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Membranes prepared by radiation grafting of binary monomers for adsorption of heavy metals from industrial wastes
Nuclear Instruments and Methods in Physics Research B 151 (1999) 386±392
www.elsevier.nl/locate/nimb
Membranes prepared by radiation grafting of binary monomers for adsorption of heavy metals from industrial wastes El-Sayed A. Hegazy, H. Kamal, N. Maziad, A.M. Dessouki
*
National Center for Radiation Research and Technology, P.O. Box 29, Nasr City, Cairo, Egypt
Abstract Preparation of synthetic membranes using simultaneous radiation grafting of acrylic acid (AAc) and styrene (Sty) as individually and in binary monomer mixture onto low density polyethylene (LDPE) has been carried out. The eect of preparation conditions such as irradiation dose, monomer concentration, comonomer composition, and solvent on the grafting yield was investigated. Characterization and some properties of the prepared membranes using dierent analytical techniques are studied, accordingly the possibility of its practical use in industrial waste treatment is determined. The swelling behavior, electrical conductivity, thermal stability, and mechanical properties of the membranes were investigated as a function of the grafting degree. The prepared cation-exchange membranes possessed good electrical and mechanical properties, high thermal stability and possess good characteristics for separation processes. These membranes have also good anity toward the adsorption or chelation with Fe3 and Pb2 ions either in mixture containing other metals or if exists alone in the waste solution. Ó 1999 Elsevier Science B.V. All rights reserved.
1. Introduction It is well known that, radiation-grafting techniques are widely used to modify both the chemical and physical properties of polymers. In addition, it is of special interest for achieving speci®cally desired membrane properties and excellent membrane quality [1±5]. In this study, membranes were prepared by radiation grafting of Styrene/Acrylic acid comonomer (Sty/AAc) onto low density polyethylene (LDPE) ®lms followed by sulphonation and alkaline treatments to confer ionic character in the graft chains. Characteriza-
*
Corresponding author.
tion and some selected properties of the prepared graft copolymers also investigated. 2. Experimental 2.1. Materials The LDPE of thickness 75 lm were provided by El-Nasr Co. for Medical Supplies, Cairo, Egypt. Acrylic acid (AAc) of purity 99%, (Merck, Germany) and styrene (Sty) GRG of purity 99% (Avondale Laboratories, UK) were used without further puri®cation. Other chemicals were of reagent grade and were used as received. Graft copolymerization, sulphonation and the alkaline treatment of the grafted ®lms as well as
0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 1 2 5 - 1
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
387
swelling, measurements, electrical conductivity and mechanical properties measurements were carried out by the same methods as described in previous studies [6±9]. The degree of grafting was determined by the percentage increase in weight as follows: Degree of grafting %
Wg ÿ W0 100; W0
where W0 and Wg represent the weights of initial and grafted ®lms, respectively.
3. Results and discussion 3.1. Eect of solvent and inhibitor concentration EtOH/H2 O mixture (80/20 wt%) is selected to be the diluent for this graft copolymerization and (0.2 wt%) FeCl3 is the suitable inhibitor concentration in which the diusivity of (Sty/AAc) comonomers into the polymer matrix is enhanced and reasonable degree of grafting is obtained with homogeneous distribution of the grafted chains in the bulk polymer (Table 1 and Fig. 1). 3.2. Eect of comonomer composition The grafting of (Sty/AAc) binary monomer mixtures of various relative compositions onto LDPE is investigated at overall comonomer conTable 1 Eect of solvent on the graft copolymerization of Sty/AAc (50/ 50 wt%) onto LDPE ®lms in presence of FeCl3 (1.5 wt%). Exposure dose 10 kGy, comonomer concentration 40 wt% and solvent composition 80/20 wt% Solvent
Degree of grafting (wt%)
H2 O MeOH MeOH/H2 O Ethanol/H2 O Isopropanol/H2 O DMF/H2 O n-butanol/H2 O Dioxane/H2 O Benzene/H2 O
27 61 41.7 105 118 105 263 82 200
Fig. 1. Eect of FeCl3 conc. on the grafting yield of Sty/AAc (40 wt%) onto LDPE ®lms. Irradiation dose: 20 kGy and comonomer composition: 20/20 wt%.
centration 40 wt% in EtOH/H2 O mixture (Fig. 2). It is obvious that, the grafting yield increases with increasing the content of Sty to reach a maximum value at comonomer composition (30/70 wt%) of (Sty/AAc). Thereafter, at higher contents of Sty, the degree of grafting falls down. Results obtained can be reasonably explained by considering the fact that styrene monomer itself acts as inhibitor to retard the homopolymerization process of acrylic acid. 3.3. Eect of irradiation time The in¯uence of exposure dose, on the grafting yield of (Sty/AAc) binary monomers onto LDPE ®lms is investigated and shown in Fig. 3. It can be seen that the higher the exposure dose, the higher
388
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
Fig. 3. Eect of irradiation dose on the grafting of Sty/AAc (50/50 wt%) binary monomers onto LDPE ®lms. Comonomer conc.: 40 wt% and FeCl3 conc.: 0.6 wt%.
