A new lead hydroxycarbonate produced during transformation of lead metal by the soil fungus paecilomyces javanicus

Previous research has demonstrated the transformation of metallic lead into pyromorphite in solid and liquid medium by several species of fungi. In this work, the soil fungus Paecilomyces javanicus was found to mediate formation of an unknown lead mineral phase after incubation in liquid media with lead shot. After 2 weeks' incubation, precipitated mineral phase particles were collected and X-ray powder diffraction (XRPD) revealed the presence of plumbonacrite (Pb₁₀(CO₃)₆O(OH)₆). After 4 weeks' incubation, the lead particles that accumulated inside the fungal pellets were transformed into a white lead-containing secondary mineral phase. Energy dispersive X-ray analysis (EDXA) and XRPD were used to attempt to identify the lead-containing secondary minerals produced. XRPD showed that lead oxalate (PbC₂O₄) and cerussite (PbCO₃) were present as lead mineral species. However, another mineral phase was present that was not identifiable by XRPD. Fourier transform infrared spectroscopy (FTIR) identified hydroxyl (−OH) and carbonate (−CO₃ ²⁻) groups as the main functional groups within this unidentified secondary mineral phase. It was therefore concluded that this mineral phase is a new species of lead hydroxycarbonate. This is the first discovery of fungal-mediated formation of plumbonacrite and a new lead hydroxycarbonate, and therefore reveals a novel step in lead carbonation by fungi.