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–, HAsO4 2–, 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– andHAsO4 2–, and a low potential for NO3 – , due to the competition with OH–. The competition between these three anions and CO3 2– has been envisaged and shows that CO3 2– 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 CO3 2– introduction in water. Moreover, arsenates are able to replace carbonates even at lower concentrations. Thismeans thatHAsO4 2– anions present a stronger affinity than CO3 2– for the LDH structure. This makes mixed oxides issued from MgAl LDH very promising materials for the removal of arsenic in polluted waters