Metal-Organic Frameworks (MOFs) are an interface between the organic and inorganic sectors, consisting of a metal ion coordinated to organic linkers forming a framework. These frameworks have been of interest because of their numerous applications in catalysis, gas separation, and drug delivery. One class of MOF Zeolitic Imidazolate Frameworks (ZIFs), has substantial stability and hydrophobic properties that make them ideal for aqueous separations. We have been working on removing organic dyes from effluent waste by incorporation of the target dye molecules into the porous ZIF because of the toxic effects these dyes can have on biological systems. In this study, we have chosen ZIF-8 for removing organic dye in aqueous because of its excellent thermal and chemical stability, relatively simple synthetic method, in addition to its intrinsic surface defects for coordinating with organic molecules. ZIF-8 is a framework of zinc tetrahedrally coordinated by imidazolate rings with negatively charged surface defects, such as hydroxide and amine groups. We hypothesize ZIF-8 will conjugate to organic dyes via a Schiff-base bond, thus remove contaminants in aqueous phase with greater efficiency than traditional methods that use TiO<sub>2</sub>. To verify our hypothesis, we have first successfully synthesized ZIF-8 nanoparticles as confirmed by X-ray powder diffraction and infrared spectroscopy studies. Subsequently, solutions of Rhodamine B and Methylene Blue were prepared and investigated for degradation in control (Milli-Q water), TiO<sub>2</sub>, and ZIF-8 environments using UV-Vis spectroscopy. We noticed that the absorbance of both Rhodamine B and Methylene Blue dyes decreased by 60% after mixing with ZIF-8 nanoparticles for less than 1 minute. Additionally, when the dye solutions were passed through a ZIF-8 embedded HPLC filter the absorbance of the filtered solution dropped noticeably as much as 63%. Preliminary results showed ZIF-8 is effective and efficient in removing both Rhodamine B and Methylene Blue dyes in solution by soaking and membrane filtering methods. Our future studies include mechanism simulation by density functional calculations and membrane fabrication to improve the efficiency of organic dye separation in aqueous solution.

Hybrid porous materials for the removal of dye-contaminated wastewater

255th National Meeting (2018)

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