A process for converting gypsum into precipitated calcium carbonate including reacting a mixture comprising gypsum and a seed, a mineral acid, or both with at least one carbonate source, whereby precipitated calcium carbonate is produced in the form of calcite and/or aragonite directly without conversion from a vaterite polymorph. Also, a process for converting gypsum into precipitated calcium carbonate including providing a mixture comprising i) gypsum ii) a seed, a mineral acid, or both iii) at least one additive selected from the group consisting of ammonium sulfate, an organic acid, or an iron material, and reacting the mixture with at least one carbonate source to produce precipitated calcium carbonate in the form of vaterite.

Methods and systems that remove impurities from phosphogypsum (PG), including from radium and heavy metal salts, and produce gypsum binders and products. In one embodiment, PG is reacted with a chloride solution in an acidic environment under mechanical manipulation and/or heat followed by galvanic and/or zeolite absorption removal of impurities.

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.

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.

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.

Disclosed are various methods for reducing levels of elemental sulfur within gypsum products such as wall board. Gypsum sometimes includes increased levels of elemental sulfur. Such sulfur can be corrosive and otherwise harmful at elevated levels. The disclosure contemplates reacting the elemental sulfur with copper to copper sulfide. This reaction has the benefit of reducing the levels of elemental sulfur present within the final gypsum product. The copper can be added at any of a variety of locations in the manufacturing process. This is a very efficient method for reducing elemental sulfur in the production of gypsum products.

Disclosed are various methods for reducing levels of elemental sulfur within gypsum products such as wall board. Gypsum sometimes includes increased levels of elemental sulfur. Such sulfur can be corrosive and otherwise harmful at elevated levels. The disclosure contemplates reacting the elemental sulfur with copper to copper sulfide. This reaction has the benefit of reducing the levels of elemental sulfur present within the final gypsum product. The copper can be added at any of a variety of locations in the manufacturing process. This is a very efficient method for reducing elemental sulfur in the production of gypsum products.

Methods and systems that remove impurities from phosphogypsum (PG), including from radium and heavy metal salts, and produce gypsum binders and products. In one embodiment, PG is reacted with a chloride solution in an acidic environment under mechanical manipulation and/or heat followed by galvanic and/or zeolite absorption removal of impurities.

There is described a method of preparing solid particles of a material, said method comprising controlling provision of a first liquid phase, wherein said first liquid phase comprises a solution of a first material through a membrane, said membrane defining a plurality of pores; and controlling provision of a second liquid phase, wherein said second liquid phase comprises a solution of a second material; reacting the first a second materials to produce a third liquid phase comprising a solution of a third material; and supersaturating the third liquid phase to form solid particles of the third material.

The present application provides a method for separating and purifying phosphoric acid and phosphogypsum from a wet-process phosphoric acid slurry, and phosphoric acid and phosphogypsum prepared thereby. The method comprises: adding an impurity-removing agent to a wet-process phosphoric acid slurry, and mixing same under the action of a microbubble external field, so as to obtain an organic phase containing colloidal impurities, and an ore slurry, from which impurities have been removed; and then sequentially subjecting the ore slurry, from which impurities have been removed, to crystallization and solid-liquid separation, so as to obtain phosphoric acid and phosphogypsum, from which impurities have been removed. In the method, by using the impurity-removing agent in cooperation with the microbubble external field, the adhesion of impurities is enhanced by using microbubbles, and energy is provided during the floating and crushing process of the microbubbles so as to crush large particles of phosphogypsum in the slurry and make the impurity-removing agent fully react with the slurry; and such process is beneficial for the dissociation, precipitation and separation of colloidal silicon and carbon impurities, such that the aim of in-situ removal and rapid separation of colloidal impurities to obtain the ore slurry, from which impurities have been removed, during a reaction process for outputting phosphogypsum is realized, and a low-impurity phosphoric acid product and phosphogypsum product can be obtained after the ore slurry, from which impurities have been removed, has been further treated.