Preparation of magnetic alginate–layered double hydroxide composite adsorbents and removal of Cr(VI) from aqueous solution

Abstract

The aim of this study was to investigate the removal of Cr(VI) from aqueous solution using magnetic alginate–layered double hydroxide (LDH) composites. Magnetic iron oxide and calcined Mg-Al LDH powders were synthesized in the laboratory. The magnetic composites were prepared through immobilization of synthetic magnetic iron oxide and calcined Mg-Al LDH powders into an alginate matrix. The magnetic composites had a particle size of 1.5 ± 0.1 mm and showed magnetic properties under an external magnetic field. Results demonstrated that the magnetic composites were effective in the removal of Cr(VI). In the magnetic composites, calcined Mg-Al LDH played a major role in the sorption of Cr(VI), whereas magnetic iron oxide provided the magnetic property along with a minor role in Cr(VI) sorption. Kinetic tests showed that Cr(VI) sorption to the magnetic composites reached equilibrium at 24 h. The maximum Cr(VI) removal capacity was 11.15 mg/g. Results also indicated that Cr(VI) removal was not sensitive to solution pH between 4.1 and 9.5. This study demonstrated the potential applications of magnetic alginate–LDH composites for chromate removal from aqueous solution in combination with magnetic separation.