Microalgae filtration by UF membranes: influence of three membrane materials

Abstract

To evaluate the impact of membrane material on the ultrafiltration performance of microalgae medium, three types of UF membranes: polysulfone membrane GR40PP (PS, MWCO = 100,000 Da), fluoro polymer membrane FS40PP (PVDF, MWCO = 100,000 Da), regenerated cellulose acetate membrane RC70PP (RCA, MWCO = 10,000 Da) were used in this work. Influence of transmembrane pressure (1.3, 1.8, 2.3 bar) and cross-flow velocity (3.86, 4.83, 5.79, 7.72 m/s) on the permeate flux was studied. It was observed that the permeate flux increased with increasing transmembrane pressure for all membranes. Moreover, permeate flux increased as the cross-flow velocity increased. The fluoro polymer membrane showed the most significant improvement of flux (from 83.27 to 136.32 L/m²h) with increase in cross-flow velocity, which may suggest that the fouling materials attached more weakly on the membrane surface as the cross-flow velocity increased. Hydrophilic RCA membrane had a much lower fouling tendency than hydrophobic PS and PVDF membranes. To maximize flux recovery for the algae-fouled membranes, NaOH, NaOCl, and Ultrasil 10 were applied as cleaning agents. Ultrasil 10 with concentration of 0.5 wt.% was more effective than other agents for membrane cleaning.

Keywords:

• Microalgae
• Ultrafiltration
• Membrane materials
• Fouling
• Cleaning

Acknowledgments

Xuefei Sun wishes to acknowledge Alfa Laval Nakskov A/S for the support of the work. Authors would like to thank Jørgen Enggaard Boelsmand at Green Center Algae Innovation Center Lolland, Denmark for providing algae suspensions and helpful discussions. This study was supported by the National Natural Science Foundation of China (Grant No. 20976140).