Ammonia gas (NH3(g)) is the most abundant alkaline gas in the atmosphere reacting with acids to form atmospheric particulate matter which causes visibility degradation and human health hazards. Deposition of NH3(g) from the atmosphere to sensitive ecosystems negatively impacts the environment due to soil acidification and eutrophication. Agriculture is the largest source of NH3(g) volatilization, therefore improving sustainable nitrogen (N) application and simultaneously controlling N-volatilization from agricultural systems is critical. Development and characterization of environmentally safe and sustainable sorbents for NH3(g) is needed to promote N-recovery in agriculture. Sorbents reclaimed from agricultural wastes may be viable substrates. This work provides a framework from thermodynamic and kinetic parameters for analyzing NH3(g) sorption-desorption using heated (150, 300 °C), struvite, (MgNH4PO4●6H2O) based products of swine (SW) and dairy (DW) waste precipitates as sorbents. Typical sorbents including a metal-organic framework (MOF) and biochar (BC-B) were included for comparison. The SW and DW sorbents before and after heat treatment were characterized using x-ray diffraction (XRD), attenuated-total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Temperature-dependent (25, 50, 60 °C) experiments were conducted to elucidate sorption capacities (mg/g) and enthalpies (J/g) by simultaneous thermal analysis-pulse thermal analysis (STA-PTA). Heating SW solids to 150 °C prior to sorption enhanced sorption capacity by 320% (SW35), and 400% (SW15) as compared to unheated solids. Heat treatment of DW resulted in slight increases in ammonia gas sorption. Analysis by ATR-FTIR confirmed changes in the vibrational modes for ammonium and hydroxyl groups in the sorbate structure after reactions with NH3(g). The retained percentage of sorptive following desorption ranged from 0-80%. Sorption activation energies and pre-exponential factors were determined by Friedman analysis and model-dependent kinetic analysis. These results indicated SW and DW solids could be useful for capturing NH3(g).

Thermochemical analysis for evaluation of ammonia gas sequestration by struvite reclaimed from livestock waste

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.