Optimisation of extraction and sludge dewatering efficiencies of bio-flocculants extracted from Abelmoschus esculentus (okra)

Lee, Siah Lee; Chong, Mei Fong; Robinson, John P.; Binner, Eleanor

Abstract

The production of natural biopolymers as flocculants for water treatment is highly desirable due to their inherent low toxicity and low environmental footprint. In this study, bio-flocculants were extracted from Hibiscus/Abelmoschus esculentus (okra) by using a water extraction method, and the extract yield and its performance in sludge dewatering were evaluated. Single factor experimental design was employed to obtain the optimum conditions for extraction temperature (25–90 °C), time (0.25–5 h), solvent loading (0.5–5 w/w) and agitation speed (0–225 rpm). Results showed that extraction yield was affected non-linearly by all experimental variables, whilst the sludge dewatering ability was only influenced by the temperature of the extraction process. The optimum extraction conditions were obtained at 70 °C, 2 h, solvent loading of 2.5 w/w and agitation at 200 rpm. Under the optimal conditions, the extract yield was 2.38%, which is comparable to the extraction of other polysaccharides (0.69–3.66%). The bio-flocculants displayed >98% removal of suspended solids and 68% water recovery during sludge dewatering, and were shown to be comparable with commercial polyacrylamide flocculants. This work shows that bio-flocculants could offer a feasible alternative to synthetic flocculants for water treatment and sludge dewatering applications, and can be extracted using only water as a solvent, minimising the environmental footprint of the extraction process.

Citation

Lee, S. L., Chong, M. F., Robinson, J. P., & Binner, E. (2015). Optimisation of extraction and sludge dewatering efficiencies of bio-flocculants extracted from Abelmoschus esculentus (okra). Journal of Environmental Management, 157, https://doi.org/10.1016/j.jenvman.2015.04.028

• Journal Article Type: Article
• Acceptance Date: Apr 16, 2015
• Online Publication Date: May 2, 2015
• Publication Date: Jul 1, 2015
• Deposit Date: Mar 1, 2016
• Publicly Available Date: Mar 1, 2016
• Journal: Journal of Environmental Management
• Print ISSN: 0301-4797
• Electronic ISSN: 1095-8630
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 157
• DOI: https://doi.org/10.1016/j.jenvman.2015.04.028
• Keywords: Bio-flocculant; Optimisation; Extraction; Okra; Sludge dewatering
• Public URL: https://nottingham-repository.worktribe.com/output/753101
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S0301479715300311