Thermodynamic studies of methylene blue adsorption onto Fe-doped sulfated titania

Abstract

Adsorption equilibrium of methylene blue onto Fe-doped sulfated titania (FST) samples was studied at different temperatures (298, 303, and 308 K). Based on the wavelength scanning from 580 to 760 nm, the wavelength of maximum absorbance of methylene blue was determined to be 666 nm and the corresponding calibration curve can be described by the equation of A = 0.0068 ? 0.1514C. The adsorption of methylene blue onto FST samples was conformed to the Langmuir isotherms. The absorption capacity of each FST sample for methylene blue increases with increasing temperature. The increase in the adsorption parameters (q m , b, and K 0 ) and the positive DH h reveal the endothermic feature of this adsorption process. The negative DG h shows the adsorption of methylene blue onto FST samples can be carried out spontaneously at the examined temperatures. Furthermore, with the calcination temperature increases, the variation in crystallization degree, the surface and the sulfur species will obviously influence the adsorption properties of FST samples and the thermodynamic parameters of this adsorption process.

Loose and Encased Graphite for Methylene Blue Adsorption: Process Optimization and Principal Component Analysis

“…The initial and final absorbance of methylene blue solutions for each set of experiments were determined by using an ultraviolet-visible spectrophotometer with the wavelength set at 666 nm [38]. The obtained absorbance values were converted to the concentration of methylene blue on the basis of a calibration curve.…”