Heavy metal migration regimes in the production of syngas from solid waste by thermal plasma treatment

In recent years, thermal plasma technology has been widely used in the harmless and resource-efficient treatment of solid waste (SW). This study investigates the migration behaviors of heavy metals during the thermal plasma treats SW to obtain the interphase structure change regimes of heavy metals. The transformation of SW under high-temperature environments was analyzed by Fluent simulation, and the composition of the crystalline phases and heavy metal content of the post-treatment slags were studied through a combination of XRD, SEM, and heavy metal leaching experiments. The results show that the thermal plasma provides a melting zone temperature of more than 4000K, and the treated slag is mostly an amorphous solid composed of glassy Si-O mesh, which effectively encapsulates heavy metals and reduces their leaching rate. Additional analysis of the migration and transformation of heavy metals during thermal plasma treatment revealed that solid-phase heavy metals primarily took the form of sulphides and sulphates, while liquid- and gas-phase heavy metals were mostly oxides and chlorides. Simultaneously, Economic analysis results showed that the thermal plasma treats SW economically with an Energetic efficiency of up to 76.7%. The results of this study providing new insights into thermal plasma treatment SW research. [Display omitted] •Thermal plasma treatment SW products are cleaner than conventional treatments.•Volatile metals such as Pb and Cd are more likely to migrate to the gas phase.•Non-volatile metals such as Zn and Cu are mostly immobilized in the solid phase.•The leaching rate of heavy metals in SW is negligible after thermal plasma treatment.•Thermal plasma treats SW economically with an Energy efficiency of up to 76.7%.