MgAl layered double oxide: One powerful sweeper of emulsified water and acid for oil purification.

We exploit a novel role of MgAl-layered double oxide (LDO) as a powerful sweeper to remove trace emulsified water and organic acids from contaminated oil. Notably, 0.4 g of LDO enable to purify 20 mL of contaminated oil with 0.2 g of water and 0.1 mL of octanoic acid, and the separation efficiency reaches 94.6 and 28.2%, respectively. The separation process is initiated with the immobilization of water droplets at the crystalline matrix of LDO (driven by the unique water memory effect), accompanied by the LDO converted to MgAl-layered double hydroxide (LDH). LDH possesses a high point of zero charge and abundant OH- and Mg2+/Al3+ on its layered surface, which enables it to remove the acids via neutralization and complexing reactions. The immobilized water and adsorbed acids are eventually swept by collecting the solids. The collected solids, mainly composed of LDH, can be regenerated to LDO for recycle through a calcination process. Economy evaluation reveals it takes $6.7 for LDO to purify every cubic meters of emulsion, much more cost-effective than the reported CaSO4•0.5H2O and Fe3O4-based adsorbents. The robust performance with the competitive economy points to the high potential of LDO for oil regeneration.