Removal and recovering of anionic and cationic dyes using Neem Leaf ash prepared at 250, 500 and 750 °C: Analyzed by adsorption isotherm and physicochemical parameters

Abstract

Need of sustainable environment to develop the green adsorbent with high efficiency, cheapest for the removal of organic pollutant from waste water. Therefore, herein, we report, the adsorption of cationic and anionic dyes on the surface of ash of dry leaves of Neem (Azadirachta indica) prepared at 250, 500 and 750 °C, a benign attempt towards waste water treatment. The UV/Visible and physicochemical analysis revealed the interaction of organic pollutants with ash of dry leaves in terms of variation in the data. In X-ray diffraction, the lower intensity counts of adsorbent after adsorption than before has inferred the dye adsorption. Cationic dyes have shown impressive adsorption up to 81.25, 71.88 and 62.50% by ash prepared at 250, 500 and 750 °C respectively as CationicMB > CationicCV > AnionicCR > AnionicMO where crystal violet has shown 91.98% adsorption. In support of this, the interaction spontaneity was analysed as Methylene BlueΔG0 > Crystal VioletΔG0 > Congo RedΔG0 > Methyl OrangeΔG0 inferring stronger adsorption with cationic dyes. The adsorption isotherms for solid (ash)-liquid (dye solution) equilibrium inferred the maximum uniform distribution of binding energy, favourability of interaction, interaction capacity and intensity associated with cationic dyes. +ve interaction sites with N atoms having greater capacity to donate lone pair as compared to S and O associated with –ve dyes. The increase in conductance, surface tension and viscosity after interaction as compared to initial dye solution, confirms the adsorption phenomenon explained with Ameta Physicochemical Adsorption Analysis model. The quantitative analysis shows that crystal violet and methylene blue have been adsorbed more than 700 mg per gram of ash. The recovered dyes have been analysed through FTIR and UV/ Visible spectroscopy. The reusability of ANL was found consistently about 81% for MB even after fifth cycle.