Manganese oxides degradation

Oxidation of arsenic-bearing pyrite with adsorption onto iron oxides and/or other metal (oxy)(hydr)oxides Nitrate reduction by pyrite oxidation (note that Appelo and Postma, 1999 referred to pure rather than arsenian pyrite) Manganese oxide reduction and release of sorbed arsenic Fe(lll) reduction on oxide surfaces changes net charge leading to arsenic desorption Iron oxide reductive dissolution and release of sorbed arsenic catalyzed by NOM degradation... 

Bao WL, Fukushima Y, Jensen KA et al (1994) Oxidative degradation of non-phenolic lignin during lipid peroxidation by fungal manganese peroxidase. FEBS Lett 354 297-300... 

Mielgo I, Lopez C, Moreira MT et al (2003) Oxidative degradation of azo dyes by manganese peroxidase under optimized conditions. Biotechnol Prog 19 325-331... 

Mn Peroxidase. The manganese peroxidase (MnP) is one of the two known enzymes capable of the oxidative degradation of lignin, an amorphous, random, aromatic polymer synthesized from p-hydroxycin-namyl alcohol, 4-hydroxy-3-methoxycinnamyl alcohol, and 3,5,-dime-thoxy-4-hydroxycinnamyl alcohol precursors by woody plants. Both enzymes contain the protoporphyrin IX heme prosthetic group, similar to the heme peroxidases with an L5-histidine and both use hydrogen peroxide as a substrate. However, the manganese peroxidase has an absolute requirement for Mn(II) to complete its catalytic cycle (50). The X-ray structure of this protein has recently appeared (51). 

A further report of the oxidation ability of manganese nodules is that of Nitta.53 Several reactions were carried out with natural manganese oxide nodules including oxidative dehydrogenations of alkanes and cycloalkanes, reduction of NO, total oxidation of CO, and use in the gettering of metal and mixed metal ions. For example, nodules were found to have a tremendous capacity for adsorption of heavy metals and toxic metals like Pb2+, and Hg2+. in addition, nodules have been used to sequester metals that are present in petroleum fractions that can contain metals like V and Ni. These metals can cause degradation of the fluid cracking catalysts even at levels as low as 1 ppm. 

The two major catalytic applications of OMS and OL materials involve oxidations and photooxidations. Some amorphous manganese oxide (AMO) systems have been prepared that are outstanding photooxidation catalysts for degradation of CHsBr and conversion of isopropanol to acetone.76 Catalytic data for several OMS and OL systems are summarized in Table VI. 

Ascorbic acid is reasonably stable in a dry state with a shelf life of about 1-3 yr (23). However, it rapidly oxidizes in solution. A 1% solution may remain at approx 80% potency after 10 d. A 0.02% solution will degrade to 0% within 3 d. Ascorbic acid is also currently available in tablet form for dechlorination applications. Release of ascorbic acid-containing waters under some conditions may reduce the pH of the receiving streams. Use of vitamin C is reported to have other potential benefits as it is an essential vitamin for healthy fish (23). Also, it can easily strip manganese oxide stains from reservoir surfaces and thereby promote better disinfection (once the vitamin C is exhausted). Vitamin C (ascorbic acid) is NSF certified, allowing it to be used in drinking water treatment to remove or reduce chlorine levels. 

As shown in Fig. 2-21, iron oxides and manganese oxides are most likely the chemical species being used as oxidants in the degradation of organic matter at this pe. 

R Lackner, E Srebotnik, K Messner. Oxidative degradation of high molecular weight chlorolignin by manganese peroxidase of Phanerochaete chrysosporium. Biochem Biophys Res Com 178(3) 1092-1098, 1991. 

It is interesting to note that the corresponding iron complexes were less reactive than their manganese analogues, while catalysts lifetimes for 1 and 2 were on the order of 1-2 hr. Thus, both catalyst appear to undergo oxidative degradation and this reaction competes with the conversion of C-H to C-OH bonds. As well, the C-H activation results clearly show a trend of C > C3 >C2 and follows the order of the bond dissociation energies(4). 

By bacterial disproportionation H S and are produced concurrently without participation of an external electron acceptor or donor (Bak and Pfennig 1987 Thamdrup et al. 1993). The biogeo-chemical transformations of sulfur in marine sediments are closely coupled to the cycles of iron and manganese. Sulfate, iron oxides, and manganese oxides all serve as electron acceptors in the respiratory degradation of organic matter. As there are also non-enzymatic reactions between iron, manganese and H S within the sediment, the quantification of dissimilatoiy, heterotrophic Fe and Mn reduction is particularly difficult. 

Krastanov A (2000) Removal of phenols from mixtures by co-immobUized laccase/tyrosinase and Polycar adsorption. J Ind Microbiol Biotechnol 24 383-388 Kuan 1C, Hen M (1993) Stimulation of manganese peroxidase activity a possible role for oxalate in lignin biodegradation. Proc Nad Acad Sci USA 90 1242-1246 Lante A, Crapisi A, Krastanov A et al. (2000) Biodegradation of phenols by laccase immobilised in a membrane reactor. Proc Biochem 36(l-2) 51-58 Lee C, Yoon J, von Gunten U (2007) Oxidative degradation of A-nitrosodimethylamine by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide. Water Res 41(3) 581-590... 

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