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Performance Evaluation and Driving Mechanisms of Synergistic Solidification with Nano-Sio2and-MICP for Sludge
CHEN Hao
Journal of Changjiang River Scientific Research Institute ›› 2024, Vol. 41 ›› Issue (12) : 117-125.
PDF(8535 KB)
PDF(8535 KB)
Performance Evaluation and Driving Mechanisms of Synergistic Solidification with Nano-Sio2and-MICP for Sludge
The development of green and low-carbon chemical solidification technology is crucial for rapid solidification of soft ground under the “Dual Carbon” context. This study introduces an innovative synergistic technology that combines active nano-SiO2with microbial induced carbonate precipitation (MICP) for sludge solidification. Through unconfined compressive strength tests, pH monitoring, Ca2+ utilization rate analysis, and scanning electron microscopy, the reinforcement efficiency and micromechanisms of this technology are examined. Key findings include: 1) An increase in compressive strength of nano-SiO2-MICP solidified sludge is observed with increasing nano-SiO2 content up to 0.1%. 2) Samples treated with 0.1% nano-SiO2at Ca2+ concentrations of 0.5, 1, and 2 mol/L exhibit compressive strength enhancements of 64.21%, 10.28%, and 75.98%, respectively, compared to those without nano-SiO2. 3) Nano-SiO2 provides new nucleation sites for MICP, fills pores, induces aragonite-to-calcite transformation, and forms cementitious gels, thereby boosting sample strength. 4) The presence of nano-SiO2enhances Ca2+ utilization and pH regulation within the pore solution. Together, microbial-induced bio-CaCO3 processes (cementation, filling, bridging) and nano-SiO2-induced physicochemical effects (new nucleation sites, micro aggregate filling, and gelling products) synergistically improve the mechanical properties of solidified sludge and optimize the microscopic structural construction.
Nano-SiO2 / microbial induced carbonate precipitation / unconfined compressive strength / Ca2+ utilization / scanning electron microscopy / solidified sludge
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Inducing calcium carbonate precipitation is another important function of urease in nature. The process takes advantage of the supply of carbonate ions derived from urea hydrolysis and of an increase in pH generated by the reaction, effects that in the presence of Ca ions lead to the precipitation of CaCO. Further to its importance in nature, if performed in a biomimetic manner, the urease-aided CaCO mineralization offers enormous potential in innovative engineering applications as an eco-friendly technique operative under mild conditions, to be used for remediation and cementation/deposition in field applications. These include among others, the strengthening and consolidation of soil/sand, the protection and restoration of stone and concrete structures, conservation of stone cultural heritage materials, cleaning waste- and groundwater of toxic metals and radionuclides, and plugging geological formations for the enhancement of oil recovery and geologic CO sequestration. In view of the potential of this newly emerging interdisciplinary branch of engineering, this article presents the principles of urease-aided calcium carbonate mineralization apposed to other biomineralization processes, and reviews the advantages and limitations of the technique compared to the conventional techniques presently in use. Further, it presents areas of its existing and potential applications, notably in geotechnical, construction and environmental engineering, and its future perspectives.
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