A method of collecting anhydrous sodium sulfate from fly ash includes heating a purified sodium sulfate solution to 60 C. to 80 C., and adding a precipitation promoter to the purified sodium sulfate solution to precipitate anhydrous sodium sulfate crystal. The method further includes cooling the purified sodium sulfate solution and the anhydrous sodium sulfate crystal to 35 C. to 55 C. for precipitating more anhydrous sodium sulfate crystal, and collecting and drying the anhydrous sodium sulfate crystal.

Described herein is a process for upgrading effluent treatment plants for pulp and paper production processes, where salts are removed from the effluent for water reuse and chemical recovery. The process comprises a first dialysis system for salt removal, a second treatment system for recovery or re-concentration, and optionally a post-treatment of the re-concentrate preventing liquid discharges to the environment. In the first system, a reversible electrodialysis or reversible pulsed step is carried out, separating the salts from the effluent, which are sent to the second treatment system to concentrate the salts (re-concentrate) or transform them into useful chemicals for the same process (recovery). Chemical recovery is achieved by electrodialysis with bipolar membranes or metathesis, to reduce the re-concentrate stream, which cannot be reused in the same plant. Lastly, this stream may be treated by spray drying, crystallization or evaporation.

Described herein is a process for upgrading effluent treatment plants for pulp and paper production processes, where salts are removed from the effluent for water reuse and chemical recovery. The process comprises a first dialysis system for salt removal, a second treatment system for recovery or re-concentration, and optionally a post-treatment of the re-concentrate preventing liquid discharges to the environment. In the first system, a reversible electrodialysis or reversible pulsed step is carried out, separating the salts from the effluent, which are sent to the second treatment system to concentrate the salts (re-concentrate) or transform them into useful chemicals for the same process (recovery). Chemical recovery is achieved by electrodialysis with bipolar membranes or metathesis, to reduce the re-concentrate stream, which cannot be reused in the same plant. Lastly, this stream may be treated by spray drying, crystallization or evaporation.

The present disclosure discloses a method for producing potassium sulfate by a metathesis process, a potassium sulfate product and a potash fertilizer, and relates to the field of potassium sulfate preparation methods. A solid ammonium sulfate and a solid potassium chloride are used as raw materials and are added in two steps for reaction, a first-stage reaction and a second-stage reaction are respectively carried out, then a third-stage reaction with hot water is carried out, and crystallization and separation are carried out, such that impurities in the product are fully removed, and meanwhile, the content of K.sub.2O in the product is increased. The potassium sulfate product with high K.sub.2O content and low chlorine content can be prepared through the three-stage reaction process provided by the present disclosure, and the method is simple and easy to implement and convenient for industrial application.

The present disclosure discloses a method for producing potassium sulfate by a metathesis process, a potassium sulfate product and a potash fertilizer, and relates to the field of potassium sulfate preparation methods. A solid ammonium sulfate and a solid potassium chloride are used as raw materials and are added in two steps for reaction, a first-stage reaction and a second-stage reaction are respectively carried out, then a third-stage reaction with hot water is carried out, and crystallization and separation are carried out, such that impurities in the product are fully removed, and meanwhile, the content of K.sub.2O in the product is increased. The potassium sulfate product with high K.sub.2O content and low chlorine content can be prepared through the three-stage reaction process provided by the present disclosure, and the method is simple and easy to implement and convenient for industrial application.

Provided is a leaching-seepage process of sodium sulfate in a thenardite tailings stack. The process includes the following steps: step 1, providing a mud reserve pit next to the thenardite tailings stack, and ditching a drainage ditch next to a bottom of the thenardite tailings stack; step 2, ditching a leaching pit on the thenardite tailings stack, injecting water, and letting the water stand to leach thenardite tailings; step 3, leaching the thenardite tailings with the water, so that a percolating fluid gradually flows out from the bottom of the thenardite tailings stack; step 4, flushing the bottom of the thenardite tailings stack with a spray gun, to mix the percolating fluid with mud to flow into the drainage ditch; and step 5, settling naturally in the mud reserve pit, and extracting a supernatant from the mud reserve pit by a water pump to obtain refined Glauber's salt water.

Provided is a leaching-seepage process of sodium sulfate in a thenardite tailings stack. The process includes the following steps: step 1, providing a mud reserve pit next to the thenardite tailings stack, and ditching a drainage ditch next to a bottom of the thenardite tailings stack; step 2, ditching a leaching pit on the thenardite tailings stack, injecting water, and letting the water stand to leach thenardite tailings; step 3, leaching the thenardite tailings with the water, so that a percolating fluid gradually flows out from the bottom of the thenardite tailings stack; step 4, flushing the bottom of the thenardite tailings stack with a spray gun, to mix the percolating fluid with mud to flow into the drainage ditch; and step 5, settling naturally in the mud reserve pit, and extracting a supernatant from the mud reserve pit by a water pump to obtain refined Glauber's salt water.

A method for forming an insoluble adduct using an acidic medium is provided. A chemical process utilizes acidic media to change the solubility behavior of metal solutes. The method can utilize Group 1 soluble alkali metals but can also be extended to any other soluble salts discussed under the solubility rules. The insoluble salts can be Group 2 alkaline earth metals or other insoluble salts. The insoluble adduct can have the designation XYZ where X is a soluble metal from a metal hydroxide or a metal oxide, Y is an insoluble metal from an insoluble metal hydroxide or an insoluble metal oxide, and Z is the acid ion from an aqueous acidic media.

A method for forming an insoluble adduct using an acidic medium is provided. A chemical process utilizes acidic media to change the solubility behavior of metal solutes. The method can utilize Group 1 soluble alkali metals but can also be extended to any other soluble salts discussed under the solubility rules. The insoluble salts can be Group 2 alkaline earth metals or other insoluble salts. The insoluble adduct can have the designation XYZ where X is a soluble metal from a metal hydroxide or a metal oxide, Y is an insoluble metal from an insoluble metal hydroxide or an insoluble metal oxide, and Z is the acid ion from an aqueous acidic media.