offered advantages such as lower membrane fouling and shorter experimental time.