Synthesis and Characterization of Zinc Oxide and Copper Doped Zinc Oxide Nanoparticles Using Orange Peel (Citrus-sinensis) Extract for Removal of Lead Ion from Waste Water

Abstract

The aim of this study was to synthesize pure and Cu doped ZnO Nanoparticles by using orange fruits peel (Citrus – sinensis) extract and metal precursor with solution combustion synthesis method and then to explore the capability of NPs as adsorbent for Pb2+ ion eradication from aqueous media by batch adsorption method. To confirm the synthesis all of the NPs were characterized using X-ray diffraction (XRD) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Ultraviolet- Diffuse reflectance (UV- DRs) spectroscopy, and Photoluminescence (PL). The XRD result revealed that the phase structure of ZnO was wurtizite with crystallite size of 11.78, 11.61, 15.38, 20.43 and 27.78 nm for pure, 2%, 5%, 10% and 15% Cu doped ZnO NPs, respectively. UV-vis DRs confirmed band gap energy of synthesized NPs was found to be 3.24 and 3.16 eV for both pure and 15% Cu doped ZnO NPs from direct transitions, respectively. Adsorption potential of the synthesized NPs, towards Pb2+ , was also investigated. The influence of important factors affecting the adsorption process was determined, including the pH value(2 – 11), contact time(10 – 110 minute), nano adsorbent dose(0.025 g – 0.16 g) and the initial metal ion concentration(1 mg/L – 60 mg/L) to optimize the conditions. The concentration of Pb2+ ion was measured on ICP-OES at recommended wave length 220 nm. The Removal efficiency for waste water concentration (1.34 mg/L) of pb2+ ion solution was 83.9 % and 88.8 % for the pure and 2 % copper doped ZnO NPs. The adsorption reaction rate was examined by comparing Pseudo first order and Pseudo second order templates. From the observed result the adsorption reaction of Pb2+ ion on the NPs was fitted Pseudo second order template. Freundlich and Langmuir isotherm models were used to evaluate the sorption of Pb2+ ion on to the sorbent. Based on the models fitting value the preferential isotherm value for Pb2+ ion adsorption on ZnO-NPs was the Freundlich model signifying chemisorption. ZnO-NPs have the potential to be used as an effective and promising adsorbent material for eliminating metal ions from water solutions.