Hydrotalcites as sorbent for 2,4,6-trinitrophenol:: influence of the layer composition and interlayer anion

This work evaluates the effects of different variables such as M-II/M-III ratio (layer charge), interlayer anion (CO32- or Cl-) and nature of the trivalent cation (Al3+ or Fe3+) in the sorption of 2,4,6-trinitrophenol (TNP) by layered double hydroxides (LDH) [(M1-xMxIII)-M-II (OH)(2)]A(n-) (x/n).mH(2)O (M-II = Mg2+,M-III = Al3+ or Fe3+, A = CO32- or Cl-, x = 0.33 - 0.20) and its calcined products M-II (1-x) M-III O-x(1 + x/2). TNP adsorption by anionic exchange is strongly affected by exchangeable interlayer anion, being dramatically favoured in the case of MgAlCl. TNP adsorption by anionic exchange on the MgAlCO3 system is very low and it is not affected by the Mg/Al ratio while it is in MgAlCl. In the case of the MgFeCl system, the higher polarizing character of Fe3+ makes the exchange reaction less favorable. TNP adsorption by reconstruction of the calcined products decreases in the order MgAlCO(3)500 > MgAlCl500 > MgFeCl500, and it is favored by the layer charge decrease.