The transformation and regulation of phosphorus in model compound and waste biomass from hydrothermal conversion

In this study, the degradation behaviour of phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) during hydrothermal conversion (HC) and the effect of alkali additives on phosphorus forms during HC of phospholipids and different phosphorus-containing wastes were investigated. The mechanism of phosphate-alkali-directed regulation and transformation was discussed and analysed with batch hydrothermal treatment experiments and characterizations such as XRD and SEM. The obtained results showed that DOPC degradation was divided into two periods, i.e., the initial accumulation of phosphorus-containing precursors with increasing temperature, followed by complete degradation to H3PO4 as treatment continued. In addition, compared with the activation of P by NaOH, Ca(OH)2 is more favourable for the stabilization of P and the migration of non-apatite inorganic phosphorus (NAIP) to apatite inorganic phosphorus (AP). The pH and appropriate feed Ca/P molar ratio during HC determine the degree to which total phosphorus is converted to Ca-bound P. The findings reveal the mechanism of phosphate-alkali-directed regulation and transformation and provide a theoretical reference for the efficient treatment of phosphorus-containing waste and the alkali-directed production of high-phosphorus bioavailability products.