Preparation and characterization of PVDF hollow fibres for the clarification of orange press liquor

In this work, poly(vinylidene fluoride) (PVDF) hollow fibres were prepared, characterized and utilised for the clarification of press liquor from orange peel processing as a pre-treatment step of an integrated membrane system aimed to recover high added value compounds from the liquor. PVDF was selected among the several available polymers due to its excellent chemical stability and the feasibility of forming hollow fibres and membranes via a phase inversion method. The produced fibres exhibited high permeability (pure water permeability ~550 Kg h-1m-2bar-1) coupled to good mechanical resistance, ensuring high transmembrane fluxes and good resistance to both operating conditions and cleaning procedures. Experimental trials were also performed in order to evaluate the effect of operating conditions, such as transmembrane pressure and feed flow rate, on the permeate flux and to optimize process conditions for the recovery of high added value compounds, such as polyphenols and antioxidants. In selected operating conditions rejections of hollow fibre membranes towards polyphenols and total antioxidant activity were of 6.2% and 9.9%, respectively.