Synthesis and characterisation of alumina-iron oxide mixed nanocomposite for removal of Congo red dye

Synthesis of mixed AlOOH and FeOOH nanocomposite was performed by using ferrous sulphate, aluminium nitrate, sodium hydroxide and ammonia solution as starting materials via hydrothermal method. X-ray diffraction (XRD), scanning electron microscope (SEM) and Elemental detection X-ray analysis (EDAX) were used to characterize the features of the mixed nanocomposite obtained by the hydrothermal synthesis. From X-ray analysis it was observed that the mixed AlOOH and FeOOH nanocomposite obtained were crystalline in nature and the crystallinity increased when the mixed oxy-hydroxide was calcined at 1000⁰ C for 2 hour. The SEM images indicated the formation of irregular shape particles, having diameter in the range of 300-500 nm. The presence of Fe, Al and O elements in the mixed composite were confirmed by the EDAX analysis. The adsorption of Congo red over the mixed nanocomposite was investigated for different parameters and the adsorption capacities were evaluated using the Langmuir and Freundlich isotherm models. The mixed oxide nanocomposite prepared by sintering the mixed oxy-hydroxide (AlOOH-FeOOH) at 5000 C showed a very high adsorption capacity of Congo red and thus these nanocomposites can be used as good adsorbents and can be used for the removal of the dye Congo red from the waste water system. The sorption of congo red dye onto the mixed nanocomposite surface follows pseudo-second order kinetics and better fitted to Freundlich isotherm model