A method for complex treatment of phosphogypsum comprising crushing of phosphogypsum and its washing with a solution of sulphuric acid, concentration 2-15%, and stirring at 50-80 C., wherein the resultant mixture is separated into a liquid fraction and a sediment containing mostly calcium sulphate, which is characterized in that metals are precipitated from the liquid fraction, mainly lanthanides, phosphates and sulphates of metals soluble in diluted sulphuric acid, and the sediment containing mostly calcium sulphate is converted in the presence of ammonia liquor and carbon dioxide to ammonium sulphate and calcium carbonate, wherein filtered and dried sediment of calcium carbonate is dissolved in a 15-30% solution of nitric acid while stirring continuously, and then the resultant CO.sub.2 is recirculated and used in the conversion of the first phase of the sediment, and the resultant mixture is separated into a solution of calcium nitrate with dissolved metals and a sediment of fluorides and silicates with metal precipitate.

The aim of the present invention is to provide a liquid or crystallized form of NPK fertilizer based on nitrate nitrogen, which is obtained on the basis of organic chemistry, from recycling agricultural and industrial wastes and waste materials through an organic microbiological nitrification process. Products such as potassium nitrate, magnesium nitrate, iron nitrate, and calcium nitrate produced in this way become environmentally friendly products.

The aim of the present invention is to provide a liquid or crystallized form of NPK fertilizer based on nitrate nitrogen, which is obtained on the basis of organic chemistry, from recycling agricultural and industrial wastes and waste materials through an organic microbiological nitrification process. Products such as potassium nitrate, magnesium nitrate, iron nitrate, and calcium nitrate produced in this way become environmentally friendly products.

The present invention relates to a plant and method for the purification of fumes from industrial discharges and/or for the recovery and reconversion of sulfur oxides and/or nitrogen oxides and/or carbon dioxide contained in said fumes. Said method comprises the passage into one or more aqueous solutions, where said aqueous solutions are selected from the group comprising: solution with an acid pH, between 0.5-1; solution at a pH between 3 and 5, at about pH 4; Ca(OH).sub.2 or CaCl.sub.2 or calcium acetate solution; solution at a pH between 8 and 9.

The present invention relates to a plant and method for the purification of fumes from industrial discharges and/or for the recovery and reconversion of sulfur oxides and/or nitrogen oxides and/or carbon dioxide contained in said fumes. Said method comprises the passage into one or more aqueous solutions, where said aqueous solutions are selected from the group comprising: solution with an acid pH, between 0.5-1; solution at a pH between 3 and 5, at about pH 4; Ca(OH).sub.2 or CaCl.sub.2 or calcium acetate solution; solution at a pH between 8 and 9.