Arsenic removal from aqueous solutions with Fe-hydrotalcite supported magnetite nanoparticle

The sorptive removal of arsenic from water by synthetically-prepared magnetic Fe-hydrotalcite (M-FeHT) seeding by nano magnetite was investigated. The synthesis of M-FeHT was achieved by a co-precipitation method. M-FeHT was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetic susceptibility analysis. Batch tests were conducted to investigate the removal mechanism of As(III) and As(V) by M-FeHT. Kinetic studies revealed that uptake of As(V) (95% removal) and As(III) ions occurs rapidly within the first 15 min, and slows thereafter. The adsorption data follow a pseudo-second-order kinetic model and fit the Langmuir isotherm well. The experimental results show that stable arsenic removal efficiency, and the capability to reduce As levels, make M-FeHT a suitable adsorbent for the treatment of As-polluted waters. After adsorption, tests were conducted with magnetic separation to determine the separability of M-FeHT from solution. At magnetic field intensity of 2 T, the efficiency of M-FeHT separation was 91%. Finally, after adsorption by M-FeHT, residual arsenic concentration decreased to less than 10 μg/L (i.e., below the threshold specified by the WHO). Fe-hydrotalcite-supported magnetite nanoparticles were not only more efficient in the removal of As but also in recovery by the magnetic separator.