U(VI) removal efficiency and mechanism of biochars derived from sewage sludge at two pyrolysis temperatures

In this study, sewage sludge-derived biochars (SSBs) were prepared at two pyrolysis temperatures of 450 °C (SSB450) and 600 °C (SSB600) for U(VI) removal. The maximum adsorption capacity of SSB450 and SSB600 was 43.13 and 47.47 mg g-1, respectively, at initial pH of 3. While the adsorption process of U(VI) onto the SSBs were accurately described by the pseudo-second-order model and Langmuir isotherm model. Ion exchange and complexation were assumed as the adsorption mechanism. The adsorption–desorption experiment showed that both the U(VI) removal efficiency and SSB regeneration efficiency were greater than 80%. Thus, the SSB has a potential application in U(VI)-containing wastewater treatment.