Parallel filtration for solid-liquid separation: A case study of highly-efficient algal removal under parallel configuration driven by magnetic force

Abstract

In traditional membrane filtration systems, the perpendicular permeate flow to the membrane surface causes the retentate to block the membrane pores, which results in an unavoidable cake resistance, thus making it difficult to achieve high filtration flux. In this study, a novel parallel filtration configuration driven by magnetic force was proposed for the removal of Microcystis flos-aquae. The results showed that the filtration flux under parallel filtration configuration reached 750,000 L⋅m−2⋅h−1 which is 3 times higher than the highest flux (280,000 L⋅m−2⋅h−1) reported in previous literature for algal removal. The permeate flow did not need to cross the cake layer, and the “pore size” of the filter chamber can be as high as 10 cm, thus resulting in negligible resistance (2.1 × 101 m−1) and higher filtration flux compared to traditional vertical filtration. For the magnetic-driven parallel filtration, the use of cationic polyacrylamide after polyaluminum chloride coagulation and magnetic particles (MPs) spiking was necessary. Increasing the MPs size and dosage further improved the filtration performance. Moreover, excessive flow velocity would affect the capture probability of algae-MPs aggregates by the magnetic field, which can be overcome by enhancing the magnetic field strength. We have developed a parallel filtration configuration for highly-efficient solid-liquid separation with simple and sustainable processes, which have the potential for rapid, efficient and large-scale applications in product purification, contaminant removal, and resource recycling in the future.