Batch experimental studies on Acid Blue 25 dye removal by synthesized chitosan containing sodium alginate and halloysite nanotubes
Ali Farzaneh, Mohammadreza Babazadeh, Ali Ehsani, Hossein Ganjidoust, Mojtaba Hadi
Abstract
An eco-friendly composite material was developed as a cost-effective and efficient adsorbent for removing Acid Blue 25 (AB25) dye from aqueous solutions. Despite extensive research on dye adsorbents, there remains a need for sustainable and high-performance materials. While chitosan and sodium alginate have shown promise individually, their composite with halloysite nanotubes (HNTs) is less explored. In this study, chitosan/sodium alginate (CSA) and chitosan/sodium alginate/halloysite nanotube (CSAH) composites were synthesized and evaluated for AB25 removal under varying conditions, including pH (3-11), contact time (2-120 min), initial dye concentrations (20-600 mg/L), and HNT content (5-30%). Characterization of the adsorbents was carried out using BET, zeta potential, FESEM, FTIR, EDX, and XRD analyses. CSAH adsorbents were prepared by incorporating different HNT ratios (5-30%) into CSA. At pH 3, CSA achieved 80% dye removal after 70 min, while CSAH with 10% HNT content (CSAH10) showed the best performance, removing 94% of dye within 30 min. Adsorption isotherms (Langmuir, Freundlich, Temkin, Redlich-Peterson, Toth) revealed that the Toth model best described the equilibrium behaviour. According to the Langmuir model, the maximum adsorption capacity of CSAH10 was 351 mg/g. Kinetic studies, including pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models, indicated that the adsorption process followed the pseudo-second-order model for both CSA and CSAH adsorbents. Regeneration tests showed a gradual decline in efficiency, with CSAH10 maintaining 58% removal after five cycles, down from 91% initially. Overall, the CSAH10 composite exhibited strong potential for practical AB25 dye removal, combining high efficiency, low cost, and relatively good reusability.