Cheap metallic iron source for hexavalent chromium removal

This work presents investigations on recovery and activation of a water treatment residue, for further reuse in another water treatment process. Bentonite, an inexpensive and readily available natural material, was used for the removal of Fe(II) from synthetic acid mine drainage (AMD). Then, iron-contaminated bentonite was recovered and treated with NaBH4 to reduce the adsorbed Fe(II) to Fe(0). Subsequently, the activated bentonite was reused for the treatment of Cr(VI) contaminated solutions. Our results clearly indicated that residues generated during treatment of AMD with bentonite can be used as cheap precursor for production a Fe(0)-based reagent with good Cr(VI) removal potential.