Cationic Basic Yellow 2 (BY2) adsorption onto manure ash: surface properties and adsorption mechanism

Abstract

Adsorption of Basic Yellow 2 (BY2) onto manure ash, a waste substance, was studied in batch and fixed-bed studies. In both systems, experiments were conducted by using the UV–visible spectroscopy and by examining the effect of different parameters. In order to obtain the adsorption mechanism of manure ash, its microstructure information must be studied. Surface area, particle size distribution (PSD), and structure of adsorbent were studied with Fourier transform infrared spectroscopy, transmission electron microscopy, and PSD. The surface measurement such as specific surface area and pore volume was measured and calculated using BET method. Nitrogen sorption measurements were employed to investigate the variation in surface and pores properties before and after dye adsorption. The experimental isotherm data were analyzed using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), Temkin, Harkins–Jura, and Frumkin isotherm equations, but high correlation coefficients (R2) confirmed the validity of Langmuir isotherm, with monolayer adsorption capacity (Q0) equal to 1,666.7 mg/g at 45°C. A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy, and entropy (∆H°, ∆G°, and ∆S°). The thermodynamics of BY2 onto manure ash system indicates spontaneous and endothermic nature of the process. The kinetic models: Lagergren's pseudo-first order, pseudo-second order, intra-particle diffusion, liquid-film diffusion, Bangham and Avrami kinetic models were applied to the experimental data. It was observed that pseudo-second-order kinetic model described the adsorption process better than any other kinetic models. The Adams–Bohart, Thomas, and Yoon–Nelson models were applied to the adsorption under varying experimental conditions to predict the breakthrough curves and to evaluate the model parameters of the fixed-bed column that are useful for process design.