Nickel concentration

The treatments used to recover nickel from its sulfide and lateritic ores differ considerably because of the differing physical characteristics of the two ore types. The sulfide ores, in which the nickel, iron, and copper occur in a physical mixture as distinct minerals, are amenable to initial concentration by mechanical methods, eg, flotation (qv) and magnetic separation (see SEPARATION,MAGNETIC). The lateritic ores are not susceptible to these physical processes of beneficiation, and chemical means must be used to extract the nickel. The nickel concentration processes that have been developed are not as effective for the lateritic ores as for the sulfide ores (see also Metallurgy, extractive Minerals recovery and processing). 

The chain-growth catalyst is prepared by dissolving two moles of nickel chloride per mole of bidentate ligand (BDL) (diphenylphosphinobenzoic acid in 1,4-butanediol). The mixture is pressurized with ethylene to 8.8 MPa (87 atm) at 40°C. Boron hydride, probably in the form of sodium borohydride, is added at a molar ratio of two borohydrides per one atom of nickel. The nickel concentration is 0.001—0.005%. The 1,4-butanediol is used to solvent-extract the nickel catalyst after the reaction. 

Nickel sulfamate is more soluble than the sulfate salt, and baths can be operated using higher nickel concentrations and higher currents. Sulfamate baths have been found to have superior microthrowing power, the abiUty to deposit in small cracks or crevices. Using one nickel salt, only a hydrometer and pH paper are needed to control the bath. A small amount of chloride salt was added as a proprietary. Highly purified nickel sulfamate concentrates are commercially available that can be used to make up new plating baths without further purification. 

Copper-alloy corrosion behavior depends on the alloying elements added. Alloying copper with zinc increases corrosion rates in caustic solutions whereas nickel additions decrease corrosion rates. Silicon bronzes containing between 95% and 98% copper have corrosion rates as low as 2 mil/y (0.051 mm/y) at 140°F (60°C) in 30% caustic solutions. Figure 8.2 shows the corrosion rate in a 50% caustic soda evaporator as a function of nickel content. As is obvious, the corrosion rate falls to even lower values as nickel concentration increases. Caustic solutions attack zinc brasses at rates of 2 to 20 mil/y (0.051 to 0.51 mm/y). 

For alloys containing up to about 27% Ni in Fe, the equilibrium phase at room temperature is bee. However, in the neighborhood of 30% Ni either the fee or bee phases can be obtained at room temperature as the result of various heat treatments. For nickel concentrations greater than 30%, the structure is fee. Hence, the unusually large volumetric phenomena are characteristic of the fee phase. 

Despite the utmost importance of physical limitations such as solubility and mixing efficiency of the two phases, an apparent first-order reaction rate relative to the olefin monomer was determined experimentally. It has also been observed that an increase of the nickel concentration in the ionic phase results in an increase in the olefin conversion. 

This has been regarded as nickel(III) and also as nickel(IV) dimethylglyoxime. t The weight of steel to be taken will naturally depend upon the nickel content. The final nickel concentration should not exceed 0.6 mg per 100 mL because a precipitate may form above this concentration. 

Recently, other authors when studying the activation of hydrogen by nickel and nickel-copper catalysts in the hydrogen-deuterium exchange reaction concentrated for example only on the role of nickel in these alloys (56) or on a correlation between the true nickel concentration in the surface layer of an alloy, as stated by the Auger electron spectroscopy, and the catalytic activity (57). 

One can readily note the close correlation between the observed variations of the catalytic activity and the evolution of surface nickel concentration (Figure 3A). However, the dramatic difference between the activity of nickel rich alloys [(Nl Sl2) and (Nl2Sl) ] and silicon rich Intermetalllcs [(Nl.Sl.) and (filSl.) ] tar exceeds... 

Nickel matte Nickel concentrate Exit gas Alloy scrap... 

A U.S. Environmental Protection Agency (U.S. EPA) study of 165 sludges showed nickel concentrations ranging from 2 to 3520mg/kg (dry basis).18 Nickel toxicity may develop in plants from application of municipal wastewater biosolids on acid soils. Nickel reduces yields for a variety of crops including oats, mustard, turnips, and cabbage. 

Strong correlations occur between concentrations of trace elements in Californian soils. Nickel concentrations in soils are strongly correlated with Cr (r = 0.95) Cu contents are also significantly correlated with Co (r = 0.81). Strong correlations between Ni and Cr and between Cu and Co are observed as well (Marrett et al., 1992). This strong correlation between trace elements indicates that these elements associate in parent materials and suggests similar physical-chemical processes governing soil formation (Bradford et al., 1996). 

