Adsorption study of anionic reactive dye from aqueous solution to Mg–Fe–CO3 layered double hydroxide (LDH)

• Published in: Applied surface science 2012-10, Vol.259, p.650-656
• Main Authors: Ahmed, I.M., Gasser, M.S.
• Format: Article
• Language: English
• Subjects: Adsorption; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Congo red (CR); Cross-disciplinary physics: materials science; rheology; Dye; Dyes; Exact sciences and technology; Hydroxides; Langmuir-Blodgett films; Magnesium; Mathematical models; Mg–Fe–LDH; Physics; Regeneration; Surface chemistry; Thermodynamic
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.07.092

Second order kinetic model for adsorption of congo red onto Mg–Fe–LDH. [Display omitted] ► Mg–Fe–CO3–LDH was utilized as an adsorbent. ► It was used for the removal of congo red (CR), an anionic dye from aqueous solution. ► The adsorption of (CR) is endothermic. ► The adsorption equilibrium was well described by the Langmuir isotherm model. ► Adsorption kinetics of (CR) was found to conform to pseudo-second order model. Mg–Fe–Cl Layered double hydroxides (LDHs) have been prepared using a method involving separate nucleation and aging steps with Mg/Fe=3. The interlayer anions readily replaced by carbonate are characterized by X-ray diffraction (XRD) and FTIR. The effects of different parameters, such as pH, contact time, concentration of dye and temperature on the capacity and adsorption mechanism of Mg–Fe–CO3–LDH in removing an anionic dye (congo red, CR) from aqueous solution were separately investigated. The results show that Mg–Fe–CO3–LDH is particularly efficient in removing CR and the dye removal increases with decreasing pH. The adsorption of CR on Mg–Fe–CO3–LDH reached equilibrium after 15min where 100mg/L CR was removed. The equilibrium isotherm indicates that the adsorption of CR onto Mg–Fe–CO3–LDH fits to Langmuir and Freundlich equation as well. The adsorption data obtained from the Langmuir model gave good values of the determination coefficient and the saturated adsorption capacity of Mg–Fe–CO3–LDH for CR was found to be 104.6mg/g. The regeneration study indicates that the prepared LDH could be used for several cycles. The thermodynamic parameters have been calculated, and the adsorption process was found to be spontaneous, endothermic in nature and follows a pseudo-second-order kinetic model.