“…Since the value of 1/n was less than 1, this suggested that the adsorption of 2,4-DCP on the DK3 was a physical process [24]. The values 1/n between 0.605 and 0.607 indicated favourable adsorption and a high affinity of DK3 for 2,4-DCP since the higher value of 1/n corresponded to greater heterogeneity of the adsorbent surface [25] which resulted from 2,4-DCP interactions with surfactant cations on the clay's surface as well as within the clay interlayer space [6,18]. Therefore, both the Freundlich and Langmuir models suggest that the adsorption capacity increased as the temperature fell, demonstrating that adsorption was exothermic [26] and both models as indicated by R 2 values (Table 2) fit the data well.…”