Iron phosphate colloid

In addition to straightforward precipitation reactions, components may dissolve and react with components already present, including atoms on colloidal surfaces. For example, phosphate may dissolve from phosphate rock and react with iron present in the soil solution or on particle surfaces to form an iron phosphate that is insoluble. 

DR. RAMESH PATEL (Clarkson College) It appears that studies on colloidal systems may represent an extremely important area for the future. We have also been doing some colloidal work, particularly dealing with the solution chemistry that precedes the formation of very highly monodispersed colloidal particles. One such system with iron phosphate has been included in the poster presentation. 

Buffle, J., R. R. De Vitre, D. Perret, and G. G. Leppard. 1989. Physico-chemical characteristics of a colloidal iron phosphate species formed at an oxic-anoxic interface of a eutrophic lake. Geochimica et Cosmochimica Acta 53 399-408. 

In addition to the widely practised deposition of phosphate films of Zn, Mn, Cr and Al, numerous patents have been taken out relating to the deposition of alternative phosphates. These include nickel phosphate, tin phosphate, lead phosphate, calcium phosphate and cobalt/iron phosphates [18]. Glassy insulative coatings on ferrous metals can be obtained from Mg/Al phosphate mixtures containing colloidal silica [18]. 

Magnuson, M.L. Lytle, D.A. Frietch, C.M. Kelly, C.A. Characterization of submicrometer aqueous iron HI colloids formed in the presence of phosphate by sedimentation field-flow fractionation with multiangle laser tight scattering detection. Anal. Chem. 2001, 73, 4815 820. 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

Hongshao Z, Stanforth R (2001) Competitive adsorption of phosphate and arsenate ongoethite. Environ Sci Technol 35 4753—4757 Hsia TH, Lo SL, Lin CF, Lee DY (1994) Characterization of arsenate adsorption on hydrous iron oxide using chemical and physical methods. Colloid Surface A 85 1-7... 

Bodies of Water and the Chemical Sediments ,— The chemistry of the deposition of salts from sea-water has already been made the subject of special research, and van t Hoff s results in this field are already familiar. The deposition of calcium carbonate awaits a similar thorough study. Allied questions are the formation of dolomite, the deposition of various salts from inclosed bodies of water, the deposition of phosphate rocks, the precipitation of colloidal suspensions of clay and other substances, and the origin of the great deposits of sedimentary iron ore. 

Zhang, X. Zhang, F. Mao, D. (1999) Effect of iron plaque outside roots on nutrient uptake by rice Oryza sativa L.) Phosphate uptake. Plant and Soil 209 187-192 Zhang,Y Charlet, L. Schindler, P.W. (1992) Adsorption of protons, Fe(II) and Al(IIl) on lepidocrocite (y-FeOOH). Colloids Surfaces 63 259-268... 

The effectiveness of zerovalent iron in removing arsenic from water also greatly depends on the properties of the iron. As(III) removal is especially effective with high surface area 1-120 nm spheres of zerovalent iron (Kanel et al., 2005). Provided that interfering anions (such as, carbonate, silicate, and phosphate) are insignificant, colloidal spheres of zerovalent iron could be injected into arsenic-contaminated soils, sediments, and aquifers for possible in situ remediation (Kanel et al., 2005, 1291). 

Leppard, G.G., DeVitre, R.R., Perret, D. and Buffle, J. (1989) Colloidal iron-oxhydroxy-phosphate the sizing and morphology of an amorphous species in relation to partitioning phenomena. Sci. Total Environ., 87/88, 345-354. 

Fig. 6.9. Log-log plot of W, for hematite (a-Fe203) colloids at pH 3.44, versus o-phosphate concentration. The arrow indicates the point of zero charge, defined operationally as the concentration of o-phosphate at which W p = 1.0 (data from L. Liang, Effects of surface chemistry on kinetics of coagulation of submicron iron oxide particles (ar-F Oj) in water, Ph.D. dissertation, California Institute of Technology, Pasadena, CA, 1988. Environmental Quality Laboratory Report No. AC-5-88).

Because of the high solubility of these bases, over-application can raise the pH above 9, which is undesirable. Owing to the monovalent nature of the associated cations (Na+ or K+), such bases act as colloid dispersants (see Chapter 9). Thus, they increase suspended solids. Additional acid ameliorates are shown in Table 12.8. These phosphate compounds are highly effective in precipitating heavy metals as well as manganese and iron. However, the use of such compounds may increase suspended solids by increasing the surface electrical potential of clays or metal-oxides (see Chapters 3 and 9). 

Colloidal iron consists mainly of colloidal solutions of hydroxides and phosphates of Fe (Fe, " 7 ) and colloidal solutions of the enumerated organic compounds (Fe , ). Direct determination of colloidal iron in sea waters is difficult and usually dissolved iron means the sum of Fe j + Fe. , . 

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