Biopolymer–soil technology is currently recognized as an environmentally friendly soil improvement method for geotechnical engineering practices. However, concerns exist regarding biopolymer fine-soil applications because the performance of biopolymers is based on an electrical interaction with clay or a pore fluid. Thus, the effect of water content and pore-fluid chemistry on biopolymer behavior in soil must first be clarified in terms of biopolymer applications. In this study, the liquid limits of xanthan gum biopolymer–treated clay–sand mixtures (clayey silt, kaolinite, montmorillonite, and sand) were obtained using three chemically distinct pore fluids (deionized water, 2 mol/L NaCl brine, and kerosene). Xanthan gum has contrary effects to the soil consistency, where the liquid limit can decrease via xanthan gum–induced particle aggregation or increase due to xanthan gum hydrogel formation. The clay-mineral type governed the xanthan gum behavior in the deionized water, while the pore-fluid chemistry governed the xanthan gum behavior in the brine and the kerosene.
Exocultured biopolymers are ecofriendly soil-stabilisation agents with superior particle bonding, hydrogel-formation characteristics and zero endoculture duration. However, the use of exocultured biopolymers for enhancing soil resistance against surface erosion by water flow is yet to be investigated. Using erosion function apparatus (EFA) in combination with an ultrasonic P-wave reflection monitoring device, the effect of exocultured biopolymers on the erosion parameters of critical shear stress and the erodibility coefficient was examined in this study in soils with different particle distributions. In this way, biopolymer soil treatment showed a ten-fold increase in critical shear stress along with a 90% reduction in erodibility coefficient; results which could be attributed to enhanced particle-to-particle contact and increased pore-fluid viscosity and pore clogging. The results of this study demonstrate the feasibility of using exocultured biopolymers in mitigating surface erosion of erosion-prone soils.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.