The Study Of Adsorption Properties For Methylene Blue Onto Metal Organic Frameworks

Over the years there has been an intensification of interest in the field of Metal-Organic Frameworks (MOFs). One of the factors influencing the explosion in MOFs research is the properties they have been shown to exhibit, including high surface area and permanent porosity. An area of research concerning MOFs which up until recently, had remained unexplored, is the use of MOFs for aqueous adsorption. Therefore, utilising the properties of large surface area and porosity for the removel of dyes in contaminated water based on the requirements environmental protection is of great current interest.The aim of this thesis was to examine the ability of Metal Organic Frameworks (MOFs) to adsorb methylene blue (MB) from dyes wastewater and to fomulate a theory. Initial work involved the synthesis of a series of classic isostructural MOFs, known as MIL-100, UIO-66and HKUST-1. Three of these frameworks were characterized by X-Ray Diffraction, which all in accordance with the original X-Ray pattern. There is no difference of the three MOFs between before and after adsorb MB, which proved through the characterization by Infrared Radiation, Thermo Gravimetric Analyzer and Scanning Electron Microscope.Studied the effect of reaction conditions (including contact time, temperature and the initial concentration) of the adsorption for methylene blue onto MOFs. The research shows that, adsorption of three MOFs can reach equilibrium state in a very short time; temperature make little of difference for the adsorption; with the methylene blue initial concentration increase, the adsorption capacity increased, but the decolourization ratio dropped. Utilizing the adsorption isotherm model and kinetic model to fit the experimental data:As to the MIL-100and UIO-66, the results corresponded well with the Langmuir isotherm, as to HKUST-1the results corresponded with the Freundlich isotherm; The experimental results of three MOFs corresponded well with those of the pseudo-second-order kinectic model.Comparing the adsorption effect and properties of three typical MOFs. The adsorption of MIL-100which has the large cages more than the UIO-66and HKUST-1which all have the parallel channel structure, so we speculate that the cages structure is in a better position for adsorption methylene blue than the parallel channel structure.The adsorption capacity of MIL-100is three times greater than UIO-66and HKUST-1, at the same time, MIL-100is a three times the surface area of UIO-66and HKUST-1, and thus assumes that the adsorption capacity of MOFs has the larger correlation with the surface area themselves. As to the pore size, MIL-100is three times bigger than HKUST-1and four to five times bigger than UIO-66, when paired with these factors, the big pore size benefits the adsorption effect.