Fig. 2. Eect of comonomer composition of Sty/AAc (40 wt%) onto LDPE ®lms. FeCl3 conc.: 0.6 wt% and irradiation dose: 20 kGy.
the grafting yield. From results, it can be assumed that the increase in exposure dose resulted in increasing the concentration of free radicals formed in the polymer substrate as well as in the (Sty/AAc) comonomer. 3.4. Swelling behavior and electrical conductivity of the prepared grafted copolymers Figs. 4 and 5 show the change in water uptake and electrical conductivity respectively with degree of grafting for the untreated and sulfonated±alkali-treated graft copolymers. It can be seen that,
Fig. 4. Water uptake percent for LDPE-g-P(Sty/AAc) as a function of degree of grafting. (-s-) untreated grafted ®lms, (-h-) sulphonated and alkali-treated grafted ®lms.
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
389
3.5. Mechanical properties Fig. 6 shows the change in tensile strength and elongation at break percent with degree of grafting for LDPE grafted with PAAc and PSty. It is obvious that both tensile strength and elongation percent decrease gradually as the degree of grafting increases. It can be suggested that the introduction of PSty and PAAc graft chain into LDPE ®lms resulted in change in its physical properties. 3.6. Thermal properties of the prepared graft copolymers Tables 2±4 show the thermal decomposition of LDPE ®lms grafted with (PSty/PAAc) with vari-
Fig. 5. Eect of degree of grafting on the electrical conductivity of LDPE-g-P(Sty/AAC). (-s-) untreated grafted ®lms, (-h-) sulphonated and alkali-treated grafted ®lms.
the water uptake percent and electrical conductivity increase with degree of grafting for both the untreated and treated graft copolymers due to the increase in number of hydrophilic groups. It is also observed that, at a given degree of grafting, the sulphonated and alkali-treated graft copolymers give higher values of water uptake percent and electrical conductivity if compared with the untreated ones. Such increment in water uptake and electrical conductivity is due to increasing the hydrophilicity of the easily ionizable groups introduced onto the graft copolymers via sulphonation and alkaline treatments. It is also found that the water uptake percent tends to level o above certain degree of grafting at which the diffusion of water through the polymer matrix is too dicult due to the formation of crosslinked network structure.
Fig. 6. Change in tensile strength and elongation at break percent with degree of grafting for LDPE ®lms. (-d-) LDPE-gPAAc, (-s-) LDPE-g-Psty, and (-n-) LDPE-g-P(Sty/AAc).
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Table 2 Thermal stability of LDPE-g-PAAc ®lms at dierent degrees of grafting and temperatures Degree of grafting (%) Blank LDPE 45 67 144
Weight loss (%) at dierent temperatures (o C) 100
200
300
400
500
600
0 2 2.7 5
0.3 4 6 9
3.5 16 19 27
13 36 34 40
94 91 83 84
98 100 100 100
Table 3 Thermal stability of LDPE-g-PSty ®lms at dierent degrees of grafting and temperatures Degree of grafting (%) 0 39.8 80 149
Weight loss (%) at dierent temperatures (o C) 100 0 0 0 0
200 0.3 0.3 0.04 0.6
300
400
500
600
3.5 5 4.3 4
13.3 15 21 19
94.2 93 91.5 96
98.2 99 94 99
Table 4 Thermal stability of LDPE-g-P(Sty/AAc) ®lms at dierent degrees of grafting and temperatures Degree of grafting (%)
Weight loss (%) at dierent temperatures (o C)
0 30 110 168
0 0 0 0
100
200
300
400
500
600
0.3 0 0.8 2
3.5 3.3 8 12
13.1 14.3 43 63
94.2 97.5 96 99
98.2 98.7 96.5 100
ous degrees of grafting copolymers at various elevated temperatures. It can be seen that the weight loss increases as the temperature is elevated and the higher the degree of grafting the higher the weight loss, at a given elevated temperature. It can be concluded that such prepared graft copolymers possessed good thermal stability below 300°C. The extent of such stability is dependent on the grafting yield and the type of grafted chains. 3.7. Chelation and complexation of metals from wastewater Figs. 7 and 8 show the metal uptake as a function of time for two metallic ions (Fe3 and
Cd2 ) using LDPE-g-P (AAc) It can be seen that, the Fe3 uptake increases with time to reach its maximum value (denoted as the maximum membrane capacity) at almost 60 min. Extension of treatment time above 60 min causes no signi®cant increase in metal uptake even after 3 h. Such behavior is also observed for Cd2 metal ions for such cationic membranes. However, the maximum Cd2 uptake is obtained after treatment time 20 min. LDPE-g-PAAc possesses high anity to adsorb Fe3 much higher than Cd2 (almost 7 times higher than that of Cd2 ). The results obtained can be reasonably explained by considering the valance of metals and their atomic radii for Fe3 and Cd2 , respectively. The trivalent Fe3 forms a
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
391
Fig. 7. Eect of immersion time on the Fe uptake by LDPE-gPAAc, having degree of grafting 80%.
