A novel functionalized carbon material for efficient thorium (IV) adsorption from strongly acidic solution

A novel type of modified pyrolytic carbon (TOPO@PyC) was successfully prepared through incorporating tri-n-octyl phosphine oxide (TOPO). The adsorption behavior of TOPO@PyC for Th (IV) under strongly acidic conditions was investigated. The TOPO@PyC exhibited rapid Th(IV) adsorption rate with equilibrium time of 40 min. In 0.1–8 mol/l HNO 3 , the Th(IV) adsorption capacity reached between 43 and 50 mg/g. The adsorption kinetics and adsorption process of TOPO@PyC for Th(IV) can be well explained through the pseudo-second-order kinetic and Langmuir isothermal adsorption model. The temperature exhibited only a minor influence on Th(IV) adsorption capacity. The microstructure and adsorption mechanism of TOPO@PyC was characterized and elucidated through various techniques including SEM-EDS, BET, TGA, FT-IR, XPS and DFT calculations. By coordinating with O atom on TOPO, Th(IV) was successfully complexed on TOPO@PyC in a ratio of 1:3. Furthermore, TOPO@PyC manifested good thermal stability and acid resistance. After five times, the Th(IV) adsorption and desorption efficiency of TOPO@PyC still exceeded 95 %. Additionally, TOPO@PyC exhibited stronger selectivity towards Th(IV) from mixed solutions. Remarkably, it recovered over 90 % of thorium and uranium from the leachate of tantalum slag. Consequently, TOPO@PyC holds considerable promise in the treatment of strongly acidic wastewater containing thorium and uranium.