Abstract
Electronic waste (e-waste) is an emerging health and environmental burden due to the toxic
substances present within e-wastes. To address this burden, e-wastes contain various base, rare earth
and noble metals, which can be recovered from these substances, thus serving as secondary sources
of metals. Pyrometallurgical and hydrometallurgical processes have been developed to extract metals
from e-waste. However, these techniques are energy-intensive and produce secondary wastes, which
will add to the operating costs of the process. However, the biohydrometallurgical approach has been
deemed as an eco-friendly, cost-effective, and environmentally friendly process that does not produce
large quantities of secondary waste. However, research has focused chiefly on one-stage bioprocesses
to recover the metals of interest and majorly on base metals recovery. Hence, this review proposes a
two-stage bio-hydrometallurgical process where the first stage will consist of acidophilic iron and
sulphur oxidising organisms to extract base metals, followed by the second stage which will consist
of cyanide-producing organisms for the solubilisation of rare earth and precious metals. The solid
waste residue that is produced from the system can be used in the synthesis of silica nanomaterials,
which can be utilised for various applications.