Improved Adsorption Performance of α-Fe₂O₃ Modified with Carbon Spheres for Cr(VI) Removal from Aqueous Solution

Carbons spheres, easily fabricated by glucose hydrolysis, were integrated with α-Fe2O3 for removing heavy metal from contaminated water. The α-Fe2O3 particles were anchored on the surface of carbon spheres and the combination of two components provided more rough surface area, enhancing the adsorption performance of α-Fe2O3. The removal efficiency of Cr(VI) on α-Fe2O3/carbon spheres was 88% in 240 min, which was 1.93 times higher than that of pristine α-Fe2O3. The investigation on adsorption kinetics and isotherm showed that the pseudo-first-order kinetic and Langmuir isotherm models could well fit the experimental data. The adsorption rate was mainly controlled by both exterior and interior surface diffusion steps. Adsorption thermodynamics investigation proved that the Cr(VI) adsorption on α-Fe2O3/carbon spheres was an endothermic (93.32 kJ · mol-1) and spontaneous (-3.96 kJ · mol-1) physical process. The adsorption capacity was 18.7 mg · g-1 and after recycling five times, the decline of adsorption capacity of α-Fe2O3/carbon spheres was 7.8%, which indicated that the adsorbents could be recycled in the removal of Cr(VI). It indicated that the hybridization with carbon spheres could enhance the adsorption performance of α-Fe2O3, which might be used as convenient adsorbent to remove heavy metal in industry.