Fixed-Bed Adsorption of an Azo Dye (Methyl Orange) onto Chemically and Thermally Regenerated Activated Carbons

In this study, the effectiveness of the recovery method for spent granular activated carbon (SGAC) for application in dye removal was evaluated. A comparative study of the textural (porosity), compositional, surface functionality, and adsorption performance of chemically (CAR400) and thermally regenerated activated carbons (CAR700 and CAR900) was conducted for the elimination of methyl orange (MO) dye by using a fixed-bed system. The results were compared with those of commercial activated carbon (CA). The influence of parameters such as the initial dye concentration, the flow rate, the internal diameter of the column, and the bed height was evaluated. Adsorption data were modelled by using the Thomas, Adams–Bohart, and Yoon–Nelson equations. The CAR400 activated carbon had a microporosity (1045 mg/g) comparable to that of the reference commercial (CA) activated carbon (1052 mg/g) but exhibited the least adsorption capacity. The breakthrough curves were best described by the Thomas model more than the Bohart–Adams and Yoon–Nelson’s models. Thomas’s model depicted that an increase in column diameter resulted in a decrease in the maximum adsorption capacity (qo). The CAR900 material exhibited the highest adsorption capacity (15.72 mg/g) comparable to that of commercial activated carbon, CA (16.90 mg/g). These results show that the physical/thermal regeneration of spent granular activated carbons (SGAC) is more suitable for the valorization of these waste materials for water purification applications