Effect of ammonoxidation on lignite properties |
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Authors: | Hrissi K Karapanagioti Stavros Kalaitzidis John Vakros Kimon Christanis Falk Liebner |
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Institution: | (1) Department of Chemistry, University of Patras, Rio-Patras, Greece;(2) Department of Geology, University of Patras, Rio-Patras, Greece;(3) Department of Chemistry, University of Natural Resources and Applied Life Sciences, Muthgasse 18, Vienna, Austria;(4) Present address: BHP Billiton Mitsubishi Alliance, Geological Services, Central Queensland Office, Peak Downs Mine, Moranbah, QLD, 4744, Australia |
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Abstract: | Oxidised lignite is a potential alternative source of N fertilizers. Ammonoxidation is the reaction of a given substrate with
oxygen in aqueous ammonia. Lignite ammonoxidation is used for converting low-rank lignite into slowly nitrogen-releasing artificial
humic matter. A lignite sample is compared before and after ammonoxidation in terms of geochemical and petrological properties,
as well as the acid–base and physical hydrophobic sorptive behavior. The most obvious change caused by ammonoxidation is the
decrease of attrinite, texto-ulminite and textinite in favor mainly of densinite and gelohuminite. In general, the ammonoxidative
reactions promote the destruction of the structured humic macerals (texto-ulminite, textinite), and the formation of gels,
which resulted in the cementation of the freely fine humic particles (attrinite). The pzc values are 3.4 and 4.3 for oxidised
and non-oxidised lignite, respectively. After ammonoxidation the contents of carboxylic and free phenolic groups are found
to be lower. The oxidised lignite shows a statistically lower sorptive capacity and affinity than the original sample due
to a possible decrease in the hydrophobicity of the lignite. |
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