The present relates to a method for producing calcium sulfate solid crystals and hydrochloric acid (HCl) from a calcium chloride solution comprising the steps of feeding a continuous stirred-tank reactor with a calcium chloride solution, sulfuric acid and water; mixing the calcium chloride solution, sulfuric acid and water in the reactor; and maintaining the reactor a temperature of less than about 70° C., converting the calcium chloride solution, sulfuric acid and water into HCl and calcium sulfate solid crystals. The method described herein can be incorporated as a means for regenerating HCl from CaCl.sub.2 solutions which are generated in the metallurgical industry when processing calcium-bearing ores for recovering metals like rare earth elements.

The present relates to a method for producing calcium sulfate solid crystals and hydrochloric acid (HCl) from a calcium chloride solution comprising the steps of feeding a continuous stirred-tank reactor with a calcium chloride solution, sulfuric acid and water; mixing the calcium chloride solution, sulfuric acid and water in the reactor; and maintaining the reactor a temperature of less than about 70° C., converting the calcium chloride solution, sulfuric acid and water into HCl and calcium sulfate solid crystals. The method described herein can be incorporated as a means for regenerating HCl from CaCl.sub.2 solutions which are generated in the metallurgical industry when processing calcium-bearing ores for recovering metals like rare earth elements.

A method for preparing α-calcium sulfate hemihydrate with calcium sulfate dihydrate includes steps of: uniformly mixing the calcium sulfate dihydrate with an additive solution, and obtaining a mixture, wherein weight percentages of the calcium sulfate dihydrate and the additive solution in the mixture are respectively 90.00-95.00% and 5.00-10.00%, and the additive solution contains water, inorganic salt, organic salt, organic acid, surfactant, and seed crystal; rising a temperature of the mixture to 130-150° C., keeping for 20-120 minutes, and the calcium sulfate dihydrate in the mixture transforming to the α-calcium sulfate hemihydrate; drying the mixture after reaction at 105-160° C., and thereafter obtaining α-calcium sulfate hemihydrate product. The used calcium sulfate dihydrate can be natural raw materials and industrial by-products. The industrial by-products can be directly applied. Through utilizing characteristics of the industrial by-products, a dehydration reaction time and a drying time are shortened, and a product quality is obviously increased.

Provided are wallboards in which gypsum core is adhered to a paper cover sheet with an adhesive. Wallboards with laminated paper cover sheets in which an inner water-absorbent cover sheet is adhered to the outer paper cover sheet are provided as well. Methods for making these wallboards are provided as well.

Provided are wallboards in which gypsum core is adhered to a paper cover sheet with an adhesive. Wallboards with laminated paper cover sheets in which an inner water-absorbent cover sheet is adhered to the outer paper cover sheet are provided as well. Methods for making these wallboards are provided as well.

In the manufacture of phosphoric acid from ore, the typical ore comprises minerals containing phosphorus and calcium along with varied amounts of other elements. Certain ores have substantial iron content which needs to be removed in order to produce quality phosphoric acid product. An improved method and associated chemical processing plant are disclosed for removing this iron. The method involves both reducing and adding oxalic acid to wet process phosphoric acid produced using an otherwise conventional manufacturing process. Iron oxalate precipitate is created which can then conveniently be separated therefrom.

In the manufacture of phosphoric acid from ore, the typical ore comprises minerals containing phosphorus and calcium along with varied amounts of other elements. Certain ores have substantial iron content which needs to be removed in order to produce quality phosphoric acid product. An improved method and associated chemical processing plant are disclosed for removing this iron. The method involves both reducing and adding oxalic acid to wet process phosphoric acid produced using an otherwise conventional manufacturing process. Iron oxalate precipitate is created which can then conveniently be separated therefrom.

The present invention relates to a process, methods and materials for generating fertilizers from seawater resources, especially in conjunction with seawater desalination plants. Here, we demonstrate that varying compositions of fertilizers such as nitrogen/potassium, nitrogen/phosphorus/potassium, nitrogen/potassium/sulfur, and nitrogen/phosphorus/potassium/sulfur, potassium/sulfur, potassium along with micro and secondary nutrients can directly be generated as part of the extraction process to meet the requirements of both starter and sustained phases of plant growth.

The present invention relates to a process, methods and materials for generating fertilizers from seawater resources, especially in conjunction with seawater desalination plants. Here, we demonstrate that varying compositions of fertilizers such as nitrogen/potassium, nitrogen/phosphorus/potassium, nitrogen/potassium/sulfur, and nitrogen/phosphorus/potassium/sulfur, potassium/sulfur, potassium along with micro and secondary nutrients can directly be generated as part of the extraction process to meet the requirements of both starter and sustained phases of plant growth.

A method of removing barium and naturally occurring radioactive material from produced water. The method includes pretreating the produced water having a pH in a range of from about 4.0 to about 10.0 with a sulfate source to form a suspension of barium sulfate, radium sulfate, or a combination thereof, treating the pretreated produced water with an anionic flocculant and gravitational])′ separating the treated produced water from the barium sulfate, radium sulfate, or a combination thereof.