Bismuth impregnated biochar for efficient uranium removal from solution: Adsorption behavior and interfacial mechanism

In this work, Bi2O3 doped horse manure-derived biochar was obtained by carbonizing the H2O2-modified horse manure loaded with bismuth nitrate under nitrogen atmosphere at 500 °C. The results showed that there was a sharp response between the as-prepared bismuth impregnated biochar and uranium(VI) species in solution, which resulted in a short equilibrium time (<80 min), a fast adsorption rate (about 5.0 mg/(g·min)), a high removal efficiency (93.9%) and a large adsorption capacity (516.5 mg/g) (T = 298 K, pH = 4, Ci = 10 mg/L and m/V = 0.1 g/L). Besides, the removal behavior of the bismuth impregnated biochar for uranium(VI) did not depend on the interfering ions and ion strength, except Al3+, Ca2+, CO32- and PO43-. These results indicated that the modified biochar might possess the potential of remediating the actual uranium(VI)-containing wastewater. Moreover, the interaction mechanism between Bi2O3 doped biochar and uranium(VI) species was further explored. The results demonstrated that the enrichment of uranium(VI) on the surface of the as-prepared biochar was controlled by various factors, such as surface complexation, ion exchange, electrostatic attraction, precipitation and reduction, which facilitated the adsorption of uranium(VI) on the bismuth impregnated biochar.