Main content area

Adsorption of reactive yellow X-RG and reactive brilliant red X-3B onto cucurbit[8]uril and cucurbit[6]uril: Effect factors, adsorption behavior and mechanism study

Li, Xiaolei, Xie, Xiaomei, Luo, Hanhan, Li, Lan, Li, Zhuang, Xue, Zhiyong, Li, Wei
Journal of colloid and interface science 2017 v.498 pp. 31-46
Fourier transform infrared spectroscopy, absorbents, adsorbents, adsorption, aqueous solutions, dyes, electrostatic interactions, metal ions, models, pH, sorption isotherms, temperature, thermodynamics, thermogravimetry, ultraviolet-visible spectroscopy, zeta potential
Cucurbit[8]uril (CB[8]) and cucurbit[6]uril (CB[6]) were applied as a high efficiency absorbent to remove reactive yellow X-RG and reactive brilliant red X-3B dyes in aqueous solution. Factors affecting adsorption such as dosage, contact time, temperature, pH value and metal cation were investigated. The adsorption isotherms for X-RG followed the Langmuir and Sips model while for X-3B followed the Freundlich model. Adsorption thermodynamic showed that X-RG and X-3B adsorption onto CB[8] and CB[6] was a spontaneous and enthalpy-driven process. Adsorption kinetics was determined to follow the pseudo-second-order model. In order to examine the adsorption mechanism, adsorbents and adsorption products of cucurbiturils were characterized further by several physicochemical techniques. FT-IR, TG analyses and DFT calculations revealed the formation of the new inclusion complexes, and Zeta potentials reveals the electrostatic interaction may be the significant driven force. UV–vis adsorption spectra were investigated by TDDFT and results showed that the main absorption bands of X-RG and X-3B mainly arisen from π→π∗ and n→π∗ transition. Encapsulated with CBn, the UV–vis absorption bands of inclusion complexes were shifted by 10–15nm due to intermolecular charge transfer (ICT).