title: Understanding the salinity effect on cationic polymers in inducing flocculation of the microalga Neochloris oleoabundans.
abstract: A mechanistic study was performed to evaluate the effect of salinity on cationic polymeric flocculants, that are used for the harvesting of microalgae. The polyacrylamide Synthofloc 5080H and the polysaccharide Chitosan were employed for the flocculation of Neochloris oleoabundans. In seawater conditions, a maximum biomass recovery of 66% was obtained with a dosage of 90mg/L Chitosan. This recovery was approximately 25% lower compared to Synthofloc 5080H reaching recoveries greater than 90% with dosages of 30mg/L. Although different recoveries were obtained with both flocculants, the polymers exhibit a similar apparent polymer length, as was evaluated from viscosity measurements. While both flocculants exhibit similar polymer lengths in increasing salinity, the zeta potential differs. This indicates that polymeric charge dominates flocculation. With increased salinity, the effectivity of cationic polymeric flocculants decreases due to a reduction in cationic charge. This mechanism was confirmed through a SEM analysis and additional experiments using flocculants with various charge densities.
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, the Netherlands. Electronic address: gerard.tlam@wur.nl.
authors.forename: G P
authors.initials: GP
authors.lastname: 't Lam
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, the Netherlands.
authors.forename: J B
authors.initials: JB
authors.lastname: Giraldo
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, the Netherlands.
authors.forename: M H
authors.initials: MH
authors.lastname: Vermuë
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, the Netherlands; Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli Federico II, Piazzale Vincenzo Tecchio, 80, 80125 Napoli, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Olivieri
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, the Netherlands.
authors.forename: M H M
authors.initials: MH
authors.lastname: Eppink
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, the Netherlands; University of Nordland, Faculty of Biosciences and Aquaculture, N-8049 Bodø, Norway.
authors.forename: R H
authors.initials: RH
authors.lastname: Wijffels
mesh_terms: D018533:Biomass; D002412:Cations / Q000737:chemistry*; D000460:Chlorophyta / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D005427:Flocculation; D058086:Microalgae / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D011108:Polymers / Q000737:chemistry*; D054712:Salinity
chemical_list: D002412:Cations; D011108:Polymers
keywords: Cationic charge; Cationic polymers; Flocculation; Harvesting; Marine microalgae; Mechanism