| non-selective hydroxyl radical (·OH) by iron interacted with hydrogen peroxide, it is still difficult to realize selective removal of harmful materials from complicated wastewaters in the presence of other pollutants. Molecular imprinted materials have been extensively studied due to their molecular recognition ability, this inspires us to study the molecular imprinted heterogeneous Fenton-like catalyst for selective removal of the organic pollutants. The molecular imprinted material was prepared with 4A zeolite as the base and methylene blue (MB) as the template molecules. After imprinted, the template molecule was washed out and iron ions were introduced to form the Fenton-like sites. Then, the molecule imprinted Fe-zeolite Fenton-like catalyst (MI-FZ) was prepared. The Fe-immobilized zeolite catalyst without molecular imprinted (FZ) was also prepared for comparison. MI-FZ and FZ were characterized by SEM, XRD, BET and FT-IR. Besides, adsorptive and catalytic conditions of MI-FZ for MB were optimized. Bisphenol A (BPA) was chosen as the interference matter to verify the selectivity of MI-FZ. In addition, the reaction mechanism and stability of MI-FZ were also investigated. The results are as follows:(1) FZ showed relative smooth surface and layered structure, while the surface of MI-FZ particle was rough and some porous structures were observed. The new diffraction peaks of MI-FZ and FZ were well matched with Fe2O3 and Fe2Al4Si5O18. Compared with the FZ, MI-FZ spectrum shows the new weak peaks of C=O and HOH, respectively. The average particle size and the specific surface area of MI-FZ were greatly bigger than FZ.(2) The adsorption of MB by MI-FZ is affected by the dosage of MI-FZ, the initial concentration of MB, pH and temperature. The results indicate that the appropriate conditions are as follows:the dosage of MI-FZ is 0.3 g/L, the initial concentration of MB is 10 mg/L, and temperature is set at 30 ℃. Moreover, adsorption efficiency is better under alkaline conditions, this may be the flocculation. Besides, adsorption of MB on the MI-FZ can be described by Langmuir adsorption model and pseudo-second adsorption kinetics, and it was mainly attributed to the chemical adsorption.(3) MI-FZ has selective adsoprtion ability for MB. The equilibrated adsorption capacity of MI-FZ (44.6 mg g-1) for MB was about three times of FZ (15.6 mg g-1), while the adsorption capacity of FZ for BPA was obviously higher than than of MI-FZ. The adsorption capability by MI-FZ in the binary system of MB and BPA was 44.7% and 14.9%, respectively. While the percent for BPA increased to 21% and decreased to 28.8% for MB by FZ.(4) The catalysis of MB by MI-FZ is affected by the dosage of MI-FZ and H2O2, pH and temperature. The results indicate that the appropriate conditions are as follows:the dosage of MI-FZ and H2O2 are 0.3 g/L and 0.16 mol/L, the initial pH is 4, and temperature is set at 30℃. Moreover, adsorption efficiency is better under alkaline conditions, this may be the flocculation. Besides, the kinetic data were well described by the first-order reaction kinetics equation.(5) The molecular imprinting process increased the Fenton-like catalytic activity of the MI-FZ towards the target pollutant MB. Over the MI-FZ and FZ, the degradation efficiency of MB was 92.2% and 76.6% after reaction of 180min, respectively. However, the efficiency of BPA reached 56.4% and 99.8% over the MI-FZ and FZ. In binary Fenton-like system, the catalytic degradation efficiency by MI-FZ for MB was 82.7% much higher than that of 37.8% for BPA. However, the catalytic efficiency by FZ decreased to 53.8% for MB and increased to 73.5% for BPA, respectively, further proving the selectivity of MI-FZ.(6) MI-FZ showed a high reactivity stability with a long life-time. The Fenton-like catalytic efficiency of MI-FZ towards the degradation of MB didn’t obviously change in first six runs. The degradation percentages of MB were kept at 87.0±5.0% in all six cycles. |
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