The use of acid-modified sepiolite and illlite minerals for the removal of congo red dye from aqueous medium

In this thesis, two clay minerals, sepiolite and illite, were modified with various acids and then tested for the removal of Congo red, an toxic dye, from aqueous solutions. Clay minerals were modified with different mineral acids and organic acids and the highest adsorption efficiencies were achieved with sulfuric acid and citric acid. The effects of process parameters such as pH, contact time, adsorbent dose, initial dye solution concentration and temperature on the removal of Congo red, which is also an anionic dye, from aqueous media by adsorption using these adsorbents were investigated. Although the highest efficiencies were achieved at the lowest pH value studied, the pH value of the aqueous phase was not changed and pH was kept around 8 in the other studies since both the efficiency values were close and the color stability was better. High agreement with the pseudo-second-order kinetic model was obtained with all adsorbents studied. Adsorption efficiency increased with adsorbent dose and decreased with dye concentration. In contrast, the highest adsorption capacity was achieved at the highest dye concentration and the lowest adsorbent dose. It was observed that the adsorption capacity increased 3-4 times with modification for both minerals. Adsorption efficiencies increased by 50% for illite, while this increase was much higher for sepiolite. For all materials, adsorption efficiency decreased with temperature and the process was shown to be exothermic. Isotherm studies showed that the equilibrium data were best explained by the Langmuir isotherm model. However, it was observed that the data were also partially compatible with the Freundlich model. Thus, in the thesis study, it was revealed that more effective adsorbents were obtained by modifying illite and sepiolite clays with acids.