Iron removal

The optimum conditions for roasting the clay and the optimum strength (30—60%) of the sulfuric acid used depend on the particular raw material. Finely ground bauxite or roasted clay is digested with sulfuric acid near the boiling point of the solution (100—120°C). The clay or bauxite-to-acid ratio is adjusted to produce either acidic or basic alum as desired and soHds are removed by sedimentation. If necessary, the solution can be treated to remove iron. However, few, if any, of the many methods claimed to be useful for iron removal have been used industrially (29). Instead, most alum producers prefer to use raw materials that are naturally low in iron and potassium. 

Equipment. From the appHcations standpoint, magnetic equipment falls into one of four broad categories tramp iron removal, magnetic particle separation and concentration, product cleaning, or eddy current separation on nonmagnetic metaUics. 

Table 2. Capacities of Magnetic Pulleys for Tramp Iron Removal, m /h...

Another process, which also generates elemental sulfur as a by-product, has been patented by Envirotech Research Center in Salt Lake City (29). In the Electroslurry process, a ball mill finely grinds a chalcopyrite concentrate, which reacts with an acidic copper sulfate solution for iron removal. The Hquor is electrolyzed and the iron is oxidized to the ferric form. This latter step leaches copper from the copper sulfide for deposition on the cathode. Elemental sulfur is recovered at the same time. 

TABLE 19-17 Tramp-Iron Removal with Plate Magnet/ 0 6 m from Top ... 

Color None Decaying organic material and metallic ions causing color may cause foaming in boilers hinders precipitation methods such as iron removal, hot phosphate softening can stain product in process use Coagulation, filtration, chlorination, adsorption by activated carbon... 

Magnetic treatment Iron removal from slag Household refuse... 

Rust a) up to 10 ppm iron removed by manganese greensand filter if pH is 6.7 or higher or... 

Color Boiler foaming Presents problems with iron removal Discoloration of mantifactured produce Adsorption (activated carbon Coagulation Filtration Chlorination... 

Cutler, Frances Casar, Douglas. Effectiveness of iron Removal by Deep-Bed Polishers. Ultrapure Water, Tall Oaks Publishing, Inc., USA, September 1998. 

How is the impurity present in pig iron removed to create high-quality steel ... 

Boyle EA, Edmonds JM, Sholkovitz ER (1977) The mechanism of iron removal in estuaries. Geochim Cosmochim Acta 41 1313-1324... 

Table 5.9 Comparison of various ionic precipitation processes for iron removal.

Matsumoto et al. demonstrated that the removal of iron from diferric transferrin by the tris-hydroxamate siderophore mimic TAGE occurs in two discreet steps (90). The slower step corresponds to iron removal from the more stable C-lobe site on transferrin and the faster step to removal from the N-lobe. The rates of removal are similar to the rates of removal of iron from diferric transferrin by desferrioxamine B (4), signifying similar mechanisms of removal between the two systems (90). 

Iron(II) porphyrin complexes, four-coordinate, 14 552-553 Iron(III) porphyrin complexes, 14 554 Iron porphyrins, 14 552-555 Iron(II) porphyrins, 14 553 Iron(III) porphyrins, 14 553 Iron(IV) porphyrins, 14 554 Iron production quicklime in, 15 61 sulfur use in, 23 591 Iron removal, in municipal water treatments, 26 124 Iron salts... 

Alternative 1 consists of preliminary treatment for heavy metals removal with the primary concern being iron removal (Figure 8.3). The levels of iron observed in the groundwater at this site would be very detrimental to the downstream treatment processes. This pretreated water would then be used for cooling tower makeup water followed by biological treatment. This approach would be the easiest and cheapest alternative. This combined process should provide effective removal of BTEX. 

Two advantages of this approach would be the minimized capital and operating costs, along with minimal space requirements. The best process (for iron removal) would probably be chemical precipitation with lime through a rapid mix, flocculation, and DAF step. DAF size requirements would be in the range of a 300- to 350-ft2 unit. Total costs for operation and maintenance of the preliminary treatment facility using an interest rate of 10% over 10 years are estimated at 0.44/1000 gal. A summary of the capital and operating cost estimates is presented in Table 8.2. 

Alternative 2 consists of preliminary treatment followed by dual-media pressure filtration, and two-stage air stripping (Figure 8.4). The preliminary treatment step for iron removal would be exactly the same as specified under Alternative 1. The filters would be recommended to remove suspended matter and particulate iron prior to the air strippers. The required filtration capacity could be provided with either a duplex system of two 60-in.-diameter filters or a triplex system of three 42-in-diameter filters. 

Fig. 2.12 Examples of non-linear Arrhenius (or Eyring) plots (a) 1u(A oh)7 " ) vs T for the base hydrolysis of trans-Co(en)2ClJ. Curvature may result when k, k2 and A// , not equalling A// in the conjugate-base mechanism (Sec. 4.3.4). Reprinted with permission from C. Blakeley and M. L. Tobe, J. Chem. Soc. Dalton Trans. 1775 (1987). (b) nk vs T for iron removal from C- and N-terminal monoferric transferrin (lower and upper scales respectively). Transferrin contains two iron binding sites = 35 A apart. Either of the two sites, designated C- and N-terminal, can be exclusively labelled by Fe(lll) ions and these may be removed by a strong ligand such as a catechol (see Sec. 4.11). Reprinted with permission from S. A. Kretschmar and K. N. Raymond, J. Amer. Chem. Soc. 108, 6212 (1986). (1986) American Chemical Society.

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