SYNTHESIS OF COPPER AND NICKEL FERRITES NANOPARTICLES USING NEEM LEAF EXTRACT FOR THE PHOTO REDUCTION OF CHROMIUM (VI)

Abstract

Photoreduction of hexavalent chromium, Cr (VI), identified as carcinogenic, tetragenic and mutagenic element, to Cr (III) believed to be an essential element using copper ferrite and nickel ferrite nanoparticles synthesized using neem leaf extract was investigated under visible light irradiation. The chemical reduction and physical methods of synthesising nanoparticles are hazardous, expensive and produce non eco-friendly by-products. This study was designed to synthesise copper ferrite and nickel ferrite nanoparticles using green approach. Copper and Nickel nanoparticles were synthesized by co-precipitation and co-reduction methods using Neem leaf extract. The synthesized copper ferrite and nickel ferrite nanoparticles were fully characterized using UV-visible spectroscopy, Fourier Transform Infra-red (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX). FTIR analyses showed that –C=N-, N-H (amine). C-O (saturated phenols) were the possible functional groups that were responsible for the reduction and stabilization of the nanoparticles. The photocatalytic activities of the nanoparticles were determined using chromate solution and the reduction efficiencies of the process were evaluated with respect to irradiation time, catalyst load, initial concentration and catalyst re-use, maximium pH was observed under acidic region for the chromium solution with the catalysts. The maximium catalyst values for chromate solution were 1.0, 2.0, 3.0, 4.0 and 5.0 for both copper ferrite and nickel ferrite nanoparticles. Ultra- violet light photoreduction for both copper ferrite and nickel ferrite gave superior photocatalytic reduction efficiencies toward the chromate solution as compared in the dark. The results revealed that the catalysts had a high photocatalytic performance that range between 79.4-94.1% for copper ferrite and 91.3-97.9% for nickel ferrite toward the chromate reduction which showed good photostability and the ability to reuse the CuFe2O4 and NiFe2O4 as photocatalysts was evaluated by four consecutive cycles under the same experimental conditions. The experiment of adding the catalysts to chromate solution which was carried out in the dark showed that adsorption of Cr (VI) was very low as compared to photoreduction under uv-light. Effect of initial concentration of Cr (VI) on catalysts was studied and its revealed that as the concentration of Cr (VI) increases, Cr (VI) reduction efficiency gradually decreases which was attributed to Beer-Lamberts law, the path length of photons entering into reaction mixture decreases with increase in Cr (VI) concentration and a fewer photons reach the catalyst surface . The pseudo- first order equation was revealed to be good agreement with the experimental data with high R2 values. The results also revealed the effect of the presence of inorganic ions (both inorganic anions and cations) affected the photoreduction process