Herein, zirconium (IV)-based MOF, UiO-66-NH2 was prepared by a facile solvothermal method. The MOF exhibit small size and large surface area, which can remove cationic dyes from aqueous solution. This adsorption selectivity is due to the favorable electrostatic interactions between the adsorbents and cationic dyes. Furthermore, owing to the individual micro pore structure of UiO-66-NH2 and its more negative zeta potential resulted from the charge balance for the protonation of –NH2, UiO-66-NH2 displays much higher adsorption capacity for cationic dyes and lower adsorption capacity for anionic dyes than UiO-66.
Synthesis of UiO-66-NH2 was performed by dissolving ZrCl4 and 2-amino-1,4-benzenedicarboxylic acid in DMF with ultrasonic vibration. The as-obtained mixture was transferred to a Teflon-lined autoclave and then maintained. The resulting solid was filtered, repeatedly washed with CHCl3 and dried at room temperature.
The most important analysis to confirm the synthesis of a desired MOF is X-ray diffractometry (XRD). XRD patterns of the sample was determined in the range of 2 = 4–50◦. The MOF pattern has been reported to have unique crystalline phases according to the computational model and synthesized sample, which is confirmed for the synthesis of the desired compound.
For applying UiO-66-NH2 as adsorbent, it was added into dye solution with continuous stirring in a dark place. Samples were filtrated. The absorbance of filtrate was tested using a UV spectrophotometer. Our Study was about the cationic dye Methylene Blue (MB) and the UV–vis spectra of its solution with UiO-66-NH2. The absorbtion peaks of MB in UiO-66-NH2 solution was rapidly descending in 5 hours, indicating that MB molecules were efficiently adsorbed by UiO-66-NH2. The dye removal efficiency was increased by time.
