204
Ind. Eng. Chem. Res. 1992,31, 204-209
(90) Gatte, R. R.; Phillips, J. Thermochim. Acta 1989, 154, 13. (91) Chorkendorf, I.; Alstrup, I.; Ullmann, S. Surf. Sci. 1990,227, 291.
(92) Alstrup, I.; Chorkendorf, I.; Ullmann, S. Surf. Sci. 1990, 234, 79. (93) Anderson, N. T.; Topsoe, F.; Alstrup, I.; Rostrup-Nielsen, J. R. J. Catal. 1987, 104, 454. (94) Imbihl, R.; Behm, R. J.; Christmann, K.; Ertl, G.; Matsushima, T. Surf. Sci. 1982, 117, 257. (95) Kortan, A. R.; Park, R. L. Phys. Rev. B 1981,23,6340. (96) Ramanathan, R.; Blakely, J. M. Mater. Lett. 1983,2, 12.
(97) Zakumbaeva, G. D.; Artamonov, S. V. React. Kinet. Catal. Lett. 1979, 10, 183. (98) Pankratiev, Yu. D.; Buyanova, N. E.; Turkov, V. M.; Shepelin,
A. P.: Malvshev. E. M.: Zhdan. P. A. React. Kinet. Catal. Lett. 1982,'20,139.
'
(99) Zakumbaeva, G. D.; Marina, N. A.; Naidin, V. A.; Dostiyarov, A. M.; Toktabaeya, N. F.; Litvyakova, E. N. Kinet. Katal. 1983, 24, 449.
Received for review September 3, 1991 Accepted September 24,1991
Preparation and Performance of Amidoxime Fiber Adsorbents for Recovery of Uranium from Seawater Tokihiro Kago, Akira Goto, Katsuki Kusakabe, and Shigeharu Morooka* Department of Chemical Science and Technology, Kyushu University, Fukuoka 812, Japan
Commercial acrylonitrile fibers of different shapes were treated in a 1.5 or 3.0 w t % NHzOH methanolic solution a t 80 "C and then a 0.1 mol-L-' NaOH aqueous solution at 30 or 80 "C. The treatment was performed for various reaction periods. The intrinsic rate of adsorption of uranium from seawater using the amidoxime fibers became maximum at a certain reaction time for the NH20H treatment as well as the NaOH treatment and was in the range of 200-600 mg per kilogram of dry fiber per day for the first adsorption run. The adsorption rate of the optimized fibers was decreased by repeating the adsorption and desorption cycle, while that of the fibers whose NaOH treatment was not sufficient was nearly constant in spite of such repetition. The tensile strength of the adsorption fibers decreased with increasing NaOH treatment period.
Introduction Since the concentration of uranium in seawater is as low as 3 mg.m-3, synthesis of a highly selective and stable adsorbent is essential for the economic recovery of uranium from seawater. Screening tests carried out by Schenk et al. (1982), Astheimer et al. (1983),and Egawa et al. (1979, 1988) revealed that amidoxime resin is most promising. Normally, amidoxime resin is used in the shape of fine particles to reduce the intraparticle mass transfer resistance, and the particles are contacted with seawater in a fluidized bed. Fibrous amidoxime adsorbents synthesized from commerical polyacrylonitrilefibers with hydroxylamine are also attractive because of the high adsorption rate due to their small diameter. Kobuke et al. (1990a) studied the nature of so-called amidoxime fiber and found that the imidedioxime group WPS dominant in reactive fibers. However, the amidoxime group is important in other cases, and no procedures are established to date for the selective production of amidoxime or imidedioxime groups. Katoh et al. (1982) prepared a 40-pm-diameter fiber that adsorbed nearly 2 g of uranium/kg of dry fiber after 7 days. Omichi et aL (1987) obtained a 40-pm-diameteramidoxime fiber which adsorbed 5 g/kg of dry fiber after 140 days. The fiber prepared by Sugasaka et al. (1981) and Takagi et al. (1989) adsorbed 10 g/kg of dry fiber in 80 days. Kobuke et al. (1988, 1990b) made a composite fiber by entrapping finely powered amidoxime into fibrils of supporting materials mixed with silica particles. However, most of the fibers showing high adsorption rates were synthesized at the sacrifice of strength. Saito et al. (1988, 1990) and Takeda et al. (1991), on the other hand, made a unique adsorbent by radiation-induced graft polymerization of acrylonitrile onto s m d polyethylene hollow fiber.
