Nano-engineered hydrated lime for hydrogen sulfide (H₂S) emission control in landfills

Abstract

Hydrogen sulfide (H₂S) is a major environmental pollutant in landfill systems due to its strong odour, toxicity, and continuous generation during the anaerobic decomposition of municipal solid waste (MSW). This study investigates the production and application of hydrated lime (Ca(OH)₂) synthesized from natural limestone (CaCO₃) for effective H₂S mitigation under simulated landfill conditions. The raw limestone contained 97.58 wt.% CaO with minor impurities of MnO (0.06 wt.%), Al₂O₃ (0.35 wt.%), and Fe₂O₃ (0.39 wt.%). A Design of Experiments (DOE) approach was employed to evaluate the effects of calcination temperature (900–1100 °C), particle size (75–500 µm), and reaction time (30–120 min) on quicklime yield and adsorption performance. The optimum condition of 1100 °C produced high-purity CaO with a maximum yield of 98.5 wt.%. XRD analysis confirmed calcite and quartz phases, while FTIR spectra revealed characteristic Ca–O bands at 742 cm⁻¹ and significant reduction of carbonate peaks, confirming effective CaCO₃ decomposition. SEM micrographs demonstrated granular and porous particles with sizes ranging from 75–150 µm, providing enhanced surface area and alkalinity for H₂S adsorption. In landfill simulation experiments conducted at 40–55 °C over 15 days, untreated waste generated peak H₂S concentrations of approximately 160 ppm, whereas hydrated lime treatments of 1%, 3%, 5%, and 8% reduced concentrations to 60, 45, 35, and 20 ppm, respectively, corresponding to mitigation efficiencies of 50–71%. The results demonstrate that high-purity hydrated lime is an effective, low-cost, and sustainable material for landfill odour control and waste stabilization applications.