2.3.1. Adsorption Kinetics

To determine the characteristics of the dye adsorption equilibrium on the molecular sieves, a study was conducted on their adsorption kinetics. For this purpose, 10 mg were taken of each of the solids synthesized and these were dispersed in 200 mL of methylene blue solution with a concentration of 50 ppm, at room temperature, under continuous agitation and complete darkness. Thereafter, every 10 min, aliquots of this suspension were extracted and their spectra were taken, considering the maximum absorbance of the methylene blue at 665 nm using a UV-Vis spectrophotometer (Spectronic Genesys 6); this procedure was repeated over a total time of 60 min. Then, through mathematical calculations and using the calibration curve method, the quantity in milligrams of methylene blue milligrams adsorbed on the solids was determined; the curve for the "*q*" coefficient (mg of methylene blue adsorbed/mg of the photocatalyst) as a function of time was obtained. This permitted determining the time interval the system should be kept in continuous agitation prior to turning on the UV lamps to determine the photodegradation capacity of suspended Nb/MCM-41 solids.
