Study of Adsorption and Intercalation of Orange-Type Dyes into Mg–Al Layered Double Hydroxide

Abstract

In the context of depollution and textile wastewater treatment, the sorption-based processes are good candidates to achieve the efficient removal of such toxics substances as dyes. In the present study, the exchange–adsorption from aqueous solutions of three azoic dyes, Methyl Orange (MO), Orange II (OII), and Orange G (OG), onto Mg–Al–LDH–NO3 layered double hydroxides (LDH, molar Mg:Al ratio of 2) was investigated through monitoring all retained and removed species in combination with direct calorimetry and X-ray diffraction measurements. Kinetic curves, determined for several initial concentrations of the three dyes, indicated that the process was fast (between 60 and 100 min) and followed the pseudo-second order model in line with the passage of the removed dye through a chemisorption stage, thus constituting the rate-limiting step. Dye adsorption isotherms (H2-type) showed some differences in the maximum adsorption quantity (5.5 mmol g–1, MO; 2.7 mmol g–1, OII; 1.7 mmol g–1, OG), consistent with anion...