The invention discloses a cyclic preparation method for producing titanium boride from intermediate feedstock sodium-based titanium-boron-fluorine salt mixture and producing sodium cryolite as byproduct, which comprises the steps: a) boric acid or boric anhydride is added with hydrofluoric acid and then with sodium carbonate solution for concentration and crystallization to generate sodium fluoborate; titanium-iron concentrate is added with hydrofluoric acid and then with sodium carbonate and sodium hydroxide to obtain sodium fluotitanate; B) the sodium fluoborate is mixed with the sodium fluotitanate, and the mixture reacts with aluminum to generate titanium boride and sodium cryolite; C) the sodium cryolite is sucked out and then fed into a rotary reaction kettle together with concentrated sulfuric acid, hydrogen fluoride gas as well as sodium sulfate and sodium aluminum sulfate are generated by reaction in the rotary reaction kettle, and the hydrogen fluoride gas is collected and then dissolved in water to obtain hydrofluoric acid aqueous solution; and D) the obtained hydrofluoric acid aqueous solution is recycled. The invention can achieve the recycling of the byproduct sodium cryolite, simplify the process flow in the preparation of titanium boride, lower the process condition and comprehensive production cost in the preparation of titanium boride, improve the production efficiency and reduce the pollution to environment.

This invention refers to a novel process to obtain magnesium hydroxide and sodium sulfate from a solid raw material, which contains sodium and magnesium soluble salts, preferably in the form of sulfates, coming from a natural source or as a byproduct of an industrial process. The process consisting in the conditioning of the raw material to guarantee the correct concentrations of sodium and magnesium sulfates that is subjected to a salting-out crystallization when mixed with sodium sulfate obtaining sodium sulfate; the resulting solution is subjected to an alkali treatment to precipitate the magnesium hydroxide and the mother liquor is fed to a regeneration stage of the alkali used in the precipitation of the magnesium hydroxide as well in the sodium sulfate solution for the crystallization. The crystallization can be performed as a multistage process countercurrent to increase the purity of sodium sulfate.

The procedure comprises obtaining a adduct of the formula 4Na₂SO₄.2H₂O₂.NaCl in a fashion integrated into the manufacture of Na₂SO₄, regardless of the production procedure for Na₂SO₄ and in any of the stages thereof, by means of the addition to a working solution that comprises Na₂SO₄, NaCl and H₂O₂ of a source of Na₂SO₄, a source of NaCl and a source of H₂O₂, in sufficient quantities to obtain said SPS adduct and the separation of said adduct. The procedure is applicable to the Na₂SO₄ producing industry and allows the impure residues, solid or in solution, of mineral origin or generated as a sub-product in other industries to be used and/or the changing of the production of sodium sulphate partially or completely, to obtain said adduct useful in washing powders as a whitener.