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Fenton oxidation of biochar improves retention of cattle slurry nitrogen
Author(s) -
Cao Xinyue,
Reichel Rüdiger,
Brüggemann Nicolas
Publication year - 2022
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.1002/jeq2.20419
Subject(s) - biochar , slurry , ammonium , chemistry , pyrolysis , nitrogen , adsorption , nitrification , ammonia , sawdust , environmental chemistry , environmental engineering , environmental science , organic chemistry
Nitrogen (N) losses during fertilization with livestock slurry, mainly in the form of ammonia (NH 3 ), can cause environmental problems and reduce fertilizer efficiency. Leonardite, which is characterized by oxygen‐rich functional groups and low pH, has been found to decrease losses of slurry N. However, leonardite, as a byproduct of open‐cast lignite mining, is not a renewable resource. The objective of this study was to modify biochar by chemical surface oxidation in order to find a sustainable but similarly effective substitute for leonardite. Biochar was produced from spruce sawdust in a pyrolysis oven at a maximum temperature of 610 °C. Then the biochar was oxidized using the Fenton reaction, with a ratio of Fe 2+ /H 2 O 2 of 1:1,000, as a source of highly reactive HO· radicals to introduce oxygen‐rich functional groups to the biochar surface. The ammonium (NH 4 + ) adsorption capacity of biochar, oxidized biochar, and leonardite was tested in ammonium sulfate [(NH 4 ) 2 SO 4 ] solution, pH‐adjusted (NH 4 ) 2 SO 4 solution, and cattle slurry. The results showed that biochar had the highest total NH 4 + adsorption of 1.4 mg N g −1 in (NH 4 ) 2 SO 4 solution, whereas oxidized biochar had the highest reversible NH 4 + adsorption of 0.8 mg N g −1 . In the pH‐adjusted ammonium solution, all materials reduced NH 3 emissions by ≥90%, and oxidized biochar reduced NH 3 emissions by 99.99%. In contrast, leonardite reduced NH 3 emissions the most in cattle slurry, and oxidation of biochar increased the reduction in NH 3 emissions from 22 to 67% compared with non‐oxidized biochar. In conclusion, biochar oxidized by means of the Fenton reaction greatly decreased NH 3 emissions by increased adsorption of NH 4 + in cattle slurry compared with non‐oxidized biochar, indicating the great potential of oxidized biochar for reducing N losses during slurry application.