Metal Reclamation

Sands used in the production of brass and bronze castings often pick up lead contamination and must be disposed of as hazardous waste. It has been reported (HazTECH News 1988) that Pittsburgh Mineral and Environmental Technology, Inc. has developed a process that can recover more than 90 percent of the metal value from the sand and render the sand nonhazardous. 

Waste Stream Management Alternatives Method Reference 

Hazardous slags Alter feed stock SR Stephens 1988 

Metals Handbook. Ninth Edition Volume 15 Casting. American Society of Metals International, Metals Park, OH. 

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Precious metals reclamation Precious metals reclamation is the recycling and recovery of precious metals (i.e., gold, silver, platinum, palladium, iridium, osmium, rhodium, and ruthenium) from hazardous waste. Because U.S. EPA found that these materials will be handled protectively as valuable commodities with significant economic value, generators, transporters, and storers of such recyclable materials are subject to reduced requirements. 

Stretford solution. Since 1987, 100% of the waste Stretford solution has been shipped to a metals reclamation facility. Vanadium is reclaimed as vanadium pentoxide. Wastewater treatment sludge. In 1987, the rehnery started a program to recycle this sludge to the coker within the refinery. At the end of 1990, 60% of the sludge was recycled to the coker. The remaining 40% was dewatered onsite at a belt filter press and then landfilled offsite or incinerated. Since 1986, the refinery has paved five plant areas to reduce the amount of dirt and debris washing into the sewer. 

The current state of the case study illustrated (Table 2) shows that technologies for reclamation (condensation, distillation, metal reclamation) or recycling (electrolyte production) are for the most part available for process emissions. Furthermore, chemicals with poor efficiency are currently used in the area of electroplating. 

Metal reclamation of sediments uses many of the same approaches as for soils, except that sediment access is often more difficult. Once removed from the bottom of a lake or river, sediments can be treated and replaced, or landfilled in a hazardous waste containment site. The actual removal of sediments involves dredging. This can pose serious problems since dredging includes the excavation of sediments from benthic anaerobic conditions to more atmospheric oxidizing conditions. This can result in increased solubilization of metals, along with increased bioavailability (see Section 10.3) and potential toxicity, and increased risk of contaminant spreading (Moore, Ficklin Johns, 1988 Jorgensen, 1989 Moore, 1994). There are ongoing discussions as to whether it is more detrimental to remove sediments, whether for treatment or removal, or simply to leave them in place. 

Metal reclamation from acid mine drainage and contaminated surface- and groundwater and wastewaters has been extensively studied. Technologies for metal removal from solution are based on the microbial—metal interactions discussed earlier the binding of metal ions to microbial cell surfaces the intracellular uptake of metals the volatilization of metals and the precipitation of metals via complexation with microbially produced ligands. 

Occupational exposure to CDDs occurs primarily through inhalation and dermal contact of fire fighters and cleanup workers involved with transformers containing PCBs and polychlorobenzenes in workers involved in incineration operations in workers in metal reclamation facilities, and in workers producing and handling pesticides, hexachlorophene, trichlorophenol, or other chlorinated compounds (e g., pentachlorophenol) that may contain small impurities of 2,3,7,8-TCDD or other CDDs (Papke et al. 1992). In addition, these authors reported that the CDD/CDF homologue profiles in whole blood of workers engaged in a variety of different chemical processes or in occupational accidents exhibited distinct CDD/CDF patterns (Papke et al. 1992). 

Liem A, Hoogerbrugge R, Koostra PR, et al. 1991. Occurrence of dioxins in cow s milk in the vicinity of municipal waste incinerators and a metal reclamation plant in the Netherlands. Chemosphere 23(11-12) 1675-1684. 

Riss A, Hagenmaier H, Weberruss U, et al. 1990. Comparison of PCDD/PCDF levels in soil, grass, cow s milk, human blood and spruce needles in an areas of PCDD/PCDF contamination through emissions from a metal reclamation plant. Chemosphere 21(12) 1451-1456. 

