Solvent-induced facile synthesis of MnFe2O4 and the As(V) removal mechanism study

MnFe2O4 has good biocompatibility and is widely used in various fields, including the environmental remediation. In this study, three kinds of MnFe2O4 were prepared conveniently via a solvent-regulated strategy, of which deionized water (H2O), ethylene glycol (EG) and methyl alcohol (MA) were used as the induction solvents. The synthesized adsorbents were explored their property differences. The pollutant removal capacity and associated mechanisms were evaluated by using As (V) as the target species. Although MnFe2O4-MA has the largest size, the specific surface area (145.57 m2/g) was the highest due to the hollow structure of it. Langmuir model proved that the maximum theoretical adsorption amounts of As(V) for MnFe2O4-H2O, MnFe2O4-EG and MnFe2O4-MA were calculated to be 15.80, 23.72 and 34.24 mg g−1. The adsorbents all conformed to the pseudo-second-order kinetics model. The results of thermodynamic experiments implied that the adsorption of As(V) by adsorbents were endothermic, but only the reaction of MnFe2O4-MA was spontaneous. According to FTIR and XPS results, the dominant mechanisms of As(V) removal included ion exchange and complexation with hydroxyl groups of MnFe2O4. The greater As(V) removal capacity by MnFe2O4-MA was ascribed to more abundance of hydroxyl functional groups and higher specific surface area. This also implied that the MnFe2O4 rich in hydroxyl groups and with lager specific surface area was successfully prepared. Therefore, this study may provide a preferable basis for selecting a solvent for MnFe2O4 synthesis.