Reswellable alginate/activated carbon/carboxymethyl cellulose hydrogel beads for ibuprofen adsorption from aqueous solutions

In this study, alginate (Alg) composite beads were prepared by blending with activated carbon (AC) to enhance adsorption capacity for ibuprofen and carboxymethyl cellulose (CMC) to create a reswellable hydrogel. The dried Alg/AC/CMC composite beads could be recovered to sizes and morphologies similar to the initial hydrogel states via a simple reswelling process; however, the dried Alg/AC composite beads without CMC could not be recovered to the initial hydrogel state. Following the reswelling process, the dried Alg/AC/CMC beads demonstrated an 86 % recovery (qe = 34.0 mg/g) in the adsorption capacity for ibuprofen compared to the initial hydrogel beads (qe = 39.6). In contrast, the reswelled Alg/AC beads exhibited only 18 % (qe = 8.6) of the initial adsorption capacity (qe = 48.1). We elucidated the effects of the substitution degree of CMC, AC content, and solution pH on the reswelling property and ibuprofen adsorption capacity of the Alg/AC/CMC composite beads. The adsorption kinetics and isotherms of the prepared composite beads in the hydrogel and reswelled states fit the pseudo-second-order and Langmuir models, respectively. Furthermore, the reswelled Alg composite beads exhibited high adsorption capacity (>93 %) after 10 cycles. Taken together, our findings indicate that the Alg/AC/CMC composite beads can be used as adsorbents without a considerable decrease in adsorption performance by reswelling the beads with distilled water after long-term storage in a dry state.