A method of treating a waste liquid includes: an aluminum dissolution step of dissolving aluminum in an acidic waste liquid and performing separation into a first treated water and a reduced heavy metal precipitate; a gypsum recovery step of adding a calcium compound to the first treated water at a liquid property of a pH of 4 or less, and performing separation into a second treated water and gypsum; an aluminum and fluorine removal step of adding an alkali to the second treated water and performing separation into a third treated water and a precipitate containing aluminum and fluorine; and a neutralization step of adding an alkali to the third treated water and performing separation into an alkali neutralization treated water and a neutralized precipitate of a heavy metal hydroxide.

Methods of recovering coal combustion products (CCPs) from coal combination byproducts are disclosed. The methods include compiling coal combustion byproducts (e.g., lignite coal and/or bituminous coal), grinding the coal combustion byproducts to form ground coal combustion byproducts with a maximum particle size of 40 microns, and separating the ground coal combustion byproducts to yield CCPs using an electrostatic precipitator. The following CCPs can be separated from the coal combination byproducts using the presently disclosed methods: fly ash, bottom ash, scrubber materials, and raw coal.

A method for the precipitation of rare earth sulphate, the method including subjecting a crude rare earth sulphate solution to precipitation in the presence of a water soluble, volatile, organic compound to produce a rare earth sulphate precipitate and an acidic supernatant. The organic compound is preferably selected from the group consisting of methanol, ethanol, iso-propanol, tert-butanol, acetone or mixtures thereof, and is preferably methanol. Preferably, the organic compound is used in the precipitation at a weight ratio of between 0.25:1 to 1.5:1, and preferably 0.5:to 1.25:1, with the crude sulphate solution.

A method for releasing impurities from a calcium-based mineral is described. The method comprises reacting a calcium-based mineral containing impurities with an aqueous solution of one or more ionic salts at a temperature of approximately 85 C. or above, wherein at least one of the calcium-based mineral and the one or more ionic salts comprises sulphate and at least one of the calcium-based mineral and the one or more ionic salts comprises ammonium, and wherein the concentration of the solution is approximately 25% or higher mass fraction, such that double salt crystals are formed and impurities are released. The method further comprises separating the double salt crystals from the impurities. Various products of the process are also described.

There is described a process for the continuous production of alpha-calcium sulphate hemihydrate, the process comprising the steps of: mixing particulate gypsum, a habit modifier and water to form a gypsum slurry. The process further comprises calcining the gypsum slurry to provide an alpha-calcium sulphate hemihydrate slurry and filtering the alpha-calcium sulphate hemihydrate slurry to separate at least one fluid stream from the slurry, measuring a first control parameter of the at least one fluid stream or the alpha-calcium sulphate hemihydrate slurry; and combining the at least one fluid stream with further gypsum, further water and further habit modifier to form a further gypsum slurry wherein the process further comprises varying the amount of further habit modifier depending on a measured value of the first control parameter. An apparatus for performing the described process is also provided.

Processes for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof. Systems for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof.

A process for extracting lithium from lithium-bearing salt brines including: (i) subjecting a feed brine to a primary evaporation step using mechanical evaporators, to form a first concentrated brine and sodium chloride; (ii) separating the sodium chloride in a salt removal step; (iii) reacting lime with the first concentrated brine in a liming step to precipitate out and discard magnesium and sulphate ions and other contaminants and to form a limed brine; (iv) subjecting the limed brine to a secondary evaporation step, to form a second concentrated brine and precipitating calcium chloride; (v) separating the calcium chloride from the second concentrated brine; (vi) reacting sodium sulphate with the second concentrated brine to precipitate out and discard calcium sulphate, to form a lithium-rich brine; (vii) reacting soda ash with the lithium rich brine thereby forming a precipitate of lithium carbonate; and (viii) separating the lithium carbonate.

The invention relates to a process for extracting metals and salts from titanium-bearing minerals such as perovskite. More particularly, although not exclusively, the invention relates to extracting titanium dioxide and optionally other compounds from melter slag derived from an iron-making process.

A process for treating a sulfurous fluid to form gypsum and magnesium carbonate, whereby the sulfurous fluid is scrubbed with a sequestrating agent to yield a scrubbed fluid, gypsum and magnesium sulfate. The flue gas desulfurized gypsum is isolated from the magnesium sulfate solution by filtration or centrifugation. The magnesium sulfate is reacted with a carbonate salt to produce a magnesium carbonate whereby the reaction conditions are controlled to control the properties of the magnesium carbonate produced.

Processes for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof. Systems for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof.