A comparative adsorption study of β-naphthol on four polymeric adsorbents from aqueous solutions

Adsorptive removal of aromatic compounds from aqueous solutions by polymeric adsorbents has attracted many concerns in recent years. A comparative adsorption study including equilibria, kinetics and column dynamics of β-naphthol from aqueous solutions was carried out using two hypercrosslinked polymeric adsorbents (HJ-1 and TEPA) we developed and two commercial polymeric adsorbents (XAD-4 and XAD-7). The adsorption isotherms could be well described by the Freundlich equation, and the adsorption equilibrium capacities of β-naphthol followed an order of qe(TEPA) > qe(HJ-1) > qe(XAD-4) > qe(XAD-7). The isosteric adsorption enthalpies on HJ-1 and TEPA decreased with increasing adsorption fractional loading, while a constant enthalpy was observed for XAD-4 and XAD-7, implying that HJ-1 and TEPA had a heterogeneous surface while XAD-4 and XAD-7 possessed a homogenous surface. The surface energetic heterogeneity of HJ-1 and TEPA could be well characterized by the Do’s model. The adsorption kinetics were fitted by both pseudo-first-order and pseudo-second-order rate equations, and the intra-particle diffusion was found to be the rate-limiting step. The adsorption breakthrough data were well correlated by the Thomas and Clark models, and the dynamic capacities for TEPA, HJ-1, XAD-4 and XAD-7 adsorbents were calculated to be 341.7, 321.6, 268.0 and 173.8 mg/g dry resin, which were within 90% of the corresponding equilibrium capacities obtained in the batch experiments.

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► Higher β-naphthol adsorption capacities than commercial XAD-4 and XAD-7.
► Different phenomena of isosteric adsorption enthalpies on different adsorbents.
► Adsorbent surface energetic heterogeneity characterized with the Do’s model.
► Breakthrough curves fitted well by the Thomas and Clark models.
► Good agreement between dynamic and equilibrium capacities.