Adsorptive removal of methyl orange dye from aqueous solution using populous leaves: Insights from kinetics, thermodynamics and computational studies

The present investigation reports an effective adsorption of methyl orange dye using the leaves of populous tree in five different forms. The physicochemical properties of all adsorbents were characterized using instrumental analyses such as Fourier transform infrared spectroscopy (FTIR), powder x-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The feasibility of populous leaves for the adsorptive removal of methyl orange dye from aqueous solution was evaluated in a batch process by varying operational parameters such as adsorbent dosage (0.2-0.6 g), solution pH 3-12, initial dye concentration (5-100 ppm), and con-tact time (10-100 min). The equilibrium data was correlated by both Freundlich and Langmuir isotherms. The maximum Langmuir monolayer adsorptive capacity was found to be 90.44 mg/g at pH 3.0 and 303.15 K with co-efficient of determination R-2 = 0.9988 for L-arginine treated populous charcoal powder. The kinetic study revealed that the system obeyed pseudo -first order kinetic model for all the adsorbents (R-2 > 0.93). The thermodynamic ad-sorption parameters showed that the adsorption process is exothermic. Using quadrate models and optimizing the conditions, the maximum adsorption capacity for all the adsorbents was observed at initial dye concentration (75 ppm), dosage of adsorbents (0.6 g) and pH (5). The computational chemistry was also used to validate the ad-sorption of methyl orange dye.