Adsorption of dye using natural clay from water

Removal of the dye methylene blue from water at different concentrations, adsorbent pH values and times was investigated. Natural clay was treated by cation exchange, which was confirmed by X-ray diffraction and infrared spectroscopy analyses. The experimental results showed that a high pH promotes adsorption. The adsorption isotherms are described by the equations of Langmuir and Freundlich isotherms. It is important to note that the quantity of calcium oxide (CaO) corresponding to calcite is higher in natural clay (9.7% by weight) compared to sodium (Na) montmorillonite fraction (2.01% by weight). This clearly shows that the clay d _hkl spacing increased from d = 13.58 Å to d = 17 Å, which could be attributed to natural clay and sodium montmorillonite, which confirms good clay purification. The maximum capacities of dyes adsorbed on natural clay and sodium montmorillonite (Q _max) are 142.85–250 and 80–277.77 mg/g, respectively. The correlation coefficients R ² = 0.99 of the Freundlich and Langmuir models for natural clays and sodium montmorillonite have the same values. This indicates that the two models are the best for the adsorption of the dye methylene blue on natural clay and sodium montmorillonite.