Fe–Ni Nanostructures and C/Fe–Ni Composites as Adsorbents for the Removal of a Textile Dye from Aqueous Solution

Abstract

Novel adsorption materials—Fe-Ni nano- structures and C/Fe-Ni composites—with the carbona- ceous material coming from sewage sludge, have been developed and evaluated to remove indigo carmine from aqueous solution. The adsorbents were characterized by transmission and scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and Brunauer- Emmett-Teller analysis. Sorption kinetics and isotherms were determined and the adsorption behaviours ana- lysed. All adsorbents here studied have exhibited good efficiency to remove indigo carmine from aqueous solution. Pseudo-second-order kinetic and Langmuir- Freundlichisothermmodels were successfully appliedto the experimental data. Fe-Ni nanostructures adsorption capacitywas977.18mg/g,followedbyC/Fe-Ni75/25% composite with 654.33 mg/g, and a lowest value, 486.41 mg/g, was obtained for C/Fe-Ni 95/5% compos- ite. It can be suggested that the sorption mechanism of the dye is chemisorption on these heterogeneous novel, cheap and efficient functional materials. All materials provide the highest adsorption capacities in pH between 4 and 10. In addition, three sorption-desorption cycles using 30% H2O2 solution and distilled water were performed; sorption efficiencies of both composites (C/FeNi 75/25% and C/FeNi 95/5%) decreases in each cycle, but this behaviour is not observed for FeNi nanoscale oxides.