Facile Synthesis of Silver Bromide-Based Nanomaterials and Their Efficient and Rapid Selective Adsorption Mechanisms Toward Anionic Dyes

A novel adsorbent of AgBr-AgBr/CTAB nano materials, which was synthesized via Tollen's reagent with the aid of hexadecyltrimethy ammonium bromide (CTAB), showed an excellent high affinity to anions and was used for removal of organic dyes in aqueous solutions. The synthesized AgBr-AgBr/CTAB was thoroughly characterized by XRD, SEM, TEM, XPS, FTIR, TGA, DLS as well as zeta potential measurements. The adsorption property and capacity of AgBr-AgBr/CTAB for organic dyes were evaluated using methylene blue (MB), rhodamine B (RhB), acid red 18 (AR-18), orange G (OG), indigo carmine (IC), and methyl orange (MO) as models. The adsorption capacity of AgBr-AgBr/CTAB complex toward four anionic dyes OG, AR-18, IC, and MO solutions was 87.43 +/- 2.03 mg g(-1), 205.89 +/- 2.12 mg g(-1), 140.42 +/- 2.13 mg g(-1), and 104.6 +/- 1.59 mg g(-1), respectively. On the other hand, this adsorbent exhibited little adsorption ability toward two cationic dyes, MB (2.99 +/- 0.40 mg g(-1)) and RhB (2.96 +/- 0.60 mg g(-1)). Interestingly, AgBr-AgBr/CTAB could be applied to efficiently adsorb anionic dyes from binary cationic-anionic dye systems with a high separation factor, and such adsorbent could be reused at least 5 times with adsorption capacities above 95%. The removal of anionic dyes followed pseudo-first-order kinetics and Langmuir isotherm model, indicating that anionic dyes were monolayerly adsorbed on our as-prepared materials. To further elucidate the adsorption mechanism, the theoretical calculation based on first-principles was also provided. The results suggested R-SO3- groups were the active sites and electrostatic attraction was the dominating contribution for the adsorption of anionic dyes.