Synthesis of Zeolite Clay/Fe-Al Hydrotalcite Composite as a Reusable Adsorbent for Adsorption/Desorption of Cationic Dyes

In this study, zeolite clay was modified with Fe-Al LDH (layered double hydroxide or hydrotalcite) under ultrasonic process and was then used to remove methyl violet (MV) and Nile blue (NB) dyes from aqueous media. Various analyses such as FT-IR, EDX, SEM, and XRD were done to evaluate the adsorbent properties. The highest sorption efficiency of MV and NB dyes was 99.15% and 98.16%, respectively, which indicate significant adsorption efficiencies. The highest adsorption efficiency of MV dye was obtained at pH 8, adsorbent dosage of 1 g/L, contact time of 40 min, dye concentration of 20 mg/L and temperature of 25 °C. Also, the highest adsorption efficiency of NB dye was obtained at pH 9, adsorbent dosage of 1.25 g/L, contact time of 40 min, dye concentration of 20 mg/L and temperature of 25 °C. In addition, the maximum adsorption capacity of MV and NB dyes was found to be 81.98 and 60.61 mg/g, respectively, which are significant values. Moreover, the maximum desorption efficiencies of MV and NB were achieved 99.14% and 98.67%, respectively. Furthermore, the sorption mechanism showed that the intraparticle and film diffusion processes are important in the adsorption process. The aforementioned adsorbent can be effectively reused for five consecutive cycles. Equilibrium and kinetic studies indicated that the Freundlich isotherm model and pseudo-second-order kinetic model fit the experimental data well.