Insights into Kinetics and Thermodynamics for Adsorption Methylene Blue Using Ecofriendly Zeolites Materials.

Different materials have been used as adsorbents for removing micropollutants from industrial effluents, with vegetal-derived activated carbon being widely reported for dye removal, especially methylene blue (MB). However, its high cost and environmental concerns have driven the search for alternative adsorbents. Beyond developing new materials, understanding the interaction mechanisms between adsorbents and adsorbates is crucial. In this investigation, sodium (NaZ) and protonic (HZ) zeotypes were synthesized using diatomaceous earth (DE) residue as a silicon source and applied to MB dye adsorption. Batch experiments investigated adsorption rates, mechanisms, and thermodynamic spontaneity. The results showed rapid adsorption kinetics, with equilibrium achieved in about 5 min, following the Avrami model. The Weber and Morris model highlighted that the boundary layer significantly affects film diffusion and intraparticle diffusion. The adsorption process reached equilibrium governed by the Freundlich model, with favorable adsorption behavior for all adsorbents (nF values between 1 and 10). Additionally, the enthalpy values were found to be +39.66, + 5.70, and +21.79 kJ mol for NaZ, HZ, and DE, respectively. This was accompanied by a decrease in Gibbs free energy with a progressive increase in temperature, indicating a more spontaneous process at higher temperatures. These results suggest that the adsorption of MB onto the synthesized zeotypes is efficient, with fast kinetics and thermodynamic favorability. The zeotypes synthesized from diatomaceous earth exhibit promising characteristics for potential large-scale applications in wastewater treatment.