Characterization of the biosorption properties of dormant spores of Aspergillus niger: a potential breakthrough agent for removing Cu2+ from contaminated water

Abstract

Recent work has focused on a new cultivation method (solid fermentation), by which a new form of Aspergillus niger was produced; the spores were characterised by a 2 μm diameter and higher biosorption capacity than that of Aspergillus niger mycelium, which was prepared using the traditional method (submerged fermentation). The results showed that the maximum biosorption capacity for Cu²⁺ of the Aspergillus niger spore was 25.3 mg g⁻¹ and that of the Aspergillus niger mycelium was only 10.1 mg g⁻¹ at a natural pH with an initial concentration of 30 mg L⁻¹. Meanwhile, the mechanism of the spores involved ion exchange (P, K, Ca and Mg), complexation (C–O, CO, C–N and C–H) and electrostatic attraction, and Cu–O was formed during the process. Moreover, the spores exhibited a short biosorption equilibrium time of 60 min over a pH range of 4.0–6.0, and the data fitted well with the pseudo-second-order kinetic equation and the Freundlich isotherm. A thermodynamic study demonstrated that the process was spontaneous and endothermic. In addition, the amplification of Aspergillus niger spores on an agricultural waste medium was from 10⁶ to 10⁹.