Extraction of phosphorus compounds from ashes from thermal processing of sewage sludge

The experimental results on the influence of temperature on the combustion process of sewage sludge, physicochemical properties of the produced ash, as well as the course of selective extraction of phosphorus compounds from the ashes with nitric acid, are presented. The selective leaching of phosphorus compounds with limited transfer of ferrous ions into solution was possible as a result of formation of sparingly soluble in nitric acid hematite phase in calcined ashes. Temperature 950 °C of thermal processing of ash was found to be mostly advantageous for selective extraction of phosphorus compounds from the ashes with nitric acid.