Abstract
A fixed bed for the sorption of phenol, m-nitrophenol (m-NP) and o-cresol employing cetyltrimethylammonium bromide (CTAB)-modified montmorillonite, XAD-4 or XAD-8 was examined both from a theoretical and experimental viewpoint. Experiments were performed using different feed flow rates, bed depths and feed sorbate concentrations. A theoretical model containing two parameters, τ and k, was proposed for describing the breakthrough curves. The two XADs and the CTAB–clay system were compared to clarify the characteristics of the adsorption mechanism and application. For the XAD systems, the breakthrough point of phenol increased with increasing bed height at the same feed flow rate. However, the bed height had little effect on the value of k. For the CTAB–clay system, the values of τ for phenol decreased with increasing feed concentration under the conditions studied. In contrast, however, the values of k increased with increasing feed concentration. The adsorption capacity (QM) of the phenolic compounds on the sorbents decreased in the order XAD-8 > XAD-4 > CTAB–clay. Although the surface area of XAD-4 was larger than that of XAD-8, the polarity of XAD-8 was greater than that of XAD-4. The adsorption rate constant k decreased in the order CTAB–clay > XAD-8 > XAD-4 for the same sorbate. For a given sorbent, the value of k decreased in the order phenol > m-NP > o-cresol.