Synthesis, Characterization, and Environmental Applications of Magnesium Aluminum (MgAl) Layered Double Hydroxides for the Removal of Nitrogen Dioxide and Chromium(VI).

The discharge of chromium from tanneries is a big danger to the environment as it contaminates waterways, degrades soil, and gives rise to long-term health risks. Concurrently, the emission of NO2 from vehicle exhaust and fossil-fuel combustion leads to hazardous air pollution, intensifying environmental degradation. In this study, we explore a feasible and straightforward strategy to remove hazardous chromium-(VI) and NO2 using layered double hydroxides. Layered double hydroxides (LDHs) are a type of advanced material with brucite-like layered structures, widely studied for their effective adsorption properties in environmental remediation. In our research, MgAl-CO3 LDH was synthesized by the coprecipitation method with a Mg2+/Al3+ molar ratio of 3:1. The synthesized adsorbent and the chromate-loaded adsorbent were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) analysis, and UV-vis diffuse reflectance spectroscopy. The results showed that the desired adsorbent was successfully made and that chromium was effectively adsorbed onto the synthetic adsorbent. The adsorption performance was tested for two pollutants: Cr-(VI) in water and NO2 in the atmosphere. Cr-(VI) removal efficiency increased with time, reaching 75.03% removal after a contact time of 60 min. NO2 removal tests using the AEROQUAL S-500 monitor showed a modest reduction of 13.4% for MgAl-CO3 and 12.3% for MgAl-CrO4 within an hour. The results indicate a similar removal percentage of NO2 by MgAl-CO3 LDH and its chromate-loaded adsorbent. In short, these LDH compounds, due to their ease of synthesis and good adsorption capability, have significant potential as a solid adsorption medium for removing atmospheric NO2 and hexavalent chromium from water. Overall, this study highlights the significant utility of Mg-Al-based LDH materials as versatile and efficient adsorbents for environmental cleanup applications in both aqueous and atmospheric systems.