Removal of Isolan Dark Blue 2SGL-01 from aqueous solutions onto calcined and uncalcined (Mg-Zn)/(Al-Fe)-(CO3)/Cl layered double hydroxides

Abstract

The adsorption process of the industrialized dye Isolan Dark Blue 2SGL-01 (IDB) onto (Mg-Zn)/(Al-Fe)-(CO3)/Cl layered double hydroxides (LDHs) coded LDH21 and LDH22 and its calcined products CLDHs (CLDH21 and CLDH22), respectively, was investigated. The characterization of LDHs and CLDHs before and after loading with IDB by Fourier transform infrared, scanning electron microscope and surface area measurements showed a typical hydrotalcite structure and confirmed the loading of IDB. The adsorption parameters; initial pH, shaking time, adsorbent dose, initial concentration of IDB dye and temperature were studied. The optimum conditions for IDB adsorption were pH 4.3 and shaking time 3 h. A complete removal of IDB (> 99%) was achieved using a dosage of 2.0 g L− 1 CLDHs or LDH22, and 3.0 g L− 1 of LDH21. The adsorption processes were suggested to be best described by the pseudo-second order kinetics and Langmuir-type adsorption isotherm with monolayer capacities of 75, 91, 427 and 530 mg g− 1, onto LDH21, LDH22, CLDH21 and CLDH22, respectively. The loaded IDB was recovered from LDHs and CLDHs adsorbent using Na2CO3. CLDH22 showed best adsorption capacity of 530 mg g− 1. Its adsorption thermodynamic parameters ∆Gadsorption, ∆Hadsorption and ∆Sadsorption indicated that the adsorption processes were spontaneous and endothermic in nature. CLDH22 was successfully applied for the removal of IDB from simulated dyeing process with removal efficiency 97%.