Mitigation of ammonia and hydrogen sulfide emissions from livestock operations using TiO2 and ZnO nanoparticles

Abstract

Hazardous gases such as ammonia (NH3) and hydrogen sulfide (H2S) are produced as part of a variety of industrial processes and in livestock production facilities. The emission of these gases poses severe risks to human and animal health, property values as well as to the environment. Several techniques including biological and physicochemical methods have been applied to remove these gases from contaminated air streams. However, most of the work focused on individual ammonia or hydrogen sulfide removal, and use of nanoparticles for simultaneous removal of these two gases has not been done yet. Thus, this work is focused on simultaneous removal of ammonia and hydrogen sulfide from livestock operations using ZnO and TiO2 nanoparticles.

Adsorption capacities and isotherms at various temperatures (22 °C, 70 °C, 140 °C and 280 °C) in the concentration range 50-50, 100-100, 200-200, 300-300, 400-400, 500-550 ppmv of NH3-H2S in laboratory scale packed-bed adsorption column was studied and developed. The equilibrium adsorption capacities of both ammonia and hydrogen sulfide increased with an increase of gas concentration. Equilibrium adsorption capacity of hydrogen sulfide increase with the increase of temperature, while there is decrease adsorption capacity of ammonia due to an increase in temperature (22 °C to 280 °C). Control experiments showed that orientation of ZnO and TiO2 nanoparticles layers in the column, as well as utilization of a homogeneous mixture of ZnO and TiO2, had no impact on adsorption capacities (12 mg/g for NH3 and 25.14 mg/g for H2S). Among the evaluated isotherms, Langmuir-Freundlich best described the equilibrium adsorption data. To understand the mechanism of simultaneous removal of NH3 and H2S from gaseous streams, characterization of the unused and exposed adsorbents was conducted by CNHS and TGA. Finally, semi-pilot scale trials using gases emitted from swine manure showed the effectiveness of nanoparticles in the removal of H2S and NH3 from representative gases.