Ind. Eng. Chem. Res. 1995,34, 869-873
869
Removal of Lead(I1) by Adsorption onto “Waste” Iron(III)/Chromium(III)Hydroxide from Aqueous Solution and Radiator Manufacturing Industry Wastewater Chinnaiya Namasivayam* and Kuppusamy Ranganathan Environmental Chemistry Division, Department of Environmental Sciences, Bharathiyar University, Coimbatore-641 046, Tamil Nadu, India
‘Waste”iron(III)/chromium(III)hydroxide has been used as an adsorbent for the effective removal of Pb(I1) from aqueous solution. The parameters studied include agitation time, Pb(I1) concentration, temperature, and pH. The percent adsorption of Pb(I1) increased with a decrease in concentration of Pb(I1) and a n increase in temperature and pH. Quantitative removal of Pb(I1) was observed a t pH L 7.0. The equilibrium data fit well with the Langmuir isotherm. The adsorption capacity (40) calculated from Langmuir isotherm was 126.55 mg/g at a n initial pH of 3.5 at 30 “C. Desorption of Pb(I1) from Pb loaded adsorbent was 56% at pH 4.0. Application of the adsorbent was successfully demonstrated using the radiator manufacturing industry wastewater. 1. Introduction
Lead(I1) is let into aquatic environment from plating, mining, smelting, storage battery, printing, tetraethyllead manufacturing, paint and dyeing industries, and glass industrial operations (Yadava et al., 1991). The toxicity and deleterious effects of lead are well documented, and its poisoning in human causes severe destruction in the kidney, reproductive system, liver, brain, and central nervous system, and sickness or death results (Manahan, 1984). The tolerance limit of lead for discharge into inland surface waters is 0.1 mg/L (ISI, 1982) and in drinking water is 0.05 mg/L (ISI, 1991) according to Indian Standards Institution. Therefore Pb(I1) should be removed from wastewaters before it mixes with water sources. Current abatement and remediation of lead in wastewater include pH adjustment with lime or alkali hydroxides, coagulationsedimentation, reverse osmosis, ion exchange ( G r o h a n et al., 1992), cementation (Agelidis et al., 1989) and activated carbon adsorption (Netzer and Hughes, 1984). Among these methods, adsorption is an attractive process. Lead removal by adsorption on manganese oxide (Gray and Malati, 19791, hydrous oxide gels (Kinniburg et al., 1976) and goethite (Balistrieri and Murray, 1982) have been studied in detail. Although they are effective, they are expensive. However, there are abundant inexpensive waste materials that can be used as adsorbents. Removal of dyes and heavy metals by nonconventional adsorbents has been recently reviewed by Namasivayam (1994). Lead removal by adsorption on china clay and wollastonite (Yadava et al., 1991) agricultural wastes like oil palm fiber and coconut husk (Latif and Jaafar, 1989), charred waste of oxalic acid plant (Nandita and Pandey, 1990), clays (Farrah et al., 1980),bottom ash (Kaur et al., 19911, and fly ash (Mathur and Rupainwar, 1988) have been investigated. Waste” Fe(III)/Cr(III)hydroxide is produced in the treatment of wastewaters containing Cr(V1). The toxic Cr(VI) is reduced to Cr(II1) under acidic condition by Fe(II), which is generated electrolytically (Ramakrishnan and Subramanian, 1987). The Fe(III)/Cr(III)ions,
* To whom correspondence should be addressed. 0888-588519512634-0869$09.00/0
produced in solution, are precipitated with lime as Fe(III)/Cr(III)hydroxides. Recently Namasivayam and coworkers have used the “waste” Fe(III)/Cr(III)hydroxide for the treatment of wastewaters from the fertilizer industry (Namasivayam, 1989), dyeing industry (Namasivayam and Chandrasekaren, 19911, dairy industry (Namasivayam and Ranganathan, 1992), distillery industry (Namasivayam and Kanagarathinam, 19921, and chromium plating industry (Namasivayam and Ranganathan, 1993). The present work deals with the adsorption of Pb(1I) from wastewater by the Fe(III)/Cr(III) hydroxide as a function of agitation time, Pb(I1) concentration, temperature, and pH. Removal of lead by the Fe(III)/Cr(III) hydroxide was also testified using radiator manufacturing industry wastewater.
