Adsorption of Dibenzothiophene by Vermiculite in Hydrophobic Form, Impregnated with Copper Ions and in Natural Form

The adsorption capacity of vermiculite, a natural clay, for removing dibenzothiphene (DBTP) from water solutions was investigated. DBTP is an organic compound with sulfur, commonly found in fossil fuels and coal. This compound can also be found in the environment due accidental spills of oil and derivatives. Due to its structure and physical-chemical properties it is considered a persistent compound. Vermiculite (VT) was used as an adsorbent in its natural form, impregnated with copper ions (Cu-VT), and hydrophobically modified (HDTMA-VT) by replacement sodium cations by hexadecyltrimethyl ammonium ion. The results showed that DBTP was adsorbed in considerable amounts by HDTMA-VT; however, the Cu-VT adsorbed DBTP in some proportions of HDTMA-VT. Because of the presence of sulfur atoms in the structure of the molecule, pi complexation can be observed. The adsorption isotherms were treated by the Freundlich equation. The values of K (f) are similar to Cu-VT and HDTMA-VT, showing that the adsorption may be either through hydrophobic interactions or interactions through the formation of pi complex. Meanwhile, the results with the VT (natural form) showed a much smaller value of K (f). It is believed, compared with the literature, and because of the chemical composition of the vermiculite, that the adsorption mechanism is also conducted by pi complexation, considering the absence of organic carbon content.