Nickel arsenates

Nickel Arsenate. Nickel arsenate [7784-48-7] Ni2(As0 2 8H20, is a yellowish green powder, density 4.98 g/cm. It is highly iasoluble ia water but is soluble ia acids, and decomposes on heating to form As20 and nickel oxide. Nickel arsenate is formed by the reaction of a water solution of arsenic anhydride and nickel carbonate. Nickel arsenate is a selective hydrogenation catalyst for iaedible fats and oils (59). 

The precipitated copper from this reaction is an important constituent of the slime that collects at the bottom of the electrolytic cells. The accumulation of copper as well as of impurities such as nickel, arsenic, antimony, and bismuth is controlled by periodic bleed-off and treatment in the electrolyte purification section. 

From blister copper, residual sulfur and impurities such as aluminum, silicon, manganese, zinc, tin, iron, nickel, arsenic, antimony and lead are first eliminated by oxidation and slagging. At the end of this stage excess oxygen remains in the partly purified copper, and this is removed by a deoxidation process. 

Figure 5.10. EPMA maps for nickel, arsenic, phosphorus and silicon in a 1st century AD Roman mattock blade. Scale bar = 1 mm. (Courtesy Dr C.J. Salter, Oxford University.)...

Refining operations have two principal wastestreams, waste electrolyte and cathode and anode washwater. Spent electrolyte is normally recycled. A bleed stream is treated to reduce copper and impurity concentration. Varying degrees of treatment are necessary because of the differences in the anode copper. Anode impurities, including nickel, arsenic, and traces of antimony and bismuth, may be present in the effluent if the spent electrolyte bleed stream is discharged. Tables 3.14 and 3.15 present classical and toxic pollutant data for raw wastewater in this subcategory. 

Coprecipitation is a partitioning process whereby toxic heavy metals precipitate from the aqueous phase even if the equilibrium solubility has not been exceeded. This process occurs when heavy metals are incorporated into the structure of silicon, aluminum, and iron oxides when these latter compounds precipitate out of solution. Iron hydroxide collects more toxic heavy metals (chromium, nickel, arsenic, selenium, cadmium, and thorium) during precipitation than aluminum hydroxide.38 Coprecipitation is considered to effectively remove trace amounts of lead and chromium from solution in injected wastes at New Johnsonville, Tennessee.39 Coprecipitation with carbonate minerals may be an important mechanism for dealing with cobalt, lead, zinc, and cadmium. 

Nielsen FH. 1982. Possible future implications of nickel, arsenic, silicon, vanadium, and other ultratrace elements in human nutrition. In Clinical and Biochemical Nutritional Aspects of Trace Elements. New York, NY Alan R. Liss, Inc., 379-404. 

The neutral solution is purified to remove impurities more noble than zinc, e g., cadmium, copper, cobalt, nickel, arsenic, antimony, and germanium. The purification is accomplished by cementation in two or more steps with the addition of zinc dust. Generally, at least one cementation step is conducted at high temperature with arsenic, antimony, or copper-arsenic added. Cadmium is usually recovered in the metallic state and copper, nickel, and cobalt are recovered as sludges if present in sufficient quantities. 

Industrial processes were developed for the selective partial hydrogenation of 4-vinylcyclohexene with Ni catalysts exhibiting minimized isomerization activity in the presence of additives298,299. For example, supported nickel arsenides prepared by reducing nickel arsenate with NaBFLt display high selectivity in the formation of 4-ethylcyclohexene (96% selectivity at 96% conversion on Ni-As-Al2C>3, 398 K, 25 atm H2, acetone additive). 

In spite of the fact that ISEs for more than 60 ions have been described so far, recent findings imply that these ISEs should be re-characterized and re-optimized for trace level applications [19]. The list of ISEs with low-level LODs needs to be expanded either by re-characterization of existing ionophores or by synthesis of new ones. Important ions for which low LODs have yet to be demonstrated are, for example, mercury, chromium, nickel, arsenate and arsenite ions. Hopefully, synthetic chemists will rise to the challenge and new, selective ionophores will be developed that will achieve this goal. 

