Background: Efficient and low-energy microalgae harvesting is essential for sustainable biofuel production. Forward osmosis (FO) has emerged as a promising alternative for microalgae separation because it operates with low energy requirements driven by osmotic pressure. Membrane properties, including porosity and hydrophilicity, play a crucial role in determining FO performance. Objectives: This study investigated the preparation and performance of cellulose acetate (CA) membranes for FO-based microalgae harvesting. Methods: Cellulose acetate (CA) membranes were fabricated using the phase inversion method with polyvinylpyrrolidone (PVP) as a pore-forming agent at concentrations of 1g, 2g, and 3g. Membrane performance was evaluated through water flux and porosity measurements. Sodium chloride (NaCl) was used as the draw solution due to its high osmotic potential and low fouling tendency. Membranes with casting thicknesses of 200µm and 250µm were tested using distilled water as the feed solution and 1M NaCl as the draw solution. The optimized membrane was further evaluated using 5M and 6M NaCl draw solutions for microalgae concentration. Results: Membrane with 200µm thickness and 3g PVP exhibited the highest water flux (2.5L m² h¹) and porosity (71%). The addition of PVP improved membrane hydrophilicity and pore formation, enhancing membrane performance. When applied for microalgae harvesting, the 6M NaCl draw solution produced higher water flux and greater biomass concentration compared to 5M NaCl due to its stronger osmotic driving force. The 6 M NaCl solution achieved an optimal biomass concentration of 848 ± 193mg L¹, whereas the 5M NaCl solution yielded 575 ± 193mg L¹. Conclusion: Optimizing membrane composition and draw solution concentration significantly enhances FO performance for microalgae harvesting. The combination of 3g PVP in a 200µm CA membrane and a 6M NaCl draw solution provides improved water flux and biomass concentration, highlighting the potential of FO membranes for energy-efficient microalgae harvesting.
Idris et al. (Wed,) studied this question.