2. Materials and Methods 2.1. Materials. “Waste” Fe(III)/Cr(III) hydroxide was obtained from Southern Petrochemical Ind. Corp. Ltd. (SPIC), Tuticorin, Tamil Nadu, India. It was ground, washed with distilled water to remove very fine particles, dried at 60 “C overnight, and sieved to 150250 pm particle size range. The characteristics of the adsorbent were as follows: Fe/Cr, 5.5 (w/w); Ca, 5%; apparent density, 0.865 g/mL; pH of 100 mg Fe(I11YCr(111) hydroxide in 50 mL of water after equilibration, 7.8; loss on ignition, 32.0%; surface area, 424.0 m2/g; porosity 63%; pHzpc,8.3. The aqueous suspension of Fe(III)/Cr(III)hydroxide (50 mg in 50 mL) did not release either Fe(II1) or Cr(II1) in the equilibriated pH range, 3.5-10.5, studied. Synthetic wastewaters of different Pb(I1) concentrations were prepared from 1000 mg/L of stock solution of lead nitrate in distilled water containing a few drops of concentrated nitric acid t o prevent hydrolysis. Ionic strength was maintained with 1 x M NaN03 and initial pH of Pb(I1) solution was 3.50, unless otherwise stated. All the chemicals used are of analytical reagent grade and were obtained from Loba and Glaxo/BDH. The radiator manufacturing industry wastewater containing lead was collected at Coimbatore and characterized as per standard procedures (APHA, 1980). 2.2. Batch Mode Adsorption Studies. The adsorption study was carried out by agitating 100 mg of
0 1995 American Chemical Society
870 Ind. Eng. Chem. Res., Vol. 34, No. 3, 1995 Table 1. Effect of Initial Concentration and Temperature on Pb(I1) Adsorption
1.6-
% adsorption
1.4-
Pb(I1) concn, mg/L
20 "C
30 "C
40 "C
100 200 300 400
95.0 75.0 59.7 52.5
98.6 83.0 70.7 62.5
99.2 93.0 78.7 65.0
1.2 1.0U
Y
Fe(III)/Cr(III)hydroxide with 50 mL of Pb(I1) solution of desired concentration in 100 mL glass conical flasks at 120 rpm for a predetermined time interval using a temperature controlled shaker. For pH studies 50 mg of the Fe(III)/Cr(III)hydroxide was mixed with 30 mL of distilled water and 5 mL of 0.1 M NaN03 and equilibrated to a desired pH using dilute HNO3 or NaOH solutions. Then 10 mL of Pb(I1) solution was added, and the pH was again adjusted to the above value, made up to 50 mL, and agitated as above for equilibrium time. The concentration of Pb(I1) was 200 mg/L. The adsorbent and adsorbate were separated by centrifugation at 10 000 rpm, 8700g for 20 min, and Pb(11) was estimated spectrophotometrically using 442pyridy1azo)resorcinol (PAR, Pollard et al., 1959). Adsorption isotherm study was carried out with different initial concentrations of Pb(I1)from 100 to 400 mg/L and a fured concentration of adsorbent, 2.0 g/L. To correct for any adsorption of Pb(I1) on containers, control experiments were carried out without adsorbent, and there was negligible adsorption by the container walls. Experiments were carried out in triplicate, and percent error was within 5%. Experiments were generally carried out with Pb(I1) concentration of 200 mg/L and at 30 "C, unless otherwise stated. 2.3. Desorption Study. After adsorption experiment with 200 mg of Pb(II)/L and 2.0 g of adsorbent& the adsorbent laden with Pb(I1) were separated and gently washed with distilled water t o remove any unadsorbed Pb(I1). Several such spent adsorbent samples were prepared. Then the spent adsorbent was agitated with 50 mL acidified water, adjusted to different pH values varying from 4 to 7, for 150 min at 120 rpm at 30 "C. The desorbed Pb(I1) was analyzed as before. To 50 mL of the industrial wastewater, different doses of adsorbent were added and agitated for 150 min. Then the supernatant was filtered by 0.22 pm membrane filter and acidified t o pH 2.0. Lead was estimated using GBC 902 double-beam atomic absorption spectrophotometer. 