Iron sorption

Burris D. R., Alien-King R. M., Manoranjan V. S., Campbell T. J., Loraine G. A., and Deng B. (1998) Chlorinated ethene reduction by cast iron sorption and mass transfer. Journal of Environmental Engineering 124(10), 1012-1019. 

The autoradiographs of the rock and mineral thin sections (Figures 4 to 6) also confirm the importance of iron oxides although biotite.(K(Mg,Fe Si AlCLQ(0H) ) and hornblende ((Na,Ca2)(Mg,Fe )(Al,Fe )(Si AlO OH ) contain ferrous iron, sorption appears to take place solely on the small opaque (iron-oxide) inclusions. In the case of biotite, these oxides are located between the basal planes, and are randomly distributed in the hornblende. Similar distributions are observed for olivine, pyroxene, and epidote. The results for pyroxene further confirm the low sorption results obtained with gabbro, where it is one of the major minerals. 

The copper-chelating abihty of sahcylaldoxime has been used to remove copper from brine in a seawater desalination plant effluent. A carbon—sorbate bed produced by sorption of the oxime on carbon proved to be extremely effective in the continuous process (99). In another apphcation, the chelating abihty of sahcylaldoxime with iron and copper was used to stabilize bleaching powders containing inorganic peroxide salts (100). 

In addition to effects on the concentration of anions, the redox potential can affect the oxidation state and solubility of the metal ion directly. The most important examples of this are the dissolution of iron and manganese under reducing conditions. The oxidized forms of these elements (Fe(III) and Mn(IV)) form very insoluble oxides and hydroxides, while the reduced forms (Fe(II) and Mn(II)) are orders of magnitude more soluble (in the absence of S( — II)). The oxidation or reduction of the metals, which can occur fairly rapidly at oxic-anoxic interfaces, has an important "domino" effect on the distribution of many other metals in the system due to the importance of iron and manganese oxides in adsorption reactions. In an interesting example of this, it has been suggested that arsenate accumulates in the upper, oxidized layers of some sediments by diffusion of As(III), Fe(II), and Mn(II) from the deeper, reduced zones. In the aerobic zone, the cations are oxidized by oxygen, and precipitate. The solids can then oxidize, as As(III) to As(V), which is subsequently immobilized by sorption onto other Fe or Mn oxyhydroxide particles (Takamatsu et al, 1985). 

Fig. 15-5 Comparative adsorption of several metals onto amorphous iron oxyhydroxide systems containing 10 M Fej and 0.1 m NaNOs. (a) Effect of solution pH on sorption of uncomplexed metals, (b) Comparison of binding constants for formation of soluble Me-OH complexes and formation of surface Me-O-Si complexes i.e. sorption onto Si02 particles, (c) Effect of solution pH on sorption of oxyanionic metals. (Figures (a), (c) reprinted with permission from Manzione, M. A. and Merrill, D. T. (1989). "Trace Metal Removal by Iron Coprecipitation Field Evaluation," EPRI report GS-6438, Electric Power Research Institute, California. Figure (b) reprinted with permission from Balistrieri, L. et al. (1981). Scavenging residence times of trace metals and surface chemistry of sinking particles in the deep ocean, Deep-Sea Res. 28A 101-121, Pergamon Press.)...

Ainsworth C.C., Pilon J.L., Gassman P.L., Van Der Sluys W.G. Cobalt, cadmium, and lead sorption to hydrous iron oxide Residence time effect. Soil Sci Soc Am J 1994 58 ... 

Elliott El.A., Liberat M.R., Eluang C.F. Effect of iron oxide removal on heavy metal sorption by acid subsoils. Water Air Soil Pollut 1986 27 379-389. 

Low temperature CO sorption experiments monitored with the IR spectroscopy were used to determine the nature of active (acid) sites present in the Fe-TON zeolites. It is well known that CO is a useful probe molecule for Lewis acid sites. Narrow and well resolved bands appear in the region 2135 - 2150 cm"1. The IR spectra of CO sorbed in amount sufficient to cover all Lewis sites in the Fe-TON of different Si/Fe ratios are presented in Figure 2A. The samples of a high iron content (Si/Fe=27, 36) showed a significantly lower thermal stability. The activation of the NFL form of these Fe-TON... 

Whereas studies have been carried out on the factors (surface coverage, residence time, pH) which influence the desorption of arsenate previously sorbed onto oxides, phyllosilicates and soils (O Reilly et al. 2001 Liu et al. 2001 Arai and Sparks 2002 Violante and Pigna 2002 Pigna et al. 2006), scant information are available on the possible desorption of arsenate coprecipitated with iron or aluminum. In natural environments arsenic may form precipitates or coprecipitates with Al, Fe, Mn and Ca. Coprecipitation of arsenic with iron and aluminum are practical and effective treatment processes for removing arsenic from drinking waters and might be as important as sorption to preformed solids. 

Armstrong, J.E. 1976. Quaternary geology, stratigraphic studies and revaluation of terrain inventory maps, Fraser Lowland, British Columbia. Geological Survey of Canada, Paper 75-1, Part A, 377-380. Bowell, R.J. 1994. Sorption of arsenic by iron oxides and oxyhydroxides in soils. Applied Geochemistry, 9, 279-286. 

Reactions between Fe(ll) in contaminated groundwater (5.8 mg/L) and oxic sediment also affected As mobility. Ferrous iron was oxidized by manganese oxides to ferric iron which precipitated as hydrous ferric oxide, creating additional sorption sites. Evidence for this reaction included an increase in ferric oxide concentrations in reacted column sediments and manganese concentrations in leachate that were greater than in the initial eluent. 

Various forms of macro- and microelements differ in their ability to migrate and redistribute among the soil profile. The elements contained in clastic minerals are practically immobile. The elements, bound to finely dispersed clay minerals, are either co-transported with clay particles, or are involved in sorption-desorption processes. Part of the elements are found in concretions and also in very thin coating films of hydrated iron oxides some elements make a part of specially edaphic organic compounds. 

This porous material is a commercial sorption material of the company Dr. Ecker GmbH (GERMANY) which is a composition of calcite, brucite, fluorite and iron hydroxides (RFA 14 % Fe203). 

The mobilization of arsenic from the tailings material seems to be a slow and continuos process attributed to reduction of iron phases. The seepage water of the middle source contains arsenite as well as arsenate in high concentrations and seems to be the only water source in contact with the tailings material. The concentrations of arsenic downstream are still high and the immobilization process by precipitation of iron hydroxide and coprecipitation or sorption of arsenic is incomplete. A reason for this may be the slow kinetics of the oxidation process and the transport of fine grained hydroxide particles. These particles are mobile and can bind the arsenic (mainly as arsenate) too. 

The immobilized arsenic in the precipitate is bound only by sorption onto the amorphous iron hydroxides. A sustainable immobilization would need additional action. 

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