* Author to whom correspondence should be addressed.
Table I. Mean Size of Fibers nominal fiber size, denier fiber component" d , of init dry fiber, pm d,ld,, for swollen fiber
3
6
15
M
B
M
20
27 0.68
41 0.91
0.91
M = monocomponent; B = bicomponent.
Their fiber is quite strong, but a further increase in adsorption rate is needed. Katoh and co-workers (Katoh and Sugasaka, 1987) prepared a ball-type adsorbents by entangling chopped fibers. A fibrous ball was formed by stirring during the amidoximation. Nobukawa et al. (1989) proposed a novel concept of the adsorption bed, according to which the fibrous ball adsorbenta are packed in cages 0.2-0.5 m thick and 3-5 m in diameter. The cages are arranged in stacks suspended by ropes from a moored buoy. Seawater permeates the fibrous bed within the pressure drop induced by ocean current. They estimated the production cost is less than $150/kg of uranium if the fiber could adsorb uranium at a rate of 4.5 g/kg of dry fiber in 40 days, about 60% of that of Sugasaka et al. (1981) and Takagi et al. (1989). According to the calculation of Morooka et al. (1991), the permeation velocity of seawater through the fibrous ball is inversely proportional to the square of the fiber diameter at a given pressure drop (Kyan et al., 1970),and the overall efficiency of the adsorption unit is a function of various factors including the fiber size. A higher adsorption rate is of course attained with a smaller fiber if the fiber is dispersed in seawater, but the fiber loses mechanical stability. These conflicting demands must be satisfied by the synthesis of fibers that are both active and strong. In the present study, amidoxime fibers are synthesized under various conditions, and the stability of the fibers
0888-5885/ 9212631-0204$03.O0/ 0 0 1992 American Chemical Society
Ind. Eng. Chem. Res., Vol. 31, No. 1, 1992 205 4
600 -
p
0
Y
(a)
(b)
Figure 1. Crowsectional shape of fibers: (a) monocomponent fiber; (b) bicomponent fiber.
regarding adsorption rate and tensile strength is studied in detail.
Experimental Section Two kinds of commercial polyacrylonitrile fibers were obtained from Mitsubishi Rayon Co.: a monocomponent fiber containing 6.9% vinyl acetate and a bicomponent fiber comprising a part blended with 5.8% methyl acrylate and 0.4% sodium methallysulfonate and a part blended with 1.2% sodium methallylsulfonate. Cross-sectional views are shown in Figure 1,and the nominal and actual sizes of the fibers are listed in Table I. The average projected diameter, d,, was determined by measuring randomly laid fiber diameters magnified on the display of a micrograph video system. The average hydrodynamic diameter defined by the following equation, dfh,was also determined. cross-sectional area dfi = 4 (1) peripheral length of cross section The fiber was treated with a 1.5 or 3.0 wt % methanolic solution of NHzOH produced by neutralization of NHzOH.HC1 with a NaOH methanolic solution. The reaction was performed at 80 "C under a pressure of 0.23 MPa for a prescribed period in a glass autoclave of 200 mL equipped with a paddle which rotated in alternate directions at intervals of 1 / 3 s to prevent entanglement. After the NHzOH treatment, the fiber was rinsed with water and then treated in a 0.1 mo1.L-' NaOH solution at 30 or 80 "C for a prescribed period. The density of the original fiber was 1.14 kgL-', that of the dry amidoxime fiber was 1.2 kgL-I, and that of the swollen amidoxime fiber was 1.04-1.14 kgL-'. The intrinsic rate of uranium adsorption excluding the liquid-side mass-transfer resistance was determined by the following procedures (Kato et al., 1990): 1. A sample of 40-90 mg of amidoxime fiber was packed in a framed space 15 mm square and 2 mm thick, sandwiched with plastic nets. The void fraction of the packing was 0.5-0.7. The frame was connected to a 15-mm-square duct, and filtered seawater a t 25 "C was passed through the fiber bed. The adsorption rate became constant when the liquid velocity was higher than 0.2 cms-'. 2. A small mass of amidoxime fiber (normally 20 mg) was sandwiched with 40-mesh polyester nets in the shape of a 25-mm-square mattress whose periphery was welded with an ultrasonic plastic welder (Morooka et al., 1990). Two or three mattresses were suspended for a prescribed number of days at 25 "C in a tank of seawater with vigorous stirring. These methods gave the same result. The latter was mostly used for the adsorptivity tests because of its simplicity, and all the adsorption rates in this article are intrinsic values. The adsorption period was fixed as 1 day unless otherwise noted. The desorption of adsorbed uranium was accomplished by contacting the adsorbent with a 1mol-L-' HC1 solution
0,
400-
C
-
z .2 @
8
200-
P
-
t
0
1
20 LO 60 NaOH treatment period Cminl
0
Figure 2. Effect of NaOH treatment period on adsorption rate: 3-denier fiber; A M conditions, 1.5% ",OH, 80 OC, 8 h; AL temperature, 80 OC. 4oc
(
,
#
I
,
6-denier
100
1u
I
I
20
30
I
I
I
Eo
40 50 NaOH treatment period t h I
Figure 3. Effect of NaOH treatment period on adsorption rate: 6-denier fiber; A M conditions, 1.5% NHZOH, 80 OC; AL temperature, 30 OC.
