Effects of adding paper-making sludge on yield and properties of extracted products from sewage sludge and enrichment of apatite inorganic phosphorus

To achieve a simultaneous improvement in the yield of extraction products and efficient transformation of phosphorus components in an efficient and economical way during the degradation solvent extraction of sewage sludge (SS), the effects of adding paper-making sludge (PS) on the yield and properties of extracted products from sewage sludge and the enrichment of apatite inorganic phosphorus were investigated in this study. The results show that during the solvent separating process of the extraction product, the extract product can be divided into two components, namely light and heavy components, based on the boiling point temperature of 1-methylnaph-thalene (1-MN) as the dividing point. The yield of heavy components is much higher than that of light com-ponents, and it increases significantly with higher PS ratio. Nitrogen-containing compounds are the main chemical compositions of the soluble, accounting for 40.50% and 45.72% in the light components of SS and PS extracts, respectively. The addition of PS changes the main chemical compositions of the heavy components of the mixture extracts due to its relatively high content of phenolic compounds and alkanes. When the PS ratio is 50%, the proportion of apatite inorganic phosphorus (AP) in total phosphorus increases to 82.38%, which is beneficial for the resource utilization of residues.