Multifunctional humate-based magnetic sorbent: Preparation, properties and sorption of Cu (II), phosphates and selected pesticides

The magnetic sorbents with various contents of humic acids (ca. 6.6-15.5%) were prepared by a simple co-precipitation procedure from Fe2+/Fe3+ salts and a commercially available alkaline humate concentrate. The sorbents were able to remove heavy metal cations (Cu2+) from waters with the sorption capacity ranging from 0.006 to 0.25 mmol/g in dependence on the content of humic acids. An ability to remove some organic compounds (triazine and organophosphate pesticides) was also demonstrated. In both cases, the presence of humic acids in the sorbents plays a crucial role in the sorption process - whereas the sorption of metal cations was attributed to the presence of acidic functional groups, the sorption of (less polar) organic compounds was attributed to the presence of glassy-state polymeric domains in the iron-humate matrix. The iron-humate sorbents were effective also in the removal of inorganic phosphorus (phosphate anions) from water. In this case, however, the removal efficiency decreased with increasing content of humic acids in the sorbent. Although the saturation magnetization decreased proportionally with increasing content of humic acids, it remained still sufficiently high for all the examined sorbents to facilitate their effective separation in magnetic field.