at 30 "C for 2 h. Uranium concentration in extract solutions was determined by ICP spectrometry at 385.96 nm, and that in seawater was evaluated as 2.9-3.1 mg.m-3 (average 3 mgm-3) by the Arsenam III method (Motojima et al., 1969). The tensile strength of amidoxime fibers was measured with a Tensilon UTM-111-500 (Toyo Baldwin Co.) at ambient temperature. The stretching rate was 20 mmmin-l, and the sample was kept wet with seawater.
Adsorption Rate of Amidoxime Fibers Figure 2 shows the effect of NaOH treatment time on the adsorption rate of uranium from seawater in the first adsorption run for the 3-denier fiber which was treated with 1.5 wt % NHzOH at 80 "Cfor 8 h. A clear optimum period for the NaOH treatment was observed. The maximum adsorption rate was larger than 600 mg per kilogram of dry fiber per day. Hereafter, this unit is expressed as mgkg-'.d-l. Figures 3 and 4 show the effect of NH20H and NaOH treatment periods on the adsorption rate for the first adsorption run. The optimum NaOH treatment period was about 40 h at 30 "C for the fiber amidoxhated for 7 h, as indicated in Figure 3. When the NaOH treatment was performed a t 80 "C, the optimum NaOH treatment period was shortened to 40-50 min for the fiber amidoxhated for 8-9 h, and the adsorption rate increased from 300 mg.kg-'.d-' to 460 mgkg-l-d-'. A higher concentration of NH20H shortened the optimum reaction period of the NHzOH treatments, but the optimum NaOH treatment period and the maximum adsorption rate were not much changed. Figure 5 shows the results for &denier
206 Ind. Eng. Chem. Res., Vol. 31, No. 1, 1992
500m
-
"
-9
b400 -
i
F
-e
Y
0,
300-
Ob
0
io
10
io
30
50
60 7b
NaOH treatment period
g
t:
200
-
-
10010
40 50 60 70 NaOH treatment period lminl
30
20
[hl
Figure 7. Effect of NaOH treatment period on swollen diameter: AM temperature,80 "C; AL temperature,30 "C; chain line (Kato et al., 1990), 15-denier: other conditions indicated in the figure.
p cn
+
500
15 P..
Y
Figure 4. Effect of NaOH treatment period on adsorption rate: 6-denier fiber; AM conditions, 1.5% ",OH, 80 " C ; AL temperature, 80 "C.
loo'
zio
J
'
50 1 I " ) I00 200 Swollen dfp Lpm 1 i
Figure 8. Effect of swollen diameter on adsorption rate of fibers with optimized NaOH treatment period: AM conditions, 1.5% ",OH, 80 "C.
2 200-
e
.-0C d
g
p 1000
/ 0 "
0
1
1
'
1
20 30 LO 50 60 70 NaOH treatment period L min I 10
Figure 5. Effect of NaOH treatment period on adsorption rate: %denier fiber; AM and AL temperature, 80 "C.
