Nickel removal

Rigorous hydrogenating conditions, particularly with Raney Nickel, remove the sulfur atom of thiophenes. With vapor-phase catalysis, hydrodesulfurization is the technique used to remove sulfur materials from cmde oil. Chemically hydrodesulfurization can be a valuable route to alkanes otherwise difficult to access. 

Kinetics studies of the hydrotreatment (and hydrocracking) of VR has led to the conclusion that most of the metals, sulfur and nitrogen removal takes place during the first 50% of the whole VR conversion [119-123], More than one reactor was needed for HDM and HDS of a Maya VR, when HDT is used as feed pretreatment [119,120], Although vanadium removal appears easier and faster than nickel removal, their kinetics results showed very similar values of the activation energy for the demetallization reactions [122],... 

In reviewing these results, we would like to emphasize the information they provide about metals deposition chemistry as well as the potential utility of the proposed regeneration process. The metals extraction studies confirm the fact that three distinct phases of vanadium occur on these catalysts and that they are of varying reactivity. By contrast, the nickel removal is essentially complete under similar conditions. We suggest... 

A cracking catalyst is subjected to two pretreatment steps. The first step effects vanadium removal the second, nickel removal, to prepare the metals on the catalyst for chemical conversion to compounds (chemical treatment step) that can... 

Nickel is removed from electroplating wastes by treatment with hydroxide, lime, and/or sulfide to precipitate the metal (HSDB 1996). Adsorption with activated carbon, activated alumina, and iron filings is also used for treating nickel-containing waste water. Ion exchange is also used for nickel removal and recovery. 

Nickel (Ni II) is poorly removed Ifom waste water in the activated sludge process because of its high solubility (Stephenson et al. 1987). Only 30 0% of nickel was removed in a pilot activated sludge plant. Nickel removal in activated sludge plants is best correlated with effluent suspended solids (Kempton et al. 1987). Nickel is predominantly soluble in the effluent. 

Precipitation can remove soluble nickel Ifom water. In aerobic waters, nickel ferrite is the most stable compound (Rai and Zachara 1984). Nickel may also be removed by coprecipitation with hydrous iron and manganese oxides. Nickel removed by precipitation and coprecipitation settles into the sediment. 

Nickel removed by coprecipitation can be remobilized by microbial action under anaerobic conditions (Francis and Dodge 1990). Remobilization results Ifom enzymatic reductive dissolution of iron with subsequent release of coprecipitated metals. A lowering of pH as a result of enzymatic reactions may indirectly enhance the dissolution of nickel. Experiments using mixed precipitates with goethite... 

The complications arising from corroded metal ion build-up have been studied by Tokuyama Soda and removal of these by electrolysis has been reported nickel removal [155] and iron removal [156] results in longer run times and greater voltage stabilities. 

In competitive demetallation experiments the same rates do not necessarily hold. Hung and Wei (1980) reported that with both Ni-etio and VO-etio in the feed, the vanadium removal rate was the same as in the individual vanadium run, whereas the nickel removal rate was suppressed to below that of vanadium removal. In a related study using a mixed Ni-T3MPP and VO-etio oil, Webster (1984) reported that VO-etio de-metallated faster than Ni-TMPP and also suppressed the metal removal rate of the latter. This inhibition phenomenon offers a partial explanation as to why in most commercial operations with real feeds vanadium is more reactive than nickel. 

Fig. 33. Relationship between vanadium and nickel removal during desulfurization of petroleum oils (Ohtsuka, 1977).

A linear relationship is often observed between vanadium removal and sulfur removal, whereas the relationship between nickel and sulfur removal is linear but of smaller slope (Massagutov et al., 1967). For asphaltene-containing stocks, this phenomenon is interpreted on the basis of heteroatom distribution within the asphaltene micelles (Beuther and Schmid, 1963). Sulfur and vanadium are concentrated on the exterior, whereas nickel is concentrated in the interior. Conversion of the asphaltene generally leads to simultaneous removal of sulfur and vanadium, whereas nickel removal is more difficult. 

