Coupling reaction and vacuum distillation to prepare β-CD-based adsorption material for organic dyes

A new method involving a coupling reaction and vacuum distillation (RVD) was introduced to prepare the β -CD cross-linking polymeric adsorbent (PCD RVD ). The preparation conditions, including the molar ratio of cross-linking agent and β -CD, dosage of the solvent, reaction time, and vacuum distillation temperature and time, were investigated in detail. Compared with a product prepared at normal pressure, PCD RVD possessed a lower content of β -CD, a higher content of carboxyl groups, a lower adsorption selectivity, and a higher efficiency as well as adsorption capacity to remove dyes methylene blue (MB), and Rhodamine B (RhB), methyl orange (MO). The PCD RVD was characterised by FT-IR, TG, and SEM, and was employed for the adsorption of MB and RhB from an aqueous solution. Results showed that the adsorption quantity of MB ( Q e,MB ) was higher than that of Q e,RhB , except in the acidic medium. The equilibrium data followed the Langmuir isotherm model, and the calculated Q m,MB and Q m,RhB were 250.0 mg/g and 231.5 mg/g, respectively. The adsorption kinetics fitted the pseudo-second-order model. It was inferred that PCD RVD exhibited a high adsorption capacity for both dyes due to its more homogeneous polymeric network formed during RVD and the higher content of carboxyl groups. The differences between Q e,MB and Q e,RhB were mainly attributed to the size of MB and RhB.