Aida Isma Idris, Fathima Hamaza Haseem Deen, Munira Mohammad, Ma. Grace C. Sumaria
Background: Efficient and energy-saving microalgae harvesting is critical for sustainable biofuel production. Forward osmosis (FO) offers a low-energy alternative driven by osmotic pressure, where membrane characteristics such as porosity and hydrophilicity strongly influence performance. Objective: This study aimed to fabricate and evaluate cellulose acetate (CA) membranes enhanced with polyvinylpyrrolidone (PVP) for improved FO performance in microalgae harvesting. Methods: CA membranes were prepared via phase inversion with varying PVP concentrations (1g, 2g, and 3g) as a pore-forming agent. Membranes with casting thicknesses of 200μm and 250μm were tested. Water flux and porosity were measured using distilled water as the feed solution and 1M NaCl as the draw solution. The optimal membrane was further tested with 5M and 6M NaCl solutions to evaluate microalgae concentration performance. Results: The membrane with 200μm thickness and 3g PVP demonstrated the highest water flux (2.5L m⁻² h⁻¹) and porosity (71%). Increased PVP content improved membrane hydrophilicity and pore structure, enhancing performance. In microalgae harvesting, the 6M NaCl draw solution generated higher water flux and biomass concentration than 5M NaCl due to its stronger osmotic gradient. The 6M NaCl achieved a biomass concentration of 848 ± 193mg L⁻¹, compared to 575 ± 193mg L⁻¹ for the 5M solution. Conclusion: Optimizing membrane composition and draw solution concentration significantly improves FO efficiency. A CA membrane with 3g PVP at 200μm thickness, combined with a 6M NaCl draw solution, offers enhanced water flux and biomass concentration, demonstrating strong potential for energy-efficient microalgae harvesting.