The extraction of rare earth elements (REEs) from phosphogypsum (PG) is of great significance for the effective utilization of rare earth resources and enhancing the resource value of PG waste residues. This study used Aspergillus niger (A. niger) fungal culture filtrate as a leaching agent to investigate the behavior of extracting REEs from PG through direct and indirect contact methods. According to the ICP-MS results, direct leaching at a temperature of 30 °C, shaking speed of 150 rpm, and a solid–liquid ratio of 2:1, achieved an extraction rate of 74% for REEs, with the main elements being yttrium (Y), lanthanum (La), cerium (Ce), and neodymium (Nd). Under the same conditions, the extraction rate of REEs from phosphogypsum using an A. niger culture filtrate was 63.3% higher than that using the simulated organic acid-mixed solution prepared with the main organic acid components in the A. niger leachate. Moreover, the morphological changes observed in A. niger before and after leaching further suggest the direct involvement of A. niger’s metabolic process in the extraction of REEs. When compared to using organic acids, A. niger culture filtrate exhibits higher leaching efficiency for extracting REEs from PG. Additionally, using A. niger culture filtrate is a more environmentally friendly method with the potential for industrial-scale applications than using inorganic acids for the leaching of REEs from PG.

Biological matter evolution provides an idea for the human design and synthesis of new materials. However, biomimetic materials only stay in laboratory-scale models, and their large-scale industrial applications are yet to be realized. Here, inspired by nacre’s architecture, we report a continuous, large-scale method to fabricate phosphogypsum composites by reactive extrusion strategy. After curing for seven days, with more than 50 wt% of beta-hemihydrate phosphogypsum (β-HPG), the compressive strength and softening coefficient were 24.98 MPa and 0.78, increasing by 110.0% and 20.0%, respectively, compared to the pouring method. The results show that the screw extrusion process can improve the mechanical strength and waterproof properties of β-HPG hydration specimens without any special chemical admixtures and cements.

Phosphogypsum (PG) is a solid waste product of the phosphoric acid industry. As it contains various rare earth elements (REEs), it is considered an important source of REEs. In this paper, direct and indirect contact methods were used to extract rare earth elements from PG by Aspergillus Niger(A. niger). the contents of REEs in the original PG sample and the leaching solution were analyzed by an inductively coupled plasma mass spectrometer (ICP-MS). Using scanning electron microscopy (SEM), the morphology of A. niger cells was analyzed before and after leaching. At optimal conditions (Temperature 30℃, oscillation speed of 150 rpm, and solid-liquid ratio of 2:1), the REE leaching rate was 74%; the dominant elements were Y, La, Ce, and Nd. It was found that A. niger and its metabolites organic acids played a decisive role in the leaching process. Compared with inorganic acid leaching of REEs from PG, using A. niger is an environmentally friendly approach with potential in the large-scale industry.