The observed ratio aaiioy/aNi agreed well with the Ni content predicted.) As discussed later, it was believed that hydrogen chemisorption was proportional to the surface nickel concentration (see Section IV). It is clear, however, that chemisorption as a method of surface area measurement must be used with discretion in the case of alloy films. 

Spectra for a series of Cu-Ni alloys have been obtained (91) and these are reproduced in Fig. 11. Because of overlapping of peaks from the component metals, separate indications of each element are only obtained from the 925 eV Cu peak and the 718 eV Ni peak. The results have only qualitative significance because the quoted nickel concentrations are bulk values. Nevertheless, they do suggest that for these particular samples of Cu-Ni alloys, the surface composition varies smoothly from pure copper to pure nickel. Auger spectroscopy has subsequently shown that the surface composition of the (110) face of a 55% Cu-Ni crystal was identical with the bulk composition (95a). Ono et al. (95b) have used the technique to study cleaning procedures argon ion bombardment caused nickel enrichment of... 

Nickel concentrations (milligrams of nickel per kilogram fresh weight [FW] or dry weight [DW]) in field collections of representative plants and animals... 

Sediment nickel concentrations are grossly elevated near the nickel-copper smelter at Sudbury, Ontario, and downstream from steel manufacturing plants. Sediments from nickel-contaminated sites have between 20 and 5000 mg Ni/kg DW these values are at least 100 times lower at comparable uncontaminated sites (Chau and Kulikovsky-Cordeiro 1995). A decrease in the pH of water caused by acid rain may release some of the nickel in sediments to the water column (NRCC 1981). Transfer of nickel from water column to sediments is greatest when sediment particle size is comparatively small and sediments contain high concentrations of clays or organics (Bubb and Lester 1996). 

Table 6.5 Nickel Concentrations in Selected Abiotic Materials...

Mosses and lichens accumulate nickel readily and at least nine species are used to monitor environmental gradients of nickel (Jenkins 1980a). Maximum concentrations of nickel found in whole lichens and mosses from nickel-contaminated areas range between 420 and 900 mg/kg DW vs. 12 mg/kg DW from reference sites (Jenkins 1980a). Nickel concentrations in herbarium mosses worldwide have increased dramatically during this century. In one case, nickel concentrations in Brachythecium salebrosum from Montreal, Canada, rose from 6 mg/kg DW in 1905 to 105 mg/kg DW in 1971 (Richardson etal. 1980). 

Data are limited on nickel concentrations in terrestrial invertebrates. Earthworms from uncontaminated soils may contain as much as 38 mg Ni/kg DW, and workers of certain termite species may normally contain as much as 5000 mg Ni/kg DW (Table 6.6). Larvae of the gypsy moth (Porthetria dispar) near a nickel smelter had 20.4 mg Ni/kg DW concentrations in pupae and adults were lower because these stages have higher nickel elimination rates than larvae (Bagatto et al. 1996). 

Waterfowl feeding in areas subjected to extensive nickel pollution — such as smelters and nickel-cadmium battery plants — are at special risk because waterfowl food plants in those areas contain 500 to 690 mg Ni/kg DW (Eastin and O Shea 1981). Dietary items of the ruffed grouse (Bonasa umbellus) near Sudbury, Ontario, had 32 to 95 mg Ni/kg DW, whereas nickel concentrations in grouse body tissues usually contain less than 10% of the dietary level. Nickel concentrations in aspen (Populus tremula) from the crop of ruffed grouse near Sudbury ranged from 62 mg/kg DW in May to 136 mg/kg DW in September (Chau and Kulikovsky-Cordeiro 1995), which shows the role of season in dietary nickel composition. 

Mammalian wildlife from uncontaminated habitats usually contain less than 0.1 to about 5 mg Ni/kg DW in tissues in nickel-contaminated areas, these same species have 0.5 to about 10 mg Ni/kg DW in tissues (Outridge and Scheuhammer 1993 Chau and Kulikovsky-Cordeiro 1995), with a maximum of 37 mg/kg DW in kidneys of the common shrew (Sorex araneus) (Table 6.6). Nickel accumulations in wildlife vary greatly between species. For example, tissues of mice have higher concentrations of nickel than rats and other rodents, while beavers and minks have higher nickel concentrations in their livers than birds in similar sites near Sudbury (Chau and Kulikovsky-Cordeiro 1995). 

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