On the other hand, further modification of nano-Fe3O4-DOP
sorbent with triethylenetetramine for the formation of nano-
Fe3O4-DOP-TETA was found to produce a novel sorbent. The metal
sorption characteristics of nano-Fe3O4-DOP-TETA with Ni(II),
Cd(II) and Pb(II) under the same conditions (pH 1.0–7.0) were
studied and the metal capacity values are compiled in Table 1. The
contribution of surface loaded TETA molecules on this sorbent was
characterized by a direct enhancement in the high tendency to
bind with the examined three metal ions in all evaluated pH
conditions (pH 1.0–7.0). This behavior can be confirmed from the
increasing order in the maximum capacity values which are foundto correspond to 466.7, 533.3 and 1000.0 mmol g1 for Ni(II), Pb(II)
and Cd(II), respectively in pH 7.0. Adsorption of metal ions to the
surface of nano-Fe3O4-DOP-TETA sorbent may be produced by the
direct complex formation with the four nitrogen donor atoms
located within the structure of TETA molecule. This behavior refers
to the high affinity and selectivity characters incorporated into
nano-Fe3O4-DOP-TETA for binding with Cd(II) in all examined pH
conditions as also represented in Fig. 4.