Highly efficient uranium (VI) capture by magnesium oxide loaded lotus seedpod-derived biochar via a hydrothermal and pyrolytic coupling process

Pollution from uranium(VI)-containing wastewater is a non-negligible part during the use of nuclear energy and becomes the urgent problem to be solved. This work coupled hydrothermal and pyrolytic process to prepare magnesium oxide loaded lotus seedpods-derived biochar (MgO-HBC) for U(VI) adsorption in aqueous solution. The coupling process significantly enhanced the surface area, thermal stability and active sites of biochar. Batch adsorption experiments showed that MgO-HBC had the characteristics of fast adsorption rate (within 30 min), high U(VI) adsorption capacity (906.5 mg∙g −1 ) and susceptibility to solution pH and temperature. The fittings of the pseudo-second-order and Langmuir model revealed a chemical adsorption process with homogeneous monolayer. Thermodynamics analysis demonstrated the spontaneity, endothermicity and randomness of adsorption process . Adsorption mechanism proved that U(VI) adsorption by MgO-HBC was through the complexation between uranyl and its hydrolysates of Mg-O. The work provided a new synthesis strategy of MgO-HBC for U(VI) pollution cleanup.