Fyson, A., M. Kalin, and L. W. Adrian. 1994. Arsenic and nickel removal by wetland sediments. In Proceedings of International Land Reclamation and Mine Drainage Conference and Third International Conference on the Abatement of Acidic Drainage. Pittsburgh, PA, pp. 1 and 109. 

Nicholas, R., Steven, PK., and Claussen, K. 2003. Lead and nickel removal using Microspora and Lemna minor. Bioresource Technology, 89 41-8. 

Figure 4-2 First-order kinetic plots based on the holdup model fot removal reactions (after Paraskox et al. 1). (a) the vanadium removal reaction, (ft) the sulfur removal reaction, (c) the nitrogen removal reaction, (d) the nickel removal reaction.

The competitive adsorption of metal ions is dependent on both the metal ions and the adsorbent, its magnitude being related to the adsorption mechanism. In the case of competition between metal ions for the same adsorption sites, it has been shown that the favored metal ion is that which presents the faster adsorption kinetics on the same activated carbon in a monocomponent solution. This is the case for the adsorption of Cu(II) and Pb(II) onto activated carbon cloths [17]. When metal ions present in solution do not interact with the same adsorption sites, the removal of both ions is not affected compared with monocomponent adsorption. For example, in a study performed with different activated carbons, nickel removal was not affected by the presence of cadmium, because the sites that interact with nickel do not strongly interact with cadmium [18]. Finally, due to the strong relationship that exists between the metal ion adsorption mechanism and pH (see Section 24.2.1.4), it as been demonstrated that competitive adsorption is also influenced by pH [19],... 

Then the NiSMM pellet was outgassed at 540 C and the reduced nickel removed by reaction with CO at about 120 C. After outgassing at 540 ammonia was adsorbed as described above (top). 

Catalytic reduction with Raney nickel removed the double bond, and the regioselective aldol - now the silyl enol ether is essential - was carried out by isolating the silyl enol ether 47 and using TiCI4 as the Lewis acid. The yield of gingerol 40 was an impressive 92%. 

Hydrogenation with Raney nickel removes the chiral auxiliary and, as we had hoped, hydrogenates the alkene from the less hindered exo-face, pushing the side chain inside the folded molecule 83. The ketone is converted into the only possible vinyl triflate for Stille coupling with a vinyl stannane to give the diene 84. 

Early applications were related to industrial processes and focussed on the sampling of metal ions in natural waters [96], the determination of phenylalanine using in-line ion-exchange [97], modelling of heavy metal adsorption [98], use of pulsed flows for nickel removal from acidic solutions [99], investigation of properties inherent to fluidised beds and transport reactors [100], and treatment of radioactive wastes [101]. The characteristics, limitations and applications of fluidised beads are provided elsewhere [102—104],... 

H. Tokuyama, S. Maeda, K. Takahashi, Development of a novel moving bed with liquid-pulse and experimental analysis of nickel removal from acidic solution, Sep. Purif. Technol. 38 (2004) 139. 

Figure 5 Nickel Removal Pseudo Turnover Frequency (atoms Ni removed ks 1nm ) Versus Time on Stream (hours) - symbols as given in Figure 2...

Most investigations (10) have revealed that vanadium removal rates exceed those as nickel in petroleum residua. In our case, the values of the rate constants are not comparable since they fit different kinetic orders. Nevertheless the percentages of nickel removal are in all cases lower than those of vanadium removal. 

The higher value of activation energy of the nickel removal reactions indicates a higher temperature dependence, it is for this that the nickel converions at high temperature (415 C) approach to those of vanadium conversions. 

Data are reported as percent nickel removed vs. pH isotherms. The James and Healy adsorption model as contained in the equilibrium computer model REDEQL2 was used to facilitate data analysis (20). In this way, an assessment of the combined effects of adsorption, complexation, and precipitation could be attempted. 

Figure 2. Nickel removal as a function of pH for varying ionic strengths (lines are predicted by REDEQL2 using pK, = iS.2, pNij> = 4.77 ( J) I=10-3, o I = io-3 (a I = 10- )...

Figure 4. Nickel removal as a function of pH in the presence of oxide surfaces I = 0.01, FeOOH = 0.59 gjh (50 m /L),...

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