Adsorptive removal of beryllium by Fe-modified activated carbon prepared from lotus leaf

Lotus leaf was used as raw material to prepare HNO₃-activated carbon with 1.5:1 (HNO₃:lotus leaf) (wt:wt) impregnation. Then, the activated carbon was modified by Fe(NO₃)₃ to obtain Fe-activated carbon (Fe-AC). The adsorption test results show that Fe-AC maximum saturated adsorption capacity (Q_m) is 45.68 mg/g when the Fe(NO₃)₃ loading is 5% of the total activated carbon, pH = 6, and the temperature is 35 ℃. The adsorption effect of Fe-AC under neutral conditions is better than that under alkaline and acidic conditions. The modified activated carbon has better adsorption selectivity. The obtained material (Fe-AC) was characterized by N₂ adsorption-desorption isotherm, SEM, FT-IR, BET, XRD, XPS, and pH_pzc. The total pore volume, specific surface area, and zero charges of modified activated carbon were increased. The types of modified functional groups were reduced, and the iron reacted with the functional groups, providing ion exchange sites for the adsorption of beryllium. The adsorption thermodynamics showed that the adsorption process was spontaneous and endothermic. The adsorption mechanism of Fe-AC to beryllium is mainly chemical adsorption.