Introduction
Experimental
Reagents and solutions
Purolite A-400TL characteristics
Methods and measurements
Kinetic studies
-
m j = 0.5 g, V = 50 mL, C o = 100, 500, 1000 mg Pd(II)/L, A = 8, V as = 180 rpm, T—ambient, t = 1 min to 4 h, bs—0.425–0.85 mm—effect of the initial Pd(II) concentration,
-
m j = 0.5 g, V = 50 mL, C o = 500 mg Pd(II)/L, A = 8, V as = 120, 150, 180 rpm, T—ambient, t = 1 min to 4 h, bs—0.425–0.85 mm—effect of agitation speed,
-
m j = 0.5 g, V = 50 mL, C o = 500 mg Pd(II)/L, A = 8, V as = 180 rpm, T—ambient, 313, 333 K, t = 1 min to 4 h, bs—0.425–0.85 mm—effect of temperature,
-
m j = 0.5 g, V = 50 mL, C o = 500 mg Pd(II)/L, A = 8, V as = 180 rpm, T—ambient, t = 1 min to 4, beads size—f 1, f 2, f 3, f 4 (0.85 > f 1 ≥ 0.6 mm; 0.6 > f 2 ≥ 0.5 mm; 0.5 > f 3 ≥ 0.43 mm, 0.43 > f 4 ≥ 0.425 mm)—effect of beads size distribution.
Equilibrium studies
Desorption studies
Breakthrough capacities
Analytical procedure
Results and discussion
Sorption capacity—effect of experimental conditions
Metal | Electron configuration | LK | Ionic structure | Complexes formed low—[Cl−]—high | Redox stability | Kinetic stability | Thermal stability | ||
---|---|---|---|---|---|---|---|---|---|
Pd(II) | d8
| 4 | Square planar | PdCl4
2−
| PdCl4
2−
| Stable | Very stable | − | |
Pd(IV) | d6
| 6 | Octahedral | PdCl6
2−
| PdCl6
2−
| Unstable | Stable | Unstable | |
Pt(II) | d8
| 4 | Square planar | PtCl4
2−
| PtCl4
2−
| Unstable | Unstable | − | |
Pt(IV) | d6
| 6 | Octahedral | PtCl6
2−
| PtCl6
2−
| Stable | Very stable | Very stable | |
Au(III) | d8
| 4 | Square planar | AuCl4
−
| AuCl4
−
| – | – | – |
Time |
F
| Plot q
t versus t
| Experimental conditions | ||||||
---|---|---|---|---|---|---|---|---|---|
Effect of initial Pd(II) concentration (mg/L) | |||||||||
HCl system | HCl–HNO3 system |
t
1/2 (s) | |||||||
t (min) | 100 | 500 | 1000 | 100 | 500 | 1000 | |||
1 | 0.71 | 0.81 | 0.91 | 0.68 | 0.55 | 0.76 | <60 s |
m
j = 0.5 g,
V = 50 mL, Co = 100, 500, 1000 mg/L in 0.1 M HCl,
A = 8, V
as = 180 rpm,
T—ambient,
t = 1 min to 4 h, bs—0.425–0.85 mm | |
3 | 0.90 | 0.93 | 0.97 | 0.85 | 0.77 | 0.78 | |||
5 | 0.95 | 0.97 | 0.99 | 0.93 | 0.88 | 0.85 | |||
10 | 1.00 | 0.99 | 0.99 | 0.98 | 0.99 | 0.88 | |||
15 | 1.00 | 1.00 | 1.00 | 0.99 | 0.99 | 1.00 | |||
30 | 1.00 | 1.00 | 0.99 | 1.00 | 1.00 | 1.00 | |||
60 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |||
120 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |||
180 | 1.00 | 1.00 | 0.99 | 1.00 | 1.00 | 1.00 | |||
240 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
Time | Effect of agitation speed (rpm) | Plot q
t versus t
| Experimental conditions | ||||||
---|---|---|---|---|---|---|---|---|---|
HCl system | HCl–HNO3 system |
t
1/2 (s) | |||||||
t (min) | 120 | 150 | 180 | 120 | 150 | 180 | |||
1 | 0.72 | 0.77 | 0.81 | 0.71 | 0.56 | 0.55 | <60 s |
m
j = 0.5 g,
V = 50 cm3, C
o = 500 mg/L,
A = 8, Vas = 120, 150, 180 rpm, T—ambient,
t = 1 min to 4 h, bs—0.425–0.85 mm | |
3 | 0.73 | 0.87 | 0.93 | 0.76 | 0.64 | 0.77 | |||
5 | 0.76 | 0.92 | 0.97 | 0.72 | 0.78 | 0.88 | |||
10 | 0.80 | 0.98 | 0.99 | 0.82 | 0.95 | 0.99 | |||
15 | 0.80 | 1.00 | 1.00 | 0.83 | 0.95 | 0.99 | |||
30 | 0.89 | 1.00 | 1.00 | 0.94 | 1.00 | 1.00 | |||
60 | 0.99 | 1.00 | 1.00 | 0.98 | 1.00 | 1.00 | |||
120 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |||
180 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |||
240 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
Time | Effect of temperature (K) | Plot q
t versus t
| Experimental conditions | ||||||
---|---|---|---|---|---|---|---|---|---|
HCl system | HCl–HNO3 system |
t
1/2 (s) | |||||||
t (min) | 298 | 313 | 333 | 298 | 313 | 333 | |||
1 | 0.81 | 0.86 | * | 0.55 | 0.83 | * | <60 s |
m
j = 0.5 g,
V = 50 cm3, C
o = 500 mg/L,
A = 8, V
as = 180 rpm, T—ambient (about 298), 313 K.
