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Petiolar felt-sheath of palm: a new biosorbent for the removal of heavy metals from contaminated water
Bioresource Technology 81 (2002) 151±153
Short communication
Petiolar felt-sheath of palm: a new biosorbent for the removal of heavy metals from contaminated water M. Iqbal a,*, A. Saeed a, N. Akhtar b a
Environment Biotechnology Group, Biotechnology and Food Research Center, PCSIR Laboratories Complex, Lahore, Pakistan b Department of Biology, Government Islamia College for Women, Cooper Road, Lahore, Pakistan Received 14 May 2001; received in revised form 14 July 2001; accepted 16 July 2001
Abstract Biosorption of heavy metals such as Pb2 , Ni2 , Cd2 , Cu2 , Cr3 and Zn2 by petiolar felt-sheath of palm (PFP) from contaminated water was examined. PFP was found to eciently remove all the toxic metal ions with selectivity order of Pb2 > Cd2 > Cu2 > Zn2 > Ni2 > Cr3 . The uptake was rapid, with more than 70% completed within 15 min. The bound metal ions were successfully desorbed and the PFP ®brous±biomass remained eective after several adsorption±desorption cycles. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Biosorption; Petiolar felt-sheath; Palm; Heavy metals
1. Introduction
2. Methods
The disposal of industrial euents containing heavy metals into natural water systems is a cause of serious environmental concern. Beyond certain limits these are toxic to living organisms and may cause serious hazards to public health (Forster and Wase, 1997). Many physico-chemical methods have been proposed for their removal from industrial euents. However, these methods are often inecient and/or cost prohibitive when used for the removal of heavy metal ions at low concentrations (Wilde and Benemann, 1993). This has led to the investigation of such alternative low cost technologies that may be eciently applied for the biosorption of heavy metals. For this purpose, numerous agro-waste biomaterials have been investigated and found useful, such as rice-husk (Munaf and Zein, 1997); soybean hulls, cottonseed hulls, rice straw, sugarcane bagasse (Marshall and Champagne, 1995); coconut shell (Bhattacharya and Venkobachar, 1984); and tea leaves (Tee and Khan, 1988). In this study the use of petiolar felt-sheath of palm (PFP), available in abundance as a waste material from palm trees, as a new biosorbent material to remove heavy metals from contaminated water was investigated.
The reticulated ®brous network of petiolar felt-sheath of palm was obtained as peelings from the trunk of palm tree Livistona chinensis (Iqbal and Zafar, 1997). The feltsheaths were washed extensively with distilled deionized water to remove dirt and other particulate matter. The washed sheaths were dried at 70 °C for 24 h, cut to particle size of 1 mm or less in the form of individual threads, oven-dried at 90 °C to constant weight, cooled and kept in a desiccator for subsequent use in the biosorption studies. Standard metal solutions of desired concentrations were prepared from stock solutions (Merck) containing 1000 2 mg/l of Pb2 , Ni2 , Cd2 , Cu2 Cr3 and Zn2 . Adsorption experiments were carried out by suspending 100 mg PFP biomass in 10 ml of each metal ion solution of known concentration and pH in polyethylene tubes placed in a tube rotator at room temperature (25 2 °C). After continuous rotation for 1 h, the tubes were centrifuged at 5000 rpm for 5 min and 100 ll of 65% HNO3 was added to the decanted supernatant. The metal ion concentration in the supernatant was determined by atomic absorption spectroscopy (UNICAM-969) and recorded as the mean of three subsequent measurements. Control experiments were also performed using the metal ion solutions in the absence of PFP biomass. All experiments were performed in triplicate. The amount of metal adsorbed was calculated from the dierence
*
Corresponding author. Fax: +92-42-5877433. E-mail address: [email protected] (M. Iqbal).
0960-8524/02/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 0 - 8 5 2 4 ( 0 1 ) 0 0 1 2 6 - 2
152
M. Iqbal et al. / Bioresource Technology 81 (2002) 151±153
between the initial and residual concentrations of the metal ions. The pH optimum of metal adsorption was examined by adjusting the metal solutions to the desired pH values of 2, 3, 4, 5, 6 and 7 with 0.1 M HCl and 0.1 M NaOH solution. The pH at the end of the metal adsorption assay was also determined. For desorption of adsorbed metal ions, metal-laden PFP ®brous±biomass was rinsed with deionized water and suspended in 0.1 M HCl. After shaking for 10 min, the biosorbent suspension was centrifuged at 5000 rpm for 5 min and the concentration of metal released into the supernatant was measured as done for metal adsorption. The regenerated PFP biomass was washed with deionized water for 3±4 times to remove any traces of acids and again suspended in metal containing solutions for the next adsorption cycle.
