Sorption of apolar and polar organic contaminants by waste tire rubber and its chars in single- and bi-solute systems

Single- and bi-solute sorption of organic compounds [1,3-dichlorbenzene (DCB), 1,3-dinitrobenzene (DNB) and 2,4-dichlorophenol (DCP)] on ground tire rubber and its chars was studied. The chars were prepared by pyrolyzing tire rubber at different temperatures (200–800 °C). Their surface area, aromaticity and hydrophobicity increase greatly with pyrolytic temperature, and the polymeric phase is partly converted into a condensed phase. The sorption of DNB and DCP increases with pyrolytic temperature and is characterized by a transition from a partition dominant to an adsorption dominant process. However, the sorption of DCB linearly decreases with the pyrolytic temperature. The enhanced adsorption of DNB and DCP on carbonized phase is primarily attributed to nonhydrophobic interactions such as π–π electron-donor–acceptor interactions and/or H bonding. The higher partition of DCB to polymeric phase is attributed to its high hydrophobicity. Competitive sorption between DCB and DCP on the tire chars is highly dependent on dissociation of the latter.

Research highlights
► Tire chars consist of dual sorptive domains, i.e., partition and adsorption.
► High hydrophobicity of apolar organic contaminant promotes its partition into polymeric phase.
► Polar aromatic contaminants show high adsorption on carbonized phase with specific interactions.
► Dissociation of ionzable organic chemical heavily influences its sorption on tire chars.