Iron oxidation kinetics

Halfmeier, H, Schafer-Treffenfeldt, W., andReuss, M., Potential ofThiobacillus ferrooxidans for Waste Gas Purification. Part 2. Increase in Continuous Ferrous Iron Oxidation Kinetics Using Immobilized Cells, / / / /. Microbiol. 

Lin, S. and Gurol, M., Catalytic decomposition of hydrogen peroxide on iron oxide kinetics, mechanism, and implications, Environ. Sci. Technol., 32(10), 1417-1423,... 

Lin, S. S. Gurol, M. D. Catalytic Decomposition of Hydrogen Peroxide on Iron Oxide Kinetics, Mechanism, and Implications, Environ. Sci. Technol. 1998, 32, 1417-1423. 

Breed A. W. and Hansford G. S. (1999) Effects of pH on ferrous-iron oxidation kinetics of Leptospirillium ferro-oxidans in continuous culture. Biochem. Eng. J. 3, 193-201. 

Freeder, B. G. et al., J. Loss Prev. Process Ind., 1988, 1, 164-168 Accidental contamination of a 90 kg cylinder of ethylene oxide with a little sodium hydroxide solution led to explosive failure of the cylinder over 8 hours later [1], Based on later studies of the kinetics and heat release of the poly condensation reaction, it was estimated that after 8 hours and 1 min, some 12.7% of the oxide had condensed with an increase in temperature from 20 to 100°C. At this point the heat release rate was calculated to be 2.1 MJ/min, and 100 s later the temperature and heat release rate would be 160° and 1.67 MJ/s respectively, with 28% condensation. Complete reaction would have been attained some 16 s later at a temperature of 700°C [2], Precautions designed to prevent explosive polymerisation of ethylene oxide are discussed, including rigid exclusion of acids covalent halides, such as aluminium chloride, iron(III) chloride, tin(IV) chloride basic materials like alkali hydroxides, ammonia, amines, metallic potassium and catalytically active solids such as aluminium oxide, iron oxide, or rust [1] A comparative study of the runaway exothermic polymerisation of ethylene oxide and of propylene oxide by 10 wt% of solutions of sodium hydroxide of various concentrations has been done using ARC. Results below show onset temperatures/corrected adiabatic exotherm/maximum pressure attained and heat of polymerisation for the least (0.125 M) and most (1 M) concentrated alkali solutions used as catalysts. 

Okereke, A. and S. E. Stevens, Jr., 1991, Kinetics of iron oxidation by Thiobacillus ferrooxidans. Applied and Environmental Microbiology 57,1052-1056. 

Table III suggests some of the proton transfer kinetic studies one is likely to hear most about in the near future. The very first entry, colloidal suspensions, is one that Professor Langford mentioned earlier in these proceedings. In the relaxation field, one of the comparatively new developments has been the measurement of kinetics of ion transfer to and from colloidal suspensions. Yasunaga at Hiroshima University is a pioneer in this type of study (20, 21, 22). His students take materials such as iron oxides that form colloidal suspensions that do not precipitate rapidly and measure the kinetics of proton transfer to the colloidal particles using relaxation techniques such as the pressure-jump method.

TABLE 12.2. Arrhenius parameters for the decomposition of catechol and hydroquinone in the presence and absence of iron oxide, assuming pseudo first-order kinetics... 

Klupinski et al. (2004) conclude that the reduction of nitroaromatic compounds is a surface-mediated process and suggest that, with lack of an iron mineral, reductive transformation induced only by Fe(II) does not occur. However, when C Cl NO degradation was investigated in reaction media containing Fe(II) with no mineral phase added, a slow reductive transformation of the contaminant was observed. Because the loss of C Cl NO in this case was not described by a first-order kinetic model, as in the case of high concentration of Fe(II), but better by a zero-order kinetic description, Klupinski et al. (2004) suggest that degradation in these systems in fact is a surface-mediated reaction. They note that, in the reaction system, trace amounts of oxidize Fe(II), which form in situ suspended iron oxide... 

Fig. 16.10 Plot showing kinetics of C CljNOj reduction (fiUed circles) occurring in conjunction with increasing photon correlation spectrometry (PCS) count rates (open circles), which are indicative of particle formation, in reaction with O.SOmM Fe(ll) (pH 7.0). (For clarity, the symbols showing measured values of [C CljNOJ are connected point to point.) The other open symbols show PCS count rates in nonreaction mixtures (i.e., without C Cl NO ) containing either O.SOmM Fe(II) (pH 7.0) or O.SOmM Ca(ll) (pH 7.0). Reprinted with permission from Klupinski TP, Chin YP, Traina SJ (2004) Abiotic degradation of pentachloronitrobenzene by Fe(ll) Reactions on goethite and iron oxide nanoparticles. Environ Sci Technol 3S 4353-4360. Copyright 2004 American Chemical Society...

Reduction of these PHMs took place in experiments containing both Fe(ll) and iron oxide minerals, under anoxic conditions. The transformation of PHMs by surface-bound Fe(ll) generally follows a pseudo-first-order kinetic rate law, expressed by... 

Tab. 10.3 Enthalpies of adsorption and kinetics of proton adsorption and desorption on iron oxides.

Ideally, a phase transformation should be investigated using a combination of techniques which enable changes in composition, structure, surface area, morphology and porosity of the solid phases and in the composition of the solution to be monitored, together with the reaction kinetics. This type of comprehensive investigation is rare for iron oxide interconversions in most cases only one or two of the above aspects of the transformation have been considered. 

Cations differ from ligands in that they influence the crystallization of ferrihydrite over a wider pH range than do ligands. They usually require mol ratios (M/(M + Fe)) of 0.05-0.1 to influence the kinetics and products of the reaction, whereas ligands are often effective at hundredfold lower concentrations. In addition, cations are often incorporated in the iron oxide structure (see Chap. 3). The effects of Ti, VO , Pb ", Cr , and the first row divalent transition elements have been investigated. These effects vary widely, although retardation predominates. 

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