Thermodynamic and kinetic studies for the removal of safranin dye from aqueous solution using nap zeolite synthesized from coal fly ash.

Zeolite was prepared from coal fly ash with sodium hydroxide in different concentration ratios at 550 °C with activation time of 12 hours by direct hydrothermal method. It was characterized by XRF,SEM, XRD and FTIR. Batch studies were conducted to study the effect of contact time, pH, amount of adsorbent, adsorbate concentration and temperature. The results revealed that the removal of Safranin dye was strongly pH dependent and maximum dye removal was observed at equilibrium pH of 9.0, optimum adsorbent dose and contact time were found to be 5 g/l and 180 minutes respectively. It was found that adsorption increased with increase in temperature thereby showing the process exothermic in nature. The experimental data were analyzed by Langmuir, Freundlich, Temkin and Dubnin isotherm models. The maximum removal of safranin dye was found to be 97.14% at 25 °C. The mechanism of adsorption was also investigated using kinetic models pseudo-first-order, pseudo-second-order, Elovich and Intra particle diffusion. [ABSTRACT FROM AUTHOR]