more stable and strong complex with the functional ±COOH groups of grafted membranes. Results show that the incorporation of styrene with acrylic acid groups has no eect on metal uptake. The selectivity of metals is determined at room temperature using atomic absorption technique as shown in Table 5. It is obvious that the anity of all grafted membranes towards Pb2 is remarkable when it exists in a mixture containing Cd2 and Pb2 . Such result is surprising; in spite of the greater ionic and atomic radii of Pb2 (1.12 and than those for Cd2 , it possesses higher 1.26 A) anity to chelate with the dierent grafted membranes. Such results may be related to the dierence in outermost shell electronic con®guration of them; Cd2 (4d10 ) and Pb2 (5d10 , 6p2 ). It is also observed that the chemical treatment of the membrane functional groups such as sulphonation
Fig. 8. Eect of immersion time on Cd uptake by: (-s-)LDPEg-PAAc, having 204% grafting. (-n-) LDPE-g-PAACÿ OOK , having 235% grafting.
has shown enhancement for Pb2 uptake by the membrane containing styrene groups either individually or in binary system (AAc/Sty).
4. Conclusion It can be concluded that such prepared, grafted membranes have good anity towards the adsorption or chelation with Fe3 and Pb2 either in a mixture containing other metals or if they exist alone in the feed solution. This is a good advantage for the possible use of such grafted membranes in wastewater treatment from heavy and
Table 5 Eect of functional groups, in the membranes, on the maximum metal ion selectivity for a mixture of Cd2 and Pb2 ions Membrane type
Degree of grafting (%)
Cd2 (mmol /g)
Pb2 (mmol /g)
LDPE-g-AACOOH LDPE-g-PAACOOK LDPE-g-PSty (Sulphonated) LDPE-g-PSty (Sulphonated) LDPE-g-P(Sty/AAc)
148 157 167 170 260
1.0 0.3 0.8 0.92 0.38
6.5 3.7 5.6 4.5 4.8
The immersion time is 2 h at 30°C.
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E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
toxic metals which is a serious problem of the environmental pollution. References [1] A. Chapiro, A.M. Jendrychowska-Bonamour, Eur. Polym. J. 20 (1984) 1079. [2] B.D. Gupta, A. Chapiro, Eur. Polym. J. 25 (11) (1989) 1145. [3] S. Munari, F. Vigo, G. Tealdo, C. Rossi, J. Appl. Polym. Sci. 11 (1967) 1563.
[4] J. Fuehrer, G. Ellinghorst, Macromolec. Chem. 113 (1983) 153. [5] G. Ellinghorst, A. Niem oller, D. Vierkotten, Radiat. Phys. Chem. 22 (1983) 635. [6] E.A. Hegazy, N.B. El-Assy, N.H. Taher, A.M. Dessouki, Radiat. Phys. Chem. 33 (1989) 539. [7] E.A. Hegazy, N.H. Taher, A. Ebide, J. Appl. Polym. Sci. 38 (1990) 1029. [8] A.M. Dessouki, N.H. Taher, H. El-Boohy, Radiat. Phys. Chem. 36 (1990) 371. [9] E.A. Hegazy, N. El-Assy, A. Dessouki, M. Shaker, Radiat. Phys. Chem. 33 (1) (1989) 13.
