Synthesis,Characterization And Dye Adsorption Properties Of 12-Tungstophosphoric Acid-based Metal Organic Framework Composite Material

Recently,with the development of society,economy and industry,organic dyes play an extremely important role in industrial production and daily life,which makes our lives colorful.However,a large amount of dye-wastewater has been directly discharged without reasonable processing,generating a tremendous threat to the aqueous environment and human health due to its toxicity and even carcinogenicity.Therefore,it is urgent to find an effective approach to harness organic dyes in dye-wastewater before discharging it into the environment.Nowadays,in the existing variety of processing methods,adsorption is a simple and convenient method of dye wastewater treatment.In this paper,a Keggin-type polyoxometalate H₃PW₁₂O₄₀(PW₁₂)was firstly incorporated into the harmless porous metal organic framework MIL-101?Fe?resulting in POM@MOF composite material(denoted as PW₁₂@MIL-101?Fe?).Moreover,the characterization and dye adsorption properties of the composite are investigated.1.Synthesis and characterization of the compositeThe composite material was synthesized by a one-pot solvothermal reaction of H₃PW₁₂O₄₀,FeCl3·6H2O and terephthalic acid?H2bdc?.We performed a detailed characterization of the composite by fourier transform infrared spectroscopy?FTIR?,X-ray powder diffraction?XRD?,thermogravimetric analysis?TGA?,inductively coupled plasma spectrometry?ICP?,scanning electron microscope?SEM?,energy spectrum analysis?EDS?,EDS elemental mapping,31 P NMR and nitrogen adsorption-desorption isotherms.These results collectively demonstrated the successful insertion of H₃PW₁₂O₄₀ within the cavities of MIL-101?Fe?.2.Study on dye adsorption properties of the composite materialThis section mainly studies the following five aspects:?1?The effect of dye concentration;?2?The calculation of adsorption capacity and adsorption rate?adsorption%?;?3?The comparison of adsorption capacity for different types of organic dyes in MIL-101?Fe?and PW₁₂@MIL-101?Fe?;?4?Selective adsorption ability of the composite material for the mixed organic dyes;?5?The reusability and stability of the composite material.The experimental results showed that for the 40 mg/L of MB,the adsorption rate of MB reached 96.2% in 30 min.In addition,the composite could rapidly remove 97.3% of MB from 1 ppm?1 mg/L?of MB dye solution.It is worth mentioning that the composite material shows an adsorption capacity of 473.7 mg/g for MB when adding 20 mg PW₁₂-5g@MIL-101?Fe?in 100 mL of 100 mg/L MB solution.In the dye adsorption test,the removal rate of the isolated MIL-101?Fe?was separately up to 30.7% and 28.3% for cationic methylene blue?MB?and rhodamine B?RhB?dyes,and 82% for anionic methyl orange?MO?dye within 30 min.However,the dye adsorption capacity of MIL-101?Fe?has greatly changed after introducing highly electronegative polyoxoanions into the framework of MIL-101?Fe?.The adsorption rate of PW₁₂@MIL-101?Fe?composite could reach 99% and 96% for cationic dyes MB and RhB,and 16% for anionic dye MO in the initial 5 min.This material can as well selectively capture the cationic dyes in MB,RhB and MO ternary mixed dye system.Furthermore,this material could be easily desorbed for reuse,and the structure of the composite material was intact during the adsorption experiment.Thus,it is a promising and environmentally friendly adsorbent for removing cationic organic pollutants in dye-wastewater.