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

Abstract : 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- 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.