一例钴基金属有机框架化合物活化过氧单硫酸盐高效降解水中亚甲基蓝研究

Co-based Metal-organic Framework for High-efficiency Degradation of Methylene Blue in Water by Peroxymonosulfate Activation

在水净化领域,基于硫酸根自由基(SO_(4)^(·-))的高级氧化工艺因其高选择性和氧化优势应用潜力巨大.开发高性能过氧单硫酸盐(PMS)催化剂是染料废水处理的研究热点.此工作中,选用5,5’-二苯醚间苯二甲酸(H4odip)和Co^(2+)离子通过溶剂热法合成得到一例新的钴基金属有机框架化合物Co(μ6-odip)_(0.5)(μ_(2)-OH_(2))_(0.5)(H_(2)O)_(2)·1.5H_(2)O(1).该化合物水稳定性和热稳定性优良且具有一定的耐酸碱性.通过X-射线单晶和粉末衍射、热重分析、元素分析和红外光谱表征了该化合物的结构及组成.化合物1属于单斜晶系C2/c空间群,晶胞参数为a=1.6101(9)nm,b=1.5508(10)nm,c=0.9660(6)nm,α=90°,β=112.70(2)°,γ=90°.通过紫外-可见分光光度计对1活化过氧单硫酸盐降解水中亚甲基蓝(MB)的性能进行测试,系统研究了1的负载量、过氧单硫酸盐的浓度、反应温度和溶液pH对染料降解性能的影响.综合化学淬灭实验和电子顺磁共振证明在1/PMS反应体系中催化降解MB的主要活性氧物种(ROS)有SO_(4)^(·-),·OH和^(1)O_(2),但O_(2)^(·-)对MB的催化降解也起到一定促进作用.实验结果表明该化合物在催化PMS过程中可作为一种高效且可重复使用的新型多相催化剂用于染料废水的修复处理.

In the field of water purification,the advanced oxidation process based on sulfate radical(SO_(4)^(•−))has great poten-tial applications due to its high selectivity and oxidation advantages.The development of high-performance peroxymonosul-fate(PMS)catalysts to produce SO_(4)^(•−)remains a research hotspot for dye wastewater treatment.In this work,a cobalt based metal-organic framework compound with formula Co(μ6-odip)0.5(μ_(2)-OH_(2))_(0.5)(H_(2)O)_(2)•1.5H_(2)O(1)was synthesized by sol-vothermal method using 5,5'-oxydiisophthalic acid(H4odip)ligand and Co^(2+)ions.The reaction solvent was acetonitrile and water,the reaction temperature was 135℃.The obtained pink crystal compound has the good water stability and acid-base resistance.The structure and composition of 1 were characterized by X-ray single crystal and powder diffraction,thermo-gravimetric analysis,elemental analysis and infrared spectroscopy.Complex 1 belongs to monoclinic system,C2/c space group with cell parameters:a=1.6101(9)nm,b=1.5508(10)nm,c=0.9660(6)nm,α=90°,β=112.70(2)°,γ=90°.Moreo-ver,the catalytic performance of 1 by peroxymonosulfate activation for degradation of methylene blue was tested in water by UV-Vis spectrophotometer.At the same time,the effects of 1 and peroxymonosulfate loading,reaction temperature and solu-tion pH on dye degradation were systematically studied.The reaction mechanism of dye degradation was explored through free radical capture experiment.The test method is to take 30 mL of dye solution(20 mg/L)in a beaker and add 3 mg 1 and 0.5 mL PMS(100 mg/L).Keep stirring throughout the experiment.At a certain time interval,the supernatant of dye solution was taken and the absorption intensity at the maximum absorption wavelength(λ=665 nm)was measured by UV-Vis spec-trophotometer to monitor the change of methylene blue(MB)concentration.The above method is also applicable to all comparison experiments.The pH of the dye solution was adjusted using hydrochloric acid and sodium hydroxide at a concentration of 0.1 mol/L.Radical scavenging agents were added to the reaction system in the free radical trapping experi ment.The experimental results show that the 1 can generate reactive oxygen species(ROS)by activating peroxymonosulfate,and rapidly degrade MB in aqueous solution,the degradation rate can reach 97.4%within 8 min,and the catalytic activity is good in a wide range of pH.The results showed that 1 and PMS loading capacity were the key factors for the degradation of dyes by activated peroxymonosulfate,and the degradation rate could be improved by increasing the compound loading ca pacity,PMS concentration and temperature.After five cycles,the compound still retained a high degradation rate of 90.8%.A comprehensive analysis of the quenching experiment and electron paramagnetic resonance(EPR)test results confirmed that the ROS produced by the 1/PMS system include SO_(4)^(•−),•OH,O_(2)^(•−) and^(1)O_(2),among which SO_(4)^(•−),•OH and ^(1)O_(2) play a major role in the catalytic degradation of MB,but O_(2)^(•−) can also promote the catalytic degradation of MB.The above research results indicate that 1 can be used as an effective and reusable heterogeneous catalyst for the treatment of dye wastewater by perox-ymonosulfate activation.