Demonstration of the ability of the bacterial polysaccharide FucoPol to flocculate kaolin suspensions

ABSTRACT

In this study, the flocculation properties of FucoPol, a bacterial extracellular polysaccharide, were investigated. FucoPol is a high molecular weight polymer and negatively charged due to the presence of glucuronic acid and the acyl groups succinyl and pyruvyl. High flocculation rate values (>70%) were achieved with a low bioflocculant dosage of 1 mg/L, for pH values in the range 3–5 and temperature within 15–20°C. The bioflocculant was also shown to be stable after freezing/thawing and heating up to 100°C. Given the polymer’s anionic character, the size of flocs formed and their surface profile, bridging seems to be the main flocculation mechanism of FucoPol. This study demonstrated that FucoPol is a promising natural, biodegradable and biocompatible alternative to the currently used synthetic or inorganic hazardous products, with potential to be used as a novel flocculation agent in several applications, such as water treatment, food or mining. Further studies will involve evaluating the reduction of cation dosage on flocculation efficiency, as well as testing the applicability of FucoPol to flocculate different types of suspended solids, such as, for example, activated carbons, soil solids or yeast cells.

GRAPHICAL ABSTRACT

KEYWORDS:

• Kaolin
• flocculation
• Enterobacter A47
• exopolysaccharide
• FucoPol

Acknowledgements

This work was supported by the Research Unit on Applied Molecular Biosciences, UCIBIO, and by the Materials Research Center, CENIMAT/i3N, which are financed by national funds from FCT/MCTES (UID/Multi/04378/2013, CTM/LA0025/2013-14 and UID/AGR/04129/2013, respectively) and co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007728), exploratory project IF/00589/2015 attributed within the 2015 FCT Researcher Program, and grants SFRH/BD/115173/2016 and SFRH/BD/131947/2017. The authors would like to thank Dr. D. Nunes (i3N/CENIMAT, FCT-UNL) for her assistance in collecting the SEM images.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Diana Araújo http://orcid.org/0000-0003-4376-6471

Patrícia Concórdio-Reis http://orcid.org/0000-0001-6143-9170

Ana C. Marques http://orcid.org/0000-0001-6878-1040

Vítor D. Alves http://orcid.org/0000-0002-4117-5582

Elvira Fortunato http://orcid.org/0000-0002-4202-7047

Maria A. M. Reis http://orcid.org/0000-0003-4000-1836

Filomena Freitas http://orcid.org/0000-0002-9430-4640

Additional information

Funding

This work was supported by European Regional Development Fund [grant number POCI-01-0145-FEDER-007728]; Fundação para a Ciência e a Tecnologia [grant number CTM/LA0025/2013-14, IF/00589/2015, SFRH/BD/115173/2016, SFRH/BD/131947/2017, UID/AGR/04129/2013, UID/Multi/04378/2013].