This investigation examines the development of titanium slag-flue gas desulfurized gypsum-Portland cement ternary composites (the ternary composites) for the solidification and stabilization of Pb-contaminated soils. The efficacy of the ternary composites is systematically evaluated using a combination of experimental methodologies, including mechanical properties such as unconfined compressive strength, stress-strain behavior and elastic modulus, leaching toxicity, XRD, TG-DTG, FTIR, XPS, and SEM-EDS analyses. The results indicate that the mechanical properties of Portland cement solidified Pb-contaminated soils are inferior to those of Portland cement solidified Pb-free soil, both in the early and later stages. However, the mechanical properties of Pbcontaminated soils solidified by the ternary composites are superior to those of the ternary composites solidified Pb-free soils in the early stage but somewhat inferior in the later stage. The ternary composites significantly decrease the leached Pb concentrations of solidified Pb-contaminated soils, which somewhat increase with the Pb content and with the pH value decrease of the leaching agent. Moreover, with much lower carbon emissions index and strength normalized cost, the ternary composites have comparable stabilization effects on Pbcontaminated soils to Portland cement, suggesting that the ternary composites can serve as a viable alternative for the effective treatment of Pb-contaminated soils. Characterization via TG-DTG and XRD reveals that the primary hydration products of the ternary composite solidified Pb-contaminated soils include gypsum, ettringite, and calcite. Furthermore, FTIR, XPS and SEM-EDS analyses demonstrate that Pb ions are effectively adsorbed onto these hydration products and soil particles.

We present an initial study on the use of contaminated soils, effectively treated through a solidification and stabilization (S/S) process that renders them inert, as encapsulated aggregates in the creation of novel metaconcretes. Several mix designs of solidified and stabilized soils are carefully examined, and their physical and mechanical properties are characterized experimentally. These properties are crucial for determining how these treated soils can be effectively incorporated into metaconcretes, a class of materials known for their unique ability to attenuate mechanical waves through resonant structures. The frequency bandgap response of metaconcretes incorporating rubber-coated aggregates made from solidified soils is studied using analytical formulations. The results indicate that the proposed reutilization technique for contaminated soils not only ensures their safety but also offers significant potential for applications in the construction of blast-protective structures and seismic-shielding metamaterials.

In recent decades, heavy industrial discharges have caused severe soil and groundwater pollution. Many areas previously occupied by industries are now represented by lands contaminated by the accumulation of toxic metals, which pose serious risks to human health, plants, animals, and surrounding ecosystems. Among the various potential solutions, the solidification and stabilization (S/S) technique represents one of the most effective technologies for treating and disposing of a wide range of contaminated wastes. This study focuses on the theoretical definition of a green material mix, which will subsequently be used in the solidification process of contaminated industrial soils, optimizing the mix to ensure treatment effectiveness. The mix design was developed through a literature analysis, representing a preliminary theoretical study. This paper explores the application of the S/S process using various additives, including Portland cement, fly ash (FA), ground granulated blast furnace slag (GGBFS), and other industrial waste materials, to create an innovative mix design for the treatment of contaminated soils. The main objective is to reduce the permeability and solubility of contaminants while simultaneously improving the mechanical properties of the treated materials. The properties of the studied soils are described along with those of the green materials used, providing a comprehensive overview of the optimization of the resulting mixtures.

Most Pb/Zn smelter contaminated sites in China are often encountered natural phenomenon known as freeze-thaw (F-T) cycles and acid rain. However, the coupled effects of F-T cycles and acidification on the release behavior of potentially toxic elements (PTEs) from soils remains unclear. A mechanistic study on PTEs release from soils was conducted by revealing the physicochemical weathering characteristics of minerals under F-T cycles combined with acidification. The results from F-T test indicated that among F-T parameters, F-T frequency were the more important factors influencing PTEs release, with the corresponding contribution ranges of 21.20-94.40 %. As pH decreased, the leaching concentrations of As, Cd, Cu, Mn, Pb and Zn did not increase under the same F-T frequency. As F-T frequency increased, the leaching concentrations of these studied PTEs also did not increase under the same pH condition. Microstructure characteristics revealed that the soils were a complex system with multi-mineral aggregates, which had experienced complex physicochemical weathering after F-T combined with acidification treatment. Combined with geochemical modeling results, PTEs release was found to be mainly influenced by the microstructure damage and proton corrosion of minerals, while little affected by their precipitation and dissolution. The mutual coupling relationships of mineral weathering and PTEs release were conducive to the better understanding of the migration behavior of PTEs in contaminated sites under complex environment scenarios. The present study results would provide theoretical instruction and technical support for the longevity evaluation of multi-metal stabilization remediation.

Little was known about the leaching behavior of potentially toxic elements (PTEs) from soils under the interaction between freeze-thaw (F-T) cycle and the solutions of varying pH values. In this study, PTEs leachability from soils before and after F-T tests was evaluated using toxicity characteristics leaching procedure (TCLP) test. The microstructure and mineralogical evolution of soil mineral particles were conducted using pores (particles) and cracks analysis system (PCAS) and PHREEQC. The results indicated that during 30 F-T cycles, the maximum leaching concentrations of PTEs were 0.22 mg/L for As, 0.61 mg/L for Cd, 2.46 mg/L for Cu, 3.08 mg/L for Mn, 29.36 mg/L for Pb and 8.07 mg/L for Zn, respectively. Under the coupled effects of F-T cycle and acidification, the porosity of soil particles increased by 4.79%, as confirmed by the microstructure damage caused by the evolution of pores and cracks. The anisotropy of soil particles increased under F-T effects, whereas that decreased under the coupled effects of F-T cycle and acidification. The results from SEM-EDS, PCAS quantification and PHREEQC modeling indicated that the release mechanism of PTEs was not only associated with the microstructure change in mineral particles, but also affected by protonation, as well as the dissolution and precipitation of minerals. Overall, these results would provide an important reference for soil remediation assessments in seasonal frozen areas.

The thermal conductivity of soils is an important factor affecting the efficiency of in-situ thermal desorption remediation of contaminated sites. Restrict the selection of in-situ thermal desorption repair methods and heating parameters. The existence of non-aqueous phase liquids (NAPLs) pollutants affects the original thermal conductivity of the soils. To obtain an accurate and efficient method to study the thermal conductivity of NAPLs-contaminated soils. In the paper, the NAPLs-contaminated soils models are established by the four-parameter random generation method, and the thermal conductivity is calculated based on the Lattice Boltzmann Method (LBM). Explore the impact of NAPLs-contaminated soil model on its thermal conductivity calculation results, and propose an optimized NAPLs-contaminated soil model. Finally, the numerical simulation results are compared with the experimental results, and a large number of calculations and statistical analyses are carried out on the thermal conductivity. The results indicate that it is feasible to combine the four-parameter random generation method with LBM to study the thermal conductivity of NAPLs-contaminated soils. The calculation accuracy of the two-dimensional model of NAPLs-contaminated soils is lower than that of the three-dimensional model, while the calculation of the three-dimensional model is too time-consuming. The optimized NAPLs-contaminated soils three-dimensional model has the characteristics of high computational accuracy and efficiency. Saturation and Nz have a great influence on the calculation time of thermal conductivity. The thermal conductivity of the two-dimensional model is more sensitive to anisotropy. With the decrease of model anisotropy, the increase of saturation, and the decrease of porosity, the calculation accuracy of thermal conductivity of two-dimensional and three-dimensional models is similar, otherwise, the calculation accuracy of two-dimensional model is lower. The influence of porosity and NAPLs content on thermal conductivity should be paid special attention to when in-situ thermal desorption.