The Applications Of Uranyl-organic Frameworks In Removal Of Environmental Pollutants

Water resources are the guarantee for human.Although the vast majority of the area on the earth is occupied by water,the fresh water resources available for human and most organisms use are very limited.Moreover,with the rapid development of the economy,the contradiction between water pollution and the rapid development of the modern economy has become increasingly prominent.The traditional sewage treatment technology is obviously out of touch with modern economy.In recent years,researchers have tried to introduce different kinds of materials into the field of wastewater treatment to find one or a class of materials that can adsorb/degrade organic pollutants in wastewater.Coordination polymers constructed by metal ions and organic ligands have attracted much attention.Due to the diversity of organic ligands,Coordination polymers have the rich structures and regular pore channels,providing a basis for further development of adsorption/photocatalytic properties.Linear uranyl ions,abundant coordination modes and strong oxidizing properties under light conditions,are used for adsorption/photocatalytic reduction in wastewater.There are 10 uranyl compounds were synthesized under the room temperature and hydrothermal conditions,in this paper:[（UO₂）（H-bdc）（bdc）_1/2（bpy）]（1）,（H₂-bpe）[（UO₂）（bdc）_4/2]（2）,（H-bpy）[（UO₂）₂（ntp）_2.5]·H₂O（3）,[（UO₂）₂（ntp）₂]（bpp）（4）,（H₂-bpe）[（UO₂）₂（ntp）₃]·2H₂O（5）,（phen）₂[（UO₂）₂（ntp）₃]·2H₂O（6）,（H₂-tmp）₂[（UO₂）（ntp）₂]·H₂O（7）,（4,4’-Hbpy）_1/2[（UO₂）（Br-bdc）（Br-Hbdc）]（8）,[（UO₂）（dbt）（4,4’-bpy）_1/2]（9）and[（UO₂）（DMSO）（L）₂]₂（10）（H₂bdc=terephthalic acid,H₂ntp=nitroterephthalic acid,H₂Br-bdc=bromoterephthalic acid,H₂dbt=2,5-dibromterephthalic acid,HL=m-methoxybenzoic acid,bpy=2,2’-bipyridine,4,4’-bpy=4,4’-bipyridine,bpe=trans 1,2-（4-pyridyl）ethylene,bpp=1,3-di（4-pyridyl）propane,phen=4,7-Phenanthroline,tmp=tetramethyl pyrazine,DMSO=dimethyl sulfoxide）.And the adsorption/photocatalytic experiments were performed with the compounds（1,2,3,4,5,7,9 and 10）.In the first part,two compounds 1 and 2 were synthesized via terephthalic acid,and the experiments of degrading tetracycline hydrochloride（TC）,chlortetracycline hydrochloride（CC）and doxycycline hydrochloride（DC）were also investigated under visible light.The results show that compounds 1 and 2 had different degradation effects on antibiotics.In the second part,five uranyl compounds were synthesized by using the nitroterephthalic acid.Among them,compounds 3 and 7 were 3D structures,and the remaining compounds were 2D layer structure.The compounds 4,5 and 7 for tetracycline hydrochloride（TC）degradation efficiency were 55.4%（4）,69.7%（5）and 76.7%（7）under the irradiation of LED lamp,respectively.The compound 3 is an adsorbent having the good adsorption effect on tetracycline hydrochloride（TC）,and its maximum adsorption capacity reachs 156.0 mg g^–1.Meanwhile,the adsorption processes toward tetracycline hydrochloride（TC）molecules are fitted well by pseudo-second order kinetic model.In the third part,two compounds 8 and 9 were synthesized by using the bromoterephthalic acid and 2,5-dibromterephthalic acid,respectively.Structural analysis shows that the compound 8 was a 2D layered structure,while compound 9 was a 3D structure further stabilized by 4,4ˊ-bipyridine.Meanwhile,we also studied degradation effect of compound 9 on tetracycline hydrochloride（TC）under the irradiation of LED light.In the fourth part,the uranyl compound 10,having an adsorption effect on the cationic dye,was synthesized at room temperature.The selective adsorption capacities of compound10 toward different dyes（RhB/MO,CV/MO,MB/MO,RhB/MB,CV/MB and R6G/MB）were investigated.Taking RhB as an example,the adsorption performance of compound 10,including the amount of adsorbent,the pH value of the solution and the initial concentration,was systematically studied,and the experimental data were fitted by the adsorption kinetics model.