3. Results and discussion The results showed that metal ions were eectively removed from aqueous solutions by PFP biomass. The maximum metal uptake capacity of the PFP biomass at equilibrium for Pb2 , Ni2 , Cd2 , Cu2 , Cr3 and Zn2 was found to be 97.8%, 75.62%, 96.35%, 91.47%, 74.21% and 79.08%, respectively. Regardless of the type of metal ion, the uptake was rapid, with more than 70% of adsorption completed within 15 min, followed by a slower uptake. This could be due to two dierent sorption
processes, fast ion exchange followed by chemisorption (Low et al., 1993). Sorption of all the six metal ions by PFP biomass was noted to be eected by changes in pH. At pH less than 2, very little sorption of all the six metal ions occurred. This could be due to the hydrogen ions competing with the cations for sorption sites. The maximum sorption was achieved at pH 4. However, there was no signi®cant dierence (Duncan's new multiple range test at P 0:05) in sorption levels with increase in pH up to 7. Investigations of pH beyond 7 were not conducted to avoid metal precipitation which may interfere with, and be undistinguishable from, accumulation. The eect of metal ion concentration on the sorption of metal ions is shown in Table 1. The amount of metal ions adsorbed per gram of the biosorbent increased with the increase in initial metal ion concentration at pH 5.0. The general binding eciency indicates a selectivity order of Pb2 > Cd2 > Cu2 > Zn2 > Ni2 > Cr3 . These results show that PFP can bind substantial amounts of the metal ions, Pb2 and Cd2 being sorbed to the greatest extent. When these results were analysed by a typical Langmuir adsorption model, the adsorption isotherms were found to ®t in this model well. The correlation coecient (r2 ) for all the metal ions was >99. Recovery of the adsorbed heavy metals and repeated usability of the adsorbent ®brous±biomass are of signi®cance from the viewpoint of practical application for the treatment of industrial euents. This aspect was investigated through desorption of Pb2 , Ni2 , Cd2 ,
Table 1 Eect of metal ion concentration on the sorption of metal ions by petiolar felt-sheath of palm (PFP) biomass; 10 ml solution of each metal (pH 5.0) was mixed with 50 mg of PFP biomass Initial metal concentration (mg/l) 5.0 10.0 25.0 50.0 75.0 100.0
Amount of metal ion adsorbed (mg/g PFP) Cd
Pb
Ni
Cu
Zn
Cr
0.99 0.01 1.92 0.04 4.57 0.22 7.88 0.32 10.1 0.51 10.8 0.47
1.00 0.00 1.96 0.03 4.49 0.19 8.06 0.16 10.2 0.53 11.4 0.55
0.80 0.02 1.59 0.07 3.48 0.12 5.67 0.18 6.18 0.26 6.89 0.15
0.96 0.03 1.91 0.05 4.11 0.11 6.57 0.09 7.59 0.20 8.09 0.32
0.83 0.05 1.51 0.04 3.40 0.06 5.25 0.15 5.84 0.30 5.99 0.28
0.76 0.04 1.45 0.08 3.00 0.27 4.93 0.26 5.29 0.41 5.32 0.34
All values are mean of concurrent triplicate observations. standard deviation. Table 2 Biosorption and desorption of heavy metal ions by petiolar felt-sheath of palm (PFP) biomass in three consecutive cycles; 10 ml solution of each metal (10 ppm, pH 5.0) mixed with 50 mg of PFP biomass Metals Cd Pb Ni Cu Zn Cr
Metal adsorbed (%)
Metal desorbed (%)
C1
C2
C3
C1
C2
C3
96.2 1.8 97.6 1.1 75.6 2.7 90.4 1.5 78.7 1.6 74.8 2.4
95.8 0.9 97.4 0.8 74.9 1.0 92.1 1.2 79.9 1.0 63.5 2.8
96.7 1.4 96.9 0.9 76.3 1.4 89.8 1.1 77.5 2.3 56.9 1.2
100 0.0 99.7 0.1 94.6 0.8 93.6 0.9 99.5 0.1 64.4 1.7
99.8 0.2 100 0.0 97.3 0.5 95.3 0.7 100 0.3 68.1 2.5
99.9 0.1 99.6 0.2 96.9 0.6 97.0 0.9 99.9 0.1 60.6 1.4
All values are mean of concurrent triplicate observations. standard deviation. C1, C2 and C3 are cycle 1, cycle 2 and cycle 3, respectively.
