DMF equilibrium extraction DMSO equilibrium extraction FAs NMR quantification PPSO Research & information: general acid value antioxidant activity bio-lubricant biodiesel biolubricant filter medium pollution filtration free fatty acids interception characteristics legislation nuclear magnetic resonance paraffin enrichment phenolics polymer-flooding produced water recycling used vegetable oil vegetable oil degumming vegetable oil filtration volatiles waste cooking oil waste cooking oils waste oil characterization waste plastic pyrolysis oil