ε-polylysine biopolymer for coagulation of clay suspensions

Abstract

The coagulation or flocculation of cohesive clay suspensions is one of the most widely used treatment technologies for contaminated water. Flocculated clay can transport pollutants and nutrients in ground water. Coagulants are used to accelerate these mechanisms. However, existing coagulants (e.g., polyacrylamide, polyaluminum chloride) are known to have harmful effects in the environment and on human health. As an alternative, eco-friendly coagulant, this study suggests ε-polylysine, a cationic biopolymer fermented by Streptomyces. A series of sedimentation experiments for various ε-polylysine concentrations were performed, and the efficiency of sedimentation with ε-polylysine was estimated by microscopic observation and light absorbance measurements. Two types of sedimentation were observed in the experiments: accumulation sedimentation (at 0.15%, 0.20%, 0.25% ε-polylysine) and flocculation sedimentation (at 0%, 0.1%, 0.5%, 1.0%, 2.0% ε-polylysine). These sedimentation types occur as a result of the concentration of counter ions. Additionally, the performance of εpolylysine was compared with that of a previously used environmentally friendly coagulant, chitosan. The obtained results indicate that flocculation sedimentation is appropriate for contamination removal and that ε-polylysine functions more efficiently for clay removal than chitosan. From the experiments and analysis, this paper finds that polylysine is an alternative eco-friendly coagulant for removing chemical contaminants in groundwater.

Effect of Pore–Fluid Chemistry on the Undrained Shear Strength of Xanthan Gum Biopolymer-Treated Clays

“…Biopolymers contain side chains (e.g., trisaccharide) that can interact with charged clay particles, counterions, and pore water through hydrogen bonding (Chenu and Guérif 1991;). Thus, biopolymers have been reported as effective and ecofriendly soil modification materials owing to their ability to clog pore spaces (Khachatoorian et al 2003;Bouazza et al 2009;Chang et al 2016a;Lee et al 2019;Zhou et al 2020) and enhance interparticle bonding between soil particles (Malik and Letey 1991;Kwon et al 2017;Latifi et al 2017;Chang et al 2020;Soldo et al 2020;Sujatha et al 2020). Moreover, biopolymers have been shown to form viscous hydrogels and interact with the charged surfaces of clays (Chang et al 2015(Chang et al , 2020.…”

“…In addition, biopolymer-based soil treatments have been shown to significantly enhance the hydraulic erosion resistance of soils (Ham et al 2018;Kwon et al 2020), which is expected to effectively mitigate erosion or scouring problems of waterfront geotechnical engineering structures. Additional studies showed that biopolymerinduced soil flocculation accelerates the settling velocity and reduces the turbidity of soil suspensions (Kwon et al 2017;Kang and McLaughlin 2020), which is useful for sludge dewatering (Guo and Wen 2020). Meanwhile, the redistribution of XG (i.e., from strong intergranular bridges to a uniform distribution around the grains) occurs during the wetting-drying cycles, which gradually reduces the overall shear strengthening effect of the biopolymer (Chen et al 2019a).…”

Shear strength behavior and parameters of microbial gellan gum-treated soils: from sand to clay

“…They are commonly used as thickeners or emulsifiers in food and medical products, due to their gelphase rheological characteristics [51]. Since the introduction of biopolymers in construction engineering [68], their use for geotechnical engineering purposes has also been explored [13,20,35,46,66]. Recent studies on microbial biopolymers externally produced in culture tanks, such as polysaccharides, have demonstrated remarkable strengthening efficiency in such applications.…”

Progress, challenges, and opportunities in enhancing NOM flocculation using chemically modified chitosan: a review towards future development

“…Other alternatives are cationic polypeptides, such as polylysine or polyarginine, which for instance have proved to be quite effective in flocculation of cohesive clay suspensions. 66 For the application as bioflocculant, Cs appears to be the most promising one, since it is available in large quantities at low cost and has already been shown to be a versatile flocculant in water treatment. 2 Applications of chitin and chitosan derivatives for the detoxification of water and wastewater were reviewed a decade ago.…”