Green Synthesis of Zinc Oxide Nanoparticles and Study of Its Adsorptive Property in Azo Dye Removal

Abstract

AbstractDyes are important colouring chemical compounds widely used in textile, paper, food, cosmetics and pharmaceutical industries. Most of the dyes are highly toxic and potentially carcinogenic. Exposure to high doses of these compounds can have severe effects in the human body. When untreated dye effluents are directly discharged into water bodies it leads to water contamination. Adsorption is an efficient method for the dye removal. It is also an economical technique. Green synthesis helps in the production of cost-effective and ecofriendly adsorbent. In this paper, green-synthesized zinc oxide nanoparticles were widely used for the removal of azo dye; methyl orange. Zinc oxide nanoparticles (ZnO NPs) were synthesized using Plectranthus Amboinicus leaf extract. The structure of nanoparticles was visualized using Field Emission Scanning Electron Microscope (FESEM). Nanoparticles due to their small size and thus large specific area are strong adsorbents. The effect of various parameters like dye dosage, zinc oxide nanoparticle loading, pH and contact time was evaluated. In batch adsorption study, maximum removal efficiency of 85.41% was obtained with zinc oxide nanoparticle dosage of 3 g initial dye concentration of 10 mg/l, pH 6 and contact time of 3 h. Adsorption parameters fitted well in the Langmuir isotherm model with a correlation coefficient (R2) of 0.975. Adsorption kinetic studies revealed that adsorption strongly followed pseudo-second order. This paper suggests a safe, economical and environment-friendly technique for the removal of azo dyes. KeywordsAzo dyeMethyl orangeZinc oxide nanoparticlesAdsorption