In the quest to remediate heavy metal-contaminated soil, a novel approach is emerging that could revolutionize the industry and offer significant benefits to the energy sector. Researchers, led by Tingting Deng from the Institute of Geotechnical Engineering at Southeast University in China, have proposed an integrated remediation technique that combines solidification/stabilization with vacuum dewatering, potentially enhancing efficiency and reducing costs.
The challenge with traditional solidification/stabilization methods is achieving uniform mixing, which is crucial for effective heavy metal immobilization. “Optimizing mixing equipment has high cost, limited site applicability, and limited effect on improving uniformity,” Deng explains. To overcome this, Deng and her team introduced a combined solidification/stabilization – vacuum dewatering technique (SSVD). This method involves increasing the water to binder ratio to ensure even mixing, followed by immediate vacuum dewatering.
Laboratory experiments and a pilot project were conducted to explore the efficiency of this approach, focusing on zinc-contaminated soil due to its known adverse effects on compressive strength and cementation speed. The results were promising. Vacuum dewatering successfully removed water from solidified soils within the initial 12 hours of setting and hardening in the field, demonstrating the feasibility of incorporating more water to improve mixing workability. Moreover, it enhanced the microstructure to prevent pollutant migration and extracted heavy metals from the solidified mass through cation exchanges.
After 28 days of curing, laboratory tests showed a significant increase in strength (1.9-4.1 times) and a substantial reduction in permeability (1.7-17.8 times) after dewatering. In the field, these values increased by 1.8 times and decreased by 1.7 times, respectively. The observed diffusivity of Zn2+ also decreased by 2.0 times after dewatering in the laboratory. Microstructure analysis revealed that vacuum dewatering significantly reduced the porosity of the solidified matrix, enhancing its integrity.
The implications for the energy sector are substantial. This integrated remediation technique could lead to more efficient and cost-effective soil treatment, particularly in areas contaminated by heavy metals. “The proposed technology holds potential for application not only in solidification/stabilization remediation but also in soft ground improvement in terms of better workability and homogeneity, stronger densification and encapsulation, and less pollutant retention and binder consumption,” Deng notes.
As the energy sector increasingly focuses on sustainable practices and minimizing environmental impact, this innovative approach could shape future developments in soil remediation. The research, published in the journal ‘Soils and Foundations’ (known in English as ‘Soil and Foundation’), offers a glimpse into a future where integrated remediation techniques could play a pivotal role in environmental conservation and industrial efficiency.