Nickel metal hydroxide

Addition of an alkali metal hydroxide solution to an aqueous solution of a nickel(II) salt precipitates a finely-divided green powder. nickel(II) hydroxide NilOHfj on heating this gives the black oxide. NiO. which is also obtained by heating nickel(II) carbonate or the hydrated nitrate. Black nickel(II) sulphide, NiS, is obtained by passing hydrogen sulphide into a solution of a nickel(II) salt. 

The extent of hydrolysis of (MY)(n 4)+ depends upon the characteristics of the metal ion, and is largely controlled by the solubility product of the metallic hydroxide and, of course, the stability constant of the complex. Thus iron(III) is precipitated as hydroxide (Ksal = 1 x 10 36) in basic solution, but nickel(II), for which the relevant solubility product is 6.5 x 10 l8, remains complexed. Clearly the use of excess EDTA will tend to reduce the effect of hydrolysis in basic solutions. It follows that for each metal ion there exists an optimum pH which will give rise to a maximum value for the apparent stability constant. 

Nickel hydroxides have been used as the active material in the positive electrodes of several alkaline batteries for over century [1], These materials continue to attract much attention because of the commercial importance of nickel-cadmium and nickel-metal hydride batteries. In addition to being the cathode active material in nickel-metal hydride batteries, Ni(OH)2 is an important corrosion product of the anode during cycling. There are several reviews of work in the field [2-10],... 

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

A redox half-reaction at an active electrode also may convert one metal salt into another. For example, the cathode In a nickel-cadmium battery is NiO(OH), which is reduced to nickel(II) hydroxide. The half-reaction reduces... 

Such a method has been patented in the U.S.31 for processing the nonferrous metal hydroxide sludge wastes containing chromium, copper, zinc, and nickel for simultaneous recovery and separation of the individual nonferrous metals sequentially. In this method, the individual nonferrous metals, such as, chromium, copper, zinc, and nickel can be individually and economically separated from the collected nonferrous metal hydroxide sludge wastes. This is achieved by the combination of the following steps performed in sequence31 ... 

FIGURE 6.3 Solubility of metal hydroxides and sulfides. (Taken from Krofta, M. and Wang, L.K., Design of Innovative Flotation-Filtration Wastewater Treatment Systems for a Nickel-Chromium Plating Plant, U.S. Department of Commerce, National Technical Information Service, Springfield, VA, Technical Report PB-88-200522/AS, January 1984.)... 

Next, a series of runs was conducted to determine the effect of various alkali metal hydroxide additions along with the sponge nickel catalyst. The 50 wt. % sodium hydroxide and 50 wt. % potassium hydroxide caustic solution used in the initial test was replaced with an aqueous solution of the alkali metal hydroxide at the level indicated in Table 2. After the reaction number of cycles indicated in Table 2, a sample was removed for analysis. The conditions and results are shown in Table 2. The results reported in Table 2 show the level of 2° Amine in the product from the final cycle. The level of NPA in all of the mns was comparable to the level observed in the initial test. No significant levels of other impurities were detected. 

Salvaga and Cavallotti [43], and Randin and Hintermann [44] advanced a metal hydroxide mechanism which involved hydrolyzed nickel ions as the actual nickel reactant in Ni-P deposition ... 

The metal hydroxides that dissolve in an excess of aqueous NH3 to form ammine complexes are derived from the twelve metals of the cobalt, nickel, copper and zinc families. Therefore, when excess NH3 is added ... 

At a nickel metal surface in alkaline aqueous medium a thin film of Ni(II) hydroxide is formed. At + 0.63 V (vs NHE) the film is oxidized to Ni(III) oxide hydroxide (a). After adsorption of the substrate at this surface (b) hydrogen atom abstraction at the a-carbon of the substrate occurs in the rate determining step (c). The intermediate radical is then further oxidized either directly (d) or indirectly (e) to the product. 

Nickel hydroxides, 17 111 Nickel—iron alloys, 17 101 Nickel—iron—aluminum catalyst, 17 121 Nickel—iron cells, 3 491—493 Nickel—iron—chromium alloy 825 in galvanic series, 7 805t Nickel—iron—chromium alloys, 17 102—103 Nickel—iron plating, 9 821 Nickel itch, 12 691, 701 Nickel—matrix composites, 17 104 Nickel metal, forms of, 17 95—99 Nickel metal hydride cells, 3 431, 471, 509-512... 

To the second half of the raffinate, ammonia is added to form a nickel ammonium complex, which is extracted with a hydroxyaryloxime (LIX84). Due to simultaneous formation of metal hydroxides, the solution is carefully... 