M. Iqbal et al. / Bioresource Technology 81 (2002) 151±153
Cu2 , Cr3 and Zn2 , adsorbed by the ®brous±biomass from the contaminated water samples and the adsorption eciency of the desorbed biomaterial in the repeatedly conducted three cycles. Observations obtained on metal adsorption±desorption for metal ions during all the three cycles were similar except Cr3 (Table 2). This indicates that the ®brous±biomass remained as active in the take-up of Pb2 , Ni2 , Cd2 , Cu2 and Zn2 after regeneration during three cycles as it was in the ®rst. In conclusion the successful application of ®brous± biomass of petiolar felt-sheath of palm (PFP) as a biosorbent introduces a new and inexpensive environment friendly system for the removal of heavy metals from aqueous media. Among other advantages of the material is desorption of heavy metals from the metal-laden biosorbent and its reusability in repeated cycles of adsorption±desorption process. Further studies on a larger scale using mixtures of heavy metals as contaminated water and euents from speci®ed industrial operations are indicated for determining the quantum level at which this process may ®nd practical application.
153
References Bhattacharya, A.K., Venkobachar, C., 1984. Removal of cadmium (II) by low cost adsorbents. J. Environ. Eng. 110, 110±122. Forster, C.F., Wase, D.A.J., 1997. Biosorption of heavy metals: an introduction. In: Wase, D.A.J., Forster, C. (Eds.), Biosorbents for Metal Ions. Taylor & Francis, London, Chapter 1. Iqbal, M., Zafar, S.I., 1997. Palm petiolar felt-sheath as a new and convenient material for the immobilization of microalgal cells. J. Indust. Microbiol. Biotechnol. 19, 139±141. Low, K.S., Lee, C.K., Lee, K.P., 1993. Sorption of copper by dyetreated oil-palm ®bers. Bioresource Technol. 44, 109±112. Marshall, W.E., Champagne, E.T., 1995. Agricultural byproducts as adsorbents for metal ions in laboratory prepared solutions and in manufacturing wastewater. J. Environ. Sci. Health A 30, 241±261. Munaf, E., Zein, R., 1997. The use of rice husk for removal of toxic metals from wastewater. Environ. Technol. 18, 359±362. Tee, T.W., Khan, A.R.M., 1988. Removal of lead, cadmium and zinc by waste tea leaves. Environ. Technol. Lett. 9, 1223±1232. Wilde, E.W., Benemann, J.R., 1993. Bioremoval of heavy metals by the use of microalgae. Biotech. Adv. 11, 781±812.
Short communication
Petiolar felt-sheath of palm: a new biosorbent for the removal of heavy metals from contaminated water M. Iqbal a,*, A. Saeed a, N. Akhtar b a
Environment Biotechnology Group, Biotechnology and Food Research Center, PCSIR Laboratories Complex, Lahore, Pakistan b Department of Biology, Government Islamia College for Women, Cooper Road, Lahore, Pakistan Received 14 May 2001; received in revised form 14 July 2001; accepted 16 July 2001
Abstract Biosorption of heavy metals such as Pb2 , Ni2 , Cd2 , Cu2 , Cr3 and Zn2 by petiolar felt-sheath of palm (PFP) from contaminated water was examined. PFP was found to eciently remove all the toxic metal ions with selectivity order of Pb2 > Cd2 > Cu2 > Zn2 > Ni2 > Cr3 . The uptake was rapid, with more than 70% completed within 15 min. The bound metal ions were successfully desorbed and the PFP ®brous±biomass remained eective after several adsorption±desorption cycles. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Biosorption; Petiolar felt-sheath; Palm; Heavy metals
1. Introduction
2. Methods
The disposal of industrial euents containing heavy metals into natural water systems is a cause of serious environmental concern. Beyond certain limits these are toxic to living organisms and may cause serious hazards to public health (Forster and Wase, 1997). Many physico-chemical methods have been proposed for their removal from industrial euents. However, these methods are often inecient and/or cost prohibitive when used for the removal of heavy metal ions at low concentrations (Wilde and Benemann, 1993). This has led to the investigation of such alternative low cost technologies that may be eciently applied for the biosorption of heavy metals. For this purpose, numerous agro-waste biomaterials have been investigated and found useful, such as rice-husk (Munaf and Zein, 1997); soybean hulls, cottonseed hulls, rice straw, sugarcane bagasse (Marshall and Champagne, 1995); coconut shell (Bhattacharya and Venkobachar, 1984); and tea leaves (Tee and Khan, 1988). In this study the use of petiolar felt-sheath of palm (PFP), available in abundance as a waste material from palm trees, as a new biosorbent material to remove heavy metals from contaminated water was investigated.
