Abstract: A process for the removal of heavy metals from an acid phosphate containing, liquid medium in which process a precipitate containing heavy metals is formed and is subsequently separated and wherein at least one of the two additives (a) sulphate ions and (b) calcium ions is added to the phosphate-containing, liquid medium under such conditions that a calcium sulphate anhydride-containing precipitate is formed.

Abstract: A process for recovering from a wet process phosphoric acid which contains uranium, a uranium containing concentrate and a purified phosphoric acid. The wet process phosphoric acid is treated with a precipitant in the presence of a reducing agent and an aliphatic ketone.

Abstract: The invention relates to the chemical removal of phosphorus compounds from waste water, this waste water being treated with one or more metal compounds, without any problems presenting themselves as regards the separation of the metal phosphate compounds. To achieve this, the waste water is treated with the metal compound in a fluidized bed of metal phosphate particles.The invention also relates to a process for the purification of waste water in which the effluent from a biological purification is subjected to the above-mentioned method for the removal of phosphorus.

Abstract: A process is described for the removal of uranium values from contaminated wet-process phosphoric acid solutions using an addition thereto of first an aliphatic ketone and then an inorganic fluoride, whereby high efficiencies in the removal of uranium as a solid, filterable precipitate are achieved.

Abstract: Process for recovering yttrium and lanthanides from wet-process phosphoric acid by adding a flocculant to the phosphoric acid, separating out the resultant precipitate and then recovering yttrium and lanthanides from the precipitate. Uranium is recovered from the remaining phosphoric acid.

Abstract: Recovery of yttrium, lanthanides and radium free calcium sulphate in a phosphoric acid process by digesting phosphate rock with an excess of phosphoric acid in the presence of more than about 5 wt.% of SO.sub.4 -ions calculated to the amount of phosphate rock, separating out the insoluble residue and recovering yttrium and lanthanides therefrom, precipitating calcium sulphate from the remaining solution with sulphuric acid and separating this calcium sulphate from the resulting phosphoric acid solution.

Abstract: A process for preparing calcium sulphate anhydrite from calcium sulphate dihydrate so that the calcium sulphate anhydrite crystals will have a predetermined average particle size. The process is conducted by recrystallizing the calcium sulphate dihydrate at moderate temperatures in the presence of sulphuric acid having a concentration of 40-65% wt. calculated relative to the quantity of liquid phase in the recrystallization mixture. The particle size of the final product is controlled by varying the temperature and residence time of the recrystallization mixture in recrystallization zone and by varying the temperature in an inverse relationship to the acid concentration.Calcium sulphate anhydrite crystals having an average particle size between about 0.5 and about 3 micron are produced by maintaining the temperature between about 40.degree. C. and 90.degree. C. and the residence time from about 5 minutes to less than about 30 minutes.

Abstract: Phosphate rock is digested with H.sub.2 SO.sub.4 into phosphoric acid and gypsum, the latter is separated off, washed and converted into anhydrite. After this first wash the gypsum is divided into a minor portion of fine crystals, which is discharged, and into a major portion of coarse crystals, which is subjected to a second wash, thereafter recrystallized into anhydrite by means of concentrated H.sub.2 SO.sub.4, the anhydrite being separated and washed and the recrystallization liquor returned to the digestion zone. The washing liquor obtained from the anhydrite wash is used for the second gypsum wash, the washing liquor obtained from this second wash is, together with water, used for the first gypsum wash, whereas the washing liquor obtained in this first wash is returned to the digestion zone. In this way practically all gypsum formed can be converted into anhydrite, while substantially all water can be functionally used without dilution of the H.sub.3 PO.sub.4 -product.

Abstract: The invention is directed to precipitating soluble nickel salts onto catalyst carriers by the addition of urea and reducing the insoluble nickel salt to the free metal to form catalyst-carrier compositions of high specific metal catalyst area wherein the amount of urea added satisfies the following equationU = f .sqroot.Ni (1)where:U = urea concentration in grams per liter;Ni = nickel ions concentration in grams per liter of water;f = a factor varying between 75/pH and 175/pH, in which pH = the pH value of the suspension of the silica in the water.

Abstract: For high-surface area hydrogenation nickel catalyst compositions, a silica carrier obtained by subjecting an alkali water glass to neutralization with sulfuric acid and spray-drying to form the silica carrier which has substantially no tendency to coalesce when used in processes requiring precipitation of an insoluble nickel compound onto the carrier.

Abstract: The invention relates to catalytic dehydrodimerization of compounds of the formula CH.sub.3 --R wherein R represents a group which is not reactive under the reaction conditions and is bonded to the methyl group by a carbon atom connected to an adjacent atom by an unsaturated bond, by catalysts, including bismuth trioxide, thallium trioxide or mixtures thereof, which are supported on basic carrier materials of high surface area.