碳黑金属酞菁原位生高价铁氧降解有机污染物

Degradation of organic pollutants by carbon black metal phthalocyanine in situ producing high valent iron

为高效去除复杂水体环境中的有机污染物,制备过氧化物模拟酶催化剂,以双氧水为氧化剂,构建环境友好型的仿生催化体系,来催化降解水体中的地塞米松有机污染物。研究催化剂的形貌及结构特征,催化体系的催化性能、循环使用性能、催化机理、催化降解产物及最终产物。结果表明:所构筑的催化体系在温和(室温、中性)及复杂水体环境中(酸性、无机盐)对地塞米松的降解率均为100%,但在碱性条件下,该催化体系对地塞米松的降解率因双氧化水分解过快而降低了28%;该催化体系经过6次循环使用后,对地塞米松的降解率仍达到95%;过氧化物模拟酶在双氧水的作用下产生对水体有机污染物降解起主要作用的高价铁氧活性种,而羟基自由基起次要作用;经过60 min反应,该催化体系将地塞米松降解为对环境不存在二次污染的小分子有机酸。该仿生催化体系的构筑为仿生催化材料在工业废水中的应用提供了新视角。

The rapid development of industry,the intensification of urbanization and the growth of population lead to human's increasing demand for clean freshwater year by year,and at the same time,human production and domestic wastewater is discharged into the environment,resulting in the scarce freshwater.Organic pollutants such as drugs,personal care products,are present at extremely low concentrations from ng L toμg L in water,but they can cause immeasurable damage to the environment and living organisms,which causes harm to the human body ultimately.So more and more researchers pay attention to the recycling of wastewater which comes from daily life,agricultural or industrial production.To respond to the"dual carbon"strategic objectives,it is necessary to efficiently degrade and remove organic pollutants in water to achieve sustainable development.Biological enzymes have high catalytic activity and strong selectivity to substrates,so we can use them to catalyze degradation of organic pollutants.However,the direct extraction of enzymes from organisms will bring high extraction cost,and the change of the application environment of enzymes will significantly reduce their catalytic activity.So we designed an environmentally friendly bionic catalyst called peroxide mimicking enzyme which can catalyze the degradation of organic pollutants in water efficiently.In peroxide mimicking enzyme,iron hexadecachlorophthalocyanine(FePcCl_(16))worked as the active site,pyridine group(Py)acted as the fifth ligand,and carbon black(CB)served as a protein skeleton.Inspired by the principle of peroxidase metabolizing drugs,we constructed the environmentally-friendly bionic catalytic system which used peroxide simulation enzyme as catalyst,and hydrogen peroxide as oxidant to catalyze the oxidative degradation of dexamethasone(DXMS).The results showed that the bionic catalytic system maintained high efficiency and stable degradation rate of DXMS in the 25-65℃ temperature range,indicating that the simulated enzyme catalyst was not sensitive to temperature.The degradation rate of DXMS was 100%in 60 min in acid or neutral conditions.It can be seen that the catalytic system was better than that of the Fenton system.At the same time,the catalytic system did not change the degradation rate of organic pollutants in the presence of inorganic salts,and the degradation rate of DXMS still reached 100%,indicating that the catalytic system still had good catalytic oxidation degradation efficiency in complex water environment.However,the degradation rate of DXMS was reduced by 28%due to the rapid decomposition of H_(2)O_(2) under alkaline conditions.Surprisingly,we found that the catalytic system had excellent recycling performance,and the degradation rate of DXMS was still 95%after six cycles of use.By adding isopropyl alcohol(IPA)and p-benzoquinone(p-BQ)into the system as trapping agents of hydroxyl radical(·OH)and superoxide radical(O·_(2)^(-))respectively,electron spin resonance(EPR)detection of·OH and O·_(2)^(-) captured by 5,5-Dimethyl-1-pyrroline N-oxide(DMPO),gas chromatography-mass spectrometry(GC-MS)for the detection of dimethyl sulfone(DMSO)oxidation product confirmed that the main active species of DXMS in the catalytic system were high-valent iron oxo(Fe(IV)O)active sites,followed by·OH.Degradation path analysis showed that the first path of DXMS degradation began with the dehydrogenation of C8 and C14,followed by hydroxylation;the second path of DXMS degradation started with the removal of HF at C8 and C9,followed by hydroxylation or demethylation at C19.After 60 min,all the intermediate products generated small molecule organic acid(succinic acid)or became mineralized.The construction of the bionic catalytic system provides a new perspective for sewage treatment.