Some dyes and Cr (VI) removal from aqueous solutions using synthetic ion exchange resins

In this study, Brilliant Blue FCF and Amaranth dyes and Cr (VI) removal were carried out using strong anionic Lewatit MP 600 and Lewatit SR 7 ion exchange resins. The resins used are an ideal sorbent for the removal of dyes and Cr (VI) from aqueous solutions. For Brilliant Blue FCF, Amaranth and Cr (VI) removal, the effects of certain parameters such as contact time, initial concentration, pH and amount of ion exchange resin on equilibrium studies were investigated. The optimum pH for Brilliant Blue FCF and Amaranth dyes with both resin was found to be in the range of 2-4 and the amount of the resin was 0.05 g. The optimum contact time for Lewatit MP 600 resin and Brilliant Blue FCF dye removal was 150 min, and Amaranth dye, the optimum contact time was 120 min. While the optimum contact time for Brilliant Blue FCF removal with Lewatit SR 7 resin was determined as 180 min and it was determined as 150 min for Amaranth dye. The optimum pH for Cr (VI) removal with both resins was found to be in the range of 2-5, the contact time was 90 minutes and resin amounts were 0.05 g. In equilibrium studies, reaching the equilibrium in a short time and removing dyes and Cr (VI) from the aqueous medium quickly showed that the efficiency of the resins to sorp these substances is high. Characterization of resins by Fourier Transform Infrared Spectroscopy (FT-IR) and surface morphology by Scanning Electron Microscope (SEM) were investigated before and after Lewatit MP 600 and Lewatit SR 7 resins adsorb dyes and Cr (VI) ions. In order to find the removal amounts of these dyes and Cr (VI) from the aqueous medium and to determine the capacity of the resins, the graphs of the dyes and Cr (VI) retained by the resin against the equilibrium dye and Cr (VI) concentrations were drawn seperately. The capacity of resins was determined by applying Langmuir, Freundlich, Dubinin-Raduskevich and Scatchard adsorption isotherm models to the graphs. It was concluded that the Langmuir isotherm model is more suitable for Brilliant Blue FCF, Amaranth and Cr (VI) removals for both resins used. According to these isotherms, the sorption capacity of Lewatit MP 600 resin for Brilliant Blue FCF, Amaranth and Cr (VI) was 65.36, 51.81, and 227.3 mg/g, respectively and the sorption capacity of the Lewatit Sybron Ionac SR 7 resin was 51.81, 65.79, and 200.0 mg/g, respectively. Appropriate models were selected for the resins used by making kinetic models. The pseudo-second-order kinetic model was more suitable than the pseudo-first-order kinetic model for Brilliant Blue FCF, Amaranth and Cr (VI) removals. From the results obtained, it is seen that these resins are suitable for removing dyes and Cr (VI) from aqueous solutions and are recommended for use in treatment plants.