Competitive removal of ternary dyes mixture from aqueous media: equilibrium, kinetic, isotherm, thermodynamic and DFT studies

The removal of a ternary mixture of cationic dyes, Basic Blue 41 (BB41), Safranin (SAF), and Basic Yellow 28 (BY28) onto Bombax buonopozense bark as a new eco-friendly adsorbent was studied experimentally and theoretically in single as in ternary system, to explore the removal efficiency of the complex mixture and the increase in the number of species in wastewater subject of removal efficiency. Several parameters like pH, adsorbent amount, and concentration effect are studied experimentally to investigate the variation of the removal efficiency of dyes in single and ternary systems. The tested adsorbent was characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and dispersive X-ray spectroscopy (EDX). Basic Blue 41 and Safranin shows a little decrease in removal efficiency between single and ternary system contrary to Basic Yellow 28, and the removal efficiency decreases from 79 to 34%, due to the competition of dyes on the active sites. The problem of interference between spectra of dyes is solved using derivative spectrometry. The adsorption of the three dyes in a single and ternary system follows the pseudo-second-order model, and Langmuir is the best model to describe the adsorption process in both systems. The theoretical study of adsorption of the ternary mixture of cationic dyes onto Bombax buonopozense adsorbent with a negatively charged surface shows that BB41 dye is more electrophilic than Safranin, and they are more electrophilic than BY28. The electrophilic power of the dye has a direct influence on the removal efficiency in the ternary system. The theoretical results are in good accordance with the experimental data reported.