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Harvesting Microalgae-Development of a Short Residence Time Method Using Rapid-response Temperature-sensitive Semi-IPN Hydrogels

Zhao, Xiaofei
http://orcid.org/0000-0002-0593-8490
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1434501731

Abstract Details

2015, Master of Science, University of Toledo, Chemical Engineering.
Microalgae cultures obtained from cultivation in open ponds are usually at low concentrations (0.5-1g/L). Direct application of conventional solid-liquid separation processes (such as filtration, centrifugation or chemical flocculation) to such dilute cultures could be either prohibitively expensive for biofuel production or may compromise biomass quality and impact downstream conversion. During this study, the research team used fast-response and high-capacity temperature-sensitive hydrogels for dewatering dilute algal slurries. These gels had semi-interpenetrating network structures consisting of polyvinyl alcohol (PVA) intercalated into poly N-isopropylacrylamide chains (PNIPAAm-PVA semi-IPN). Further, these stimulus-sensitive gels collapse and release the absorbed medium at relatively low temperature (>32°C), which allows recovery (and reuse) of the hydrogels using low-quality waste heat. In this study, we first compared the swelling/deswelling kinetics and mechanical properties of semi-IPN hydrogels with more conventional PNIPAAm hydrogels. Our results showed that semi-IPN10 gels (containing 10% PVA and 90% PNIPAAm) exhibited rapid swelling and deswelling kinetics with rates that were nearly two-fold higher than PNIPAAm gels. Further, compression-stress measurements and rheological studies showed that the semi-IPN gels had greater elasticity and compression resistance than PNIPAAm. As such, the PNIPAAm-PVA semi-IPN hydrogels are expected to be less susceptible to breakage during the dewatering process. Subsequently, we demonstrated the feasibility of using semi-IPN hydrogels for harvesting microalgae by stagewise exposure of deswollen hydrogels to dilute microalgae cultures. We observed that the semi-IPN hydrogels rapidly uptake the aqueous medium and exclude microalgae cells, which results in an increase in the concentration of the residual culture. Through use of high gel loadings, we were able to increase the concentrations of cultures from nearly 1g/L to >10g/L in 3 stages over a net residence time less than 1.5h. Finally, our studies demonstrated that the concentrated cultures remained viable and photosynthetically-active; the recovered aqueous medium was also able to sustain re-growth of cultures.
Sridhar Viamajala, Ph.D. (Committee Chair)
Constance Schall, Ph.D. (Committee Member)
Sasidhar Varanasi, Ph.D. (Committee Member)
79 p.
Chemical Engineering; Energy; Environmental Engineering; Food Science
microalgae; harvesting; semi-IPN; hydrogel; temperature-sensitive; dewatering

Recommended Citations

Citations

  • Zhao, X. (2015). Harvesting Microalgae-Development of a Short Residence Time Method Using Rapid-response Temperature-sensitive Semi-IPN Hydrogels [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1434501731

    APA Style (7th edition)

  • Zhao, Xiaofei. Harvesting Microalgae-Development of a Short Residence Time Method Using Rapid-response Temperature-sensitive Semi-IPN Hydrogels. 2015. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1434501731.

    MLA Style (8th edition)

  • Zhao, Xiaofei. "Harvesting Microalgae-Development of a Short Residence Time Method Using Rapid-response Temperature-sensitive Semi-IPN Hydrogels." Master's thesis, University of Toledo, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1434501731

    Chicago Manual of Style (17th edition)

toledo1434501731
921
© 2015, some rights reserved.Creative Commons License Harvesting Microalgae-Development of a Short Residence Time Method Using Rapid-response Temperature-sensitive Semi-IPN Hydrogels by Xiaofei Zhao is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Toledo and OhioLINK.