Novel Biosorption Capacity of Newly Isolated Fungus Cladosporium sp. strain F1 to Uranium Phosphate and Lead Iodide Minerals

Abstract

The newly isolated fungus Cladosporium sp. strain F1 was applied to remove uranium and lead phosphate minerals through biosorption processes and used to recover lead iodide minerals, which could be released from perovskite solar cells by water. Cladosporium sp. strain F1 was first isolated from contaminated solution containing U(VI) and phosphate in our laboratory. The hyphae of Cladosporium sp. strain F1 were heavily encrusted with pre-synthesized uranium phosphate minerals under a wide range of pH conditions. SEM and TEM images showed that nanorods and nanoplates of uranium phosphate minerals at pH 4 and 5, and pH 6, 7, and 8, respectively, were tightly adsorbed along the hyphae of Cladosporium sp. strain F1, while only a few uranium phosphate minerals were observed on the hyphae of Aspergillus niger VKMF-1119. To investigate the fungal biosorption of other heavy metal phosphate minerals, Cladosporium sp. strain F1, A. niger VKMF-1119, and Mucor ramannianus R-56 were studied to adsorb pre-synthesized cadmium, chromium, lead, and zinc phosphate minerals. Among them, Cladosporium sp. strain F1 l extensively adsorbed lead phosphate nanoparticles on the hyphae under a wide range of pH conditions, while A. niger VKMF-1119 and M. ramannianus R-56 adsorbed small amounts of lead phosphate nanoparticles. ICP-MS results proved quantitatively that the biosorption capacity of Cladosporium sp. strain F1 to uranium phosphate and lead phosphate minerals was much higher than those of A. niger VKMF-1119 and M. ramannianus R-56 under the applied pH conditions. In addition, Cladosporium sp. strain F1 was examined to adsorb lead iodide minerals which could be easily released from perovskite solar cells by water. Cladosporium sp. strain F1 adsorbed large amounts of lead iodide minerals than A. niger VKMF-1119 and M. ramannianus R-56 under all pH conditions. After biosorption of lead iodide minerals on Cladosporium sp. strain F1, the solvents including DMF, DMSO, and NMP were added to recover lead iodide minerals adsorbed on strain F1. Aqueous DMSO (50%) at pH 2 (70°C) released the minerals more than 99%. Considering physical mobility and chemical stability of uranium phosphate minerals and lead phosphate minerals under in situ oxidizing environmental conditions, the application of Cladosporium sp. strain F1 could be the novel strategy for the remediation of uranium and lead contamination in sediments and aquifers under a wide range of pH conditions where large amounts of phosphate are present in the environment. Moreover, practical recovery of lead from perovskite solar cells using Cladosporium sp. strain F1 may be applicable due to its high biosorption capacity to lead iodide minerals contained in perovskite. Further works are necessary to investigate the biochemical mechanism for extensive adsorption of uranium phosphate, lead phosphate, and lead iodide minerals onto the cell wall of the fungus Cladosporium sp. strain F1.