./
200 [
BOT 15
1
1 0
45min
W C 50min
2.75
50 1
I
2
3
I
I I I I l l
5
1
1
IO
20 30 Adsorption perlod I d I
Figure 9. Relationship between uranium adsorbed and adsorption period.
'0
h 60 10 20 30 LO 5 0 70 NOOH treatment period Cminl
Figure 6. Effect of NaOH treatment period on swollen diameter: AM and AT temperature, 80 "C.
fiber. The optimum period for the NHzOH and NaOH treatment was shortened by increase in NH20H concentration. The maximum adsorption rate exceeded 300 mg.kg-'.d-'. Figure 6 shows the effect of NaOH treatment on the projected diameter of fibers swollen in seawater at 298 K. After treatment a t 80 "C for 50-60 min, the diameter became 3-fold before the alkali treatment regardless of the original fiber size. When the fibers were treated at 30 "C,
however, the degree of swelling was not so high as that of the fibers treated at 80 OC,as illustrated in Figure 7. Figure 8 reveals that the adsorption rate of uranium is inversely proportional to the swollen diameter of the fibers and is correlated by separate lines for different series of experiments. These fibers were prepared by the treatment with optimum period for each preparation condition. Fibers with higher swelling ratio adsorb a larger amount of uranium. The adsorption rate is proportional to the 1/2 power of the contact time before 7 days, as shown in Figure 9. The above results imply that the adsorption is controlled by the diffusion of U02(C03)34-ions in the fiber matrix if enough functionalitiesare formed by the NH20H treatment. However, the distribution of functionalities having different reaction rates is a factor which should be clarified. To evaluate the local amount of functionalities formed in the fiber, the adsorption of Cu(I1) ion was performed. A small amount of the fiber (0.05-0.1 g) was immersed in 10 mL of a 0.05 mo1.L-' CuClz solution which was main-
Ind. Eng. Chem. Res., Vol. 31, No. 1, 1992 207
h
'
+
m F
i
' D
1
6-denier
' 8
0.2 0
IO 20 30 40 50 60 70 NaOH treatment period [min, h J
Figure 13. Relationship between tensile strength and NaOH treatment period 6-denier fiber.
l . l . l l l l . l l l l . . l l l l . ~
IO
20
30
28 CdQgrQQl
was observed in the range of N/C = 0.34-0.35. The decrease in nitrogen content by the NaOH treatment is explained by the formation of cyclic imidedioxime group and the decomposition of amidoxime to amide (Shouteden, 1957).
Figure 10. XRD patterns of 3-denier fibers: (a) untreated; (b) after NHzOH treatment with 1.5% NHzOH at 80 OC for 10 h; (c) after further NaOH treatment at 30 "C for 20 h.
-
s* s-
OH-
R-C-N=OH
I
NH2
I
OH 0
2
4
"2OH
6
8
1
0
treatment period
1
2
H+
-
0-
I
0.3
-
OH R-C-N--OH I NH, -H+
R-C-NH-OH
--c
IJp I ',
R-C-NH-OH
Lhl
NH,
Figure 11. Effect of NHzOH treatment period on atomic ratio N/C.
'
h)O-H
0
II
R-C-NH,
-t
",OH
f
OH-
(3)
The amide group is further decomposed to a carboxylic group. 0
0.1
II
R-C-NHp 0
IO 20 30 40
50 60
NaOH treatment perlod Imln, hJ
Figure 12. Decrease in atomic ratio N/C during NaOH treatment: 6-denier fiber.
tained at pH 4.5 with an acetic acid-odium acetate buffer, and was shaken for a prescribed period at 25 "C. The radial distribution profile of Cu in the fiber analyzed with electron probe microanalysis (Hitachi 2300) suggests that functional groups capable of Cu adsorption were formed even in the central region of the fiber. This is in agreement with the result of Hirotsu et al. (1988). Figure 10 shows the changes in the X-ray diffraction (XRD) pattern (CuKa target) due to the NHzOH and NaOH treatment. The disappearance of the peak a t 28 = 16.8' which is characteristic of polyacrylonitrile means that the crystalline structure of the fiber was transformed to an amorphous one by the NHzOH and NaOH treatment. Figure 11 indicates the change in the atomic ratio of nitrogen to carbon in the amidoxime fibers. The nitrogen content increased with increasing NHzOH treatment time. Then the N/C ratio decreased with NaOH treatment time as indicated in Figure 12. The highest adsorption rate
-
R-COOH
( 4)
As shown in Figures 6 and 7, the alkali treatment increased the swelling of the fiber and, therefore, the diffusivity of uranyl ions in the matrix. The nitrogen content decreased gradually with increasing treatment period. The decrease in adsorption rate after the optimum alkali treatment period is probably due to the loss of amidoxime and imidedioxime functionalities by eqs 3 and 4. Imidedioxime, amidoxime, and amide groups axe also subject to decomposition in the desorption step with HC1.
