RETENTION OF SOME METAL-IONS ON SILICA-GEL MODIFIED WITH ALIZARIN RED-S

Retention of 11 metal ions from aqueous solutions in pH range: 1-7 was investigated using silica gel treated with a mixture of Aliquat 336 and Alizarin Red S (ARS) as a sorbent. It was found that Fe(III), Al and to a lesser degree also Ni were retained at pH less-than-or-equal-to 4; Cu, Co, Zn, Cd and Pb were retained at higher pH values whereas Mg, Ca and Cr(III) were not retained even at pH 7. All retained metals can be quantitatively eluted from the sorbent with 0.01 mol 1-1 solutions of nitric acid which removes only very small amounts (0.2%) of ARS from the sorbent. The percentage of ARS eluted from the sorbent increases in the following order of acids (at their constant concentration): H2SO4 < HCI < HNO3 < HClO4.