Solubilization of struvite and biorecovery of cerium by Aspergillus niger

Cerium has many modern applications such as in renewable energies and the biosynthesis of nanomaterials. In this research, natural struvite was solubilized by Aspergillus niger and the biomass-free struvite leachate was investigated for its ability to recover cerium. It was shown that struvite was completed solubilized following 2 weeks of fungal growth, which released inorganic phosphate (Pi) from the mineral by the production of oxalic acid. Scanning electron microscopy (SEM) showed that crystals with distinctive morphologies were formed in the natural struvite leachate after mixing with Ce3+. Energy-dispersive X-ray analysis (EDXA), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of cerium phosphate hydrate [Ce(PO4)·H2O] at lower Ce concentrations and a mixture of phosphate and cerium oxalate decahydrate [Ce2(C2O4)3·10H2O] at higher Ce concentrations. The formation of these biogenic Ce minerals leads to the removal of > 99% Ce from solution. Thermal decomposition experiments showed that the biogenic Ce phosphates could be transformed into a mixture of CePO4 and CeO2 (cerianite) after heat treatment at 1000 °C. These results provide a new perspective of the fungal biotransformation of soluble REE species using struvite leachate, and also indicate the potential of using the recovered REE as biomaterial precursors with possible applications in the biosynthesis of novel nanomaterials, elemental recycling and biorecovery. Key points • Cerium was recovered using a struvite leachate produced by A. niger. • Oxalic acid played a major role in struvite solubilization and Ce phosphate biorecovery. • Resulting nanoscale mineral products could serve as a precursor for Ce oxide synthesis.

Two-Phase Synthesis of Fe Doped Cerium Phosphate Ultra-fine Nanocrystals for Efficient Oxygen Evolution

It is very important and challenging to develop electrocatalysts with high performance and economic benefits. In this work, ultra-fine Fe doped CePO4 nanocrystals (Fe-CePO4) were prepared by a simple two-step...

The preparation temperature influences the physicochemical nature and activity of nanoceria

Cerium oxide nanoparticles, so-called nanoceria, are engineered nanomaterials prepared by many methods that result in products with varying physicochemical properties and applications. Those used industrially are often calcined, an example is NM-212. Other nanoceria have beneficial pharmaceutical properties and are often prepared by solvothermal synthesis. Solvothermally synthesized nanoceria dissolve in acidic environments, accelerated by carboxylic acids. NM-212 dissolution has been reported to be minimal. To gain insight into the role of high-temperature exposure on nanoceria dissolution, product susceptibility to carboxylic acid-accelerated dissolution, and its effect on biological and catalytic properties of nanoceria, the dissolution of NM-212, a solvothermally synthesized nanoceria material, and a calcined form of the solvothermally synthesized nanoceria material (ca. 40, 4, and 40 nm diameter, respectively) was investigated. Two dissolution methods were employed. Dissolution of NM-212 and the calcined nanoceria was much slower than that of the non-calcined form. The decreased solubility was attributed to an increased amount of surface Ce4+ species induced by the high temperature. Carboxylic acids doubled the very low dissolution rate of NM-212. Nanoceria dissolution releases Ce3+ ions, which, with phosphate, form insoluble cerium phosphate in vivo. The addition of immobilized phosphates did not accelerate nanoceria dissolution, suggesting that the Ce3+ ion release during nanoceria dissolution was phosphate-independent. Smaller particles resulting from partial nanoceria dissolution led to less cellular protein carbonyl formation, attributed to an increased amount of surface Ce3+ species. Surface reactivity was greater for the solvothermally synthesized nanoceria, which had more Ce3+ species at the surface. The results show that temperature treatment of nanoceria can produce significant differences in solubility and surface cerium valence, which affect the biological and catalytic properties of nanoceria.

Synthesis and Characterization of Novel -Type Zirconium Phosphate-Crystalline Cerium Phosphate/ Polyaniline, Polyindole, Polycarbazole, Polyaniline-co-Polyindole, and Polyaniline-co-Polycarbazole Composites

-Type zirconium phosphate,-Zr(HPO4)2-.1.77H2O (-ZrP), crystalline cerium phosphate, Ce(HPO4)2.1.33 H2O (CePc), and [-Zr(HPO4)2]0.30 [Ce (HPO4)2]0.70 .2H2O composite were prepared and characterized by chemical, XRD, TGA, FT-IR and scanning electron microscopy(SEM). [-Zr(HPO4)2]0.30[Ce(HPO4)2]0.70/polyaniline, polyindole, polycarbazole, polyaniline-co-polyindole, polyaniline-co-polycarbazole composites were prepared via in-situ chemical oxidation of the monomers aniline, indole , carbazole, and (1:1moler ratio) of co-monomers aniline-indole, aniline- carbazole, respectively, that was promoted by the reduction of part of Ce(IV) ions present in the inorganic matrix. A possible explanation is part of CePc is attacked by the monomers, and the co-monomers, respectively, converted to cerium (III) orthophosphate (CePO4). The resultant novel composites were characterized by elemental (C,H,N) analysis, FT-IR, and (SEM). From elemental (C,H,N) analysis ,the amount of organic materials present in [-Zr(HPO4)2]0.30 [Ce (HPO4)2]0.70/ polyaniline, polyindole, polycarbazole composites were (23.44, 5.24 and 33.02 % in wt. ), respectively. The amount of resultant copolymers were (Pani 5.92, PIn 7.48 % in wt) and (Pani 1.42, PCz 2.48 % in wt ) These composites can be considered as novel conducting inorganic-organic composites, ion exchangers , solid acid catalysts and sensors.

Vapour-Phase Selective O-Methylation of Catechol with Methanol over Metal Phosphate Catalysts

Guaiacol (2-methoxyphenol), an important fine chemical intermediate, is conventionally synthesized by liquid-phase processes with expensive, corrosive and toxic methylating agents such as dimethyl sulphate and dimethyl iodide. Recently, vapour-phase alkylation of catechol (1, 2-dihydroxybenzene) with methanol for the synthesis of guaiacol in the presence of heterogeneous catalysts has received more attention, as the route is economical and environmentally friendly. However, most of the investigated catalysts exhibited unsatisfactory catalytic performance for industrial applications. In this study, five metal phosphates M-P-O (M = La, Ce, Mg, Al, Zn) catalysts were synthesized and tested in the selective O-methylation of catechol with methanol. Among these catalysts, cerium phosphate (CP) showed the highest catalytic activity and guaiacol yield. Lanthanum phosphate (LP) was the second most active, which was still obviously better than magnesium phosphate (MP) and aluminium phosphate (ALP). Zinc phosphate (ZP) was not active in the reaction. Relevant samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), N2 adsorption-desorption, temperature programmed desorption of NH3 or CO2 (NH3-TPD, CO2-TPD). The suitable acid-base properties contribute to the superior catalytic performance of CP. Long-term stability and regeneration tests were also studied.