| Palladium ions,as a precious metal with excellent performance,is in increasing demand.At the same time,the content of palladium ion in industrial wastewater is also increasing.The wastewater containing palladium has serious harm to the environment and human health,and palladium ions have high economic value.Therefore,the selective adsorption of palladium ions is particularly important.Two kinds of palladium ion imprinting materials were designed and prepared for selective removal of palladium in water.The details are as follows:1.For the first time,the density functional theory?DFT?was used to design palladium ion imprinted adsorbents.By optimizing the adsorptive configurations of a-Pd-IIP,b-Pd-IIP and c-Pd-IIP with different Pd?II?/ATU ratios.The adsorptive energies of the three materials calculated by DFT are–13.978 eV?b-Pd-IIP?,8.764eV?a-Pd-IIP?and–3.587 eV?c-Pd-IIP?,respectively.The relationship between adsorption energy and adsorption capacity was obtained by deducing the formula of site energy,and the correlation coefficient between adsorption energy and adsorption capacity was as high as 0.985 by isothermal adsorption experiment.In addition,the theoretical maximum adsorption capacity(89.89 mg g-1)of b-Pd-IIP materials with the largest absolute adsorption energy was obtained by isothermal adsorption experiments,which was much larger than that of other reported palladium ion imprinting materials.The optimum ratio of Pd?II?to functional monomers is 2:3 by ultraviolet-visible spectrophotometry,which is in good agreement with the results of adsorption energy calculated by DFT.Finally,XPS analysis of three ion imprinting materials before and after adsorption was carried out,and it was found that the adsorption sites of these three materials were on S element of functional monomer.The results were in good agreement with those of DFT when optimizing the adsorption configuration,which verified the accuracy of DFT optimizing the adsorption configuration.According to the results of UV-Vis spectroscopy and XPS analysis,the rationality and feasibility of DFT method for optimizing adsorption configuration and designing palladium-imprinted materials can be demonstrated.2.The adsorption properties of these three ion-imprinted materials were studied.The effect of pH on the palladium ion imprinted materials designed and synthesized by DFT was studied.The optimum adsorption pH of the three imprinted materials was 3.By studying the kinetic experiments of three imprinted materials,it is found that the three materials are more in line with the quasi-second-order adsorption model,which indicates that the adsorption process is chemical adsorption,and this result is consistent with the conclusion of D-R model analysis.Furthermore,the best material is b-Pd-IIP material with the largest adsorption energy by BET data combined with Weber and Morris model analysis of kinetics.The adsorptive selectivity experiments of the materials show that all three materials have good selectivity.In addition,the recycling experiments show that these three materials have certain practical application value,especially b-Pd-IIP.A series of studies on the adsorption properties of these three materials have been carried out,and the conclusion is the same as that predicted by DFT calculation,that is,the best material of the three palladium ion imprinting materials is b-Pd-IIP material.Finally,the energy distribution curves of binding sites of three materials were analyzed.The model of temperature and adsorption capacity of b-Pd-IIP material was established by introducing average site energy and calculating the expected value of average site energy,and the relationship between them was studied.The linear correlation coefficient between temperature and the maximum adsorption capacity of the adsorbent can be obtained as high as 0.983by calculating the relevant parameters.3.The factors affecting the synthesis of temperature-sensitive palladium ion imprinting were investigated,and the optimum proportion of materials was synthesized and their adsorption properties were studied.First,the feasibility of the synthesis of thermosensitive palladium ion imprinted materials was verified by the measurement of swelling rate and adsorption experiments.Then the effect of temperature sensitive palladium ion imprinted gel on the adsorption capacity was studied,and the conclusion was obtained.In addition,the effects of functional monomers,thermosensitive functional monomers and crosslinking agents on the properties of thermosensitive materials were investigated by synthesizing thermosensitive materials with different ratios.The following conclusions were obtained:?1?The larger the amounts of functional monomers added,the better the adsorption performance.?2?Temperature-sensitive functional monomers do not significantly affect the adsorption capacity of the material,but significantly affect the temperature-sensitive properties.?3?When the crosslinking agent MBA:EDGMA is7:3,the comprehensive properties of the material are the best.Through the above series of exploratory experiments,the optimum ratio of temperature sensitive palladium ion imprinting gel was ATU?0.15 mmol?,NIPAAm?10 mmol?,Na2PdCl4?0.1 mmol?,MBA?0.7 mmol?,EDGMA?0.3 mmol?,AIBN?0.1644?,ethanol?6 mL?and pure water?2 mL?.In addition,the lowest critical dissolution temperature of the best material?35??was obtained by swelling ratio test.After synthesizing the material with the best performance,the optimum pH of the material is 3 through the analysis of the materials'pH experiment.Finally,three temperature isothermal adsorption experiments were carried out to verify that the material had the temperature sensitive and imprinted effect,and the material was more in line with the Langmuir model.The theoretical adsorption capacity of the thermosensitive ion imprinted gel was 92.081 mg g-1,which had excellent adsorption properties compared with other palladium ion imprinted materials. |
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