Self-assembly of Cucurbit[6]uril-Silicotungstic acid and adsorption properties for cationic dyes

The development of environmentally friendly adsorbents with low cost and high selectivity is often more able to meet the needs of practical applications. In this study, a novel adsorbent Q[6]-STA capable of rapidly and effectively adsorbing cationic dyes was prepared by self-assembly of cucurbit[6]uril (Q[6]) and silicotungstic acid (STA). Q[6]-STA assembly has good thermal stability and significantly improved specific surface area and porosity. The adsorption capacities of Q[6]-STA for crystal violet (CV), malachite green (MG) and methylene blue (MB) are 475.59, 351.98 and 238.16 mg/g, respectively. The efficient adsorption performance for cation dyes is attributed to the high electronegativity of Q[6]-STA surface. This also makes the adsorbent exhibit high selectivity for cationic dyes in anionic/cationic mixed dyes. Thermodynamic analysis shows that the adsorption procedure of Q[6]-STA is unprompted and endothermal. Electrostatic interaction and π-π conjugation effect are possible adsorption driving forces. In the regeneration experiment, the adsorbent is easy to be separated and desorbed, can be recycled, and has good stability.