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Ammonium phosphomolybdate [APM, (NH4)3PMo12O40·xH2O] is a versatile inorganic compound having diverse applications in the catalysis and dielectrics fields and high adsorption capacity for large metal cations due to its negatively charged cage-like structure with hollow cavities. In this study, APM was synthesized via a precipitation method and several parameters, such as the solid-to-liquid ratio (S : L), pH value, initial metal concentrations, adsorption isotherms, temperature effect, adsorption kinetics, shaking time, and interference of multiple ions were investigated for the effective removal of Pb2+ ions from aqueous media. The experimental results revealed that 100% of the Pb2+ ions were successfully adsorbed at the surface of APM at pH values from 2 to 6. Under the optimized conditions, the maximum adsorption capacity of 951.65 mg g−1 for Pb2+ ions on the APM was obtained at an S : L ratio of 0.1 g L−1 based on the Freundlich adsorption model. The adsorption equilibrium was achieved within an hour. The presence of alkali and alkaline metal ions did not interfere with Pb2+ adsorption, indicating the high selectivity toward Pb2+ ions. The Pb2+ ion adsorption mechanism was determined using DFT calculations, which revealed that Pb2+ is likely to interact directly with the 4 O atoms of the H-quadrate site, which hints towards the formation of a PbMoO4 complex, in reasonable agreement with the experimental findings. It was further confirmed using DFT that the exchange of Pb2+ ions with NH4+ ions is energetically favorable. Because of its high removal efficiency, selectivity, easy synthesis and handling, cost-effectiveness, fast kinetics, high stability in acidic pH and effective adsorption of Pb2+ ions even in the presence of alkali and alkaline metal ions, the APM sorbent can potentially be used to remove toxic Pb2+ ions from aqueous solutions for commercial applications. [ABSTRACT FROM AUTHOR]

Biomaterials must be biocompatible and provide excellent mechanical strength when used as bone and dental implants. To enhance the physical, mechanical and biological properties, a unique cerium-doped hydroxyapatite–sodium alginate (Ce–HAp–SA) biocomposite was synthesized using the wet precipitation method. The XRD patterns of the pristine and doped samples matched well with hydroxyapatite (HAp) and the appearance of characteristic peaks of HAp in the FTIR spectra confirmed the successful synthesis of HAp and Ce–HA–SA. The SEM micrographs clearly showed the presence of pores in the doped samples, while a density of 3.0 g cm−3 was obtained. The maximum microhardness of 27.5 GPa was achieved in the 2 wt% Ce-doped sample. The anti-bacterial activity of the HAp–SA composite increases as the Ce concentration increases. A 37 day ion release test in simulated body fluid (SBF) verified that no Ce ions leached under physiological conditions. The results showed that the Ce–HAp–SA composite could be a promising material for bone and teeth implants, because of its excellent physical, mechanical and biological properties. [ABSTRACT FROM AUTHOR]

Fluoride toothpastes have made a significant contribution towards oral hygiene. This study proposes instrumental neutron activation analysis (INAA) as a suitable technique for determining fluorine in toothpastes. The method involved a 10 s irradiation, followed by 10–20 s decay, and counting for 10 s, using a pneumatic system and high purity germanium detector. All irradiations were performed at miniature neutron source reactor with thermal neutron flux 1 × 1012 cm−2 s−1. Since Na was present in all toothpastes, the quantification of fluorine required correction for 23Na(n,α)20F threshold reaction. Fluorine determination was validated by analysing the samples by ion chromatography. All toothpastes were also analysed for other elements by k0-INAA and ICP-OES. Both techniques quantified 28 elements including Al, As, Ba, Ca, Ce, Cl, Co, Cr, Cu, F, Fe, Hf, K, La, Mg, Mn, Na, P, S, Sb, Sc, Si, Sm, Sn, Sr, Ta, Ti and Zn. This study, categorized toothpastes in five groups based on concentrations of Ca, P and Ti. [ABSTRACT FROM AUTHOR]