Solidification-stabilization technique

Solidification/Stabilization technologies are techniques designed to be used as final waste treatment. A major role of these processes is posttreatment of residuals produced by other processes such as incineration or chemical treatment. In some cases, solidification/ stabilization processes can serve as the principal treatment of hazardous wastes for which other detoxification techniques are not appropriate. High volume, low toxicity wastes (such as contaminated soils) are an example of this application. 

The costs associated with solidification/stabilization (S/S) technologies have generally been considered low compared with those for other treatment techniques. The reasons for this are the availability of rather cheap raw materials (e.g., fly ash, cements, lime) used in the more popular processes, simple processing requirements, and the use of readily available equipment from the concrete and related construction industries (D150141, p. 7.99). 

In addition, this volume examines various hazardous waste treatment/ disposal and minimization/prevention techniques as promising alternatives for sustainable development,by (a) presenting solidification/stabilization treatment processes to immobilize hazardous constituents in wastes by changing... 

Major categories of industrial waste solidification/stabilization systems are cement-based processes, pozzolanic processes (not including cement), thermoplastic trohniques, organic polymer techniques, surface encapsulation techniques, and self-cementing techniques (for high calcium sulfate sludges). Vitrification (discussed previously) can also be considered a solidification process. 

In general, solidification/stabilization technology is considered a last approach to the management of hazardous wastes. The aim of these techniques is a stronger fixation of contaminants to reduce the emission rate to the biosphere and to retard exchange processes. Two objectives can be distinguished ... 

The two geochemical fields of application can directly be connected with the major fields of environmental technology - civil engineering on the one side and chemical engineering on the other side. On the one hand, we have techniques such as solidification, stabilization, enclosure walls to inhibit escape of pollutants from... 

As the first reported quasicrystals were metastable phases at room temperature produced by rapid solidification, they were consequently of poor quality. Stable quasicrystals have since been discovered that have revealed very high strucmral perfection, even comparable to single crystals. This discovery made it possible to apply conventional solidification techniques. The preferred method appears to be system-specific, as it depends on the temperature stability of the quasicrystalline phase. If the quasicrystal is only stable at elevated temperatures, for example, it can decompose into a crystalline phase if the melt is solidified slowly. If the phase is thermodynamically stable down to room temperature, as is the case for Al-Pd-Mn, quasicrystals can be grown with conventional cooling rates (e.g. 10°C/h). 

DSSC systems, and that through novel techniques the shortcomings in the use of RTILs can be overcome. Kubo et al. reported that the quasi-solidification with a gelator is valid for long-term stability at 85°C as shown in Figure 15.7. The decrease in the normalized efficiency of the iodide-based RTIL without a gelator was found to be due to the decrease in the triiodide and adsorbed dye onto the Ti02 [23, 25]. 

Stabilization/solidification of hazardous liquids and sludges by combination of the waste with Portland cement to form a cement paste has been studied as a way to minimize environmental impact. The structure of the paste resists physical attack and the alkaUne nature of the material resists chemical attack, making the technique attractive as a disposal alternative for heavy metal sludges. 

Metal(loid)-contaminated soil can be remediated by chemical, physical, or biological techniques (or a combination of all three). The technology applied is often specific to the metal(loid) contaminant to be removed and the site characteristics and may be further classified into in situ and ex situ categories. In situ remediation takes place on site and does not require excavation of the contaminated soil, limiting the exposure pathways to other organisms, including humans. Many in situ teclmiques aim to stabilize the metal(loid) fraction in the soil via specific soil amendments (e g., lime), vitrification, electrokinetics, solidification (thermal treatments) or passive remediation methods. Such techniques do not reduce the total... 

The solidification of HLLW, followed by geologic deposition, is piesaatly considered as the only realistic technique to create conditions for a safe long term disposal of HAW. The objectives of solidification is to immobilize the radioactive elem ts and to reduce the volume to be stored. The solidified product must be nondispersable (i.e. not finely divided as a powder), insoluble, and chemically inert to the storage environment, be thermally stable, have good heat conductance (this determines the maximum radioactivity and volume of the final product), be stable against radiation (up to 10 Gy), and have mechanical and structural stability. 

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