Development of polyethyleneimine-starch fibers stable over the broad pH range for selective adsorption of gold from actual leachate solutions of waste electrical and electronic equipment

Polyethyleneimine (PEI)-starch fibers were fabricated as adsorbents for the selective recovery of gold from waste electrical and electronic equipment (WEEE). They were prepared by a simple method of spinning a mixture of PEI and starch in a glutaraldehyde solution, which is a crosslinking agent. The PEI-starch fibers were stable over the broad pH range, thereby suggesting that they are highly applicable for various types of wastewater. The characterization and adsorption mechanism of the PEI-starch fibers were investigated by BET, FT-IR, XRD, and XPS analyses. According to the Langmuir model, the maximum Au(III) uptake by the PEI-starch fibers was estimated to be 1055.59 ± 63.78 mg/g at pH 1.0. The adsorbed Au(III) was sequentially reduced to Au(I) and then Au(0) owing to electron transfer when N–C and C–OH present in the PEI-starch fibers were oxidized to N[dbnd]C and C[dbnd]O, respectively. Moreover, PEI-starch fibers were stable in WEEE-leached aqua regia (diluted to pH 1.0) and bioleaching solution (pH 9.3) and showed excellent selectivity for gold.