Phosphorus (P) recovery from incinerated sewage sludge ash (ISSA) has attracted increasing attentions in recent years. In this study, the P recovery was comparatively investigated on two types of ISSA for sewage sludge pretreated by Fenton's reagent, and a composite conditioner of Fenton's reagent and lime (referred to as ISSA-F and ISSA-FL, respectively). ISSA derived from raw sludge (referred to as ISSA-RS) was studied as the control group. The P species results showed that the proportions of AP (Ca-bound P) and NAIP (Al/Fe-bound P) in the ISSA samples were significantly affected by the added Fe and Ca elements in the sludge conditioner. The order of leaching efficiency of P in different ISSA samples was ISSA-F (100%) > ISSA-RS (94.4%) > ISSA-FL (83.1%), which was significantly related to the Ca content in those ISSA samples. Higher Ca content in the ISSA-RS and ISS-FL samples induced calcium oxalate precipitation during leaching process, which hindered the release of P from ISSA. P recovery product mainly composed of aluminum hydroxyphosphate was prepared from the purified solutions leached from different ISSA samples. Moreover, acid-leaching residues of different ISSA samples after P recovery were proposed to be reutilized as cement mortar additives by replacing 15 wt% of cement. The mechanical strength of the test cement mortar specimens with acid-leaching residues was comparable to that of the control cement mortar specimen without residue.
- Aluminum hydroxyphosphate
- Fenton's reagent and lime
- Incinerated sewage sludge ash
- Phosphorus recovery
- Residue reutilization