Enhancing Microalgal Biomass Productivity in Floating Photobioreactors with Semi-Permeable Membranes Grafted with 4-Hydroxyphenethyl Bromide

摘要

Microalgal biomass productivity of semi-permeable membrane photobioreactors (SPM-PBRs) highly depends on diffusion of nutrient ions from surrounding environment through SPMs. The objective of this study was to enhance microalgal biomass productivity in floating photobioreactors (PBRs) with semi-permeable membranes (SPMs) grafted with 4-hydroxyphenethyl bromide (4-HPB) by increasing ion permeabilities and reducing biofouling of SPMs. In this study, we investigated the reduction of biofouling and improvement of biomass productivity by grafting 4-HPB onto SPMs which could decrease hydrophobicity. The degree of alkylation could be increased by up to 4.9%, with water contact angles on alkylated SPM surfaces decreased from 102.5 degrees to 58.2 degrees, indicating decreased surface hydrophobicity. Ion and water permeabilities of SPMs were increased in alkylated SPMs by 148% and 200%, respectively, compared to non-treated SPM control. Moreover, biomass productivity of PBRs with alkylated SPMs was 75% (740 mg m(-2) day(-1)) higher than that of the control. Biofouling was also remarkably reduced by up to 40% in 4-HPB grafted SPMs after cultivation of microalgae. These results suggest that decreasing hydrophobicity of SPMs by grafting 4-HPB could enhance biomass productivity in SPM-PBRs through improving ion permeability and reducing biofouling.