Experimental study on the removal of Congo Red by adsorption using waste foundry sand

Abstract

This work aimed to explore the potential of using waste foundry sand (WFS) as an adsorbent for the removal of Congo Red (CR) dye from aqueous solutions. As a low-cost, sustainable adsorbent. The adsorbent was characterized by X-Ray Diffractometer and Fourier Transformer Infrared Spectroscopy (FTIR) techniques, Boehm titration, and pHPZC. The Box Behnken design (BBD) of experiments was applied to determine the influence of initial concentration (A), mass of adsorbent (B), and pH (C) for the CR dye elimination from the aqueous system. The significant interaction between the factors is BC with p-value < 0.05. The adsorption process followed pseudo-second-order kinetic model. The equilibrium data were fitted to Langmuir, Freundlich and Temkin isotherms. Based on R2 , the equilibrium adsorption data was better fitted to Langmuir isotherm model than any other model. The adsorption reached equilibrium after 60 min and the maximum adsorption capacity was about 36.16 mg/g at 20°C according to the Langmuir model. The results indicated that the removal efficiency of 20 mg/L CR reached approximately 90.49% and the adsorption yield is 62.34%. Thermodynamic parameters of the adsorption (∆H°, ∆S° and ∆G°) were also determined and it was found that the adsorption of Congo Red by WFS was a spontaneous process and endothermic.