In iron hydroxides

Copper was shown to be much more mobile with about 28% total Cu being water soluble or easily extractable 40-50% in iron hydroxide phases and only about 20-30% in the residual. 

B. Daus, H. Weiss, R. Wennrich (1998) Arsenic speciation in iron hydroxide precipitates.- Talanta 46, 867 - 873... 

Jing, C Korflatis, G.P. and Meng, X. (2003) Immobilization mechanisms of arsenate in iron hydroxide sludge stabilized with cement. Environmental Science and Technology, 37(21), 5050-56. 

In the experiments which we carried out with Vorob yeva, the change in iron hydroxide sediments in the parent solution (concentration of NaCl 17 -20 g/1) was studied in the course of 8.5 years. 

Pyrite and marcasite are the major minerals forming the sulfide cement, as identified by XRD and optical microscopy. These sulfides occur as both well-formed cubes and anhedral masses. Arsenic-rich areas (up to 1% by weight as estimated by EDS) occur in the pyrite and marcasite crystals as well as in iron hydroxides, but no separate arsenopyrite phase has been identified. Colloidal size (10-20 nm) iron hydroxide phases were identified using TEM. TEM-EDS analysis showed qualitative differences in arsenic, nickel, and zinc in the iron hydroxides on a nanometer scale. 

Cornu, S., Montague, D., and Conil, P. (2004). Comparison of sequential and kinetic extractions for As speciation in contaminated soils. C. R. Geosci. 336, 1007-1015. Daus, B., Weiss, H., and Wennrich, R. (1998). Arsenic speciation in iron hydroxide pre-... 

CC Davis, H-W Chen, M Edwards. Re-examining the role of silica sorption in iron hydroxide surface chemistry. Environ Sci Technol, submitted for publication. 

NBO, also included those due to oxygen present in iron hydroxides and sulphate groups. In addition, adsorbed water has to be considered together with the BO-peak [58]. The iron peak in the non-contact region was very pronounced and metallic iron was detected at 706.7 eV. On some samples, small peaks at 711.8 eV assigned to iron hydroxide were found [7, 58]. 

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). 

Foulants enter a cooling system with makeup water, airborne contamination, process leaks, and corrosion. Most potential foulants enter with makeup water as particulate matter, such as clay, sdt, and iron oxides. Insoluble aluminum and iron hydroxides enter a system from makeup water pretreatment operations. Some well waters contain high levels of soluble ferrous iron that is later oxidized to ferric iron by dissolved oxygen in the recirculating cooling water. Because it is insoluble, the ferric iron precipitates. The steel corrosion process is also a source of ferrous iron and, consequendy, contributes to fouling. 

More recendy, the molten caustic leaching (MCL) process developed by TRW, Inc. has received attention (28,31,32). This process is illustrated in Eigure 6. A coal is fed to a rotary kiln to convert both the mineral matter and the sulfur into water- or acid-soluble compounds. The coal cake discharged from the kiln is washed first with water and then with dilute sulfuric acid solution countercurrendy. The efduent is treated with lime to precipitate out calcium sulfate, iron hydroxide, and sodium—iron hydroxy sulfate. The MCL process can typically produce ultraclean coal having 0.4 to 0.7% sulfur, 0.1 to 0.65% ash, and 25.5 to 14.8 MJ/kg (6100—3500 kcal/kg) from a high sulfur, ie, 4 wt % sulfur and ca 11 wt % ash, coal. The moisture content of the product coal varies from 10 to 50%. 

Metal depositors. Metal-depositing bacteria oxidize ferrous iron (Fe ) to ferric iron (Fe ). Ferric hydroxide is the result. Some bacteria oxidize manganese and other metals. Gallionella bacteria, in particular, have been associated with the accumulation of iron oxides in tubercles. In fact, up to 90% of the dry weight of the cell mass can be iron hydroxide. These bacteria appear filamentous. The oxide accumulates along very fine tails or excretion stalks generated by these organisms. 

The destiny of most biological material produced in lakes is the permanent sediment. The question is how often its components can be re-used in new biomass formation before it becomes eventually buried in the deep sediments. Interestingly, much of the flux of phosphorus is held in iron(lll) hydroxide matrices and its re-use depends upon reduction of the metal to the iron(ll) form. The released phosphate is indeed biologically available to the organisms which make contact with it, so the significance attributed to solution events is understandable. It is not clear, however, just how well this phosphorus is used, for it generally remains isolated from the production sites in surface waters. Moreover, subsequent oxidation of the iron causes re-precipitation of the iron(lll) hydroxide floes, simultaneously scavenging much of the free phosphate. Curiously, deep lakes show almost no tendency to recycle phosphorus, whereas shallow... 

Table 3.40 Bimetallic corrosion between nickel-iron alloys in sodium hydroxide ...

Discussion. Minute amounts of beryllium may be readily determined spectrophotometrically by reaction under alkaline conditions with 4-nitrobenzeneazo-orcinol. The reagent is yellow in a basic medium in the presence of beryllium the colour changes to reddish-brown. The zone of optimum alkalinity is rather critical and narrow buffering with boric acid increases the reproducibility. Aluminium, up to about 240 mg per 25 mL, has little influence provided an excess of 1 mole of sodium hydroxide is added for each mole of aluminium present. Other elements which might interfere are removed by preliminary treatment with sodium hydroxide solution, but the possible co-precipitation of beryllium must be considered. Zinc interferes very slightly but can be removed by precipitation as sulphide. Copper interferes seriously, even in such small amounts as are soluble in sodium hydroxide solution. The interference of small amounts of copper, nickel, iron and calcium can be prevented by complexing with EDTA and triethanolamine. 

Iron dextran injection contains a complex of iron hydroxide with dextrans of average molecular weight between 5000 and 7000, and is used for the treatment of iron-defieiency anaemia in situations where oral therapy is ineffeetive or impractical. The sodium salt of sulphurie aeid esters of dextran, i.e. dextran sodium sulphate, has anti-eoagulant properties eomparable with heparin and is formulated as an injection for intravenous use. 

The reductase in Geobacter sulfurreducens is located in the outer membrane and a soluble Fe(III) reductase has been characterized from cells grown anaerobically with acetate as electron donor and Fe(III) citrate or fumarate as electron acceptor (Kaufmann and Lovley 2001). The enzyme contained Fe, acid-labile S, and FAD. An extracellular c-type cytochrome is distributed in the membranes, the periplasm, and the medium, and functions as a reductase for electron transfer to insoluble iron hydroxides, sulfur, or manganese dioxide (Seeliger et al. 1998). 

Early measurements of " Th were on seawater samples and Th was co-precipitated from 20-30 L of seawater with iron hydroxide (Bhat et al. 1969). This procedure may not recover all of the " Th in the sample, and an alpha emitting Th isotope (e g., °Th or Th) is added as a yield monitor. Following chemical purification of the Th fraction by ion exchange chromatography, the Th is electrodeposited onto platinum or stainless steel planchets. The planchets are then counted in a low background gas-flow beta detector to measure the beta activity and subsequently with a silicon surface barrier detector to determine the alpha activity of the yield monitor. The " Th activity is thus determined as ... 

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