Experimental Studies On The Removal Of Nitrobenzene From Waste Water Using Metal-Organic Frameworks

As we all know, a variety of toxic organic compounds exist in waste water. When the untreated water are directly discharged into aquatic environment, humans will suffer from serious injuries. Thus, it is a big problem to efficiently remove these hazardous injurants. Metal-organic frameworks (MOFs) are a kind of new nanoporous hybrid materials with high surface area and porosity as well as good thermal and chemical stability, which have been used for gas storage and separation, catalysis, light, electricity, magnetism and drug delivery. Considering the lack of studies on the liquid adsorption and separation, we systematically investigated the adsorption performance of the MOFs for poisonous nitrobenzene (NB) in this work. The research contents are as follows:1. In order to ensure the diversity of the MOFs, we synthesized twenty MOFs with different structure and good hydrothermal stability by solvent/hydrothermal method, such as MIL-53s, MIL-68s, MIL-100s, UO-66(Zr)-X, CAUs and ZIFs. Then a series of characterization were conducted for the activated MOFs, such as powder X-ray diffraction pattern (PXRD), N2adsorption and desorption isotherms at77K, Fourier transform infrared spectra (FTIR), thermogravimetry (TGA) and scanning electron microscope (SEM).2. We studied the NB adsorption on various water-stable MOFs by batch adsorption and UV spectrophotometry, such as MIL-53(A1, Fe), MIL-100(Cr, Fe), MIL-68(Al, In), UiO-66(Zr), UiO-66(Zr)(-NH2,-NO2), ZIFs-7,-8, and CAUs-1,-6. After the preliminary screening, CAU-1and MIL-68(Al) exhibited the best adsorption amounts, which are around970±10and1130±10mg·g-1under the optimum conditions, respectively. The pseudo-second-order, Weber-Morris intraparticle and monolayer Langmuir model were found to be suitable for depicting the NB adsorption process on these two MOFs. The regenerated MOFs still kept the good adsorption capacities. The two Al-MOFs are promising adsorbents for efficient capture of NB from waste water.3. MIL-53(Al, Fe), MIL-53(A1)-1,4-NDC, MIL-53(A1)-NH2, MIL-100(Fe, Al, Cr), MIL-68(Al, In), MIL-68(In)-NH2, UiO-66(Zr)(-1,4-NDC,-2,6-NDC), CAUs-1,-6, CAU-1-(OH)2and ZIFs-7,-8were investigated for the structure-property relationship of MOFs on NB adsorption. The results showed that the nature of metal, the types of organic linker, the performance of framework flexibility as well as the interaction between H2O and MOFs all play an important role in adsorption.