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Soil Remediation
Published in Kathleen Sellers, Fundamentals of Hazardous Waste Site Remediation, 2018
Vitrification is a thermal treatment process that melts soil or sludge into a glasslike material. This material comprises fused inorganic oxides, notably silica oxides, but not organics. Nonvolatile metals are immobilized within the glass. Volatile metals—such as lead, cadmium, and zinc—volatilize. These metals must be captured in the off-gas treatment system. Organic compounds pyrolyze or combust. Vitrification requires an extraordinary amount of energy: some 800 to 1000 kWh per ton of soil processed in situ.45 Because of the energy required to vitrify waste, this type of treatment is used to treat relatively small quantities of wastes which are difficult to treat by other methods. Vitrification can be used to treat radioactive wastes, metal sludges, asbestos-containing waste, or soil or ash contaminated with metals. While soil or waste containing organic contaminants can be treated using vitrification, vitrification technologies are usually directed toward inorganic contamination.
Solving Past Challenges
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
Vitrification is used in a number of countries (e.g., United States, United Kingdom, Russia, Japan, and France) to immobilize heat-generating HLW from reprocessing. Vitrification is attractive because of the high capability of glass to reliably immobilize a range of elements; the production technology adapted from glass manufacture is simple and proven over many decades; the small volume of the resulting glassy wasteform; the high chemical durability of glassy wasteforms in contact with natural waters; and the high tolerance of glasses to radiation damage.35 The open and random glass structure is able to accommodate most of the periodic table, and radioactive species can go into the glass network or other sites. For example, alkalis (137Cs, 90Sr) sit on the large Na site in a sodium borosilicate glass. The borosilicate glass compositions used are very similar to Pyrex (which used to be made by Corning for cookware). The exact compositions of nuclear waste glasses are tailored for easy preparation and melting, avoidance of phase separation and uncontrolled crystallization, and acceptable chemical durability, for example, leaching resistance. Vitrification can be performed at temperatures below 1200°C, thus avoiding excess radionuclide volatilization and maintaining viscosities below 10 Pa·s to ensure high throughput and controlled pouring into canisters.
The role of polysaccharides and cellulose for modern science and technology
Published in Gennady E. Zaikov, Chemistry of Polysaccharides, 2005
So, there are two principle ways of transformation from equilibrium liquid aggregate state into solid one: they are crystallization and vitrification. Crystallization is a process of transformation from the state of short range ordering to the long range one, i.e. it is a process of neq phase formation. Vitrification is a process of transformation of thin fluid into solid state without phase change, i.e. process with maintenance of short range ordering. Crystallization occurs at strictly defined temperature calling temperature of crystallization or melting, and lower this temperature the equilibrium state is crystal one because thermodynamic potential of crystal is lower than of liquid.
A Review on Heavy Metals Contamination in Soil: Effects, Sources, and Remediation Techniques
Published in Soil and Sediment Contamination: An International Journal, 2019
Changfeng Li, Kehai Zhou, Wenqiang Qin, Changjiu Tian, Miao Qi, Xiaoming Yan, Wenbing Han
Vitrification, or molten glass, is a method of solidification/stabilization requiring thermal energy (1400–2000°C), which can be achieved by mixing the contaminated soil with glass-forming precursors, heating the mixtures until they liquidize, and obtaining an amorphous homogeneous glass after the liquid cools (Yao et al., 2012). Heavy metals can be immobilized by two main interactions with the glass matrix: chemical bonding and encapsulation (Navarro, 2012). The heating temperature of the vitrification process is the key factor in the immobilization of heavy metals in contaminated soils. The efficient additives in the vitrification may improve the encapsulation of contaminants and their possible leaching capacity (Guo et al., 2006).
Feasibility study on the use of thiosulfate to remediate mercury-contaminated soil
Published in Environmental Technology, 2019
Chao Han, Hui Wang, Feng Xie, Wei Wang, Ting’an Zhang, David Dreisinger
Various detoxification/remediation technologies for disposing of mercury-contaminated soils have therefore been developed. In the amalgamation process, Hg0 dissolves in other metallic ions, such as copper, to form solid solutions or semi-solid alloy ‘amalgam’. As this process is reversible, mercury can be released from these alloys by heating [16]. The elemental mercury can also react with elemental sulfur to form mercury sulfide (HgS), which is kinetically stable at room temperature [17]. The processes using HgS or HgSe for mercury stabilization are commonly used in HgO wastes and those solid wastes containing a large amount of mercury [18–19]. In adsorption treatments, adsorbents, mainly activated carbons, are used to stabilize Hg0 [20]. Thermal desorption, retorting and roasting, which all employ heating (at low or high temperatures), have been commonly used to treat mercury-contaminated soil, sediments and other solid wastes [21–24]. For the stabilization/solidification processes, the vitrification process is a high-temperature treatment technology designed to immobilize contaminants by incorporating them into vitrified end product. The research of Huang et al. showed that decontamination at higher temperature (>673 K) can lower Hg content to the regulation level [25]. Stabilization or immobilization can also be obtained through the formation of stable compounds or water non-soluble compounds which can be classified depending on the encasing materials, such as Portland cement, sulfur polymer cement, sulfide and phosphate binders, cement kiln dust, polyester resins and polysilioxane compounds [26–29]. Nowadays, it is difficult to judge which is the best technology to be applied, depending on the chemical and physical properties of the wastes to be treated.