t = 1 min to 4 h, bs—0.425–0.85 mm | |
3 | 0.93 | 0.98 | 0.77 | 0.94 | |||||
5 | 0.97 | 0.99 | 0.88 | 0.97 | |||||
10 | 0.99 | 1.00 | 0.82 | 0.95 | |||||
15 | 1.00 | 1.00 | 0.83 | 0.95 | |||||
30 | 1.00 | 1.00 | 0.94 | 1.00 | |||||
60 | 1.00 | 1.00 | 0.98 | 1.00 | |||||
120 | 1.00 | 1.00 | 1.00 | 1.00 | |||||
180 | 1.00 | 1.00 | 1.00 | 1.00 | |||||
240 | 1.00 | 1.00 | 1.00 | 1.00 |
Time | Effect of beads size | Plot q
t versus t
| Experimental conditions | ||||||
---|---|---|---|---|---|---|---|---|---|
HCl system | HCl–HNO3 system |
t
1/2 (s) | |||||||
t (min) |
f
3
|
f
4
|
f
1, f
2
|
f
3
|
f
4
|
f
1, f
2
| |||
1 | 0.80 | 0.82 | ** | 0.78 | 0.80 | ** | <60 s |
m
j = 0.5 g,
V = 50 cm3, C
o = 500 mg/L,
A = 8, V
as = 180 rpm,
T—ambient,
t = 1 min to 4, beads size—f
1, f
2, f
3, f
4
0.85 > f
1 ≥ 0.6 mm, 0.6 > f
2 ≥ 0.5 mm, 0.5 > f
3 ≥ 0.43 mm, 0.43 > f
4 ≥ 0.425 mm | |
3 | 0.92 | 0.93 | 0.87 | 0.89 | |||||
5 | 0.96 | 0.98 | 0.90 | 0.91 | |||||
10 | 1.00 | 1.00 | 0.96 | 0.96 | |||||
15 | 1.00 | 1.00 | 0.99 | 0.97 | |||||
30 | 1.00 | 1.00 | 0.99 | 0.99 | |||||
60 | 1.00 | 1.00 | 0.99 | 0.95 | |||||
120 | 1.00 | 1.00 | 0.99 | 0.99 | |||||
180 | 1.00 | 1.00 | 0.99 | 0.99 | |||||
240 | 1.00 | 1.00 | 1.00 | 1.00 |
Effect of agitation speed
Effect of temperature
Effect of bead size distribution
Equilibrium studies
Isotherm model applied | Parameters | |||||
---|---|---|---|---|---|---|
Equation | No. | Plot | Symbols | |||
Langmuir |
\( \frac{{C_{\text{e}} }}{{q_{\text{e}} }} = \frac{1}{{Q_{\text{o}} b}} + \frac{{C_{\text{e}} }}{{Q_{\text{o}} }} \)
| (3) |
C
e/q
e vs C
e
|
Q
0—the Langmuir monolayer sorption capacity (mg/g),
b—the Langmuir constant related to the free energy of sorption (dm3/mg),
R
L—separation factor or equilibrium parameter,
k
F—the Freundlich adsorption capacity (mg/g), 1/n—the Freundlich constant related to the surface heterogeneity |
Q
o (mg/g) | 404.15 |
b (dm3/mg) | 0.0106 | |||||
R
L
| 0.4868 | |||||
R
2
| 0.9448 | |||||
Freundlich |
\( \log q_{\text{e}} = \log k_{\text{F}} + \frac{1}{n}\log C_{\text{e}} \)
| (4) | log q
e vs log C
e
|
k
f (mg/g) | 51.25 | |
1/n
| 0.2745 | |||||
R
2
| 0.9266 |
Fitting | |
---|---|
Column experiment
Desorption and reusable properties of purolite A-400TL
0.1 M HCl—100 mg Pd (II)/L | |||||||
---|---|---|---|---|---|---|---|
Eluting agent |
S
1
|
D
1
|
S
2
|
D
2
|
S
3
|
D
3
| |
1 | 0.1 M HNO3
| 100.0 | 0.5 | 99.8 | 0.6 | 99.8 | 0.6 |