The reticulated ®brous network of petiolar felt-sheath of palm was obtained as peelings from the trunk of palm tree Livistona chinensis (Iqbal and Zafar, 1997). The feltsheaths were washed extensively with distilled deionized water to remove dirt and other particulate matter. The washed sheaths were dried at 70 °C for 24 h, cut to particle size of 1 mm or less in the form of individual threads, oven-dried at 90 °C to constant weight, cooled and kept in a desiccator for subsequent use in the biosorption studies. Standard metal solutions of desired concentrations were prepared from stock solutions (Merck) containing 1000 2 mg/l of Pb2 , Ni2 , Cd2 , Cu2 Cr3 and Zn2 . Adsorption experiments were carried out by suspending 100 mg PFP biomass in 10 ml of each metal ion solution of known concentration and pH in polyethylene tubes placed in a tube rotator at room temperature (25 2 °C). After continuous rotation for 1 h, the tubes were centrifuged at 5000 rpm for 5 min and 100 ll of 65% HNO3 was added to the decanted supernatant. The metal ion concentration in the supernatant was determined by atomic absorption spectroscopy (UNICAM-969) and recorded as the mean of three subsequent measurements. Control experiments were also performed using the metal ion solutions in the absence of PFP biomass. All experiments were performed in triplicate. The amount of metal adsorbed was calculated from the dierence
*
Corresponding author. Fax: +92-42-5877433. E-mail address: [email protected] (M. Iqbal).
0960-8524/02/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 0 - 8 5 2 4 ( 0 1 ) 0 0 1 2 6 - 2
152
M. Iqbal et al. / Bioresource Technology 81 (2002) 151±153
between the initial and residual concentrations of the metal ions. The pH optimum of metal adsorption was examined by adjusting the metal solutions to the desired pH values of 2, 3, 4, 5, 6 and 7 with 0.1 M HCl and 0.1 M NaOH solution. The pH at the end of the metal adsorption assay was also determined. For desorption of adsorbed metal ions, metal-laden PFP ®brous±biomass was rinsed with deionized water and suspended in 0.1 M HCl. After shaking for 10 min, the biosorbent suspension was centrifuged at 5000 rpm for 5 min and the concentration of metal released into the supernatant was measured as done for metal adsorption. The regenerated PFP biomass was washed with deionized water for 3±4 times to remove any traces of acids and again suspended in metal containing solutions for the next adsorption cycle.
3. Results and discussion The results showed that metal ions were eectively removed from aqueous solutions by PFP biomass. The maximum metal uptake capacity of the PFP biomass at equilibrium for Pb2 , Ni2 , Cd2 , Cu2 , Cr3 and Zn2 was found to be 97.8%, 75.62%, 96.35%, 91.47%, 74.21% and 79.08%, respectively. Regardless of the type of metal ion, the uptake was rapid, with more than 70% of adsorption completed within 15 min, followed by a slower uptake. This could be due to two dierent sorption
processes, fast ion exchange followed by chemisorption (Low et al., 1993). Sorption of all the six metal ions by PFP biomass was noted to be eected by changes in pH. At pH less than 2, very little sorption of all the six metal ions occurred. This could be due to the hydrogen ions competing with the cations for sorption sites. The maximum sorption was achieved at pH 4. However, there was no signi®cant dierence (Duncan's new multiple range test at P 0:05) in sorption levels with increase in pH up to 7. Investigations of pH beyond 7 were not conducted to avoid metal precipitation which may interfere with, and be undistinguishable from, accumulation. The eect of metal ion concentration on the sorption of metal ions is shown in Table 1. The amount of metal ions adsorbed per gram of the biosorbent increased with the increase in initial metal ion concentration at pH 5.0. The general binding eciency indicates a selectivity order of Pb2 > Cd2 > Cu2 > Zn2 > Ni2 > Cr3 . These results show that PFP can bind substantial amounts of the metal ions, Pb2 and Cd2 being sorbed to the greatest extent. When these results were analysed by a typical Langmuir adsorption model, the adsorption isotherms were found to ®t in this model well. The correlation coecient (r2 ) for all the metal ions was >99. Recovery of the adsorbed heavy metals and repeated usability of the adsorbent ®brous±biomass are of signi®cance from the viewpoint of practical application for the treatment of industrial euents. This aspect was investigated through desorption of Pb2 , Ni2 , Cd2 ,
