FIELD: chemistry.
SUBSTANCE: invention relates to extraction of valuable substances, primarily phosphate, from products contained in waste water sludge or formed from treating waste water, specifically: waste water sludge, ash formed from burning waste water sludge, or slag formed from treating waste water sludge or contained therein, by extraction. The method includes preparing a suspension of a product contained in waste water sludge or formed from treating waste water in water, alcohol, water-alcohol mixture or aqueous solution, adding to said suspension carbon dioxide (CO2) gas or supercritical carbon dioxide (scCO2) as an extraction agent, separating undissolved solid substances from the liquid suspension agent, removing carbon dioxide from the suspension agent, precipitating valuable substances dissolved in the suspension agent and separating said substances from the suspension agent.
EFFECT: economically effective method for selective separation, recuperation of valuable substances, primarily phosphorus, and also, at certain conditions, metals and nonmetals from waste water sludge or ash formed from burning waste water sludge.
11 cl, 3 ex
