Evaluation of potassium ferrate activated biochar for the simultaneous adsorption of copper and sulfadiazine: Competitive versus synergistic

Combined pollution caused by organic pollutants and heavy metals pose a significant challenge to the adsorption process. In this study, iron-modified biochar (Fe-BC) was prepared by using ferrate (K2FeO4) and wheat stalk as the precursors for the adsorption of copper (Cu2+) and sulfadiazine (SDZ), especially under combined pollution scenarios. Iron modification not only enlarged the surface area but also loaded iron oxide nanoparticles on biochar surface. Accordingly, Fe-BC exhibited better adsorption capability of Cu2+ and SDZ than the pristine biochar (BC). The corresponding maximum adsorption capacities of Fe-BC700 were 46.85 mg g(-1) and 45.43 mg g(-1) towards Cu2+ and SDZ, respectively. Interestingly, the adsorption was elevated in binary-pollutants system, suggesting a synergistic effect, which was probably attributed to the mutual bridging effects and complexation between Cu2+ and SDZ. The loaded iron oxide particles could serve as a physical barrier to separate the adsorptions of Cu2+ and SDZ and thus inhibited the competitive adsorption. Meanwhile, theoretical calculation demonstrated that sulfonamide group was the most probable binding site. Columns packed with Fe-BC700 showed better performances for Cu2+ and SDZ removal in binary system (635.73 BV for Cu2+ and 4846.26 BV for SDZ) than in single systems (571.60 BV for Cu2+ and 3572.06 BV for SDZ), which was consistent with batch adsorption experiments. These results demonstrated the potential application of Fe-BC700 for simultaneous adsorption of Cu2+ and SDZ and provided a cost-effective way for the remediation of organic and inorganic pollutants.

Automated summary

Iron-modified biochar (Fe-BC) prepared in this study showed enhanced adsorption capability for copper and sulfadiazine compared to pristine biochar (BC). The iron modification enlarged the surface area and loaded iron oxide nanoparticles on biochar surface, improving the adsorption efficiency. In the binary-pollutants system, there was a synergistic effect on the adsorption of Cu2+ and SDZ, possibly due to mutual bridging effects and complexation between the two pollutants. Fe-BC700 exhibited better removal efficiency for Cu2+ and SDZ in the binary system compared to single systems.