Facile synthesis of Fe and N co-coped biochar from low temperature pyrolysis of lignin waste for superefficient Th(IV)/U(VI) separation: Performance and mechanism

This study synthesized a nitrogen and iron co-doped biochar (Fe-N/BC) through a facile process of direct py-rolysis from lignin waste at a low temperature. The introduction of Fe and N can not only promote physical properties such as compact pores, high surface area, stable crystal, and magnetically recyclable ability, but also greatly enhance the electron transfer capacity of biochar surface through introducing electrophilic groups, for instance, C-N, pyrrolic N, C--O, Fe3+, and C-C--O. Moreover, 74.0 mg/g of U(VI) and 360.3 mg/g of Th(IV) was adsorbed by the optimal Fe-N/BC-200, and a high separation index (171147) was obtained. Fe-N/BC out-performs most of biochars from the point of adsorption capacity and cost consumption. Hence, this study reports an economically advantageous method for synthesizing Fe and N co-coped biochar with excellent separation capacity for U(VI)/Th(IV), making it a competitive alternate for other Fe and N co-coped biochar on industrial-scale.