Studies of Mono- and Polynuclear Iron Hydroxy Complexes in Brown Coal

Domazetis, G.; Raoarun, Monthida; James, B. D.; Liesegang, J.

doi:10.1021/ef050001i

Cited by 25 publications

(36 citation statements)

References 30 publications

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“…Sodium and iron in the coal and char was also measured by acid extraction and atomic absorption spectrometry (AAS) as previously described. 24,25 Pyrolysis. Samples consisted of acid-washed coal and coal with known amounts of added iron (a sample of coal containing sodium was also included, to determine any impact sodium may exert on the pyrolysis results).…”

Section: Methodsmentioning

confidence: 99%

“…23 Our interest in low-temperature pyrolysis stems from investigations on the catalytic gasification of low-rank coals, particularly, Australian and German brown coal with added sodium or calcium and also added transition-metal species such as iron or nickel hydroxyl species. [24][25][26] Differentiation between thermolysis of metal complexes and the chemistry that may be attributed to any catalyst species, if present, requires an understanding of the initial molecular structure of the added metal complex and the molecular transformations of the inorganic complex within the coal substrate upon heating. It is necessary, therefore, to relate product formation (such as CO 2 and CO) with the transformation of inorganic species at low temperatures, because these events form inorganic complexes that may be subsequently involved in gasification chemistry.…”

Section: Introductionmentioning

confidence: 99%

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Low-Temperature Pyrolysis of Brown Coal and Brown Coal Containing Iron Hydroxyl Complexes

2006

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The concentrations profiles of CO 2 and CO have been measured at 150-600 °C from the pyrolysis, at slow heating rates, of acid-washed brown coal and brown coal containing iron hydroxyl complexes. CO 2 formation was greater at low temperatures, but CO increased relative to CO 2 with an increasing temperature. The ratio CO 2 /CO was larger for coal with iron, compared to that from acid-washed coal. The iron species in the chars were Fe 2 O 3 at 200-400 °C, Fe 2 O 3 and Fe 3 O 4 at 400-600 °C, and Fe 0 at 700 °C; inorganic carbonate was also detected. Although conventional chemical kinetic simulations could reproduce the total weight loss of coal with temperature, such calculations could not simulate the measured CO 2 and CO concentration profiles. Decarboxylation reactions may proceed via a number of reaction routes, including ones involving intermediate species. Semiempirical quantum mechanics modeling (SE-QM) of decarboxylation using three carboxylic compounds provided a relative order of decomposition as carboxylic acid ∼ carboxylate . radical. SE-QM and single-point self-consistent field (1scf) calculations, using 2D and 3D models of brown coal, were conducted to provide changes in the heats of formation for models after the loss of carboxyl groups. Such calculations also indicated that hydrogen transfer from a phenoxyl group to a carbanion was energetically favored. The formation of the various iron oxides in coal was modeled by (i) decarboxylation reactions via an iron-carbonato complex decomposing into CO 2 and a µ-oxo iron complex and (ii) decarboxylation of coal via the reduction of iron complexes and the formation of organic radicals.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low-Temperature Pyrolysis of Brown Coal and Brown Coal Containing Iron Hydroxyl Complexes

2006

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“…The chelation ratio of Fe 3+ increases with the increase in reaction time when the reaction time is less than 55 minutes; however, the chelation ratio decreases again when the reaction time is more than 55 minutes. With the increase in pH, the hydroxide complex of Fe 3+ slowly transforms to the multinuclear ions structure . The reaction rate of the multinuclear ions complex is slower than the mononuclear ions complex.…”

Section: Resultsmentioning

confidence: 99%

Chelation of metal ions with citric acid in the ammoniation process of wet‐process phosphoric acid

Wan

Luo

et al. 2019

Can J Chem Eng

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A new process is proposed in which citric acid is added during the ammoniation process of wet-process phosphoric acid (WPA) to chelate metal ions to produce fertilizer ammonium dihydrogen phosphate (MAP) containing medium trace elements. The parameters of the chelation reaction were studied systematically and the results show that the optimal reaction condition is pH 3.0, reaction time 60 minutes, temperature 50.0 C, and citric acid content 1.48%. The XRD patterns show that the waterinsoluble compounds are complex mixtures, and the composition of the waterinsoluble compounds are changed through the addition of citric acid. FTIR and XPS analyes further demonstrate that water-insoluble compounds are complex mixtures. The XRD patterns of the MAP products indicate that the structure and morphology of the MAP were changed by the addition of citric acid. In addition, the contents of major elements, medium elements, and trace elements in the MAP product are 68.72%, 0.24%, and 0.50%, respectively, which is consistent with the relevant China national standard. K E Y W O R D Sammonium dihydrogen phosphate, chelation, citric acid, wet-process phosphoric acid

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“…To protect water environment, effective disposal of lignite-derived water to avoid direct discharge is prerequisite. More important, applying appropriate methods to treat the lignite-derived water for reuse may have great significance in China, where has serious water shortage [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Remediation of Iron, Manganese, and Organic Pollutants in Lignite‐Derived Water Using an Upflow Biological Aerated Filter

Zhang

Wang

et al. 2013

CLEAN Soil Air Water

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A large amount of lignite-derived water is created during the process of refining lignite. The concentration of Fe, Mn, phenol, and some other organic pollutants of the lignitederived water is above the discharge permit or circulating cooling water reuse standard in China. A laboratory-scale upflow biological aerated filter (UBAF) was developed to treat this lignite-derived water. Three kinds of coke powders, as waste products in the coal chemical industry with 0.1-0.4 mm, 0.5-1.0 mm, and 1.0-2.0 mm in diameter, were tested as the UBAF's carrier materials. A comparative study of gas-water ratio for the UBAF is presented. The studies presented in this paper demonstrate that with coke powder diameter of 0.5-1.0 mm and gas/water ratio of 7:1, the UBAF reactor can achieve optimal removal efficiency. After the UBAF treatment, the removal efficiency of Fe, Mn, and phenol was found to be 38. 4-62.5%, 56.6-74.3%, and 89.5-94.3%, respectively. The lignite-derived water can meet the discharge permit to surface water and reuse standard for circulating cooling water after the treatment by UBAF. The coke powder, as a waste material, can be used as a support material for UBAF very well.

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Studies of Mono- and Polynuclear Iron Hydroxy Complexes in Brown Coal

Cited by 25 publications

References 30 publications

Low-Temperature Pyrolysis of Brown Coal and Brown Coal Containing Iron Hydroxyl Complexes

Low-Temperature Pyrolysis of Brown Coal and Brown Coal Containing Iron Hydroxyl Complexes

Chelation of metal ions with citric acid in the ammoniation process of wet‐process phosphoric acid

Remediation of Iron, Manganese, and Organic Pollutants in Lignite‐Derived Water Using an Upflow Biological Aerated Filter

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