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 degrees 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, C-i = 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.

Automated summary

The Bi2O3 doped horse manure-derived biochar exhibited efficient removal of uranium(VI) from wastewater, with short equilibrium time, fast adsorption rate, and high adsorption capacity. The removal behavior of uranium(VI) by the biochar was not affected by interfering ions and ion strength, except for a few specific ions. The enrichment of uranium(VI) on the surface of the biochar was controlled by multiple factors.