Multistage recovery process of seaweed pigments: Investigation of ultrasound assisted extraction and ultra-filtration performances

The objectives of this study were first to evaluate the performance of seaweed pigments' recovery through ultrasound assisted extraction (UAE) and ultra-filtration (UF), and second to investigate the membrane fouling mechanism and evidence the threshold flux during filtration. The pigments' recovery from the extract was performed using 5 kDa and 10 kDa ultra-filtration membranes. Results showed that increasing the extraction temperature in the range of 40-60 °C was proportional to chlorophyll extraction efficiency, while the maximal carotenoid yield was achieved at 50 °C. Ultrasonic power (from 100 W to 300 W) facilitated the extraction of both chlorophylls and carotenoids. Results from ultra-filtration showed that most pigments (>90%) were available in permeate through 10 kDa membrane, while 5 kDa membrane partially retained the pigments. Filtration resistance was quantified with resistance-in-series' model, showing that the cake layer was the most important fouling resistance during filtration. Threshold flux at different rotation speeds (200 and 600 rpm) was determined by trans-membrane pressure stepping tests, which were around 10 and 14.5 L/m2 h, respectively. Results from this study demonstrated the efficiency of the multistage process involving UAE and UF to enhance the recovery of pigments from brown seaweeds.