Removal of toxic hexavalent chromium from aqueous solution by nickel ferrite-polyaniline nanocomposite

Cr(III) and Cr(VI) are toxic metal ions and available in trace amounts in aquatic system. These ions can easily enter into the human body and particularly Cr(VI) can cause serious health problems. As per government regulations, it is necessary that all the industries, before discharging the effluents containing chromium, should reduce the level below the allowable limit. A number of methods have been developed to remove chromium ions particularly Cr(VI) from aqueous solutions. In this paper, we prepared NiFe2O4-PANi nanocomposite and used it for the removal of Cr(VI) from the aqueous solution of K2Cr2O7. The process of adsorption was studied by varying pH of the solution, adsorbent dose, metal ion concentration, and contact time. The adsorption studies were also made using PANi alone as an adsorbent. The results showed that the nanocomposite gave good results. The removal of Cr(VI) was maximum at pH similar to 2.0. The adsorption isotherm was verified on the basis of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. Langmuir adsorption model provided the best fit of the data. It was found that pseudosecond-order equation fitted the kinetic data. The mechanism of adsorption has been discussed and a model is proposed.