The coordination atmosphere of the metal ion in solution can also be expected to affect the reaction rate. Microanalytical results indicate that the active catalysts in cobalt and nickel systems could well be metal thiolic species produced in situ. However, these complexes are appreciably more soluble in the, alkaline solutions than are metal hydroxides (see, for example, the analysis results reported in Table IV), and it is not possible on the present evidence to differentiate between catalysis as a result of increased solubility (comparing metal hydroxides and metal thiolic complexes), and catalysis as a result of differences in the allowed ease of electron transfer. It is apparent, however, that most of the metals investigated (Table I) are poor catalysts because they form only the insoluble hydroxide complexes. 

If finely divided nickel is mixed with silver nitrate in presence of liquid ammonia at low temperature and ammonia allowed to evaporate spontaneously in absence of moisture, pale violet crystals of composition Ni(N03)2.9NH3 separate. The substance decomposes on treatment with -water, with formation of metallic hydroxide and evolution of ammonia.3... 

A conventional wastewater treatment system with an average flow rate of 160,000 gpd produces effluent suitable for NPDES discharge. Metal hydroxide sludges are dewatered in a 15 cu. ft filter press producing more than one half ton of filter cake per day. The filter cake is further dewatered in a 7 cu. ft, batch-type sludge dryer. Based upon recommendations by their consultant, the firm also uses the sludge dryer to dehydrate nickel strip solutions. Two reverse osmosis systems are used for partial nickel recovery. Trivalent chromium is recovered by drag-out control and evaporation. 

The yield is based on L-ascorbic acid (1) or the salt of 1, when this is possible. Each of a variety of metals (cadmium, cobalt, iron, magnesium, manganese, nickel, and zinc) was individually added to aqueous, or water-methanol, solutions of 29. The yields of L-ascorbic acid ranged from 40 to 85%. These reactions presumably proceed by way of the metal hydroxide. The yield is based on the weight of the salt of L-ascorbic acid. The yield is for the conversion of 28 into 29 into 1. Compound 29 was prepared by using Amberlite 200 (H+) ion-exchange resin it was also prepared directly from 27. 

Aq. ammonia dissolves many of the heavy metal hydroxides—e.g. zinc, cadmium, cobalt, nickel, copper, and silver hydroxides chromic hydroxide dissolves in this... 

Use of metal hydroxides opens some possibilities in the discussed syntheses. Thus, as a result of interaction (3.83) of (5-ketoimines 656 with divalent nickel, copper, and cobalt hydroxides in acetone solution, the p-ketoiminates 657 were obtained [205] ... 

It has been shown that the required loading levels of metal hydroxides to flame retard polyolefins can be reduced by the addition of transition metal oxides as synergistic agents. For example, a combination of 47.6% MH modified with nickel oxide in PP gave a UL94 V-0 flammability rating, which would require -55% of unmodified MH.4 These systems, however, can only be used where the color of the product is not important. 

To check the hypothesis that steam causes volatilization of copper, nickel and cobalt, two experiments were performed with a clean X-AI2O3 slice above a NiO/a-Al2C>3 sample [29]. The sample and the slice were separated from each other by two pieces of platinum wire (0 0.25 mm). The experimental set-up is shown in the inset of fig, 6, After treatment at 1000 °C for 70 hours in N2/O2/30% HjO or a dry N2/O2 gas flow, the bottom side of the upper a-AI2O3 slice was analyzed with RBS (figure 6). Clearly, in the presence of steam some nickel had been deposited onto the slice, but when steam had been absent no nickel was detected. We thus conclude that some nickel species, formed under the influence of steam, disappeared from the Ni0/a-Al203 sample into the vapour phase. We attribute this loss to the formation of volatile metal hydroxides 29,30. This is supported by Fourier Transform Infra Red (FTIR) Spectroscopy experiments [31]. 

In the reduction of nitrobenzene in a 2% aqueous sodium-hydroxide solution, according to previous publications, azoxy-benzene is formed at platinum and nickel electrodes, azobenzeno at lead, tin, and zinc cathodes, and aniline at copper cathodes especially in the presence of copper powder. It was found that, in an unchangeable experimental arrangement, a cathodo potential of 1.8 volts, as measured in connection with the deci-normal electrode, could be carried out with all the chosen cathodes and additions. At this constant potential, by using different metals and adding various metallic hydroxides, the whole reduction was carried out and the nature and quantity of the reduction products determined in each case. It turned out that the emphasized differences in the results disappeared and that, with an equal potential of all cathodes, similar yields of azoxybenzene and aniline and traces of azobenzene resulted. The cathodes were of platinum, copper, copper and copper powder, tin, platinum with addition of stannous hydroxide zinc, platinum with addition of zinc hydroxide, lead, platinum with addition of lead hydroxide, and nickel. The yields of azoxybenzene varied from 41-65% of aniline 23-53%. 

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