3. Results and Discussion 3.1. Effect of Agitation Time, Initial Concentration, and Temperature. Removal of Pb(I1) increased with agitation time and attained equilibrium at 150 min for all the initial concentrations of Pb(I1) and temperatures studied. The percent adsorption increased with decrease in Pb(I1) concentration and increase in temperature. The data are shown in Table 1. The increase in adsorption of Pb(I1) with temperature is probably "activated diffusion". Such activated adsorption would widen and deepen the very small micropores, i.e., cause "pore burrowing" and so create more surface for adsorption (Giles et al., 1974). Thermodynamicalparameters can be calculated using the following relations (Singh et al., 1988; Namasivayam
0.8-
-
0. 6-
0.40- 2 -
3.0
3.1
3.2
3.3
3
LxlO T
-1
(K
3.4
3.5
)
Figure 1. van't Hoff plot for the adsorption of Pb(I1) on Fe(III)/ Cr(II1) hydroxide. Table 2. Thermodynamical Parameters temp, "C
K,
-AGO, kJ/mol
20 30 40 50
3.00 4.88 13.29 39.00
2.68 3.99 6.73 9.84
A€P, kJ/mol AS", J/(mol/K) 68.13
240.05
and Ranganathan, 1993):
K, = CA/Ce AGO = -RT In K,
lOgK,=--
AS" 2.303R
Aw 2.303RT
(2) (3)
where K, is the equilibrium constant, Ce is the equilib~ the rium concentration in solution (mg/L), and C A is solid-phase concentration at equilibrium (mg/L) AGO, AHO,and AS" are changes in free energy, enthalpy, and entropy, respectively. Figure 1shows a van't Hoff plot of log K,vs 1IT. AH" and AS" were obtained from the slope and intercept of the van't Hoff plot and are presented in Table 2. The positive value of AHO confirms the endothermic adsorption of Fe(III)/Cr(III) hydroxide. The negative values of AGO (Table 2) indicate that the adsorption is spontaneous. The positive value of AS" suggests the increased randomness at the solid-solution interface during the adsorption of Pb(11)ions on Fe(III)/Cr(III)hydroxide. In the adsorption of Pb(II), the adsorbed solvent molecules, which are displaced by the adsorbate species gain more translational entropy than is lost by the adsorbate ions, thus allowing for the prevalence of randomness in the system (Vishwakarma, 1989). 3.2. Adsorption Isotherm Studies. The equilibrium data were correlated both by Langmuir and Freundlich equations. The data fit better with Langmuir isotherm for different temperatures studied. The Langmuir treatment is based on the assumptions that maximum adsorption corresponds to a saturated monolayer of adsorbate molecules on the adsorbent surface, that the energy of adsorption is constant, and that there is no transmigration of adsorbate in the plane of the surface (Yenkie and Natarajan, 1991). The isotherm
Ind., Eng. Chem. Res., Vol. 34, No. 3, 1995 871 Corr.coetft
100-
0 20’C 0.9922 A 30’C 0,9930 0 40.C 0.9946
2.0-
$
1.6-
--
60-
i
-1
0
80-
1.2-
a 40-
s
Id,,
20
3
4-
A
5
6’
I
I
I
I
I
7
8
9
10
11
PH
Ce ( m g / L )
Figure 2. Langmuir plots for the adsorption of Pb(I1) on Fe(III)/ Cr(II1) hydroxide for different temperatures.
Figure 3. Effect of pH on removal of Pb(I1) in the presence ( 0 ) and absence ( 0 )of Fe(III)/Cr(III)hydroxide.