www.elsevier.nl/locate/nimb
Membranes prepared by radiation grafting of binary monomers for adsorption of heavy metals from industrial wastes El-Sayed A. Hegazy, H. Kamal, N. Maziad, A.M. Dessouki
*
National Center for Radiation Research and Technology, P.O. Box 29, Nasr City, Cairo, Egypt
Abstract Preparation of synthetic membranes using simultaneous radiation grafting of acrylic acid (AAc) and styrene (Sty) as individually and in binary monomer mixture onto low density polyethylene (LDPE) has been carried out. The eect of preparation conditions such as irradiation dose, monomer concentration, comonomer composition, and solvent on the grafting yield was investigated. Characterization and some properties of the prepared membranes using dierent analytical techniques are studied, accordingly the possibility of its practical use in industrial waste treatment is determined. The swelling behavior, electrical conductivity, thermal stability, and mechanical properties of the membranes were investigated as a function of the grafting degree. The prepared cation-exchange membranes possessed good electrical and mechanical properties, high thermal stability and possess good characteristics for separation processes. These membranes have also good anity toward the adsorption or chelation with Fe3 and Pb2 ions either in mixture containing other metals or if exists alone in the waste solution. Ó 1999 Elsevier Science B.V. All rights reserved.
1. Introduction It is well known that, radiation-grafting techniques are widely used to modify both the chemical and physical properties of polymers. In addition, it is of special interest for achieving speci®cally desired membrane properties and excellent membrane quality [1±5]. In this study, membranes were prepared by radiation grafting of Styrene/Acrylic acid comonomer (Sty/AAc) onto low density polyethylene (LDPE) ®lms followed by sulphonation and alkaline treatments to confer ionic character in the graft chains. Characteriza-
*
Corresponding author.
tion and some selected properties of the prepared graft copolymers also investigated. 2. Experimental 2.1. Materials The LDPE of thickness 75 lm were provided by El-Nasr Co. for Medical Supplies, Cairo, Egypt. Acrylic acid (AAc) of purity 99%, (Merck, Germany) and styrene (Sty) GRG of purity 99% (Avondale Laboratories, UK) were used without further puri®cation. Other chemicals were of reagent grade and were used as received. Graft copolymerization, sulphonation and the alkaline treatment of the grafted ®lms as well as
0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 1 2 5 - 1
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
387
swelling, measurements, electrical conductivity and mechanical properties measurements were carried out by the same methods as described in previous studies [6±9]. The degree of grafting was determined by the percentage increase in weight as follows: Degree of grafting %
Wg ÿ W0 100; W0
where W0 and Wg represent the weights of initial and grafted ®lms, respectively.
3. Results and discussion 3.1. Eect of solvent and inhibitor concentration EtOH/H2 O mixture (80/20 wt%) is selected to be the diluent for this graft copolymerization and (0.2 wt%) FeCl3 is the suitable inhibitor concentration in which the diusivity of (Sty/AAc) comonomers into the polymer matrix is enhanced and reasonable degree of grafting is obtained with homogeneous distribution of the grafted chains in the bulk polymer (Table 1 and Fig. 1). 3.2. Eect of comonomer composition The grafting of (Sty/AAc) binary monomer mixtures of various relative compositions onto LDPE is investigated at overall comonomer conTable 1 Eect of solvent on the graft copolymerization of Sty/AAc (50/ 50 wt%) onto LDPE ®lms in presence of FeCl3 (1.5 wt%). Exposure dose 10 kGy, comonomer concentration 40 wt% and solvent composition 80/20 wt% Solvent
Degree of grafting (wt%)
H2 O MeOH MeOH/H2 O Ethanol/H2 O Isopropanol/H2 O DMF/H2 O n-butanol/H2 O Dioxane/H2 O Benzene/H2 O
27 61 41.7 105 118 105 263 82 200
Fig. 1. Eect of FeCl3 conc. on the grafting yield of Sty/AAc (40 wt%) onto LDPE ®lms. Irradiation dose: 20 kGy and comonomer composition: 20/20 wt%.
centration 40 wt% in EtOH/H2 O mixture (Fig. 2). It is obvious that, the grafting yield increases with increasing the content of Sty to reach a maximum value at comonomer composition (30/70 wt%) of (Sty/AAc). Thereafter, at higher contents of Sty, the degree of grafting falls down. Results obtained can be reasonably explained by considering the fact that styrene monomer itself acts as inhibitor to retard the homopolymerization process of acrylic acid. 3.3. Eect of irradiation time The in¯uence of exposure dose, on the grafting yield of (Sty/AAc) binary monomers onto LDPE ®lms is investigated and shown in Fig. 3. It can be seen that the higher the exposure dose, the higher
388
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
Fig. 3. Eect of irradiation dose on the grafting of Sty/AAc (50/50 wt%) binary monomers onto LDPE ®lms. Comonomer conc.: 40 wt% and FeCl3 conc.: 0.6 wt%.
