Fig. 2. Phenanthrene sorption isotherms: (A) the source humic acid (HA); (B) montmorillonite and montmorillonite–HA complex at a HA to clay ratio of 1 to 5; and (C) kaolinite and kaolinite–HA complex at a HA to clay ratio of 1 to 5. The inserted graphs in (B) and (C) are the isotherms in linear scale of (B) and (C), respectively.