Industrial Solid Waste-Based Layered Double Hydroxide Composite with Enhanced Adsorption Affinity to Congo Red, Acid Red, and Reactive Red

The synthesis of hierarchically porous materials from industrial solid waste as catalysts or adsorbents has attracted much attention in environmental pollution control. The present work highlights the synthesis of a series of MgFeAl layered double hydroxide (LDH) with different ratios of Mg/(Fe + Al) from red mud and ferronickel slag under different pH to decolorize three red dye solutions, namely, Congo red (CR), acid red (AR), and reactive red (RR). The maximum adsorption capacity (386.1 mg.g −1 ) for CR was obtained by the MgFeAl-LDH sample with Mg/(Fe + Al) mole ratio of 2 synthesized under pH 10. The optimized synthesis parameters led to a high surface area and large pore volume of MgFeAl-LDH, thereby enhancing the mass transfer of adsorbate to the active sites of the adsorbent. Further, the MgFeAl-LDH sample was also efficient in removing AR (120.9 mg.g −1 ) and RR (114 mg.g −1 ). Moreover, the adsorption kinetics and isotherms of MgFeAl-LDH fitted well with the pseudo-second-order and Langmuir models, respectively. The MgFeAl-LDH system developed a valuable approach to utilize industrial waste for dye removal.