Author(s)

GUADALUPE VALDES LABRADA, SURAJ KUMAR, BERNARDO PREDICALA, MEHDI NEMATI

Abstract

Generation and emission of hazardous gases such as hydrogen sulphide (H₂S), and ammonia (NH₃ from industrial settings and livestock production facilities represent one of the major air pollution challenges. Traditional approaches like physicochemical processes used in industrial settings, and diet manipulation, manure confinement, and addition of inhibitors commonly employed in livestock operations are associated with technical drawbacks, excessive cost, inability to completely eliminate pollutants, and difficulty of implementation on a small scale. Thus, there is a need for development of more effective and feasible technologies. One such innovative approach is the use of nano-based adsorbents to mitigate the emission of these air pollutants. Effective capture of individual H₂S and NH₃ using metal oxide nanoparticles (ZnO and TiO₂) have been reported in our earlier work. To evaluate the potential for wider applications, we have now investigated simultaneous capture of NH₃, H₂S, and odours by a mixture of ZnO and TiO₂ nanoparticles and a tailor-made composite adsorbent (ZnO and TiO₂ nanoparticles deposited on activated carbon). Laboratory work with pre-mixed gases of various compositions revealed that an increase of H₂S and NH₃ concentrations led to higher adsorption capacities with both nano-adsorbents. Higher temperatures enhanced the adsorption of H₂S but led to lower adsorption capacities for NH₃. Characterization of adsorbents through CNHS analyses, thermogravimetry, FT-IR and XRD revealed that ZnO and TiO₂ both adsorbed NH₃ and H₂S. While ZnO had a much higher affinity for H₂S through chemisorption, TiO₂ was more effective in adsorption of NH₃ by physisorption. Results from trials conducted in a semi-pilot scale adsorption system fed with swine manure gases, and those in a livestock research facility where a nano-based circulation–filtration system was deployed in a real situation confirmed the effectiveness of nano-adsorbents in capture of NH₃, H₂S, and odours from representative gases in real settings.

Keywords

ammonia, hydrogen sulphide, odour, nano-based emission control, pilot trial