Britholites derivatives of apatite’s that contain lanthanium and neodymium in the serial compounds Sr8La2−xNdx(PO4)4(SiO4)2F2 with 0 ≤ x ≤ 2 were subject of the present investigation. The solid state reaction was the route of preparing these materials. Several techniques were employed for the analysis and characterization of the synthesized powders. The chemical analysis results indicated that molar ratio Sr+La+NdP+Si was of about 1.67 value of a stoichiometric powder. The X-ray diffraction data showed single-phase apatites crystallizing in hexagonal structure with P63/m space group were successively obtained. Moreover, the substitution of lanthanium by neodymium in strontium phosphosilicated fluorapatite was total. This was confirmed by the a and c lattice parameters contraction when (x) varies coherently to the sizes of the two cations. The infrared spectroscopy and the 31P NMR (MAS) exhibited the characteristic bands of phosphosilicated fluorapatite. The pressureless sintering of the material achieved a maximum of 89% relative density. The sintered specimens indicated that the Nd content as well as the heating temperature affected the ionic conduction of the materials and the maximum was 1.73 × 10−6 S cm−1 obtained at 1052 K for x = 2.

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Industrial phosphoric acid is an omnipresent product in the food industry and in the production of fertilisers and detergents. The presence of impurities in the raw material results in a relatively charged acid with various chemical species at the expense of its quality and use. These impurities include sulfate ions that precipitate into phosphoric acid during its manufacture. A desulfation is thus necessary. This study focuses on the reduction of free sulfates in phosphoric acid as impurities. This resulted in the use of three different adjuvants: lime, limestone, and barium carbonate. Three initial sulfate levels mainly contained in phosphoric acid were investigated: 2%, 4% and 6%. After experimentation, the comparison between the resulting yields allows considering barium carbonate as the most effective adjuvant. The desulfation efficiency was 95% in a very short stirring time of 15 min, independently of the initial sulphate content of phosphoric acid. The tests carried out with lime and limestone also lead to very interesting desulfation rates for phosphoric acid with an initial sulfate content of 2 or 4%.