An industrial waste salt resourceful treatment method comprises the following steps: the industrial waste salt is sequentially subject to dissolving, chemical pre-purification, deep purification, organic matter concentration reduction, adsorption and oxidation decolorization and multi-effect evaporative crystallization to respectively obtain sodium sulfate, sodium chloride and sodium nitrate crystals; the crystallization temperature of sodium sulfate is in a range of 75° C. to 85° C.; the crystallization temperature of sodium chloride is in a range of 60 to 70° C.; and the crystallization temperature of sodium nitrate is in a range of 45° C. to 55° C. An industrial waste salt resourceful treatment device is further provided.

An industrial waste salt resourceful treatment method comprises the following steps: the industrial waste salt is sequentially subject to dissolving, chemical pre-purification, deep purification, organic matter concentration reduction, adsorption and oxidation decolorization and multi-effect evaporative crystallization to respectively obtain sodium sulfate, sodium chloride and sodium nitrate crystals; the crystallization temperature of sodium sulfate is in a range of 75° C. to 85° C.; the crystallization temperature of sodium chloride is in a range of 60 to 70° C.; and the crystallization temperature of sodium nitrate is in a range of 45° C. to 55° C. An industrial waste salt resourceful treatment device is further provided.

A process and a system allow producing sodium hydrosulfite crystals. A suspension containing sodium hydrosulfite is provided. The sodium hydrosulfite crystals are separated from a remainder of the suspension. The separated sodium hydrosulfite crystals are cooled to a stable temperature. The suspension may be obtained by raising a pH and lowering a temperature of a solution containing sodium hydrosulfite. A partial precipitation of the sodium hydrosulfite to form the crystals may be facilitated by addition of a nucleating agent to the suspension.

A method of treating fly ash containing sodium sulfate from a recovery boiler of a chemical pulp mill. This method includes at least the following steps: a) ash is dissolved in an aqueous solution and the pH of the solution is adjusted with alkali for precipitating impurities, b) the solution is filtered for removing the impurities containing precipitate, c) sodium sulfate is crystallized from the solution and the crystals are separated from the solution by filtering or by centrifugation, and d) the crystallized sodium sulfate is used as initial material for producing sodium and sulfur containing chemicals or as process chemical.

A method of treating fly ash containing sodium sulfate from a recovery boiler of a chemical pulp mill. This method includes at least the following steps: a) ash is dissolved in an aqueous solution and the pH of the solution is adjusted with alkali for precipitating impurities, b) the solution is filtered for removing the impurities containing precipitate, c) sodium sulfate is crystallized from the solution and the crystals are separated from the solution by filtering or by centrifugation, and d) the crystallized sodium sulfate is used as initial material for producing sodium and sulfur containing chemicals or as process chemical.

According to some embodiments there is provided a process for the recovery of SOP from Sulphate bearing mineral and Carnallite or Sylvenite, comprising: Dissolving Carnallite in water to obtain Sylvenite and high Magnesium Chloride brine; Adding Sodium Sulphate to said Carnallite to produce mixture of Kainte\Leonite, KCl and NaCl precipitant and brine containing Mg Cl.sub.2, KCl, NaCl; Separating the NaCl from the mixture; Obtaining a precipitant mixture of Leonite with KCl; Filtering said Leonite and washing with water to yield pure mixture of Leonite with KCl; Adding KCl to the Leonite with the KCl; and Decompose said Leonite with the KCl to SOP.

According to some embodiments there is provided a process for the recovery of SOP from Sulphate bearing mineral and Carnallite or Sylvenite, comprising: Dissolving Carnallite in water to obtain Sylvenite and high Magnesium Chloride brine; Adding Sodium Sulphate to said Carnallite to produce mixture of Kainte\Leonite, KCl and NaCl precipitant and brine containing Mg Cl.sub.2, KCl, NaCl; Separating the NaCl from the mixture; Obtaining a precipitant mixture of Leonite with KCl; Filtering said Leonite and washing with water to yield pure mixture of Leonite with KCl; Adding KCl to the Leonite with the KCl; and Decompose said Leonite with the KCl to SOP.

An industrial waste salt resourceful treatment method comprises the following steps: the industrial waste salt is sequentially subject to dissolving, chemical pre-purification, deep purification, organic matter concentration reduction, adsorption and oxidation decolorization and multi-effect evaporative crystallization to respectively obtain sodium sulfate, sodium chloride and sodium nitrate crystals; the crystallization temperature of sodium sulfate is in a range of 75° C. to 85° C.; the crystallization temperature of sodium chloride is in a range of 60 to 70° C.; and the crystallization temperature of sodium nitrate is in a range of 45° C. to 55° C. An industrial waste salt resourceful treatment device is further provided.

An industrial waste salt resourceful treatment method comprises the following steps: the industrial waste salt is sequentially subject to dissolving, chemical pre-purification, deep purification, organic matter concentration reduction, adsorption and oxidation decolorization and multi-effect evaporative crystallization to respectively obtain sodium sulfate, sodium chloride and sodium nitrate crystals; the crystallization temperature of sodium sulfate is in a range of 75° C. to 85° C.; the crystallization temperature of sodium chloride is in a range of 60 to 70° C.; and the crystallization temperature of sodium nitrate is in a range of 45° C. to 55° C. An industrial waste salt resourceful treatment device is further provided.

The invention is in the field of landfill leachate, in particular the invention is directed to a method for purifying landfill leachate comprising water, dissociated ions and organic compounds, wherein the method comprises providing the leachate in a eutectic freeze crystallization (EFC) crystallizer and carrying out eutectic freeze crystallization by reducing the temperature of the leachate to a first eutectic point to obtain a first mixture comprising ice and a first crystalline salt. Further the ice and the first crystalline salt are separated into an ice stream and a crystalline salt stream.