The removal of dye from aqueous solution using alginate-halloysite nanotube beads

The halloysite nanotube (HNT) has already been extensively investigated to remove various organic pollutants and metal ions, and how to prepare the beads with excellent absorbability, stability, and reusability is critical to its practical application. In this study, we prepared a new kind of porous beads by immobilizing halloysite nanotubes with alginate (Alg). The as-prepared product was characterized by scanning electron microscope (SEM). The SEM image shows that hybrid bead is a porous structure comprised of accumulated halloysite nanotubes. Besides, the batch and column adsorption experiments of methylene blue (MB) were applied to evaluate its adsorption performance. In batch adsorption, the influences of pH, contact time and temperature on its adsorption capacity were investigated. The adsorption kinetic and isotherm models were established, and the maximum adsorption capacity of about 250 mg/g at 308 K can be deduced from the model. After 10 successive adsorption–desorption cycles, the removal efficiency of MB could be kept above 90%. Furthermore, the results of column experiments indicate that the removal efficiency could maintain above 90% after 1500 bed volumes of waste-water were treated. The obtained results indicated that the Alg–HNT hybrid beads could be an effective adsorbent in practical application for dye removal.

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► Prepared a new bead absorbent using halloysite nanotube and alginate.
► The maximum adsorption capacity to MB can achieve 250 mg/g.
► The adsorbate still has a high adsorption capacity after10 regeneration cycles.
► Hybrid beads show excellent mechanical strength and stability in the water.