Highly efficient removal of Congo red on calcined MgAl-layered double hydroxide with microporous structure

MgAl-layered double hydroxide (MgAl-LDH) is used as a promising adsorbent for efficient removal and rapid separation of Congo red (CR) contaminants. In this work, MgAl-LDH was fabricated by co-precipitation method and calcined further at different temperatures to obtain calcination products (MgAl-CLDH). The effects of various physicochemical conditions such as calcined temperature, initial dye concentration, adsorbent dosage, solution pH, and contact time on adsorption were studied in the adsorption experiment. The results show that MgAl-CLDH at 500 degrees C (CLDH-500) with a surface microporous structure completely removes the interlayer anions and other impurities. CLDH-500 is efficient for the removal of CR and has a high adsorption capability of 327 mg/g for CR compared with that of MgAl-LDH of 238 mg/g. The dynamics and isotherms fit better with the pseudo-second-order (R-2 > 0.98) and Langmuir (R-2 > 0.90) models, demonstrating the chemisorption, monolayer, and endothermic process. The adsorption thermodynamic data illustrate that the adsorption process of MgAl-LDH and CLDH on CR is endothermic, spontaneous, and thermodynamically feasible. Moreover, CLDH-500 maintains high removal efficiency and structural composition after five cycles. As revealed in Fourier transform infrared spectra and X-ray diffraction patterns before and after adsorption, the adsorption mechanism is mainly attributed to the intercalation and electrostatic interaction. Overall, this work demonstrates a facile strategy for the design and fabrication of highly efficient adsorbents for the wastewater treatment.