Heavy Metal Immobilization by Phosphate-Solubilizing Fungus and Phosphogypsum Under the Co-Existence of Pb(II) and Cd(II)
Globally, phosphogypsum (PG) is the primary by-product of the phosphorus industry. <i>Aspergillus niger</i> (<i>A. niger</i>), one of the most powerful types of phosphate-solubilizing fungi (PSF), can secrete organic acids to dissolve the phosphates in PG. This study investig...
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| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Agronomy |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4395/15/7/1632 |
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| Summary: | Globally, phosphogypsum (PG) is the primary by-product of the phosphorus industry. <i>Aspergillus niger</i> (<i>A. niger</i>), one of the most powerful types of phosphate-solubilizing fungi (PSF), can secrete organic acids to dissolve the phosphates in PG. This study investigated heavy metal (HM) remediation by PG and <i>A. niger</i> under the co-existence of Pb and Cd. It demonstrated that 1 mmol/L Pb<sup>2+</sup> stimulated the bioactivity of <i>A. niger</i> during incubation, based on the CO<sub>2</sub> emission rate. PG successfully functioned as P source for the fungus, and promoted the growth of the fungal cells. Meanwhile, it also provided sulfates to immobilize Pb in the solution. The subsequently generated anglesite was confirmed using SEM imaging. The immobilization rate of Pb reached over 95%. Under co-existence, Pb<sup>2+</sup> and 0.01 mmol/L Cd<sup>2+</sup> maximized the stimulating effect of <i>A. niger</i>. However, the biotoxicity of Pb<sup>2+</sup> and elevated Cd<sup>2+</sup> (0.1 mmol/L) counterbalanced the stimulating effect. Finally, 1 mmol/L Cd<sup>2+</sup> dramatically reduced the fungal activity. In addition, organic matters from the debris of <i>A. niger</i> could still bind Pb<sup>2+</sup> and Cd<sup>2+</sup> according to the significantly lowered water-soluble Pb and Cd concentrations. In all treatments with the addition of Cd<sup>2+</sup>, the relatively high biotoxicity of Cd<sup>2+</sup> induced <i>A. niger</i> to absorb more Pb<sup>2+</sup> to minimize the sorption of Cd<sup>2+</sup> based on the XRD results. The functional group analysis of ATR-IR also confirmed the phenomenon. This pathway maintained the stability of Pb<sup>2+</sup> immobilization using the fungus and PG. This study, hence, shed light on the application of <i>A. niger</i> and solid waste PG to remediate the pollution of Pb and Cd. |
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| ISSN: | 2073-4395 |