Removal of As(V) from aqueous solution using modified Fe ₃ O ₄ nanoparticles

The removal of arsenic contamination from the aqueous environment is of great importance in the conservation of the Earth's water resources, and surfactants are a promising material used to modify magnetic nanoparticles to improve adsorption properties. Therefore, it is important to develop efficient and selective adsorbents for arsenic. Surface modification of Fe 3 O 4 was carried out using anionic, cationic and zwitterionic surfactants to obtain composite Fe 3 O 4 @SDS, Fe 3 O 4 @CTAB, Fe 3 O 4 @SNC 16 and Fe 3 O 4 @NPC 16 (collectively referred to as Fe 3 O 4 @surfactants). The synthesized composite Fe 3 O 4 @surfactants magnetic nanoparticles were characterized by XRD, TEM and FTIR. The As(V) removal characteristics of the composite magnetic nanoparticles from the aqueous solution were evaluated by adsorption batch experiments which indicated the possibility of effective application of the surfactant-modified Fe 3 O 4 magnetic nanoparticles for the removal of As(V) from aqueous solution. The adsorption equilibrium of the composites was reached in 30 min and the kinetic data followed the pseudo-second-order model. Langmuir equation could represent the adsorption isotherm data very well. Moreover, under the identical conditions, Fe 3 O 4 @CTAB showed maximum capacity of adsorption for As(V) (55.671 mg g −1 ), with its removal efficiency being much higher than that of the other composites. In addition, the Fe 3 O 4 @surfactants composite magnetic nanoparticles retained 93.5% of its initial arsenic removal efficiency even after re-using it five times. The mechanism of arsenic adsorption by Fe 3 O 4 @surfactants composite magnetic nanoparticles was proved to be complexation via electrostatic attraction, which was mainly innersphere in nature.