چكيده به لاتين
The present thesis is organized through four research projects. In the first project, the metal organic framework named as MIL-68(Al) was prepared by solvothermal method with a little modification in synthesis and activation process, following by characterization with FT-IR, XRD, N2 adsorption- desorption, SEM and TG/DTA methods. The activated product was then applied as a sufficient substrate for investigation the sorption behaviour of two cationic dyes, Methylene Blue and Rhodamine B, from single and binary aqueous solutions. The sorption process in batch system as well as the effects of different variables such as adsorbent dosage, ionic strength, pH, contact time in ultrasonic bath and initial dye concentration on removal efficiency was analyzed by one at the time and also experimental design methods. Central composite design was used in order to optimize the effective parameters on removal process. The possible interactions between variables were also explored by response surface methodology approach. Isotherm studies was performed using various models and the maximum monolayer adsorption capacity corresponding to Langmuir isotherm was obtained to be 1734 mg.g-1 for Methylene Blue and 1056 mg.g-1 for Rhodamine B in single solution and also 227 mg.g-1 and 29 mg.g-1 for Methylene Blue and Rhodamine B in binary mixtures, respectively. The well enough agreement between experimental results and pseudo-second order kinetics model was confirmed by fitting the raw data with different kinetics models. The sorbent could be regenerated by methanol and reused for subsequent runs. The feasibility of the simultaneous dyes adsorption in real samples was another part of this study. In second project, the as-prepared metal organic framework was utilized in order to simultaneous removal of Malachite green and Methylene blue with sever spectra overlapping. The second-order derivative spectrophotometric method was proposed as an authentic way to measure the concentration of each dye in two-component samples even for study in real sample solutions. The impact of variables on simultaneous sorption of these dyes, optimization of the condition and patterning the sorption process was carried out through central composite design-response surface methodology. Low quantities of adsorbent for about 5.5 mg and short reaction times within 5 min as well as a high maximum adsorption capacity of 500 mg.g-1 for Mthylene Blue and 142 mg.g-1 for Malachite Green were some of the most valuable achievements in the current study. An investigation through the kinetics of the adsorption, the effect of salts with different concentrations on sorption efficiency, the reusability of the sorbent and finally the real sample analysis are another parts of this project. In third project, the simultaneous determination of three dyes, named as Methylene green, Methyl Orange and Azocarmine B with high spectra overlapping was performed with emphasis on the worthwhile role of chemometry aspects for analysis of the complex samples. Three separate methods including derivative spectrophotometry, partial least square (PLS) and orthogonal signal correction- PLS were applied in order to resolve the overlapping and to process the spectra. According to the results, the latter technique revealed the best applicability for simultaneous measurement of dyes concentration in terms of possessing the minimum prediction error in both lab-prepared and real samples. Furthermore, the data which are pre-processed by OSC filtering method showed simple calibration model with less number of factors. In fourth project in order to facilitate and industrialize the synthesis rout, the metal organic framework, MIL-68(Al), was prepared by using the microwave radiation method for the first time. The effect of different variables including reaction temperature, concentration of precursors and reaction time on qualitative and quantitative features of the final product was examined. Compared with the sample synthesized under 19h-reflux process, the microwave synthesis method can be regarded as a superior and promising technique due to the yielding a homogenous and pure product kept its physical and chemical origin within a very short reaction time and no water wastage. Central composite design- response surface methodology was performed in order to evaluate the application of MIL-68(Al) for simultaneous removal of Methyl Orange and Methyl Green dye molecules from aqueous solutions under room temperature and pH 6. Adsorption isotherm and kinetic parameters were estimated under optimized condition. The maximum monolayer adsorption capacity of the sorbent for simultaneous removal of Methyl Orange and Methyl Green was evaluated to be 200 mg.g-1 and 166 mg.g-1 after about 4 min agitation. According to the kinetics studies, the sorption percentage of both dyes onto the sorbent reach to equilibrium after about 3 min and pseudo- second order model is fitted best to the experimental data. Many apparatus was applied to make contacts between the sorbent and guest species and then compared with each other. The results verified the advantages of ultrasonic waves to provide more effective contact which leads to accelerate the removal process. Further studies on the comparison between two MIL-68(Al) samples prepared by reflux and microwave radiation methods presented some remarkable information about the effect of synthesis route on structural characteristics and selectivity of the product. The significance decrease in removal efficiency of the sorbent for dyes uptake in real samples containing a complex matrix was another outcomes of this project.
