Removal of trace concentration Sb(V) in textile wastewater by Mn-doped Fe3O4: The mechanisms of Mn affect adsorption performance

Mn-doped Fe 3 O 4 with different Mn/Fe ratios were synthesized to remove 200 μg/L aqueous Sb(V) in simulated textile wastewater under neutral pH. The synthesized materials were characterized by XRD, XPS, and FTIR to confirm the Mn had been successfully doped into the lattice of Fe 3 O 4 . The optimum ratio of initial Mn/Fe appeared at 1:3, with the actual Mn/Fe ratio of 0.22, which was determined by the acid digest experiment. In contrast to the original Fe 3 O 4 , Mn doping increased the maximum adsorption capacity from 64.66 mg/g to 176.03 mg/g, and the adsorption capacity for 200 μg/L Sb(V) was enhanced from 0.74 mg/g to 1.51 mg/g. Mn affects the adsorption performance of materials through three main methods, decreased the particle size by hampering the crystal growth, which brought increased specific surface area leading to a higher adsorption capacity; reduced the distribution of Fe on the surface of materials, which results in lower adsorption capacity; increased the binding energy of Fe–O bonds, thus reducing the number of hydroxyl groups on the surface of materials, thereby reduce the adsorption capacity of the material. Synthesized Mn-doped Fe 3 O 4 possesses good magnetic separation performance and reusability, thus could be a promising adsorbent to remove trace concentration Sb(V) in aqueous solutions. • Mn was successfully doped into Fe 3 O 4 lattice by a solvothermal method. • Mn doping could increase the maximum adsorption capacity of material by three times. • Mn-doped Fe3O4 behaved well in removing trace concentration Sb(V). • The optimum Mn content for adsorbent was illustrated. • The mechanisms of Mn affect adsorption performance were exhibited.