Tensile Strength of Amidoxime Fibers Figures 13 and 14 show that the tensile strength of the amidoxime fiber decreases with increasing alkali treatment time. The strength of the 15-denier amidoxime fiber prepared by Kat0 et al. (1990) is not much reduced by the alkali treatment, and the adsorption rate is lower than that of the fiber prepared in the present work. Figure 15 shows that the tensile strength decreases greatly when the fiber swells. The difference in tensile strength under the conditions shown in Figures 13 and 14 is explained by the difference in the degree of swelling. As illustrated in Figure 15, the relationship between the tensile strength and the swollen diameter is not affected by NHzOH concentration.
208 Ind. Eng.Chem. Res., Vol. 31, No. 1, 1992 500
100
-
40 0
0
I
p 0
2 E ;300
-E
A
05 I
0
l
l
,5
,
F
IO 20 30 LO 50 60 70 NaOH treatment period Lmln h l
w
Figure 14. Relationship between tensile strength and NaOH treatment period: 15-denier fiber. I
I
I
20
I l l l l l
P 200
I
I
6-denier
I
0,
I00 1
2
3 L 5 Number of cycles
6
7
Figure 17. Changes in adsorption rate by number of adsorption 80 "C, 9 h; AL cycles: 6-denier fiber; AM conditions, 1.5% ",OH, conditions, 80 "C.
-a,
'5
1
-
0.5
--
F
AL 3 0 m i n
B
S
-
fm
4 5 rnin
A '
L
I
i
I
I 1 1 1 1 1 1 1
Swollen dfp Lpm I
Figure 15. Relationship between tensile strength and swollen d,. Keys are the same as in Figures 17 and 18 for each fiber size.
0.2 I
'
0
I
1 2 Number of cycles
Figure 18. Changes in tensile strength by number of adsorption 80 O C , 9 h; AL cycles: 6-denier fiber; AM conditions, 1.5% ",OH, conditions, 80 O C . 7 400 0
packed in 2-cm-diameter spherical shells made of plastic net, as illustrated in Figure 3 of Morooka et al. (1991), and the balls were kept in the sea for 30 days. Fibers of tensile strength less than roughly 5 mN could not sustain the initially homogeneous packing state in the shells. Further study is required to balance the adsorption rate and stability of the fiber.
il .P 200
4
100
01
01
,
I
I
I I I I I I
0.5
1
I
1
Tensile strength x I O 2
I
I l 1 I I l
IO
5
I
tN1
Figure 16. Relationship between adsorption rate and tensile strength (0) AM conditions, 1.5% ",OH, 80 O C , 9 h, or 3% ",OH, 80 O C , 2.75 h; AL conditions, 80 "C,treatment period varied. ( 0 )AM conditions, 1.5% ",OH, 80 O C , 7 h; AL conditions, 30 O C , treatment period varied. (*) Takagi et al. (1989).
