Mitigation of low methane content landfill gas through visible-near-infrared photocatalysis over Y2O3:Er3+/Graphene/TiO2

Untreated low methane (CH4) content (less than 10%) landfill gas within the post-methanogenic stage is currently vented into the atmosphere, constituting an important source of anthropogenic greenhouse gas (GHG). Development of a proper mitigation process for low CH4 gas is therefore necessary for landfills. In this study a special photocatalyst, Y2O3:Er3+-TiO2-0.05% graphene (GR), was synthesized by sol-gel method and then characterized; it showed a good response to visible-near-infrared (Vis–NIR) sunlight. The corresponding absorption edge was 354 nm, and upconversion fluorescence peaks of ultraviolet (364 nm) and violet (408 nm) emissions were acquired under 980 nm excitation. Y2O3:Er3+-TiO2-GR was developed and tested for removal of low CH4 landfill gas under Vis–NIR light irradiation, and a maximum photodegradation rate of 45.1% for CH4 was obtained using the photocatalyst Y2O3:Er3+-TiO2-0.05% GR with a light intensity of 2050 mW m−2. The corresponding CH4 content decreased from 10% to 5.5%, mitigating almost half of GHG during the post-methanogenic stage. The intermediate products of CH4 degradation were CO, OH, O−, CO2 and H2O traced by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This research proposes a new approach for reducing the GHG effect of low CH4 content landfill gas.