Leaching resistance

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

In contrast, disilicate glasses containing U 4+ showed much less leach resistance. The 4+ glass was only slightly more leach resistant than pure sodium disilicate glass which is water soluble. For 4+ glasses, the ph of the leach solution... 

However, given that other, supposedly stable and leach-resistant catalysts that we had previously studied seemed to operate solely by a leaching mechanism, with no supported Pd apparently active for the reaction (vide supra) and that other authors had found precatalysts of this type to operate by solely a leaching mechaiusm in Heck conversions of aryl iodides (19), we decided to investigate this system further using the solid poison testing method. 

Forms a strong, dense, leach-resistant final product that is an analog of naturally occurring phosphate minerals. 

Electro-Pyrolysis, Inc. (EPI) has developed the direct current (DC) graphite arc furnace vitrification technology for the ex situ treatment of wastes. The arc furnace can be operated as an oxidation or reduction process. The vendor states that DC arc melter treatment produces a leach-resistant solid and reduces the volume of wastes that require disposal. 

Forrester Environmental Services, Inc., has developed a group of technologies for the stabilization of wastes containing heavy metals, such as lead, cadmium, arsenic, mercury, copper, zinc, and antimony. These technologies have been used in both industrial pollution prevention and remediation applications. One version of the technology involves the use of water-soluble phosphates and various complexing agents to produce a less soluble lead waste. This process results in a leach-resistant lead product. 

The ISV process uses electricity to heat and melt soil and other earthen materials contaminated with organic, inorganic, and radioactive compounds. Organic compounds undergo pyrolysis (thermal decomposition in the absence of oxygen). The pyrolyzed compounds then migrate to the surface zone, where they are collected and oxidized in a collection hood. Inorganic and radioactive components are incorporated as oxides into a leach-resistant vitrified product. 

Treated wastes are bound in a durable, leach-resistant glass. 

MeItTran, Inc. (MeItTran), has developed the Ultimate Solution, an ex situ vitrification technology that uses a direct current (DC) arc system to treat hazardous wastes. The vendor claims that organic materials are destroyed by the technology and that inorganic materials are melted and cooled into a leach-resistant final waste form. RIMS were unable to obtain information from the vendor in regards to performance or commercial availability. 

Vitrification is the process of converting materials into a glass or glasslike substance. Vitrification allows for the treatment of many different kinds of waste and produces a final waste form that typically is durable and leach resistant. During the process of thermal vitrification, organic contaminants are typically destroyed, and inorganic materials are melted. 

Permanently binds metals in a leach-resistant solid. 

Produces a stable, leach-resistant, vitrified final waste form. 

RocTec stabilization is a process to transform incinerator ash and other materials into small briquettes, which are then sintered to increase their strength, make them leach resistant, and reduce their volume. A ceramic stabilization process, it is applicable for metal oxide matrices containing metals designated as toxic under the Resource Conservation and Recovery Act... 

Carbon supported powdered palladium catalysts have been widely used in the chemical industry. In addition to activity and selectivity of those catalysts, the recovery rate of the incorporated precious metal has a major impact on the economic performance of the catalyst. In this study, the effects of catalyst age, oxidation state of the incorporated metal and temperature treatment on the palladium leaching resistance as well as on activity and dispersion of carbon supported palladium catalysts were investigated. 

Leaching Resistance of Precious Metal Powder Catalysts - Part 2 475... 

Timmons, D. M. Thompson, L. E. 1996. Geochemical and petrographic studies and the relationships to durability and leach resistance of vitrified products from the in-situ vitrification process. In Proceedings of the International Topical Meeting on Nuclear and Hazardous Waste Management SPECTRUM 96. American Nuclear Society, Inc., La Grange Park, 1026-1029. 

Fly ash increases the density, decreases the permeability, and increases the leaching resistance of Ordinary Portland Cement (OPC). It is a truism that The leach resistance of solidified cement-waste systems can be improved by any process which accelerates curing, limits porosity, or chemically bonds fission product or actinide elements. (Jantzen et al., 1984). Supercritical C02 treatment of a modified Portland cement is expected to further increase the density over the untreated material, so that a reduced porosity and improved leachability should result. In addition, the high silica content of fly ash, with its well-known sorbent properties toward actinides and certain other radionuclides, enhances the immobilization characteristics. 

The incorporation of fly ash lowers the initial heat evolution during setting, thereby reducing the incidence of cracking and spalling. It is desirable to maintain the modified cement in monolithic form for optimum leach resistance. 

The accelerated carbonation reactions have also been shown to improve the immobilization properties of Portland cements used as radioactive was-teforms. The formation of carbonates eliminates the potential problem of radiolysis while at the same time improving the leaching resistance. The resulting carbonate matrix, which is more thermodynamically stable relative to the untreated cement, would also be preferred for the underground disposal of the wasteforms. Incorportion of fly ash into the cement-type wasteform further enhances the favorable properties of this waste type. 

Leach Resistance of Iodine Compounds in Portland Cement... 

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