Comparative Metal Ion Binding to Native and Chemically Modified Datura innoxia Immobilized Biomaterials - Biomaterials: Physics and Chemistry - page 145

the history of exposure appears to impact apparent steady state binding metal ion capacities
of the biomaterial.

1.00E-06 1.00E-06

8.00E-07 8.00E-07

6.00E-07 6.00E-07

B

A

4.00E-07 4.00E-07

2.00E-07 2.00E-07

0.00E+00 0.00E+00

0 0 0 0 0 0
Effluent Volume (mL)

0 0 0 0 0 0
Effluent Volume (mL)

1.50E-06

1.00E-06

D

8.00E-07

1.00E-06

6.00E-07

C

4.00E-07

5.00E-07

2.00E-07

0.00E+00 0.00E+00

0 .51 .52 .5
Effluent Volume (mL)

0 0 0 0 0 0
Effluent Volume (mL)

Fig. 1. Effluent profiles resulting from solutions of (A) 0.2mM Zn 2+ (), (B) followed by 0.2
mM Ni 2+ (□), followed by 0.2mM Cd 2+ () pumped through a column packed with
chemically modified D. innoxia .(D) Effluent profile of first 1.0M HCl wash of the metal-laden
material.

3.2 Modified material three-metal sequential study
Total amounts of metal bound to the native and modified materials at each stage of the
sequence are listed in Table 2. Although the average amount of the fist metal ion bound was
24.5 µmol g -1 , the average total metal ion bound after exposure to the second and third
metals was 31.0 µmol g -1 . This increase in the amount of metal captured by the biomass
could be indicative of either the presence of metal ion-specific binding sites, or some degree
of competitive metal ion binding.
Simultaneous exposure of the biosorbent material to an equimolar solution of all three
metal-ions (0.2 mM) was undertaken. Figure 2A shows the resulting effluent concentration
profile. Even with a total metal ion concentration of 0.6 mM, the effluent concentration
maximized at only 94% of the influent concentration (i.e., 0.19 mM). The modified
biomaterial average capacity with simultaneous exposure was 41.72 mol g -1 biomaterial.
Specifically, total amounts of metal ion bound were 13.24, 14.17, and 14.31 mol g -1 for Ni 2+
Zn 2+ Cd 2+ , respectively. This suggests no significant binding preference of the D. innoxia cell
material for these ions.
Figure 2B shows the effluent concentration profile of the subsequent 1.0 M HCl metal-ion
recovery/strip step. Total metal ion recovered from the two acid washes was 27.48 mol g -1 .