Migration behavior of phosphorus during microwave-assisted co-hydrothermal carbonization and co-pyrolysis of chemical...

Recycling of phosphorus (P) from chemical sludge (CS) is important for alleviating P resources shortage and solving P pollution. In this study, the transformation behavior and the mechanism of P during microwave-assisted co-hydrothermal carbonization (co-HTC) and co-pyrolysis of CS and corncob was investigated. The results showed that microwave could enhance the process of co-HTC and co-pyrolysis, and made P enriched in hydrochar and biochar. Microwaves made the content of orthophosphate (Ortho-P) and pyrophosphate (Pyro-P) in hydrochar and biochar increase, as well as making the organic phosphorus (OP) convert into inorganic phosphorus (IP). Meanwhile, the results also showed that P-containing minerals existed as Al-P and Fe-P in hydrochar and existed as Ca-P and Mg-P minerals in biochar. Furthermore, microwave assistance also could significantly improve the bioavailability of P. The results of this study may provide a basis for the P recovery from chemical sludge, as well as for clean and efficient utilization of hydrochar and biochar.