Contaminated solidification

The other two methods used by industry to examine the purity of maleic anhydride are the crystallization point (168) and color deterrnination of the sample (169). These tests determine the temperature at the point of solidification of the molten sample and the initial color properties of the melt. Furthermore, the color test also determines the color of the sample after a two-hour heat treatment at 140°C. The purpose of these tests is to determine the deviation in properties of the sample from those of pure maleic anhydride. This deviation is taken as an indication of the amount of contaminants in the maleic anhydride sample. 

Low Level Waste Treatment. Methods of treatment for radioactive wastes produced in a nuclear power plant include (/) evaporation (qv) of cooling water to yield radioactive sludges, (2) filtration (qv) using ion-exchange (qv) resins, (J) incineration with the release of combustion gases through filters while retaining the radioactively contaminated ashes (see Incinerators), (4) compaction by presses, and (5) solidification in cement (qv) or asphalt (qv) within metal containers. 

U.S. EPA, Silicate Technology Corporation s Solidification Stabilisation Technology for Organic and Inorganic Contaminants in S oils Applications Analysis Report, EPA/540/AR-92/010, Washington, D.C., 1992. 

Critical factors. In general, porosity is caused by the entrapment of gas during the welding process or during solidification of the weld metal. Surface contamination may provide a gas source during the welding operation. 

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. 

As a first step in the selection process, the applicability of the various solidification/ stabilization processes for specific contaminants can be determined using Table 12. Since these waste treatment systems vary widely in their applicability, cost, and pretreatment requirements, many are limited as to the types of waste that can be economically processed. Waste characteristics such as organic content, inorganic content, viscosity and... 

Solidification Solidifying liquid or gel contaminants can enhance the physical removal. The mechanisms of solidification can be described as follows ... 

We need to keep in mind the disposal costs in all of the mechanisms for solidification. With the first method, keep in mind that free liquids are typically not allowed in most disposal scenarios. And adding too much adsorbent can substantially add to disposal costs. Make this point clear to your field people. As far as using polymerization catalysts and chemical reagents, keep in mind disposal costs. Ensure that you are cognizant of disposal costs of spent catalyst prior to using this scenario. As far as freezing is concerned, consider the cost to keep the contaminants frozen and what the downsides are. The downsides besides cost include measures in case of power failure and use of freezing equipment after wastes have been disposed. 

In this process EAF dust, other zinc-bearing wastes, recycled materials, coke or coal, lime, and silica are mixed and fed to a rotary furnace. The zinc and other volatile nonferrous metals in the feed are entrained in the furnace off-gas and are carried from the furnace to an external dust collection system. The resulting oxide (zinc calcine) is a crude zinc-bearing product that is further refined at zinc smelters. A byproduct of the process is a nonhazardous, iron-rich slag that can be used in road construction. Solidification technologies change the physical form of the waste to produce a solid structure in which the contaminant is mechanically trapped. 

Solidification and stabilization processes. These immobilize the contaminants through physical or chemical processes. Solidification involves the entrapment of contaminants into a consolidated mass and stabilization is the conversion of contaminants to a chemical form that is less available. 

Apart from the sorption capacity and cost, an important property for these materials was their ability to retain the adsorbed contaminants during and after solidification by a hydraulic binder, as all wastes (including spent adsorbents) from the wetland have to be disposed of remotely. The central... 

After solidification, the ingots are shaped using diamond-coated band saws or wires in an abrasive medium in order to have square multicrystalline or pseudosquare rounded angle monocrystalline blocks. This process removes the outer parts of the ingots, generally out of specification for dimensions and with some contamination from the containers or the furnaces. 

The WetOx process can concentrate radioactive contaminants, causing a shift in classification from class A to class B waste. This will have an impact on the selection of solidification media and could effect burial surcharges. The following materials cannot be processed by the WetOx process spent oil, ammonia, polyvinyl chloride, polyethylene, and rubber. 

Cement-based stabiUzation/solidification (S/S) is a technology for the in situ or ex situ treatment of hazardous wastes and hazardous waste sites. It is a process that uses cement and other additives or processes to physically and/or chemically immobilize the hazardous constituents of contaminated soils, sludges, sediments, or liquid wastes. The objective is to prevent the migration of contaminants in the environment by forming a solid mass. 

The HAZCON solidification process is an ex situ technology for the immobilization of metals and inorganic hazardous wastes in wet or dry soil and sludges. The technology is a cement-based process in which the contaminated material is mixed with pozzolanic materials such as Portland cement, a patented additive called Chloranan, and water. The process is capable of treating solids, sludges, semisolids, or liquids. The mixture hardens into a cohesive mass that immobilizes heavy metals. 

The SSM/TEVE system is best suited for removing VOCs, and has been shown to reduce the average soil concentration of VOCs by 90%. The shallow soil mixing technology is also used to mix various solidification/stabilization slurries into the soil for the treatment of inorganic contaminants (including radionuclides). (Refer to the Geo-Con in situ solidification/stabilization process). 

During bench-scale studies on ACT using sediments from the New Bedford Harbor Superfund Site, the Toxicity Characteristic Leaching Procedure (TCLP) concentrations of many contaminants increased or remained unchanged following treatment. Based on these results, researchers stated that solidification/stabilization methods such as ACT were not appropriate for the treatment of polychlorinated biphenyls (PCBs) or semivolatile organic compounds (SVOCs) at the site. The study also indicated that the compressive strength of ACT [45 to 80 pounds per square inch (psi)] was relatively low compared to other solidification/stabilization materials that were tested. 

The soil-cement mixing wall (SMW) is an in situ technology for the fixation, stabilization, and solidification of soils contaminated with metals and semivolatile organic compounds. SMW can be used to treat soils contaminated with pesticides, polychlorinated biphenyls (PCBs), phenols, and poly aromatic hydrocarbons (PAHs) to depths of up to 100 ft. The technology uses hollow-stem augers to inject solidification/stabilization agents and blend them with the soil. 

The Soliditech solidification and stabilization process was used to treat 3000 drums of sand, top soil, clay, and rock from contaminated oilfields in Odessa, Texas. According to the vendor, the 3.5-week-long project cost 850 per day (D213241, p. 49). 

Komatsu, F., Sawada, Y., Ohtsuka, K. OHUCHI, J. 1981. Development of a new solidification method for wastes contaminated by plutonium oxides. In Management of Alpha-Contaminated Wastes. IAEA, Vienna, 325-337. 

A concern raised during full scale operations of the CHEMFIX process was the possibility of contaminant leaching from freshly treated, moist material. During normal processing procedures, treated material would be transferred directly onto the solidification cell. It would be this material that exhibited the potential for contaminant leaching in those 48 hours it took to physically solidify. To determine when the metals were actually bound in the product matrix, a TCLP analysis was done on a series of treated samples over a period of curing times. The results are illustrated in Table 4. 

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