Efficient separation of phenol from oil by acid-base complexing adsorption

Separation of phenolic compounds from coal tar oil has good commercial value. In this paper, we tried to use the H-bonding or Lewis acid-base interaction to chemically adsorb phenolic compounds that were both Brønsted acid and Lewis base. Hexamethylenetetramine (HMT), 1,2,4-triazole, and AlCl3 were selected as sorbents, and their adsorptive behavior were studied experimentally and theoretically. These sorbents can adsorb phenol from n-hexane oil. HMT showed the amazing phenol adsorbance (Qe,max > 3500 mg/g), non-corrosiveness, stable physical state, good recycling, and oil-insoluble merit. In contrast, AlCl3 was unrecoverable and triazole was partially oil-soluble, and thus they were not as good as HMT. Further, naphthalene or benzothiophene hardly hinders phenol adsorption on HMT (Qe,max > 3400 mg/g in 5 wt% benzothiophene or naphthalene oil); whereas, quinoline interfered with the adsorption (Qe,max > 970 mg/g in 5 wt% quinoline oil). Therefore, HMT might be an excellent sorbent for phenol, showing the best capacity heretofore.