Figure 16 indicah the relationship between the strength and the adsorption rate of the fiber prepared. When the fiber is used as an adsorbent of uranium in seawater, it is packed in a cage and undergoes many adsorption-desorption cycles. If its strength is not sufficient, the fiber gradually deteriorates and accumulates in a local part of the cage when the initial void fraction is larger than 0.8. Then the contact between fiber and seawater becomes worse because seawater flows primarily through the loosest part of the bed. The fibers prepared in this study were
Repetitive Test Figure 17 indicates the effect of the number of cycles on the adsorption performance of the 6-denier fiber prepared with 1.5 wt % NH20H. The adsorption rate of the fiber treated with the alkali at 80 "C for 45 min, the optimum period with respect to the first adsorption, was decreased by 50-60% after the first cycle of adsorption and desorption. The adsorption rate of the fiber treated with the alkali for 30 min, which is shorter than the optimum time, did not change with number of cycles. The adsorption rate of the 6-denier fiber prepared with 3 wt % NHzOHwas also decreased sharply by the first cycle, but settled at 250 mg.kg-'.d-' during the second to fifth cycles. This adsorption rate is higher than the value for the composite fibers synthesized by Kobuke et al. (l988,1990b), but further repeating runs must be performed with the fibers prepared in this study. The change in tensile strength with number of adsorption-desorption cycles is also dependent on the alkali treatment period. As shown in Figure 18, the fiber pre-
Ind. Eng. Chem. Res., Vol. 31, No. 1, 1992 209
6-denier
A
0.2
0
1
2 3 4 5 Number of CyClQS
6
7
Figure 19. Changes in atomic ratio N/C by number of adsorption cycles: 6-denier fiber; AM conditions, 1.5% ",OH, 80 OC, 9 h; AL conditions, 80 "C.
pared by the NaOH treatment at 80 "C for 30 min was stronger than those treated for 45 and 60 min, but the strength decreased with number of cycles. The tensile strength of the latter fibers, however, increased somewhat with number of cycles. Figure 19 indicates that the N/C ratio also changed with number of adsorption cycles. After the seventh run, the swollen fiber diameter became smaller than that in the first cycle as plotted in Figure 6.
Conclusion Commerical acrylonitrile fibers were treated with NHzOH and then NaOH solutions under various conditions, and amidoxime fibrous adsorbenta were prepared. The adsorption rate of the 6-denier fiber prepared was about 250 mg.kg-'.d-' after five repetitions of the adsorption and desorption cycle. The strength of the fiber was sufficient for packing in the adsorption unit. The principle of the design of the adsorption unit was described in a previous paper (Morooka et al., 1991). Acknowledgment We are grateful to Profs. H. Egawa of Kumamoto University and S. Furusaki and K. Saito of the University of Tokyo for useful discussion. This work was partially supported by the Grants-in-Aid on Priority-Area Research received from the Ministry of Education, Science and Culture, Japan (Grant No. 01603533 and 02203104). Nomenclature AM = NHzOH treatment AL = NaOH treatment dfh = hydrodynamic mean diameter of fiber, m d, = projected mean diameter of fiber, m a = (swollen fiber volume)/(dry fiber volume) Registry No. U, 7440-61-1. Literature Cited Astheimer, L.; Schenk, H. J.; Witte, E. G.; Schwochau, K. Development of Sorbers for the Recovery of Uranium from Seawater. Part 2. The Accumulation of Uranium from Seawater by Resins Containing Amidoxime and Imidoxime Functional Groups. Sep. Sci. Technol. 1983, 18, 307-339. Egawa, H.; Harada, H. Recovery of Uranium from Seawater by Using Chelating Resins Containing Amidoxime Groups. Nippon Kagaku Kaishi 1979, 958-959. Egawa, H.; Nonaka, T.; Nakayama, M. Influence of Crosslinking and Porosity on the Uranium Adsorption of Macroreticular Chelating
