| The large-scale production and extensive use of drugs and personal care products(PPCPs)negatively impact the aquatic environment and human health,and thus become another hot research topic after the typical pollutants.Metal Organic Framework(MOF)is a new nano-porous crystalline material.The adsorption capacity of an adsorbent based on MOF is much higher than that of a traditional adsorbent,and it has the advantages of high removal efficiency,no secondary pollution,and simple operation.However,most current studies are conducted in a single system,ignoring the presence of a large amount of humic acid(HA)in the actual water body,so the obtained results and rules don't reflect the actual aquatic environment.In this paper,MOF-100(Fe)material prepared by hydrothermal method was used as an adsorbent to test with a typical pollutant of PPCPs-diclofenac sodium(DCF),and the adsorption characteristics of MOF-100(Fe)on DCF with the effect of humic acid on removing DCF in water were carefully studied.The interaction between humic acid and adsorption system was analyzed and discussed in detail.This paper also provides a theoretical basis and an application guidance for the further development of MOF adsorption materials.The morphology and crystal structure of the prepared MOF-100(Fe)matched with theoretical expections-most of the MOF-100(Fe)materials are microporous.According to the investigation of adsorption characteristics of MOF-100(Fe)on DCF,the results showed that the maximum saturated adsorption capacity of MOF-100(Fe)was 500 mg/g,which indicates an ideal adsorption performance.DCF mainly covered the surface of the adsorbent in the form of a single molecular layer.The adsorption process was a spontaneous,reversible and directly increasing heat absorption process.The interaction forces between MOF-100(Fe)and DCF include electrostatic interaction,pi-pi interaction and hydrogen bonding.Considering different factors on the removal efficiency of DCF in DCF+HA mixed system,the experimental results showed that the removal efficiency of DCF decreased significantly with an increase in the humic acid concentration.The presence of free ions in the reaction solution and an increase in slotion pH also lower the removal efficiency of DCF.There is a competitive adsorption relationship among free ions,humic acid,and DCF in this particular adsorption system.Experimental results about the interaction between humic acid and adsorption system suggested the existence of humic acid accelerated the destruction of the molecular structure of MOF-100(Fe).On the one hand,the equilibrium of iron ion dissolution was shifted to the right,so that the complexation reaction between the dissolved iron ions and humic acid results in the quenching of the fluorescence peak of humic acid.On the other hand,the TOC dissolution increased continuously,and the increasing rate of TOC dissolution positively correlated to the increase of humic acid concentration.As a conclusion,when there is no humic acid,the adsorbent MOF-100(Fe)is stable in aqueous solution,and the iron ion concentration is lower than the current standard,so the use of the adsorbent is safe.Nonetheless,with the presence of humic acid,the stability of MOF-100(Fe)adsorbent in aqueous solution is significantly lowered,and the iron ion concentration is higher than the current standard,especially under high concentration of humic acid. |
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