Removal of Congo Red by Carbonized Low-Cost Adsorbents: Process Parameter Optimization Using a Taguchi Experimental Design

The Taguchi method was applied as an experimental design to establish the optimum conditions for the removal of congo red (CR) in batch experiments. The chosen experimental factors and their ranges were: pH (2 to 10), temperature [(40 to 60) degrees C], contact time [(5 to 500) min], and concentration of CR [(10 to 500) mg.L(-1)]. The orthogonal array L(25) and "the larger, the better" response were selected to determine optimum removal conditions onto commercial and low-cost adsorbents. The adsorbents were also characterized for their valuable adsorbable properties such as point of zero charge and carbon specific surface area. The influence of the different factors on the adsorption of CR from solution is explained in terms of electrostatic interactions by considering the dye species and the character of the surface. The exhausted low-cost adsorbents along with the sorbed CR can be used as such or as fire briquettes to recover their energy value, and resulting bottom ash may be used to make fire bricks.