PVDF/LiCl membrane for up-concentration of Nannochloropsis sp. microalgae harvesting and its cleaning

The increased concentration of Nannochloropsis sp. microalgae during the harvesting process is of great importance economically. Separation of Nannochloropsis sp. using Polyvinylidene Fluoride (PVDF) polymeric membrane was studied with the addition of 2% LiCl to improve up-concentration performance. The Hermia model is used to predict the type of fouling on the membrane. Cleaning with NaOCl 1000 ppm solution was carried out to overcome fouling on the membrane. PVDF/LiCl membranes were prepared using the immersion-precipitation phase inversion method. The results showed that the addition of LiCl caused an increase in membrane hydrophilicity as indicated by a decrease in the value of the contact angle from 94.8° to 70-84°. Membrane morphology changed from finger-like to sponge-like. The concentration of Nannochloropsis sp. increased from 563.92 to 5097.5 ppm. The membrane performance after cleaning is still very good because it produces recovery is more than 89.924%, and the microalgae rejection is 100%. It was concluded that the PVDF membrane after the addition of LiCl could improve the up-concentration performance of Nannochloropsis sp. and NaOCl solution was very effective in overcoming fouling on the membrane.