Beyond the saturation adsorbent dosage (for example, from Fig. 7, for initial dye concentration of 25 mg/L, the saturation dosage was 0.5 g/L), the decrease in the removal rate (hence in adsorption capacity) with further increases in adsorbent dosages from 0.5 to 1.0 g/L could be well attributed to the adsorption competition among adsorbent and the split in the concentration gradient as already proposed by Kumar et al.