Flocculation as Method for Optimizing Crossflow Microfiltration
Author
Rosenkjær, Pernille Malthe
Term
4. term
Education
Publication year
2010
Submitted on
2010-12-15
Pages
84
Abstract
Dette speciale undersøger, hvordan flokkulering som forbehandling kan forbedre crossflow-mikrofiltrering af polystyrenpartikler i demineraliseret vand. Flokkulering bruger polymerer til at få små partikler til at klumpe sig sammen, så de er lettere at filtrere. Vi vurderer flokkulanters egenskaber – struktur, molekylvægt og ladningstæthed – ved at teste tre polymerer i et modelskala-laboratoriesystem: Zetag 7631 (lineær, høj molekylvægt), polyDADMAC (lineær, lav molekylvægt) og Zetag 7867FS40 (krydsbundet). Polymerdoseringen fastsættes ud fra ladningsforholdet (CR), et mål for balancen mellem partiklernes og polymerens elektriske ladninger; for hver polymer testes CR0.5, CR1 og CR2. Ydelsen vurderes med kritisk permeatflux, den højeste flux hvor membranen ikke tilstoppes (fouling). Resultaterne viser, at den kritiske flux stiger med stigende ladningsforhold, og at en lineær polymer med høj molekylvægt giver den bedste filtrering og den højeste kritiske flux.
This thesis examines how flocculation as a pretreatment can improve crossflow microfiltration of polystyrene particles in demineralized water. Flocculation uses polymers to make small particles clump together, which helps them filter more easily. We evaluate flocculant properties—structure, molecular weight, and charge density—by testing three polymers in a model-scale laboratory crossflow microfiltration system: Zetag 7631 (linear, high molecular weight), polyDADMAC (linear, low molecular weight), and Zetag 7867FS40 (cross-linked). Polymer dosage is set using the charge ratio (CR), a measure of the balance between the charges of the particles and the polymer; three levels are tested for each polymer: CR0.5, CR1, and CR2. Performance is assessed by the critical permeate flux, the highest flux at which no fouling (membrane clogging) occurs. The study finds that the critical flux increases as the charge ratio increases, and that using a high–molecular-weight linear polymer gives the best filtration results and the highest critical flux.
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