Polyethyleneimine functionalized alginate composite fiber for fast recovery of gold from acidic aqueous solutions

In this paper, PEI-Alginate fibers were prepared using a more environmentally friendly method for the recovery of gold (Au (III)) from acidic wastewater. Adsorption results show that PEI plays a major role in the recovery of Au (III), and the maximum adsorption capacity of Au (III) was 644.92 ± 43.06 mg/g calculated by Langmuir model at pH 1, 25 °C. In addition, the constants k₁ and k₂ was 0.7044 ± 0.1038 L/min and 0.0025 ± 0.0002 g/mg min were calculated by pseudo-first-order and pseudo-second-order, which was outstanding compared to the most of the adsorbents reported in the literature. The mechanism of adsorbent preparation, characterization of adsorbents and adsorption-reduction mechanism of Au (III) were analyzed by Field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that Au (III) was adsorbed by electrostatic attraction between protonated nitrogen-containing functional groups (=NH⁺-, and –NH₂⁺-/-NH₃⁺) and AuCl₄⁻. Furthermore, Au (III) was reduced to Au(I) and Au (0) during the adsorption process, and -NH-/-NH₂, –NH₂⁺-/-NH₃⁺, and C–O provided electrons for Au (III) reduction and then they were oxidized to =N-, =NH⁺-, and C=O, respectively.