Abstract: A method of substantially removing a trace metallic contaminant from a liquid containing the same comprises,adding an oxidizing agent to a liquid containing a trace amount of a metallic contaminant of a concentration of up to about 10.sup.-1 ppm, the oxidizing agent being one which oxidizes the contaminant to form an oxidized product which is insoluble in the liquid and precipitates therefrom, and the conditions of the addition being selected to ensure that the precipitation of the oxidized product is homogeneous, andseparating the homogeneously precipitated product from the liquid.

Abstract: A process is provided wherein solid mixtures of metal chlorides of, for example, ferric chloride, ferrous chloride, vanadium chloride and chromium chloride are (1) mixed with an alkaline material such as, for example, calcium oxide, calcium hydroxide and calcium carbonate, followed (2) by adding water to the resulting mixture to granulate said mixture whereby the metal chlorides are rendered substantially insoluble in water.

Abstract: An aqueous ferrous sulfate waste stream is converted into sludge and improved water effluent by a preferably ambient indoor temperature and pressure flow process comprising: turbulently mixing said stream with a substantial excess of gaseous oxygen and a small excess of impalpable calcium carbonate in a reaction zone until the iron content of said stream is virtually all sludged; classifying resulting sludge into a coarser solids fraction (a portion of which is recycled to the sludging operation) and an aqueous suspension of finer solids; and separating finer solids from such aqueous suspension. As such streams usually contain free sulfuric acid, it is desirable to first precipitate from the stream a primary gypsum product by neutralization prior to such sludging operation.

Abstract: A method is provided for treating waste water containing solids of difficultly-soluble compounds of at least one heavy metal, the method comprising the steps of adding an amount of ferrous ions to said waste water corresponding on a molar basis to about 2 to 100 times the total molar amount of heavy metal present in said waste water, adding an alkaline substance to said waste water in an amount corresponding to about 0.9 to 1.2 equivalent of free acid present in said waste water, and stirring the waste water without aeration at a temperature of at least about 40.degree. C., whereby insoluble ferrite crystals are precipitated having said heavy metal incorporated therein.

Abstract: Iron is removed from grits, e.g. crushed corundum by contacting the grits with aqueous hydrochloric acid for dissolving of the iron and provision of a suspension of the grits in the acedic aqueous medium; water is added to the suspension and it is then centrifuged; water is added to the grit-rich fraction and the resulting suspension is subjected to a second centrifuging step.

Abstract: Nickel values contained in oxidic ores are recovered by leaching with sulfuric acid. The ore is slurried with water, preheated to a leaching temperature between about 230.degree. C and about 300.degree. C and the preheated slurry is fed to one or more vigorously agitated autoclaves, operating continuously in series. Sulfuric acid is added incrementally to the preheated slurry to minimize the amount of iron and aluminum in solution until between about 0.15 part and about 0.8 part of acid per part of dry ore is added to the slurry, thereby minimizing the deposition of scale in the autoclaves.

Abstract: Metal hydroxides such as Fe(OH).sub.2, Fe(OH).sub.3 and Sn(OH).sub.2 are prepared in the form of spherical particles of uniform and controlled size suitable for tagging with a radioactive element such as technetium-99m. Aqueous suspensions of such tagged particles are useful in scintigraphy as lung scanning agents.

Abstract: The leaching efficiency of nickeliferous lateritic ore is optimized by scalping the ore to remove a coarse low-nickel fraction and provide a fine nickel-rich fraction which is then high pressure leached in a sulfuric acid solution by controlling the parameters temperature, pulp density, the rate of acid addition, leaching time, agitation rate, etc., whereby a pregnant solution is obtained with the nickel to (Fe+Al+Cr) ratio exceeding about 2.

Abstract: Sulfate solutions containing at least one valuable metal from the group: Fe, Ni and Co, particularly solutions resulting from the leaching of lateritic ores or concentrates, are treated to recover the valuable metal. The latter is precipitated by treating the solution with magnesium hydroxide. The resulting magnesium-containing solution is treated with lime under controlled conditions to precipitate relatively fine particles of magnesium hydroxide and relatively coarse particles of gypsum. The difference in particle size is relied on to separate the magnesium hydroxide (for recycling) from the gypsum (which is calcined to regenerate lime).