Suspensions iron hydroxide

Nagano,T Isobe, H. Nakhshima, S. Ashisa-ki,M. (2002) Characterization of iron hydroxides in a weathered rock surface by visible microspectroscopy. Appl. Spectr. 56 651—657 Nagano,T Mitamura, H. Nakayama, S. Na-kashima, S. (1999) Formation of goefhite and hematite from neodymium-containing ferri-hydrite suspensions. Clays Clay Min. 47 748-754... 

Deposition of iron in the form of suspensions when hot springs mix with sea waters first occurs in the upper layers of the sea, in which case almost pure iron hydroxide is formed. Gradual dilution leads to expansion of the region where suspended iron sediment is deposited in the water. With depth, the iron hydroxides are replaced by clastic silica. 

Diphenyl Mercury Adsorption. Adsorption of DPM from seawater onto amorphous iron hydroxide, manganese oxide and bentonite clay was not detected in this study. A comparison of standard diphenyl mercury solutions in seawater with Identical solutions to which sediment phase had been added and shaken for 48 hours was routinely performed as part of the isotherm determination. There was no significant difference in the concentration of dissolved diphenyl mercury for standard. versus standard plus solid phase for any of the suspensions of amorphous, Fe(OH)-, MnO, or bentonite in seawater, implying no significant adsorption of DPM from seawater onto these phases under the concentrations studied. If lower concentrations of DPM could have been used (ppb or lower) it is possible that adsorption might have been detected. 

Aging of Suspension of Freshly Precipitated Iron Hydroxide... 

Figure 2.20 Correlation of outer charge vs. pH as a result of tittering iron hydroxide (FeOOH) suspension with density 90 mg l (Dzombak and Morel, 1990 White, 1997).

FIGURE 13.7 Preparation and characterization of single-walled nanotube (SWNT) forest formed by metal-assisted deposition of oxidized, shortened SWNTs. (a) Schematic representation of SWNT forest preparation. Shortened, open-ended SWNTs with carboxyl-functionalized ends are produced by oxidation of SWNTs. A suspension of SWNTs is introduced to a metal surface functionalized with iron hydroxides. An SWNT forest results as SWNTs vertically align via self-assembly. (Part a adapted with permission from Chattopadhyay, D., Galeska, I., and Papadimitrakopoulos, F., Metal-assisted organization of shortened carbon nanotubes in monolayer and multilayer forest assemblies, J. Am. Chem. Soc., 123,9451-9452,2001. Copyright 2001 American Chemical Society.) Cyclic voltammograms (scan rate 300 mV s ) of (b) SWNT forest electrodes in pH 5.5 buffer with and without 0.2 mM HjOj. (Continued)... 

Since alkoxides of low formal charge metals are highly condensed and therefore poorly reactive, the synthesis of many perovskites (ticanium. zirconium, niobium, barium, strontium or lead) can take place by hydrolysis of the alkoxide by an aqueous suspension of hydroxide (Ba, Sr) [121] or by an aqueous solution of a lead complex such as the acetate [122]. Iron is introduced as acetylacetonate in the case of PbFeo.jNbo.sOi [123]. The calcination temperature varies with the nature of the metallic cation. It must be adjusted if the formation of undesirable phases is possible, such as the pyrochlore phase in the case of PbMgo.33Nbo.66O3 and PbZri, (Ti 03 [122]. A fast ramp rate prevents or minimizes its formation. 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Iron Reduction. The reduction of nitrophenols with iron filings or turnings takes place in weakly acidic solution or suspension (30). The aminophenol formed is converted to the water soluble sodium aminopheno1 ate by adding sodium hydroxide before the iron-iron oxide sludge is separated from the reaction mixture (31). Adjustment of the solution pH leads to the precipitation of aminophenols, a procedure performed in the absence of air because the salts are very susceptible to oxidation in aqueous solution. 

Iron disulfide is obtained from its naturally occurring minerals, pyrite and marcasite. In the laboratory it may be prepared along with iron(II) sulfide by passing dry hydrogen sulfide through a suspension of hydrated iron (III) oxide or iron(III) hydroxide in alkaline medium. The unstable product formed decomposes to FeS2 and FeS. 

The process can be accelerated by operating at 150 °C under pressure this technique also improves pigment quality [3.19]. Rapid heating of a suspension of iron oxide hydroxide with the necessary quantity of Fe(OH)2 to ca. 90 °C also produces black iron oxide of pigment quality [3.20], [3.21],... 

Orange iron oxide with the lepidocrocite structure (y-FeOOH) is obtained if dilute solutions of the iron(II) salt are precipitated with sodium hydroxide solution or other alkalis until almost neutral. The suspension is then heated for a short period, rapidly cooled, and oxidized [3.22], [3.23],... 

In the first stage, nuclei are prepared by precipitating iron(II) sulfate with alkali (e.g., sodium hydroxide solution) at 20-50 °C with aeration (c). Depending on the conditions, yellow, orange, or red nuclei may be obtained. The suspension of nuclei... 

Miscellaneous class reactions. (Section 9.5.) Determine the eifect of the following class reagents upon small portions of the original mixture (for some of the tests an aqueous solution or suspension may be used) (i) bromine in dichloro-methane solution (ii) potassium permanganate solution (iii) alcoholic silver nitrate solution (iv) 2,4-dinitrophenylhydrazine reagent (v) Schiffs reagent (vi) acetyl chloride (vii) benzoyl chloride (in the presence of aqueous sodium hydroxide) (viii) iron(m) chloride solution and (ix) bromine water. 

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