Synthesis,Characterization Of ZIF-8 Composites And Their Application Of Removal Contaminants

Zeolite Imidazole Frameworks?ZIFs?have unique properties due to their similar structure to zeolites,and have broad application prospects in the fields of catalysis,energy storage,separation and environmental remediation.The functional composite formed by ZIF-8 wrapped nano-zero-valent iron?nZVI?combines the high adsorption selectivity of MOFs and the high reaction activity of nZVI,which has potential technology based on adsorption and degradation for environmental remediation.Therefore,this thesis aims to use ZIF-8 as a basis,subsequently,new hybrid ZIF-8-Fe and ZIF-8-Fe/Ni as the functional MOFs-Nano materials were synthesis and were used to remove antibiotics and heavy metal contaminants.Firstly,the mixed pollutants of tetracycline?TC?and oxytetracycline?OTC?were removed by ZIF-8,where the effects of temperature,concentration,dosage and pH on the adsorption capacity were investigated.The maximum adsorption capacity for TC and OTC were 303.0 and 312.5 mg g^-1 at 303 K,respectively.The batch experiments showed that the adsorption of the two antibiotics followed the pseudo-second-order kinetic model and best fitted the Langmuir adsorption model.In addition,on the basis of results from combined with the characterization,it was proposed that TC and OTC and ZIF-8 are adsorption mechanisms through electrostatic attraction and?-?stacking interaction.Secondly,a new ZIF-8-Fe functional composite was synthesized.Characterizations proved that ZIF-8 cavity contains nZVI,the performance of ZIF-8,ZIF-8-Fe and nZVI to remove Cu²⁺and norfloxacin mixed pollutants were compared,where the removal efficiency of heavy metal Cu²⁺by ZIF-8-Fe was slightly higher than that of ZIF-8,but it was significantly higher than nZVI.In addition,the removal efficiency of norfloxacin ZIF-8-Fe was 52.64%,while the removal efficiency of norfloxacin by ZIF-8 and nZVI were38.90%and 20.75%,respectively.This indicated that the functional material has a potential to removemixed contaminants.To confirm the degradation mechanism,Cu²⁺was selected as a target and Cu⁰ or Cu?I?existed after the removal of Cu²⁺by ZIF-8-Fe was observed confirming that Cu²⁺was reduced by nZVI.The adsorption-reduction mechanism is proposed,which is based on the adsorption of Cu²⁺by ZIF-8 and the reduction of Cu²⁺by nano-iron.Finally,the bimetallic nano Fe/Ni was wrapped in ZIF-8 to form a new ZIF-8-Fe/Ni,and the removal of oxytetracycline hydrochloride?OTC?by ZIF-8,ZIF-8-Fe and ZIF-8-Fe/Ni was compared.The results showed that the removal efficiency of oxytetracycline were 40.0%?ZIF-8?,58.5%?ZIF-8-Fe?and 74.6%?ZIF-8-Fe/Ni?,respectively when the initial concentration was 20 mg L^-1.The best removal efficiency was obtained from ZIF-8-Fe/Ni.Thus,the removal of oxytetracycline using ZIF-8-Fe/Ni was systematically investigated.The results showed that the reaction of removing oxytetracycline followed to the pseudo second-order kinetic model.