The adsorption of Reactive Black 5 and Reactive Red 239 in aqueous solution on cetyltrimethylammonium bromide (CTAB)−zeolite was studied in a batch system. The natural zeolite and CTAB-modified zeolite were characterized by FT-IR and SEM analysis. Experiments were performed at different conditions such as initial dye concentration, contact time, temperature, and pH. CTAB modification covered the zeolite surface with positive charges, and the adsorption capacity of zeolite increased. The adsorption capacity of Reactive Red 239 was found to be two times higher than Reactive Blue 5 due to the hydrophilicity of the dye molecules. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms at different temperatures, and the Freundlich agrees very well with the experimental data. The pseudo-second-order model provided a very good fitting (R 2 > 0.992) for the two anionic dyes. The calculated maximum adsorption capacity (q e,calcd) increased with increasing initial dye concentration, but there is no linear relationship with pH and temperature. Thermodynamic parameters such as change in free energy (ΔG 0), enthalpy (ΔH 0), and entropy (ΔS 0) were also determined.

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Adsorption of Reactive Yellow 176 onto zeolite in a fixed-bed column system was investigated. To increase the adsorption capacity, we modified the surface of natural zeolite with a cationic surfactant (HTAB). The adsorption tests consisted of the modification of zeolite with HTAB followed by the dye removal in the column. The zeolite that was modified at 3 g/L HTAB concentration showed the best performance in adsorbing the yellow dye. The column with a 3 cm diameter and different bed heights of 25, 35, and 50 cm treated 24, 36, and 66 L at the breakthrough point, respectively, for 50 mg/L Reactive Yellow 176 dye solution at a flow rate of 0.050 L/min. The bed depth service time (BDST) model proved to be effective in the comparison of column variables. The minimum bed height, the adsorption rate constant, and the adsorption capacity of the HTAB modified zeolite for yellow dye removal were found to be 12.02 cm, 6.432 × 10 -3 L/(mg h), and 12.05 g/L, respectively. Color removal efficiencies of the simulated and real textile wastewaters were evaluated and adsorption capacity in the simulated textile wastewater and the real textile wastewater showed 25 and 62% decrease compared to the yellow dye solution. The column regeneration was also evaluated using a solution consisting of 30 g/L NaCl and 1.5 g/L NaOH with a pH value of 12 at 25 cm bed height with a flow rate of 0.050 L/min at temperatures 30 and 60 °C. Desorption efficiency increased from 23 to 90.6% with the increase in temperature from 30 to 60 °C.