Enhanced heavy metal stabilization and phosphorus retention during the hydrothermal carbonization of swine manure by in-situ formation of MgFe2O4

Hydrothermal carbonization is an efficient technique for the disposal of livestock manure, enabling its harmless treatment, quantity reduction, and resourceful utilization. Co-hydrothermal of modified materials facilitates the production of more valuable carbonaceous materials. However, further exploration is needed to understand their potential impact on the environmental risks associated with livestock manure disposal and the application of products derived from it. Therefore, the carbonization degree, heavy metals stabilization, and phosphorus retention during the hydrothermal treatment of swine manure were systematically investigated in this study under the influence of in-situ formed MgFe2O4. The results revealed that the in-situ formation of MgFe2O4 improved the dehydration and decarboxylation of organic components in swine manure, thereby improving its carbonization degree. Furthermore, both hydrothermal carbonization and MgFe2O4 modified hydrothermal carbonization resulted in an enhanced stabilization of heavy metals, leading to a significant reduction in their soluble/exchangeable fraction and reducible fraction. Phosphorus was predominantly retained in the hydro chars, with the highest retention rate reaching 88%, attributed to the significant decrease in soluble and exchangeable phosphorus fractions facilitated by the in-situ formation of MgFe2O4. Moreover, MgFe2O4 modified hydrochars exhibited remarkable adsorption capacity for Pb(II) and Cu(II) without any leaching of heavy metals. Overall, the findings indicated that the in-situ formation of MgFe2O4 positively influenced the hydrothermal of swine manure, improving certain economic benefits in its practical application.

Automated summary

This study investigated the influence of in-situ formed MgFe2O4 on the hydrothermal treatment of swine manure. The results showed that the in-situ formation of MgFe2O4 improved the dehydration and decarboxylation of organic components in swine manure, thereby improving its carbonization degree. Furthermore, it enhanced the stabilization of heavy metals and the retention of phosphorus. MgFe2O4 modified hydrochars exhibited remarkable adsorption capacity for Pb(II) and Cu(II) without any leaching of heavy metals.