2 | 1.0 M HNO3
| 100.0 | 10.5 | 99.8 | 8.0 | 99.8 | 8.2 |
3 | 2.0 M HNO3
| 100.0 | 19.4 | 99.7 | 13.1 | 99.8 | 12.9 |
4 | 3.0 M HNO3
| 100.0 | 25.9 | 99.8 | 16.1 | 99.8 | 15.6 |
5 | 4.0 M HNO3
| 100.0 | 30.5 | 99.8 | 20.3 | 99.9 | 17.4 |
6 | 0.1 M HCl | 100.0 | 0.1 | 99.8 | 0.0 | 99.9 | 0.1 |
7 | 1.0 M HCl | 100.0 | 1.9 | 99.9 | 2.0 | 99.8 | 2.5 |
8 | 2.0 M HCl | 100.0 | 5.4 | 99.9 | 4.7 | 99.9 | 5.8 |
9 | 3.0 M HCl | 100.0 | 8.0 | 99.9 | 7.4 | 99.9 | 8.6 |
10 | 6.0 M HCl | 100.0 | 24.3 | 99.9 | 19.1 | 99.9 | 18.1 |
11 | 0.5 M NH4OH | 100.0 | 44.9 | 99.8 | 22.4 | 99.6 | 19.1 |
12 | 1.0 M NH4OH | 100.0 | 42.9 | 99.8 | 23.3 | 99.6 | 17.5 |
13 | 2.0 M NH4OH | 100.0 | 46.9 | 99.8 | 23.2 | 99.8 | 18.3 |
14 | 3.0 M NH4OH | 100.0 | 44.8 | 99.8 | 21.4 | 99.8 | 17.7 |
15 | 4.0 M NH4OH | 100.0 | 43.8 | 99.7 | 24.5 | 99.8 | 18.9 |
16 | 0.5 NaOH | 100.0 | 23.9 | 99.9 | 14.3 | 99.9 | 5.1 |
17 | 1.0 M NaOH | 100.0 | 27.3 | 99.9 | 20.6 | 99.9 | 16.8 |
18 | 2.0 M NaOH | 100.0 | 35.2 | 99.9 | 20.8 | 99.9 | 17.4 |
19 | 3.0 M NaOH | 100.0 | 37.5 | 99.9 | 22.4 | 99.9 | 18.5 |
20 | 0.5 M H2SO4
| 100.0 | 0.2 | 99.9 | 0.2 | 99.9 | 0.2 |
21 | 2 M H2SO4
| 100.0 | 3.3 | 99.9 | 2.8 | 99.8 | 2.6 |
22 | 4 M H2SO4
| 100.0 | 5.2 | 99.9 | 3.9 | 99.8 | 3.4 |
23 | 1.0 M TU | 100.0 | 40.0 | 99.1 | 23.3 | 99.3 | 14.4 |
24 | 1.0 M TU—0.1 HCl | 100.0 | 41.7 | 99.7 | 25.0 | 99.0 | 16.2 |
25 | 1.0 M TU—0.1 HNO3
| 100.0 | 38.0 | 99.4 | 14.1 | 99.6 | 15.0 |
-
sorption SBA resin capacities are high and even after three cycles of sorption–desorption these values remain almost unchanged—the capacity reduction is smaller than 1 %. The advantage of this resin is the fact that it can be used many times without significant reduction of capacity.
-
desorption effectiveness of desorption studies is not satisfactory enough. Application of acids gives desorption yield in the range from 0.1 to 30.5 % (D1), from 0 to 20.3 % (D2), and from 0.1 to 18.5 % (D3). Better % of desorption was obtained by using basic solution but the desorption yield did not exceed 47 %. Acidic solutions of TU and those without acid in this case did not give satisfactory results either. The % of desorption usually decreases with the next cycle of sorption–desorption. In the calculation of % D, e.g., in the second step, the amount of Pd(II) not desorbed in the first cycle was taken into account and added to the amount of Pd(II) retained in the second step of sorption.