Distillers’ grains anaerobic digestion residue biochar used for ammonium sorption and its effect on ammonium leaching from an Ultisol

Abstract

The aim of this work was to explore the potential application of biochar from distillers' grains anaerobic digestion residue pyrolyzed at 700 °C (ADR-DG₇₀₀) to ammonium (NH₄⁺) adsorption from aqueous solution, as well as its effect on NH₄⁺ leaching from an Ultisol. The adsorption kinetic of NH₄⁺ on the ADR-DG₇₀₀ could be described by an Elovich model (R² = 0.995), and the combined Langmuir-Freundlich model (R² = 0.997) fitted the isotherm data better than the Langmuir, Freundlich, Redlich-Peterson, and Temkin models with a maximum adsorption of 11.41 mg N g⁻¹. The NH₄⁺ adsorption on ADR-DG₇₀₀ was mainly controlled by the cation exchange, the surface complexation with oxygen-containing functional groups of carboxyl C〓O (C▬O) and carbohydrate C▬OH, as well as the electrostatic interactions with Si▬O▬Si functional group. In addition, the ADR-DG₇₀₀ soil application reduced 2.48–20.67% of NH₄⁺-N leaching loss after nitrogen fertilizer application in an Ultisol. These results suggested that the ADR-DG₇₀₀ could be a sorbent for NH₄⁺-contaminated water as well as an inhibitor for soil NH₄⁺ leaching.