Agrogenic waste-derived biochar as green functional material for aqueous adsorption of uranium (U6+) radio-pollutant: A review

Uranium is a versatile radioactive element employed in various high-stakes applications including nuclear power generation, nuclear weapons, radiation therapy, geological dating, nuclear submarines and ships, etc. However, the escape of uranium to the environment has become a serious pollution and health concern, especially the pollution of water bodies. Thus, the goal of this study is to review the sequestration of uranium radio-pollutants using agrogenic waste-derived biochar (AWDBC) and empirically discuss key findings. Notably, the adsorption capacity analysis found that various AWDBC has a maximum uranium removal capacity of 4.71 to 1527.02mg/g (with modified AWDBC coming to the fore) and can be reused up to 3-6 cycles with an average adsorption efficiency of 40 - >96% at the nth cycle. Moreover, it was discovered that the best-fit isotherm and kinetic modeling are the Langmuir and pseudo-second-order models with R2 ranging from 0.85-1.0. Thermodynamically, the majority of the adsorption operations are spontaneous processes associated with a disorder upsurge at the solid-liquid interface. Also, from the mechanism standpoint, chemisorption, electrostatic interactions, π-π interactions, ion exchange, and complexation through oxygen-containing functional groups govern the uranium sequestration operation. In the end, areas for future research works were highlighted based on knowledge gaps identified in order to inform future researchers on possible aspects of the research to improve in the field. The findings of this study suggest that uranium in wastewater and industrial runoffs can be eco-successfully removed by green adsorption techniques utilizing agrogenic waste-derived biochar.