Tri-nickel Diarsenide, Ni3As2, is formed by reducing nickel arsenate or a mixture of nickel oxide and arsenious oxide with potassium cyanide,7 and also when reduced nickel is heated at 800-1400° C. in vaporised arsenic chloride.8 It is a grey substance, which melts at 1000° C. density 7-86. It is soluble in acids and fused alkalies. 

ASzNisOg (s) 3NiO AS2O5 (s) Nickel Arsenate As2Ni30s (s) 3NiO AS2O5 (s)... 

In contrast, the remaining trace elements of nutritional interest are silicon, vanadium, chromium, manganese, nickel, arsenic, selenium, molybdenum, tin, and perhaps cadmium. These elements present serious problems of analysis in the concentration range that is of interest to the nutritionist. Only a few specialized laboratories have developed expertise... 

The hydrogenation of 4-vinylcyclohexene (46) to 4-ethylcyclohexene (47) was also reported to take place over a supported nickel arsenide, Ni-As(B), which was prepared by the sodium borohydride reduction of nickel arsenate supported on either silica 2,83 or alumina. " These catalysts, however, fimction best in the presence of additives. When the reaction was run in pentane at 125 C and 25 atmospheres of hydrogen in the presence of a small amount of acetone, the product mixture at 96% conversion was 96% 4-ethylcyclohexene (47) and 4% ethylcyclohexane (48). No isomeric olefins were detected. " ... 

A Ni-As(B) catalyst prepared by the borohydride reduction of alumina-supported nickel arsenate gave, on hydrogenation of 1-bromo-l 1-hexadecyne (13) in the presence of a small amount of acetone, a 97% yield of the alkene (14) having a 92 5 cis/trans ratio. No hydrogenolysis of the carbon-bromine bond occurred. "> 2 Borohydride reduction of cobalt acetate gave a Co(B) catalyst that was somewhat less active than Ni(B) but that was quite selective in alkyne semihydrogenations (Eqn. 16.20). ... 

In contrast to the extensive data collected on trace-mineralized rocks between ore districts, less information is available on the arsenic contents of the ore deposits. Because iron sulfide minerals are typically gangue phases, they are commonly ignored in trace element studies of ore deposits, which tend to focus on ore minerals such as sphalerite and galena. Therefore, there have not been extensive analyses for arsenic in iron sulfides in many of the MVT ore districts or trace-mineralized areas. However, a few studies on trace element contents in iron sulfides from the Ozark region have been performed. Wu et al. (1996) analyzed 80 pyrite and marcasite samples from the Viburnum Trend of the Southeast Missouri Lead District and found arsenic in concentrations of 2 to 900 ppm. Bhati and Hagni (1980) also analyzed iron sulfide minerals from this area, but did not publish results for arsenic. Hagni (1993) described the relatively rare occurrence of nickel-arsenic-sulfide ores from the Magmont-West ore deposit of the Viburnum Trend. Leach et al. (1995) list arsenic as a trace constituent in ores from the Northern Arkansas and Southeast Missouri MVT ore districts, but without abundances specified. 

Carbon monoxide Metals (nickel, arsenic, cadmium)... 

Arsenical Blood Agents are incompatible with strong oxidizers and various metals (e.g., aluminum, copper, brass, nickel). Arsenical Blood Agents may decompose on exposure to light to produce hydrogen gas and arsenic metal. Solid agents will react with water to form arsine gas (ASH3). 

Arsenic, normally considered a notorious catalyst poison, actually promoted the selectivity of 1-bromo-ll-hexadecyne hydrogenation over a catalyst formed by the action of borohydride on alumina-supported nickel arsenate [18] ... 

Anke M, Arnhold W, Groppel B, Krause U and Langer M (1991b) Significance of the essentiality of fluorine, molybdenum, vanadium, nickel, arsenic and cadmium. Acta Agron Hung 40(1—2) 291 — 215. 

NbB2 NIOBIUM DIBORIDE 1159 Ni3(As04)2 NICKEL ARSENATE 1201... 

The nickel-arsenic phase diagram [61YUN], [87S1N/NAS] is moderately complex, with the compounds Ni5As2(cr), Nii Asg(cr) (nickel-deficient Ni3As2(cr)), NiAs(cr) and NiAs2(cr) (with a p to a conversion near 870 K). 

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