Removal of 2‐naphthoxyacetic acid from aqueous solution using quaternized chitosan beads

Abstract

The present study investigates the use of quaternized chitosan hydrogels for the adsorption of an aromatic organic carboxylate, 2‐naphthoxyacetic acid (2‐NAA), to demonstrate the applicability of this type of adsorbent towards the removal of naphthenic acids (NAs) from oil sands process‐affected water (OSPW). The effects of varying three processing parameters on the physical and adsorption characteristics of the resulting adsorbents were investigated, namely the density, degree of cross‐linking, and degree of quaternization of the hydrogel beads. Their effects on the swelling behaviour and Langmuir adsorption capacity of 2‐NAA were reported. The Langmuir adsorption isotherm provided adequate fit for the equilibrium adsorption data (R2 ≥ 0.99), while the pseudo second order rate equation described the kinetic adsorption data quite well (R2 ≥ 0.95). The effects of adsorbate concentration, adsorbent dosage, agitation rate, ionic strength, pH, and temperature on the adsorption process were also studied. At the initial concentration of approximately 200 mg/L, up to 91 % of 2‐NAA was adsorbed. The best quaternized chitosan hydrogel adsorbents reported in this study possessed a maximum adsorption capacity of 315 mg/g.