Environmental Context. Humic substances can be used during treatment of wastewater, groundwater, leachates, and soil in various environmental engineering technologies, in which these abundant natural macromolecules can substitute for activated carbon and other, more expensive, organic and inorganic adsorbents. Moreover, toxic organic compounds can, once immobilized on the humates, become incorporated into the humate chemical structure and thereby circumvent the need for desorption. However, the complex chemical nature and inhomogeneous physical form of these materials means absorption mechanisms will be complicated and no single mechanism describes the process; in this study metals, organochlorines, and dyes are shown to be absorb differently.

Abstract. Iron humate, produced from low-rank brown coal, can be used as an effective sorbent for substances as different as metal ions and low-polarity organic compounds (chlorophenols). The sorption capacities ranged from 0.024 to 0.324 mmol g^–1 for metal ions and from 0.016 to 0.037 mmol g^–1 for chlorophenols. Evidently, different mechanisms are responsible for the sorption of various chemical pollutants from aqueous solutions. Multimode sorption mechanisms play an important role also in the sorption of ionic compounds such as basic dyes in the presence of oppositely charged surfactants.