Determination of some aromatic pollutants in aqueous media by using polymeric calixarenes in quartz crystal microbalance (QCM)

In this study, it was aimed to investigate the sensing properties of QCM sensors coated with Merrifield resin based on calix[4]arene derivative in aqueous media of phenols, which are aromatic compounds with different structures that cause water pollution. For this purpose, firstly, sensor molecules were designed for the detection of different aromatic pollutants using the three-dimensional structure of calix[4]arene molecule. The upper part of the calix[4]arene structure was derivatized with different functional groups. The structures of the obtained derivatives calix[4]arene derivatives (3, 4 and 5) were elucidated by 1H-NMR spectroscopy and FT-IR spectroscopy methods. Polymeric calix[4]arene-Merrifield polymeric structures (MER-3, MER-4 and MER-5) were obtained as a result of the reaction of the hydroxyl groups at the bottom of the obtained calix[4]arene derivatives with Merrifield resin containing benzylchloride group and the structures of the polymers were characterized by FT-IR spectroscopy. After the preparation of the solutions of the prepared monomeric and polymeric structures, thin film layers were formed on QCM crystals using the solution soaking method. Thus, the sensing properties of QCM sensors coated with calix[4]arene derivative-bonded Merrifield resin against different aromatic pollutants (phenol (FEN, resorcinol (REZ), paracetamol (PAR), p-nitrophenol (PNF) and p-chlorophenol (PKF)) in aqueous media were investigated. In order to examine the properties of phenolic pollutants with different structures at different pH values, analyte solutions were prepared at pH 2-6-10 and used in sensing studies. Both monomeric and polymeric calix[4]arene derivatives were coated on the QCM sensor surface and the frequency change values of the new QCM sensors against different aromatic pollutants were investigated at different pH conditions. According to the results obtained for the monomeric calix[4]arene 3 derivative, the highest detection values were observed at pH 10. It was observed that the detection increased with the conversion of phenol and its derivatives into phenolate anionic structure formed as a result of proton loss in basic environment, while the detection decreased in the presence of electron withdrawing groups such as nitro and amide. In the QCM results coated with Merrifield resin containing polymeric calix[4]arene derivative, it was observed that it showed compatibility with the monomeric structure, but the frequency change decreased with the decrease in the amount of calixarene bound. According to the results obtained, it was determined that among the prepared monomeric and polymeric calix[4]arene derivatives coated QCM sensors, the calix[4]arene derivative 4-bonded Merrifield resin (MER-4) coated QCM sensor showed the best sensing property against FEN among different phenolic aromatic pollutants in aqueous media. Thereupon, the adsorption isotherm parameters of the MER-4 coated QCM sensor were determined by performing sensing studies at different FEN concentrations. The LOD value of the developed sensor was calculated as 0.0006 M.