End-of-life MoS₂-enabled device and material transformation in landfill leachate and its effect on the landfill microbiome

The safety of nano-enabled devices must be assessed throughout the device lifecycle. Landfills are the end-of-life repository for functional devices; however, the dynamism of leachate age and complexity of leachate chemistry make material safety assessments challenging. This study evaluates the transformation and effects of water treatment membranes and transistors enabled with MoS₂—a transition metal dichalcogenide (TMD) used in electronic transistors and futuristic wearable electronics—in complex landfill conditions. Device decay and MoS₂ transformation are studied with a suite of characterization tools. The effects of MoS₂ colloids on microbial diversity in young and mature landfill leachates are investigated. Results indicate that MoS₂-enabled membranes and transistors become attached to residues from the leachate but do not undergo major chemical decay. Furthermore, complex environments like leachates are robust, resisting microbiome changes upon exposure to MoS₂. The results obtained under the specific study conditions indicate that disposal of MoS₂-enabled devices in landfills does not induce significant deleterious effects on the landfill in the absence of photo-transformation (as is the case in covered landfills). However, further studies are needed to assess whether a high concentration of MoS₂, a likely result of its accumulation in the landfill over time, has the potential to substantially change the leachate microbiome.