Table 1 Eect of metal ion concentration on the sorption of metal ions by petiolar felt-sheath of palm (PFP) biomass; 10 ml solution of each metal (pH 5.0) was mixed with 50 mg of PFP biomass Initial metal concentration (mg/l) 5.0 10.0 25.0 50.0 75.0 100.0
Amount of metal ion adsorbed (mg/g PFP) Cd
Pb
Ni
Cu
Zn
Cr
0.99 0.01 1.92 0.04 4.57 0.22 7.88 0.32 10.1 0.51 10.8 0.47
1.00 0.00 1.96 0.03 4.49 0.19 8.06 0.16 10.2 0.53 11.4 0.55
0.80 0.02 1.59 0.07 3.48 0.12 5.67 0.18 6.18 0.26 6.89 0.15
0.96 0.03 1.91 0.05 4.11 0.11 6.57 0.09 7.59 0.20 8.09 0.32
0.83 0.05 1.51 0.04 3.40 0.06 5.25 0.15 5.84 0.30 5.99 0.28
0.76 0.04 1.45 0.08 3.00 0.27 4.93 0.26 5.29 0.41 5.32 0.34
All values are mean of concurrent triplicate observations. standard deviation. Table 2 Biosorption and desorption of heavy metal ions by petiolar felt-sheath of palm (PFP) biomass in three consecutive cycles; 10 ml solution of each metal (10 ppm, pH 5.0) mixed with 50 mg of PFP biomass Metals Cd Pb Ni Cu Zn Cr
Metal adsorbed (%)
Metal desorbed (%)
C1
C2
C3
C1
C2
C3
96.2 1.8 97.6 1.1 75.6 2.7 90.4 1.5 78.7 1.6 74.8 2.4
95.8 0.9 97.4 0.8 74.9 1.0 92.1 1.2 79.9 1.0 63.5 2.8
96.7 1.4 96.9 0.9 76.3 1.4 89.8 1.1 77.5 2.3 56.9 1.2
100 0.0 99.7 0.1 94.6 0.8 93.6 0.9 99.5 0.1 64.4 1.7
99.8 0.2 100 0.0 97.3 0.5 95.3 0.7 100 0.3 68.1 2.5
99.9 0.1 99.6 0.2 96.9 0.6 97.0 0.9 99.9 0.1 60.6 1.4
All values are mean of concurrent triplicate observations. standard deviation. C1, C2 and C3 are cycle 1, cycle 2 and cycle 3, respectively.
M. Iqbal et al. / Bioresource Technology 81 (2002) 151±153
Cu2 , Cr3 and Zn2 , adsorbed by the ®brous±biomass from the contaminated water samples and the adsorption eciency of the desorbed biomaterial in the repeatedly conducted three cycles. Observations obtained on metal adsorption±desorption for metal ions during all the three cycles were similar except Cr3 (Table 2). This indicates that the ®brous±biomass remained as active in the take-up of Pb2 , Ni2 , Cd2 , Cu2 and Zn2 after regeneration during three cycles as it was in the ®rst. In conclusion the successful application of ®brous± biomass of petiolar felt-sheath of palm (PFP) as a biosorbent introduces a new and inexpensive environment friendly system for the removal of heavy metals from aqueous media. Among other advantages of the material is desorption of heavy metals from the metal-laden biosorbent and its reusability in repeated cycles of adsorption±desorption process. Further studies on a larger scale using mixtures of heavy metals as contaminated water and euents from speci®ed industrial operations are indicated for determining the quantum level at which this process may ®nd practical application.
153
References Bhattacharya, A.K., Venkobachar, C., 1984. Removal of cadmium (II) by low cost adsorbents. J. Environ. Eng. 110, 110±122. Forster, C.F., Wase, D.A.J., 1997. Biosorption of heavy metals: an introduction. In: Wase, D.A.J., Forster, C. (Eds.), Biosorbents for Metal Ions. Taylor & Francis, London, Chapter 1. Iqbal, M., Zafar, S.I., 1997. Palm petiolar felt-sheath as a new and convenient material for the immobilization of microalgal cells. J. Indust. Microbiol. Biotechnol. 19, 139±141. Low, K.S., Lee, C.K., Lee, K.P., 1993. Sorption of copper by dyetreated oil-palm ®bers. Bioresource Technol. 44, 109±112. Marshall, W.E., Champagne, E.T., 1995. Agricultural byproducts as adsorbents for metal ions in laboratory prepared solutions and in manufacturing wastewater. J. Environ. Sci. Health A 30, 241±261. Munaf, E., Zein, R., 1997. The use of rice husk for removal of toxic metals from wastewater. Environ. Technol. 18, 359±362. Tee, T.W., Khan, A.R.M., 1988. Removal of lead, cadmium and zinc by waste tea leaves. Environ. Technol. Lett. 9, 1223±1232. Wilde, E.W., Benemann, J.R., 1993. Bioremoval of heavy metals by the use of microalgae. Biotech. Adv. 11, 781±812.