A new adsorbent of amidoxime functionalized porous corn stalk carbon and its adsorption properties for U(VI) from seawater

In this research, the polydopamine coating method and acrylonitrile addition grafting method were used to obtain corn stalk carbon modified by –C≡N (CSC@CN). Next, the amidoxime-modified corn stalk carbon was synthesized using a hydroxylamine hydrochloride electrophilic addition method. This modified carbon material was used as an adsorption material of uranyl ions. A series of experimental results showed that at a temperature of 298 K, the solid-liquid ratio is 0.4 g/L, the initial concentration of uranium solution is 150 ppm with pH = 6, and the adsorption time is 420 min, achieving the maximum adsorption capacity of uranium of 230.58 mg/g. The kinetic study of the adsorption process showed that it conformed to the quasi-second-order kinetic model, which belonged to chemisorption, and the Langmuir model, which belonged to monolayer adsorption. Thermodynamic studies showed that the standard enthalpy change \(\Delta {\text{H}}^{0} \; < \;0\) $\mathrm{\Delta }{\text{H}}^0<0$ , indicating that the adsorption process was endothermic. The standard Gibbs free energy change \(\Delta {\text{G}}^{0} \; < \;0\) $\mathrm{\Delta }{\text{G}}^0<0$ , indicating that the adsorption reaction was spontaneous. Furthermore, entropy \(\Delta {\text{S}}^{0} > 0\) $\mathrm{\Delta }{\text{S}}^0>0$ , suggesting an increase in confusion at the solid-liquid interface during the adsorption process.