Removal of nigrosine by MgO nanoparticles, green synthesized using Madhuca longifolia flower extract

Green synthesis methods, nowadays, are being looked upon as a potential alternative to the already prevalent chemical and physical methods of synthesis of nanoparticles. In this present study, magnesium oxide (MgO) nanoparticles were synthesized from the flower extract of Madhuca longifolia by using microwave as a heating source. Morphological and compositional study was done using scanning electron microscopy along with energy-dispersive X-ray analysis (EDX). The functional group analysis was done by Fourier transform infrared spectroscopy. The synthesized magnesium oxide nanoparticles were used for the removal of nigrosine dye, and the removal took place in the presence of Ultra-Violet light (photocatalysis), exhibiting appreciable photocatalytic activity. The process of dye removal was optimized using Taguchi, and it was found that dye concentration was the major factor in the removal process. An experimental dye removal efficiency of 86% was obtained through the process. Further, experiments on adsorption kinetics and adsorption isotherms were done, and it was found that the process followed intra-particle diffusion rate kinetics and Freundlich’s adsorption isotherm model (indicating multilayer adsorption). The effect of temperature on the process of adsorption was also studied, and it was observed that higher temperatures facilitated better adsorption rates. Maximum adsorption took place at 60 °C, but the percentage removal at 60 °C was only 2 % higher, as compared to that at 45 °C. So, the dye removal process was carried out at 45 °C, taking into consideration the economics of the process. This was the first instance when magnesium oxide nanoparticles were synthesized from the flower extract of Madhuca longifolia and used as an adsorbent for the removal of nigrosine dye.