Cooperative adsorption behaviours of 1-naphthol and 1-naphthylamine onto nonpolar macroreticular adsorbents

In this study, the adsorption behaviours of 1-naphthol, 1-naphthylamine and 1-naphthol/1-naphthylamine mixtures in aqueous solutions on nonpolar macroreticular adsorbents (NDA100 and Amberlite XAD4) were investigated in single or binary batch system at 293, 303 and 313 K, respectively. The results showed that all the adsorption isotherms of 1-naphthol and 1-naphthylamine on both adsorbents in both systems can be well fitted by Langmuir equation, and 1-naphthylamine is adsorbed to a larger extent than 1-naphthol on both adsorbents because of its greater electronic density of the aromatic ring of 1-naphthylamine. Owing to the greater surface area and micropores, NDA100 displays much higher adsorption capacity toward both adsorbates than XAD4. It is noteworthy that at higher equilibrium concentrations, the total uptake amounts of 1-naphthol and 1-naphthylamine in all binary-component systems are remarkably higher than that in single-component systems. The excess was observed on the adsorbent surface at saturation, which is presumably due to the cooperative effect arisen from the hydrogen bonding or weak acid-base interaction between 1-naphthol and 1-naphthylamine. The cooperative coefficients of them on XAD4 are notably larger than those on NDA100 for the more appropriate pore size of XAD4.