Modeling of adsorptive removal of benzalkonium chloride from water with a polymeric adsorbent

Abstract

Adsorptive removal of cationic surfactants from water by using a hydrophobic polymer adsorbent was investigated. Equilibrium and kinetics of benzalkonium chloride (BKC) adsorption on Amberlite XAD-16 were studied in a batch adsorber. Because commercial BKC products are mixtures of C 12 and C 14 homologues, these data were measured for each homologue. The adsorption isotherms were correlated with the competitive Langmuir model, and intraparticle mass transfer kinetics with a Fickian pore diffusion model assuming local equilibrium in the pores. Fixed-bed adsorption experiments were used to determine the dynamic loading capacity of the adsorbent. The saturation capacity was found to be large (200 BV), but the effective capacity was smaller (80 BV) due to high mass transfer resistance. It was shown that regeneration of the loaded adsorbent can be intensified by using an organic co-solvent (ethanol). With 50 wt% ethanol in the desorbent, the regeneration of the column was completed a hundred times faster than with pure water. A mathematical model was derived to describe the influence of ethanol on the adsorption of the BKC homologues. When applied in the column simulation, the proposed model yielded a very good prediction of column performance over a wide range of desorbent concentrations. Process performance aspects, such as the influence of the desired surfactant removal percentage on productivity, were discussed on the basis of simulation results.