Method for complex treatment of phosphogypsum

A method for complex treatment of phosphogypsum, said method comprising breaking up of phosphogypsum, washing the phosphogypsum with a solution of sulphuric acid, and stirring the mixture of phosphogypsum and sulphuric acid at a temperature between about 50° C. and about 80° C., wherein the solution of sulphuric acid has a concentration between about 2% to about 15%,

• wherein the resultant mixture of phosphogypsum and sulphuric acid is separated into a liquid fraction and a sediment containing mostly calcium sulphate characterized in that metals are precipitated from the liquid fraction,
• wherein the sediment containing mostly calcium sulphate is converted in the presence of ammonia liquor and carbon dioxide to provide ammonium sulphate and calcium carbonate,
• wherein the calcium carbonate is filtered and dried, and dissolved in a solution of nitric acid at a concentration between about 15% to about 30% while stirring continuously, and
• wherein CO2 is formed, recirculated, and used in the fist-phase conversion of the sediment, and
• wherein the resultant mixture is separated into a solution of calcium nitrate with dissolved metals and a sediment of fluorides and silicates with metal precipitate,
• characterized in that a solution of sodium hydroxide is added to the sediment of silicates with metals, and the resultant mixture is heated to a temperature of about 100° C. to about 300° C., and after metal silicates are dissolved, water is added to the mixture to reduce viscosity of the solution, after which the process of metals precipitation is applied with the use of strong reducers, and the resultant mixture is separated to obtain a sediment of noble metals as a semi-finished product for further processing, and liquid glass which after concentrating is a finished sellable product.

A method for complex treatment of phosphogypsum, said method comprising breaking up of phosphogypsum, washing the phosphogypsum with a solution of sulphuric acid, and stirring the mixture of phosphogypsum and sulphuric acid at a temperature between about 50° C. and about 80° C., wherein the solution of sulphuric acid has a concentration between about 2% to about 15%,

• wherein the resultant mixture of phosphogypsum and sulphuric acid is separated into a liquid fraction and a sediment containing mostly calcium sulphate characterized in that metals are precipitated from the liquid fraction,
• wherein the sediment containing mostly calcium sulphate is converted in the presence of ammonia liquor and carbon dioxide to provide ammonium sulphate and calcium carbonate,
• wherein the calcium carbonate is filtered and dried, and dissolved in a solution of nitric acid at a concentration between about 15% to about 30% while stirring continuously, and
• wherein CO2 is formed, recirculated, and used in the fist-phase conversion of the sediment, and
• wherein the resultant mixture is separated into a solution of calcium nitrate with dissolved metals and a sediment of fluorides and silicates with metal precipitate,
• characterized in that the solution of calcium nitrate is neutralized with ammonia liquor or ammonium to a pH of about 7 to about 9 and trimercaptotriazine trisodium salt is added to precipitate metals, and what is obtained is a fertilizer of mainly calcium nitrate in the form of a solution which is a finished product, and a concentrate of metal complexes which is a semi-product for further processing.