Adsorptive removal of Congo red dye from wastewater by mixed iron oxide–alumina nanocomposites

Nanocomposites composed of mixed iron and aluminium oxide (Fe2O3–Al2O3), have been synthesized by hydrothermal method, and further used as adsorbent for the adsorptive decolorization of Congo red dye from an aqueous system. The as-prepared nanomaterials were sintered at 500 °C and 1000 °C, to obtain pure Fe2O3–Al2O3 mixed composites. The XRD studies confirmed the formation of pure and crystalline FeOOH–AlOOH (as-prepared), γ-Fe2O3–Al2O3 at 500 °C and α-Fe2O3–Al2O3 phases at 1000 °C. The morphology and size of the obtained nanocomposites were characterized by SEM and TEM. Effects of pH, contact time, initial concentration of adsorbate have been studied. The optimum pH for maximum removal of Congo red in all the three phases of nanocomposites was found to be 7. The maximum removal capacity was 498 mg/g for γ-Fe2O3–Al2O3 phases. Among the three different adsorbents, γ-Fe2O3–Al2O3 shows complete removal within 15 min of contact time.