Comparison of the fluoride, arsenate and nitrate anions water depollution potential of a calcined quintinite, a layered double hydroxide compound

The potential for removing anionic pollutants such as F−, HAsO42−, and NO3− from water by mixed oxides issued from the moderate thermal treatment of quintinite (Mg4Al2 LDH) has been studied. This compound shows good trapping properties for F− and HAsO42−, and a low potential for NO3−, due to the competition with OH−. The competition between these three anions and CO32− has been envisaged and shows that CO32− is able to easily replace F− and NO3−, making the mixed oxides issued from MgAl LDH an inappropriate trap for F− and NO3−. However, only small amounts of arsenic are released after the CO32− introduction in water. Moreover, arsenates are able to replace carbonates even at lower concentrations. This means that HAsO42− anions present a stronger affinity than CO32− for the LDH structure. This makes mixed oxides issued from MgAl LDH very promising materials for the removal of arsenic in polluted waters.