Remediation of lead-contaminated water by geological fluorapatite and fungus Penicillium oxalicum
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Phosphate-solubilizing fungi (PSF) can secrete large amounts of organic acids. In this study, the application of the fungus Penicillium oxalicum and geological fluorapatite (FAp) to lead immobilization was investigated. The formation and morphology of the lead-related minerals were analyzed by ATR-IR, XRD, Raman, and SEM. The quantity of organic acids secreted by P. oxalicum reached the maximum on the fourth day, which elevated soluble P concentrations from 0.4 to 108 mg/L in water. The secreted oxalic acid dominates the acidity in solution. P. oxalicum can survive in the solution with Pb concentration of ~ 1700 mg/L. In addition, it was shown that ~ 98% lead cations were removed while the fungus was cultured with Pb (~ 1700 mg/L) and FAp. The mechanism is that the released P from FAp (enhanced by organic acids) can react with Pb2+ to form the stable pyromorphite mineral [Pb5(PO4)3F]. The precipitation of lead oxalate also contributes to Pb immobilization. However, lead oxalate is more soluble due to its relatively high solubility. P. oxalicum has a higher rate of organic acid secretion compared with other typical PSF, e.g., Aspergillus niger. This study sheds light on bright future of applying P. oxalicum in Pb remediation.
KeywordsPenicillium oxalicum Lead immobilization Phosphorus release Fluorapatite Pyromorphite Geomicrobiology
We thank Mr. Letian Dai and Mr. Fuwei Wang for assistance in fungus isolation and culture.
This work was partially supported by Natural Science Foundation of Jiangsu Province of China (No. BK20150683), China Postdoctoral Science Foundation (No. 2017M610330), the Fundamental Research Funds for the Central Universities (No. KYTZ201404 and KYZ201712), and the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (PPZY2015A061).
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Conflict of interest
The authors declare that they have no conflicts of interest.
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