Towards sustainable mass production of metallic nanoparticles: selective synthesis of copper nanoparticles directly from malachite ore

Abstract

Continued industrial development and burgeoning pressure to solve global challenges, including climate change and non-pharmaceutical pathogen management, will drive an urgent up-scaling in global nanoparticle production this Century. Conventional nanoparticle synthesis is typically a linear multistage approach comprising mining, benefaction, refining, reagent synthesis and then nanoproduct synthesis, which is both energy and resource intensive. Herein we present a new approach using nanoscale Cu (nCu) as an example: the translocation of nanoparticle synthesis into the subsurface and into one step. Malachite ore was first leached with H2SO4 or CH3COOH (0.5M, 1:10 solid-liquid ratio), partially neutralised using 0.01-0.5M NaOH or NaCO3 respectively and then exposed to nanoscale zerovalent iron (nZVI) (4.0 g/L), which acted as both a selective and rapid (<240 s) chemical reducing agent but also a magneto-responsive nCu recovery vehicle. Conversion of Cu from ore to discrete Cu0 35 /Cu2O nanoparticles was up to 31.1 wt.% with purities of up to 81.70 wt.% Cu (or 98.59 wt.% Cu and O) detected using HRTEM. This work therefore provides a first proof-of-concept of a new direct and one-pot “in situ” nanoparticle mass production route, which is conceptually possible for a wide range of engineered nanomaterials, including those containing Ni, Cr, U, Pb, Ag and Au, and therefore has the potential to yield transformative environmental and economic benefit across mining and raw material synthesis industries.