Fig. 2. Eect of comonomer composition of Sty/AAc (40 wt%) onto LDPE ®lms. FeCl3 conc.: 0.6 wt% and irradiation dose: 20 kGy.
the grafting yield. From results, it can be assumed that the increase in exposure dose resulted in increasing the concentration of free radicals formed in the polymer substrate as well as in the (Sty/AAc) comonomer. 3.4. Swelling behavior and electrical conductivity of the prepared grafted copolymers Figs. 4 and 5 show the change in water uptake and electrical conductivity respectively with degree of grafting for the untreated and sulfonated±alkali-treated graft copolymers. It can be seen that,
Fig. 4. Water uptake percent for LDPE-g-P(Sty/AAc) as a function of degree of grafting. (-s-) untreated grafted ®lms, (-h-) sulphonated and alkali-treated grafted ®lms.
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
389
3.5. Mechanical properties Fig. 6 shows the change in tensile strength and elongation at break percent with degree of grafting for LDPE grafted with PAAc and PSty. It is obvious that both tensile strength and elongation percent decrease gradually as the degree of grafting increases. It can be suggested that the introduction of PSty and PAAc graft chain into LDPE ®lms resulted in change in its physical properties. 3.6. Thermal properties of the prepared graft copolymers Tables 2±4 show the thermal decomposition of LDPE ®lms grafted with (PSty/PAAc) with vari-
Fig. 5. Eect of degree of grafting on the electrical conductivity of LDPE-g-P(Sty/AAC). (-s-) untreated grafted ®lms, (-h-) sulphonated and alkali-treated grafted ®lms.
the water uptake percent and electrical conductivity increase with degree of grafting for both the untreated and treated graft copolymers due to the increase in number of hydrophilic groups. It is also observed that, at a given degree of grafting, the sulphonated and alkali-treated graft copolymers give higher values of water uptake percent and electrical conductivity if compared with the untreated ones. Such increment in water uptake and electrical conductivity is due to increasing the hydrophilicity of the easily ionizable groups introduced onto the graft copolymers via sulphonation and alkaline treatments. It is also found that the water uptake percent tends to level o above certain degree of grafting at which the diffusion of water through the polymer matrix is too dicult due to the formation of crosslinked network structure.
Fig. 6. Change in tensile strength and elongation at break percent with degree of grafting for LDPE ®lms. (-d-) LDPE-gPAAc, (-s-) LDPE-g-Psty, and (-n-) LDPE-g-P(Sty/AAc).
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E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
Table 2 Thermal stability of LDPE-g-PAAc ®lms at dierent degrees of grafting and temperatures Degree of grafting (%) Blank LDPE 45 67 144
Weight loss (%) at dierent temperatures (o C) 100
200
300
400
500
600
0 2 2.7 5
0.3 4 6 9
3.5 16 19 27
13 36 34 40
94 91 83 84
98 100 100 100
Table 3 Thermal stability of LDPE-g-PSty ®lms at dierent degrees of grafting and temperatures Degree of grafting (%) 0 39.8 80 149
Weight loss (%) at dierent temperatures (o C) 100 0 0 0 0
200 0.3 0.3 0.04 0.6
300
400
500
600
3.5 5 4.3 4
13.3 15 21 19
94.2 93 91.5 96
98.2 99 94 99
Table 4 Thermal stability of LDPE-g-P(Sty/AAc) ®lms at dierent degrees of grafting and temperatures Degree of grafting (%)
Weight loss (%) at dierent temperatures (o C)
0 30 110 168
0 0 0 0
100
200
300
400
500
600
0.3 0 0.8 2
3.5 3.3 8 12
13.1 14.3 43 63
94.2 97.5 96 99
98.2 98.7 96.5 100
ous degrees of grafting copolymers at various elevated temperatures. It can be seen that the weight loss increases as the temperature is elevated and the higher the degree of grafting the higher the weight loss, at a given elevated temperature. It can be concluded that such prepared graft copolymers possessed good thermal stability below 300°C. The extent of such stability is dependent on the grafting yield and the type of grafted chains. 3.7. Chelation and complexation of metals from wastewater Figs. 7 and 8 show the metal uptake as a function of time for two metallic ions (Fe3 and
Cd2 ) using LDPE-g-P (AAc) It can be seen that, the Fe3 uptake increases with time to reach its maximum value (denoted as the maximum membrane capacity) at almost 60 min. Extension of treatment time above 60 min causes no signi®cant increase in metal uptake even after 3 h. Such behavior is also observed for Cd2 metal ions for such cationic membranes. However, the maximum Cd2 uptake is obtained after treatment time 20 min. LDPE-g-PAAc possesses high anity to adsorb Fe3 much higher than Cd2 (almost 7 times higher than that of Cd2 ). The results obtained can be reasonably explained by considering the valance of metals and their atomic radii for Fe3 and Cd2 , respectively. The trivalent Fe3 forms a
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
391
Fig. 7. Eect of immersion time on the Fe uptake by LDPE-gPAAc, having degree of grafting 80%.
