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Harvesting microalgae is an important process to be carried out in the production of biodiesel from microalgae. The method of harvesting by filtration technique provides many advantages over other methods. Polymer is a membrane material that is often used for harvesting microalgae. However, polymer membranes have limited hydrophobic properties, thus, modification was needed to improve the hydrophilic properties and performance of polymer membranes. The polyvylene fluoride (PVDF) flat-sheet membrane has advantages over other membrane materials which are rated with a flux rate of 67.3 L / m2h and a rejection value of 100%. Then, the development with hollow fiber modulation on the PVDF membrane was considered very suitable, which was reported to have succeeded in increasing the membrane flux in the harvest of Scenedemus Acuminatus reaching up to 5136 L / m2h. The addition of PVDF with the inorganic additive LiCl was successful in increasing its hydrophilicity as  the water permeation size increased up to 542 L / m2h. In addition, the use of triethyl phosphate (TEP) as a solvent is more environmentally friendly and compatible with PVDF membranes. As a result, it can increase membrane porosity by up to 92.7%. Apart from improving the membrane material, this review also reports the design and economic analysis to produce an effective and efficient of polymeric membranes for microalgae harvesting.

One of the biggest challenges in implementing microalgae-based biofuels is the effective harvesting process. Filtration membrane has become one of the flexible methods in microalgae harvesting. This study investigated the harvesting of Nannochloropsis sp. using a modified PVDF membrane at various LiCl as an additive with N-methyl-2-pyrrolidone (NMP) solvent. Harvesting of Nannochloropsis sp. with PVDF membrane has never been reported before. The addition of LiCl can improve the performance of PVDF membrane due to LiCl has a great affinity for water, resulted in inducing the formation of the pore structure of membrane. The optimum membrane composition was determined at various LiCl additive from 1% to 3% (w/w). The hydrophilicity of the membrane increased as indicated by the increasing of water permeance, which were 516, 546, 660, and 614 L/m2h bar for neat PVDF, PVDF/LiCl-1, PVDF/LiCl-2, and PVDF/LiCl-3 membrane, respectively. PVDF/LiCl-2 membrane showed the highest water permeance and the highest total average permeance (150 L/m2h bar) with 100% rejection of Nannochloropsis sp. harvesting. The membranes was cleaned using sodium hypochlorite, citric acid, and nitric acid. The SEM results showed that the membrane after cleaning appears the algae particles in the membrane pore. Furthermore, algae particles were almost not visible on cleaned membrane. The FTIR results showed an absorption at 3401 cm-1, which was a characteristic of the hydrogen N-H bond, also including a typical amide uptake (C=O) at 1648 cm-1 indicating protein appearance. Moreover, the cleaned membrane did not appear any absorption that indicates the foulant.