Resin Containing Amidoxime Groups. J . Macromol. Sci. Chem. 1988, A25, 1407-1425. Hirotau, T.; Katoh, S.; Sugasaka, K.; Takai, N.; Seno, M.; Itagaki, T. Kinetics of Adsorption of Uranium on Amidoxime Polymers from Seawater. Sep. Sci. Technol. 1988,23,49-61. Kato,T.; Kago, T.; Kusakabe, K.; Morooka, S.; Egawa, H. Preparation of Amidoxime Fibers for Recovery of Uranium from Seawater. J. Chem. Eng. Jpn. 1990,23, 744-750. Katoh, S.; Sugasaka, K. Study on the Development of the Adsorbent for Extraction of Uranium from Seawater. Bull. SOC.Sea Water Sci. Jpn. 1987,40,265-274. Katoh, S.; Sugasaka, K.; Sakane, K.; Takai, N.; Takahashi, H.; Umezawa, Y.; Itagaki, K. Enhancement of the Adsorptive Property of the Amidoxime Group Containing Fiber by Alkaline Treatment. Nippon Kagaku Kaishi 1982, 1455-1459. Kobuke, Y.; Tabushi, I.; Aoki, T.; Kamaishi, T.; Hagiwara, I. Composite Fiber Adsorbent for Rapid Uptake of Uranyl from Seawater. Znd. Eng. Chem. Res. 1988,27, 1461-1466. Kobuke, Y.; Tanaka, H.; Ogoshi, H. Imidedioxime as a Significant Component in So-called Amidoxime Resin for Uranyl Adsorption from Seawater. Polym. J. 1990a, 22, 179-182. Kobuke, Y.; Aoki, T.; Tanaka, H.; Tabushi, I.; Kamaishi, T.; Hagiwara, I. Recovery of Uranium from Seawater by Composite Fiber Adsorbent. Ind. Eng. Chem. Res. 1990b, 29, 1662-1668. Kyan, C. P.; Wasan, D. T.; Kintner, R. C. Flow of Single-phase through Fibrous Beds. Ind. Eng. Chem. Fundam. 1970, 9, 596-603. Morooka, S.; Kusakabe, K.; Kago, T.; Inada, M.; Egawa, H. Fluidization of Smell Mattresses Containing Amidoxime Fiber for Adsorption of Uranium from Seawater. J . Chem. Eng. Jpn. 1990, 23, 18-23. Morooka, S.; Kato, T.; Inada, M.; Kago, T.; Kusakabe, K. Modeling of an Adsorption Unit Packed with Amidoxime Fiber Balls for the Recovery of Uranium from Seawater. Ind. Eng. Chem. Res. 1991, 30, 190-196. Motojima, K.; Yamamoto, T.; Kato, Y. 8-Quinolinol Extraction and Spectrophotometric Determination of Uranium with Arsenau, 111. Jpn. Anal. 1969,18, 208-212. Nobukawa, H.; Tamehiro, M.; Kobayashi, M.; Nakagawa, H.; Sakakibara, J.; Takagi, N. Development of Floating Type Extraction System of Uranium from Seawater Using Seawater Current and Wave Power. J. Shipbuilding SOC.Jpn. 1989,165, 281-292. Omichi, H.; Katakai, A.; Sugo, T.; Okamoto,J.; Kato, S.; Sakane, K.; Sugasaka, K.; Itagaki, T. Effect of Shape and Size of Amidoxime-Group-ContainingAdsorbent on the Recovery of Uranium from Seawater. Sep. Sci. Technol. 1987,22, 1313-1325. Saito, K.; Uezu, K.; Hori, T.; Furusaki, S.; Sugo, T.; Okamoto, J. Recovery of Uranium from Seawater Using Amidoxime Hollow Fibers. AIChE J . 1988,34,411-416. Saito, K.; Yamaguchi, T.; Uezu, K.; Furusaki, S.; Sugo, T.; Okamoto, J. Optimum Preparation Conditions of Amidoxime Hollow Fiber Svnthesized by Radiation-Induced Grafting. J. ADDLPolvm. Sci. 1990,39, 2153-2163. Schenk, H. J.; Astheimer, L.; Witte, E. G.; Schwochau, K. Development of Sorbers for the Recoverv of Uranium from Seawater. 1. Assessment of Key Parameters &d Screening Studies of Sorber Materials. Sep. Sci. Technol. 1982,17, 1293-1308. Shouteden, F. L. M. Polyacrylamidoximes. Makromol. Chem. 1957, 24,25-49. Sugasaka, K.; Katoh, S.; Takai, N.; Takahashi, H.; Umezawa, Y. Recovery of Uranium from Seawater. Sep. Sci. Technol. 1981,16, 971-985. Takagi, N.; Hirobu, T.; Sakakibara, J.; Katoh, S.; Sugasaka, K. Preparation of Fibrous Adsorbent Containing Amidoxime Groups from Composite Poly(acrylonitri1e) Fiber and Ita Adsorption Ability for Uranium. Bull. SOC.Sea Water Sci. Jpn. 1989, 42, 279-283. Takeda, T.; Saito, K.; Uezu, K.; Furusaki, S.; Sugo, T.; Okamoto, J. Adsorption and Elution in Hollow-Fiber-Packed Bed for Recovery of Uranium from Seawater. Znd. Eng. Chern. Res. 1991, 30, I
__
185-190.
Received for reuiew June 17, 1991 Accepted September 4, 1991
