Simple and Combined Acidic Extraction of Phosphorus from Sewage Sludge Ash

A comparative behavior of inorganic and organic acids as extraction agents for phosphorous extraction from sewage sludge ash provided by a municipal wastewater plant from Timis County, Romania, was studied in this work. The physical-chemical and morphological properties were determined by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy. Batch simple extraction experiments with hydrochloric acid, sulfuric acid and citric acid were conducted on the sewage sludge ash for phosphorous extraction. The operating conditions for acidic extraction with each acid and combination of sulfuric acid and citric acid were optimized in relation to the acid type, concentration and liquid:solid (LS) ratio. The combination of sulfuric acid and citric acid in volumetric ratio of 0.5 was chosen as optimum extraction agent for phosphorus recovery.