#isotherm

The commercial bentonite shows promise as a sorbent for the removal of hazardous Congo Red (CR) dye from aqueous solutions. The bentonite clay was characterized by XRD and FTIR analyses. The adsorption performance of CR on bentonite is highly influenced by the variation of pH, adsorbent dose, and initial dye concentration. More than 75% color removal was observed in the pH range 2.5-3.5. The optimum pH value for the studied CR-bentonite system was observed to be 3.0±0.1 with a bentonite dose of 2 g L-1 at 20 ± 2 ○C temperature, and an initial dye concentration of 180 mg L-1. The mechanism for the adsorption of anionic CR dye onto oxide surfaces of bentonite involves a surface complexation phenomenon in the adsorption process. Equilibrium data of single-component batch adsorption were modeled using the most popular two-parameter isotherms. The parameter values of each isotherm model were determined from the corresponding linear plot. The maximum Langmuir adsorption capacity was recorded to be Qm = 65 mg g-1 at the set of optimum conditions. In this study, many commonly used error functions were used to estimate the error deviation between theoretically and experimental predicted equilibrium adsorption data. The order of deviation was: Dubinin-Radushkevich (D-R) model > Langmuir model > Temkin model > Harkins-Jura model > Halsey model > Freundlich model, which indicated that the Freundlich isotherm model was the best one in describing the adsorption equilibrium of the recent study case of CR dye on bentonite. The obtained data are useful for industries to design of commercial adsorbers for color removal from aqueous solutions.