Bimetallic iron particles

Module 1 Synthesis of nanoscale bimetallic iron particles. The module has been created according to existing literatirre. Nanoscale iron particles are synthesized by mixing NaBH4 (0.25 M) and FeCl3 6H20 (0.045 M) solutiorrs (1 1 volitme ratio) (8). The reaction is as follows ... 

Module 2 Using nanoscale bimetallic iron particles for groundwater remediation. This module has been created according to existing literature. Trichloroethylene (TCE), one of the most ubiquitous soil and groundwater contaminants, is used as a sample contaminant. The reductive dehalogenation of TCE via zero-valent nano iron particles can be described by the following equation (29) ... 

In a similar study, Zhang and Wang (1997) studied the reaction of zero-valent iron powder and palladium-coated iron particles with trichloroethylene and PCBs. In the batch scale experiments, 50 mL of 20 mg/L trichloroethylene solution and 1.0 g of iron or palladium-coated iron were placed into a 50 mL vial. The vial was placed on a rotary shaker (30 rpm) at room temperature. Trichloroethylene was completely degraded by palladium/commercial iron powders (<2 h), by nanoscale iron powder (<1.7 h), and nanoscale palladium/iron bimetallic powders (<30 min). Degradation products included ethane, ethylene, propane, propene, butane, butene, and pentane. The investigators concluded that nanoscale iron powder was more reactive than commercial iron powders due to the high specific surface area and less surface area of the iron oxide layer. In addition, air-dried nanoscale iron powder was not effective in the dechlorination process because of the formation of iron oxide. 

Terrapure Systems, L.L.C. (Terrapure), is currently developing palladized iron remediation technology (PIRT). The deposition of small amounts of palladium (approximately 0.05 wt%) on the surface of iron particles may result in a bimetallic surface that can cause the dechlorination of aqueous organic compounds. The developers claim that the technology can be used as an in situ or ex situ process and can be applied to aqueous contaminants and soil. PIRT has been evaluated in bench-scale tests and is not currently commercially available. 

Ultrasonic irradiation of solutions containing volatile organometaUic compounds such as Fe(CO)j, Ni(CO), and Co(CO)3NO produced porous, coral-like aggregates of amorphous metal nanoparticles [25]. A classic example is the sonication of Fe(CO)j in decane at 0 C under Ar, which yielded a black powder. The material was >96% iron, with a small amount of residual carbon and oxygen present from the solvent and CO ligands. Bimetallic alloy particles have also been prepared in this way. Sonication of FeCCO) and Co(CO)3NO leads to Fe-Co alloy particles [26]. Nanostructured MoS can be synthesized by the sonication of Mo(CO)g with elemental sulphur in 1,2,3,5-tetramethylbenzene under Ar [27]. Metal nitrides are prepared by the sonication of metal carbonyls under a mixture ofNH3andH2atO°C [28]. 

In contrast to the behavior of CO, the decomposition of ethylene is a facile process when performed on a nickel catalyst, but does not occur when the hydrocarbon is passed over iron. Based on these data we can rationalize the observed deactivation behavior observed in the present investigations according to the notion that at 725°C, the surface of the bimetallic particles become enriched in nickel, a condition that favors decomposition of adsorbed ethylene molecules, but is inert with regard to catalyzed disproportionation of CO. Subsequent lowering of the temperature to 600°C results in the restoration of the original surface composition and the concomitant attainment of the initial catalytic reactivity pattern. 

As mentioned above, the addition of promoters, and even the formation of bimetallic particles, can provide carbon-supported iron catalysts with better performances in CO hydrogenation. The method of preparation of these systems is going to determine the final effect, always taking advantage of the relative inertness of the carbon surface. The interaction between the different components of the active phase can be maximized by using mixed-metal carbonyl complexes. Furthermore, use of these precursors allows for the preparation of catalysts with... 

Galvanic corrosion or bimetallic corrosion is important to consider since most of the structural industrial metals and even the metallic phases in the microstructure alloys create galvanic cells between them and/or the a Mg anodic phase. However, these secondary particles which are noble to the Mg matrix, can in certain circumstances enrich the corrosion product or the passive layer, leading to a decrease or a control of the corrosion rate. Severe corrosion may occur in neutral solutions of salts of heavy metals, such as copper, iron and nickel. The heavy metal, the heavy metal basic salts or both plate out to form active cathodes on the anodic magnesium surface. Small amounts of dissolved salts of alkali or alkaline-earth metal (chlorides, bromides, iodides and sulfates) in water will break the protective film locally and usually lead to pitting (Froats et al., 1987 Shaw and Wolfe, 2005). 

The use of commercially available zero-vale 12nt-metal powders for the degradation of halogenated aliphatics is well documented (4). Nanoscale Fe° has a much smaller grain size than commercially available powdered iron, making it much more reactive. Nanoiron and nanoscale bimetallic particles have been shown to be extremely effective for the reductive dehalogenation of common soil and ground water contaminants such as chlorinated methanes (5), chlorinated ethanes (5) and chlorinated ethenes (7, 8) and essentially eliminate all the undesirable byproducts (P). 

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