Recovery of phenolic compounds from orange press liquor by nanofiltration

This research was undertaken in order to evaluate the potential of a nanofiltration (NF) process for the separation and concentration of phenolic compounds from press liquors obtained by pigmented orange peels. Four different spiral-wound NF membranes, characterised by different molecular weight cut-off (MWCO) (250, 300, 400 and 1000 Da) and polymeric material (polyamide, polypiperazine amide and polyethersulphone), were investigated. The rejection of the investigated membranes towards anthocyanins, flavonoids and sugars was evaluated in order to identify a suitable membrane to separate phenolic compounds from sugars. The performance of the investigated NF membranes was also evaluated in terms of permeate flux and antifouling performance. The obtained results indicated a reduction of the average rejection towards sugars by increasing the MWCO of the selected membranes, while the rejection towards anthocyanins remained higher than 89% for all the NF investigated membranes. The NFPES10 membrane showed the lowest average rejection towards sugar compounds and high rejections towards anthocyanins (89.2%) and flavonoids (70%). Permeate flux values at lower transmembrane pressures were also remarkably higher than the other investigated NF membranes.