Novel organic/inorganic hybrids composed of halloysite nanotubes (HNTs) and a cationic polymer were prepared through a simple mixing method. The hybrids provide more gaps for water permeation than the pristine HNTs when used as column adsorbents, and quick dye removal from polluted water was achieved.Dyes are widely used in industrial products including paper, textile, printing, plastic, etc. However, because of their complex substituted aromatic groups, most dyes show great resistance to the decomposition by chemical, physical, and biological treatments. Furthermore, their degradation may generate other undesirable toxic and carcinogenic products. 13 Adsorption has been applied as an efficient and economical approach for dye removal from wastewater.4,5 Many low-cost naturally occurring mesoporous adsorbents have been widely investigated for water purification, such as zeolites, kaolinite, and montmorillonite. However, none of them show high adsorption capacity for both positive and negative dyes. 611 Recently, halloysite nanotube (HNT) nanoclay materials have attracted great interest in academia and industry due to their hollow tubular structure, high surface area, and the asymmetric chemical structures of the inner and outer surfaces. HNTs have wrapped layer morphologies with negatively charged SiOH on the external surface and positively charged AlOH on the inner surface, which enable the HNTs to adsorb both positive and negative pollutants.
1215Although HNTs show significant adsorption capacity for various dyes, they cannot be directly used for dye removal from aqueous solution, because HNTs form a stable colloidal suspension in water, making their separation from water very difficult. Besides, compacted HNTs do not supply enough pathways for water permeation during column filtration. Recently, HNT/polymer (alginate, chitosan) hybrid beads have been applied to solve these problems for dye removal applications. However, the preparation procedures are complicated and post-treatment is necessary. 16,17 In order to overcome the drawbacks of HNTs mentioned above, we designed a novel HNT/polyelectrolyte hybrid adsorbent, which is prepared by simple mixing of pristine HNTs and a cationic synthetic copolymer of poly(acrylamide-codiallyldimethylammonium chloride) [P(AAm-co-DADMAC)]. The effects of adsorbent dose, temperature, initial concentration, and contact time on the adsorption of cationic dye Basic Blue 7 (BB7) from aqueous solution were investigated. The equilibrium isotherms, kinetics data, and thermodynamic parameters were calculated to understand the adsorption mechanism of BB7 onto the hybrids.HNTs were purchased from Sigma-Aldrich and dried at 150°C for 3 days under vacuum before use. HNTs have diameters of 3070 nm with lengths of 200 nm to 2¯m. P(AAm-co-DADMAC) (acrylamide composition: 55 wt %) 10 wt % aqueous solution was purchased from Sigma-Aldrich and used as received (Figure 1a). 3 g of HNTs were dispersed in deionized water (20 mL) by sonication for 15 min. Subsequently, 7.9 mg mL ¹1 P(AAm-co-DADMA...
