Conversion of secondary aluminum dross into hierarchical carbonate-intercalated Mg-Al layered double hydroxide for efficient CO2 capture

This paper explores the preparation of hierarchical Mg-Al layered double hydroxide (LDH) from secondary aluminum dross waste for the first time. The aluminum content of the waste was initially extracted in the form of a sodium aluminate solution using a multistep wet chemical process. CO3-intercalated Mg-Al LDH was then prepared at pH values of 9 and 11 by adding magnesium chloride to a mixed solution of sodium aluminate and sodium carbonate. The X-ray diffraction (XRD) analysis revealed that a pure LDH structure could be formed at pH 11. The quantification of the XRD data revealed that the synthesized LDH had an interlayer spacing of 3.1 & Aring;. The microstructural porosity was 0.76 cm3/g, and the specific surface area was 134 m2/g. The field emission scanning electron microscopy (FESEM) analysis revealed a hierarchical layered structure composed of flake-like particles in the microstructure. The elemental mapping of the synthesized LDH showed a proper distribution of Mg, Al, C, and O. The synthesized Mg-Al-CO3 LDH was then used for a study on CO2 capture. The CO2 capture experiments demonstrated that the amount of CO2 adsorption is influenced by temperature, gas pressure, adsorbent mass, and exposure duration. Investigating the effects of time and temperature revealed that a CO2 adsorption of 0.94 mmol/g can be achieved at a temperature of 25 degrees C during a 90-minute exposure period. Varying the gas pressure from 1 to 2.5 bar, while maintaining a constant temperature of 25 degrees C and an adsorbent mass of 1.5 g, resulted in an increase in CO2 adsorption from 1.7 to 2.3 mmol/g. Reusability tests showed that the LDH could maintain a satisfactory adsorption value of 0.84 mmol/g after 5 cycles, indicating its potential for repeated use.