Synthesis Of A Novel Cucurbituril Polymer And Its Adsorption Mechanism For Sulfonamide Antibiotics

Cucurbit[n]uril is a new kind of host macrocylic compound which have attracted much attention following the calixarene, crown ether, cyclodextrin. Because its structure is shaped like a pumpkin, so named cucurbituril.(CB[n], n=5-14, abbreviated CB[n] or Q[n]). Due to the rigid hydrophobic cavity and two smaller electronegative ports, they can accommodate hydrophobic guest molecule whose size and shape matched the cavity, and can form strong complexes with metal cations and other electron deficient ions. Cucurbituril can used in the fields of molecular machine, molecular catalysis, drug release and control, wastewater treatment and biological engineering, etc.In the 90's of the last century, the researchers regarded CB[n] as a new kind of environmental protection material in the environmental management. The dissolution of cucurbituril can increase when the aqueous solution exist acid and cations, which makes it less efficient in wastewater treat as adsorbent. CB[n] can maintain good chemical stability in strong acid or strong alkaline environment, and it is difficult to react with other substances. It is also hard to immobilize CB[n] on carrier materials. The present steps of cucurbituril derivative are tedious, time-consuming, and low yield. Therefore, it is necessary to synthesize cucurbituril derivative with advantages of simple step, short time, high adsorption properties and high yield. Thus, the cucurbituril will be widely used in the control environmental pollution.This paper synthesize new cucurbit[6]uril polymer without any template. The interaction between the sulfa molecules and hydroxyCB[6] were studied. And the adsorption process between the sulfa molecules and new cucurbit[6]uril polymer were also studied, in order to provide method and scientific basis for the removal of the sulfonamide antibiotics in wastewater.This experiment synthesizes hydroxyCB[6] by conventional method. The inclusion interaction of hydroxyCB[6] with sulfadimethoxine sodium salt(SDM) or sulfadiazine sodium salt(SDZ) were studied by UV spectra. The complex constants of hydroxyl cucurbit[6]uril with SDM or SDZ were determined according to the Benesi-Hildebrand. The results showed that the ratio of the inclusion complexes formed is 1:1. And the thermodynamic data showed that the main driving forces are Charge-dipole and hydrophobic interaction between host and guest. The process of the inclusion is an enthalpy driven and spontaneous self-exothermic.In this experiment, we use hydroxyCB[6] as raw material, ?, ?'-dichloro-p-xylene as cross-linking agent, by the nucleophilic substitution reaction, the new cucurbit[6]uril polymer was produced. This substance is insoluble in water and has three-dimensional network structure. The product was characterized by IR, NMR, SEM, MFS and Zeta potential. In addition, the interaction between new cucurbit[6]uril polymer and dyes was studied by fluorescence spectrophotometer. The results showed that polymer would be fluorescent quenched by dyes and dyes would be fluorescent enhanced by polymer. The fluorescence quenching effect is methyl orange?orange??orangeG, and the fluorescence enhancing effect is orangeG?orange??methyl orange.This experiment also investigated cucurbit[6]uril polymer adsorption properties of SDM and SDZ. The adsorption process can be best described by the pseudo-second-order kinetic model. SDM reached adsorption equilibrium in 48 h, and SDZ reached adsorption equilibrium in 96 h. The effect of pH of the solution on the adsorption showed: acidic condition is favorable to adsorb SDM, and alkaline condition inhibits to adsorb SDM for polymer, the optimum equilibrium pH value is 2.48. In the initial concentration of 20 mg/L SDM, the maximum adsorption can reach 6.38mg/g. For SDZ, the optimum equilibrium pH value is 7.07, the maximum adsorption is 2.55 mg/g, neutral environment is suitable to adsorption. Adsorption was inhibited in strong acidic and strong alkalic environment. Ionic strength greatly impact on the adsorption capacity, and the effect of divalent metal cations larger than monovalent metal ions. At low concentration, the adsorptive capacity of the polyer increased with the increase of the ionic concentration, but in high concentration, the adsorptive capacity of the polymer was inhibited with the increase of the ionic concentration. Compared with SDM, divalent metal cations with low concentration are more helpful to adsorb SDZ for the polymer than monovalent metal ions, but divalent metal cations with high concentration have the opposite effect. The analysis data by “Sum of normalized errors”(SNE) method showed the Henry adsorption isotherm model was in accordance with the adsorption process of SDM and SDZ. The thermodynamic data showed that ?G<0, ?H>0, ?S>0. ?G<0(|?G|<20 kJ/mol), which indicated that the adsorption process is mainly physical adsorption, and the adsorption is spontaneous, high temperature is beneficial to adsorb. ?H>0 and ?S>0 demonstrated the adsorption belongs to entropy increased and endothermic adsorption process. The whole adsorption process is the result of hydrophobic interaction, hydrogen bonding interaction and van Edward force interaction.