Metallic mercury is mostly a problem in confined spaces or where it is handled in industrial processes or in laboratories. It is not generally an environmental problem, more likely an industrial hazard. However, metallic mercury does occur naturally (it was mined in Spain and Slovenia, for example) and the use of mercury for metal reclamation is a potential environmental hazard in countries such as Brazil where miners use it to extract gold from river sediments. Inorganic and organic mercury may be produced from the metallic mercury during its use and subsequent release into the environment. 

Watanabe I, Kawano M, Tatsukawa R (1993) Consumption trend and environmental research on brominated flame retardants in Japan and the formation of polyhalogenated dibenzofurans at the metal reclamation factory. Document distributed at the OECD Workshop on the Risk Reduction of Brominated Flame Retardants, Neuchatel, Switzerland... 

After PCDEs were detected in a fly ash from a municipal waste incinerator in Finland [36], the occurrence of PCDEs in combustion wastes has not been studied much. PCDEs could be formed during incomplete combustion by condensation from chlorophenols as has been indicated for PCDDs [54], but de novo synthesis is also possible [55]. The formation of chlorinated compounds is always possible during combustion in the presence of organic material and chloride. The formation of PCDEs de novo in combustion has been described in the literature review of Kurz s thesis [4]. Briefly, diphenyl can be formed from the phenoxy radical and benzene which in turn can be formed from alkene radicals. If the formed molecule does not already contain chlorine, chlorination of diphenyl ether can occur, e.g., in the presence of HCl. It has been suggested, however, that PCDEs, in contrast to PCDDs and PCDFs, are not formed to a great extent de novo on solid surfaces or in the gas phase in thermal processes during metal reclamation processes [56]. When PCDEs were analyzed in emission samples of a metal reclamation plant in Finland, all PCDEs were below 4 ng nr3. 

Pine needles from the surroundings of metal reclamation plant probably contained PCDTs in low concentrations. Quantitative determinations were not made due to much interference by other compounds of similar type [49]. The concentrations of TeCDDs were in the range of 5-50 pg/g per dry weight of needles and the concentrations of TeCDFs in the range of 4-15 pg/g. Quite high concentrations of alkylated dibenzothiophenes in pine needles in a recipient area of the emissions from a pulp and paper mill have been measured, which might suggest that PCDTs could also be taken up by needles [56]. 

Nevertheless, both hazardous and inert residues are solid wastes and require landfill. Dumping solid waste to landfill, even non-hazardous clean wastes, is not sustainable and is not entirely green . An ideal green technology is one that consumes all materials involved in the production process to produce only re-useable or new products, without generating solid waste that requires disposal to landfill. Such smelters can be found in Trail, British Columbia, Canada at the Cominco lead and zinc primary smelter and in Malaysia in Kuala Lmnpur at the Metal Reclamation primary and secondary lead smelter [21]. 

The International Metals Reclamation Company, Inc. (INMETCO), located in Ellwood City, Pennsylvania, began operations in 1978 as a metals recycler. INMETCO is committed to the concept of sustainable development, which requires... 

Since 1995, consumer and industrial Ni/Cd battery recycling in the U.S. has been primarily done at the International Metals Reclamation Company, Inc. (INMETCO) using a process licensed from SAFT NIFE. The cadmium is distilled from the plates using a low temperature thermal process, and the material is used for new battery production. The nickel content of the battery goes into the standard INMETCO stainless steel remelt alloy production. In general, this thermal recovery process makes up the majority of the world recycling capacity. The cadmium is recovered and purified as the metal or can be converted to cadmium oxide. 

Today, RCE cells find continuing use in controlled metal reclamation in a recent study, attention was focused on the recovery of precious metals from spent automobile exhaust catalysts [67]. 

Another practical approach is to promote electrolyte turbulence via the use of an expasded-mesh electrode in a solution containing fluidized inert particles (typically 1 mm glass ballotini). This is the principle of the Chemclec cell (Fig. 7.4) which has been widely applied to metal finishing, j tographic silver-recovery and precious metal reclamation prooeu. ... 

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