(3) addition to the light phase of 80 mg/L of Na2SO4 and further centrifugation (5 min, 5000 rpm) to remove residual
water. The biodiesel % mass fraction in the light phase was determined by measuring the refractive index (λ ) 589.3 nm) of
the oil/biodiesel mixture with a MASELLI LR-01 refractometer (three readings for each sample).