more stable and strong complex with the functional ±COOH groups of grafted membranes. Results show that the incorporation of styrene with acrylic acid groups has no eect on metal uptake. The selectivity of metals is determined at room temperature using atomic absorption technique as shown in Table 5. It is obvious that the anity of all grafted membranes towards Pb2 is remarkable when it exists in a mixture containing Cd2 and Pb2 . Such result is surprising; in spite of the greater ionic and atomic radii of Pb2 (1.12 and than those for Cd2 , it possesses higher 1.26 A) anity to chelate with the dierent grafted membranes. Such results may be related to the dierence in outermost shell electronic con®guration of them; Cd2 (4d10 ) and Pb2 (5d10 , 6p2 ). It is also observed that the chemical treatment of the membrane functional groups such as sulphonation
Fig. 8. Eect of immersion time on Cd uptake by: (-s-)LDPEg-PAAc, having 204% grafting. (-n-) LDPE-g-PAACÿ OOK , having 235% grafting.
has shown enhancement for Pb2 uptake by the membrane containing styrene groups either individually or in binary system (AAc/Sty).
4. Conclusion It can be concluded that such prepared, grafted membranes have good anity towards the adsorption or chelation with Fe3 and Pb2 either in a mixture containing other metals or if they exist alone in the feed solution. This is a good advantage for the possible use of such grafted membranes in wastewater treatment from heavy and
Table 5 Eect of functional groups, in the membranes, on the maximum metal ion selectivity for a mixture of Cd2 and Pb2 ions Membrane type
Degree of grafting (%)
Cd2 (mmol /g)
Pb2 (mmol /g)
LDPE-g-AACOOH LDPE-g-PAACOOK LDPE-g-PSty (Sulphonated) LDPE-g-PSty (Sulphonated) LDPE-g-P(Sty/AAc)
148 157 167 170 260
1.0 0.3 0.8 0.92 0.38
6.5 3.7 5.6 4.5 4.8
The immersion time is 2 h at 30°C.
392
E.-S.A. Hegazy et al. / Nucl. Instr. and Meth. in Phys. Res. B 151 (1999) 386±392
toxic metals which is a serious problem of the environmental pollution. References [1] A. Chapiro, A.M. Jendrychowska-Bonamour, Eur. Polym. J. 20 (1984) 1079. [2] B.D. Gupta, A. Chapiro, Eur. Polym. J. 25 (11) (1989) 1145. [3] S. Munari, F. Vigo, G. Tealdo, C. Rossi, J. Appl. Polym. Sci. 11 (1967) 1563.
[4] J. Fuehrer, G. Ellinghorst, Macromolec. Chem. 113 (1983) 153. [5] G. Ellinghorst, A. Niem oller, D. Vierkotten, Radiat. Phys. Chem. 22 (1983) 635. [6] E.A. Hegazy, N.B. El-Assy, N.H. Taher, A.M. Dessouki, Radiat. Phys. Chem. 33 (1989) 539. [7] E.A. Hegazy, N.H. Taher, A. Ebide, J. Appl. Polym. Sci. 38 (1990) 1029. [8] A.M. Dessouki, N.H. Taher, H. El-Boohy, Radiat. Phys. Chem. 36 (1990) 371. [9] E.A. Hegazy, N. El-Assy, A. Dessouki, M. Shaker, Radiat. Phys. Chem. 33 (1) (1989) 13.