Removal and biomineralization of Pb2+ in water by fungus Phanerochaete chrysoporium
2020
Zhao, Wei-Wei | Zhu, Gangqiang | Daugulis, Andrew J. | Chen, Qi | Ma, Hong-Yan | Zheng, Peng | Liang, Jian | Ma, Xiao-kui
The removal and biomineralization of Pb²⁺ (200 mg/L) in water were investigated utilizing mature mycelia of Phanerochaete chrysoporium. Mycelial dosage, initial Pb²⁺ concentration, solution pH and treatment time all were shown to have an influence on Pb²⁺ removal. Granular, lead-containing precipitation was formed on the fungal hyphae upon exposure to lead nitrate, which was confirmed from scanning electron micrograph/Energy Dispersive Spectrometer (SEM/EDS). Energy dispersive X-ray spectroscopic analysis revealed the presence of lead (48.5% by weight) along with phosphorus in the precipitate. This extracellular precipitate was further identified as pyromorphite lead hydroxyphosphate [Pb₅(PO₄)₃OH] by X-ray powder diffraction (XRD) analysis. During Pb²⁺ removal, size-enlarged mineral precipitation, and clustered nanospherical particles formed on the hyphae were revealed by SEM/XRD. A remarkable increase of mycelial phosphatase activity of 1.5 times that of the control and decreased phosphate concentration in solution (16.76 mg/L to 1.39 mg/L) initially upon exposure to Pb²⁺ suggested that phosphatase may hydrolyze organic phosphorus into inorganic phosphate and release it into solution, participating in the biomineralization of Pb²⁺. Toxicity tests showed that the toxicity of Pb²⁺ polluted water decreased after treatment. The results clearly demonstrate previously unknown lead biomineralization as pyromorphite through fungal phosphatase.
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