On the role of organic matter composition in fresh-water kaolinite flocculation

Guo, C. and Guo, L. and Bass, S. and Manning, A.J. and Jin, Z. and Zhou, Y. (2023) On the role of organic matter composition in fresh-water kaolinite flocculation. Journal of Environmental Management, 345.

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Official URL: https://doi.org/10.1016/j.jenvman.2023.118576


Organic matter has long been understood to affect fine sediment flocculation, yet the specific effects of different types of organic matter remain only partially understood. To address this knowledge gap, laboratory tank experiments were conducted in fresh water to investigate the sensitivity of kaolinite flocculation to varying organic matter species and contents. Three species of organic matter (xanthan gum, guar gum and humic acid) were investigated at varying concentrations. Results revealed a significant enhancement in kaolinite flocculation when organic polymers (xanthan gum and guar gum) were introduced. In contrast, the addition of humic acid had minimal influence on aggregation and floc structure. Notably, the nonionic polymer guar gum demonstrated greater efficacy in promoting the development of floc size compared to the anionic polymer, xanthan gum. We observed non-linear trends in the evolution of mean floc size (Dm) and boundary fractal dimension (Np) with increasing ratios of organic polymer concentration to kaolinite concentration. Initially, increasing polymer content facilitated the formation of larger and more fractal flocs. However, beyond a certain threshold, further increases in polymer content hindered flocculation and even led to the break-up of macro-flocs, resulting in the formation of more spherical and compact flocs. We further quantified the co-relationships between floc Np and Dm and found that larger Np values corresponded to larger Dm. These findings highlight the significant impact of organic matter species and concentrations on floc size, shape and structure, and shed light on the complex dynamics of fine sediment and associated nutrients and contaminants in fluvial systems.

Item Type: Article
Subjects: Maritime > General
Divisions: Maritime
Depositing User: Helen Stevenson
Date Deposited: 31 Jul 2023 12:40
Last Modified: 31 Jul 2023 12:40
URI: http://eprints.hrwallingford.com/id/eprint/1550

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