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

Abstract

Phytoextraction uses plants to accumulate valuable elements into their biomass from soil or water. The hyperaccumulator 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.

Economic and Environmental Sustainability of Biogenic Synthesis of Indium-Graphitic Material from Electronic Waste

“…Based on our previously published experimental data, indium uptake from the slurry decreased by 18.33% when the pH modification step was omitted. 11 For the BG1 scenario, the moisture content reduction before pyrolysis was achieved through 48 h of drying. Again, based on our experimental study, drying the biomass at 100 °C for 1 h yielded comparable moisture loss, facilitating efficient pyrolysis.…”

“…pH modification of the slurry was assumed to have a low effect on the efficiency of the product but higher effects on the cost and impact. Based on our previously published experimental data, indium uptake from the slurry decreased by 18.33% when the pH modification step was omitted . For the BG1 scenario, the moisture content reduction before pyrolysis was achieved through 48 h of drying.…”

“…This sustainability analysis was conducted for a previously reported synthesis methodology developed by the authors. This synthesis process has three main system assemblies: phytoextraction for resource recovery, pyrolysis for graphitization, and processing of the metal-graphitic material (GM) . In this biogenic process, indium-rich e-waste (i.e., LCD) was transformed into a slurry using physical techniques of crushing and mixing.…”

“…The overall goal of this study was to characterize the sustainability of a novel methodology for indium recovery through phytoextraction and conversion into indium-graphitic composites that have been previously developed by the author. , In particular, the objectives of this study were to (1) characterize financial and environmental sustainability, (2) elucidate drivers for this novel process to inform opportunities for scaling up, and (3) compare outcomes with conventional recovery and synthesis methods. We conducted a combined TEA and LCA to evaluate the sustainability of recovery of indium from end-of-life LCD screens using the hyperaccumulator plant Eleocharis acicularis and subsequent translation into the value-added composite.…”

“…This synthesis process has three main system assemblies: phytoextraction for resource recovery, pyrolysis for graphitization, and processing of the metal-graphitic material (GM). 11 In this biogenic process, indium-rich e-waste (i.e., LCD) was transformed into a slurry using physical techniques of crushing and mixing. The prepared e-waste slurry was used as a growth medium for Eleocharis acicularis plant for 15 days at room temperature.…”