Biogenic Synthesis of Self-Incorporated Indium Graphitic Composites from Electronic Waste Using Eleocharis acicularis

Phytoextraction uses plants to accumulate valuable elements into their biomass from soil or water. The hyper-accumulator plant Eleocharis acicularis was used to extract indium, a strategic element, from end-of-life liquid crystal display (LCD) waste. Plants were exposed to 300 and 600 mg indium/L indium tin oxide (ITO) solutions at pH 5 for 15 days. Indium biomass accumulation levels were 58.9 +/- 0.0 and 122.4 +/- 13.8 mg indium/g dry weight, respectively. To simulate real-world e-waste phytomining, plants were exposed to a suspension with 800 g LCD particles/L at pH 3. Indium uptake after 15 days of exposure was 52.8 +/- 0.9 mg indium/g biomass dry weight. Additionally, E. acicularis tolerated high acidity and salinity (up to 20 g salt/L and pH 3), making it a good candidate for metal phytoextraction from e-waste. The resulting indium-containing biomass was then submitted to pyrolysis, which produced a layered graphite-like material containing dispersed indium and characterized by higher electrical conductivity (1.47 +/- 0.45 S/m) than commercial graphite under similar conditions. Our results showed for the first time that E. acicularis is efficient in the extraction of indium from e-waste and that indium-exposed biomass can be used as a precursor for production of high-value metal graphite biocomposites.

Automated summary

Phytoextraction using Eleocharis acicularis plants proved to be effective in extracting indium from e-waste, with resulting biomass suitable for production of high-value metal graphite biocomposites. The pyrolysis of indium-containing biomass produced a graphite-like material with dispersed indium and higher electrical conductivity compared to commercial graphite.