(Periyasamy and Namasivayam, 1994):
Table 3. Equilibrium Parameter, RL Pb(I1) concentration, mg/L temp, “C
100
200
300
400
20 30 40
0.140 0.096 0.045
0.076 0.051 0.023
0.052 0.034 0.015
0.039 0.025 0.012
data in Figure 2 are well described by the linear form of the Langmuir equation (Langmuir, 1918; Haggerty and Bowman, 1994):
-Ce_- 1 qe
QO
+-QOCe
(4)
where C, is the equilibrium concentration ( m a ) , qe is the amount adsorbed at equilibrium (mg/g), and b is the “affinity” parameter or Langmuir constant (IJmg), and QOis the “capacity” parameter (mg/g). QOand b were determined from the slopes and intercepts of the straight line plots at temperatures 20, 30, and 40 “C and are 109.9 mg/g and 0.061 IJmg; 126.58 mg/g and 0.094 IJg; 133.3 mg/g and 0.214 IJmg, respectively. The QO and b values for the adsorption of Pb(I1) on china clay in the temperature range 20-40 “C were reported to be in the range 0.415-0.347 mg/g and 12.05-1.44 Umg, respectively; and on wollastonite, QOand b were in the range 0.308-0.234 mg/g and 1.43 to 1.35 IJmg, respectively (Yadava et al., 1991). The QOvalue for the adsorption of Pb(I1) has been reported by Larsen and Schierup (1981) as 19.5 mglg for activated carbon. The essential characteristics of a Langmuir isotherm can be expressed in terms of a dimensionless constant separation factor or equilibrium parameter, RL (McKay et al., 1982). RLdescribes the type of isotherm. RLis defined by RL = 141 bCo) where b is Langmuir constant and COis initial concentration of Pb(I1). RLvalues between 0 and 1 indicate favorable adsorption of Pb(I1) on Fe(III)/Cr(III)hydroxide for all concentrations of lead and temperatures studied (Table 3) (Periyasamy and Namasivayam, 1994). 3.3. Adsorption Dynamics. The two important aspects for parameter evaluation of the adsorption study are the kinetic and the equilibria of adsorption. The adsorption of heavy metals from liquid phase t o solid phase can be considered as a reversible reaction with an equilibrium being established between two phases (Orhan and Buyukgungor, 1993). A simple first-order kinetic model is represented by the Lagergren equation
+
where k a d is the rate constant of adsorption, q and qe are the amounts of Pb(I1) adsorbed (mg/g) at time t (minutes) and at equilibrium time, respectively. Linear plots of log(q, - q ) vs t (not shown) indicate the applicability of Lagergren equation. The k a d values calculated from the slopes of the linear plots for different Pb(I1) concentrations (100,200,300, and 400 m a ) were found to be around 2.0 x IJmin. The k a d values calculated from the slopes of the linear plots (not shown) for different temperatures (20,30, and 40 “C)were found to be around 2.0 x Umin for a Pb(I1)concentration of 200 m a . There was no significant change in k a d value with increase in temperature and Pb(I1) concentration. 3.4. Effect of pH. Figure 3 shows that increasing pH increases the removal of Pb(II),both in the presence and absence of Fe(III)/Cr(III)hydroxide. Precipitation of Pb(0H)z begins at pH 6.3. Removal of Pb(I1)is more efficient in the presence of Fe(III)/Cr(III)hydroxide. At pH L 7.0 complete removal of lead was observed from 200 mg/L of Pb(I1) solution by Fe(III)/Cr(III)hydroxide. The observed pH effect is in agreement with the study of Aualiitia and Pickering (Aualiitia and Pikering, 1987) on the removal of Pb(I1) by Fe(0H)DeOOH. Appreciable adsorption of Pb(I1) occurred at pH values below 8.3, the pH,,, of the adsorbent though the adsorbent surfaces were mostly positively charged (Namasivayam and Ranganathan, 1993). Since electrostatic attraction was not possible between positively charged adsorbent surfaces and positively charged metal ion species, Pb2+ and or PbOH+ it seems that some nonelectrostatic force called specific adsorption was involved in the process of adsorption (Kinniburgh et al., 1976). In alkaline media, lead species such as PbOH+ and Pb(OH)d4+ are present (Farrah and Pickering, 1977). In the alkaline pH, the highly negatively charged adsorbent surface favors quantitative removal of Pb(11)from solution. 3.6. Desorption Study. Desorption studies help evaluate the mechanism of adsorption and recover heavy metals and the adsorbent for recycling. The percent desorption of Pb(I1) from the spent Fe(III)/Cr(111) adsorbent (100 mg) loaded with 8.3 mg of Pb(I1) increased from 2.0%at pH 7.0 t o 56%at pH 4.0 (Figure 4). Hence regeneration of Pb(I1) and reutilization of the “waste” Fe(III)/Cr(III) hydroxide are possible to some extent. The desorption study indicates that ion exchange seems to be important in the adsorption process
872 Ind. Eng. Chem. Res., Vol. 34, No. 3, 1995
8s1
A
lotor 60-
providing the “waste” Fe(III)/Cr(III) hydroxide sample and Bharathiar University for providing Central Instrumentation Lab facilities. K.R. is grateful t o Council of Scientific and Industrial Research (CSIR),New Delhi for the award of Senior Research Fellowship (SRF).
LO-
Literature Cited
8o
$
20I
0
PH
Figure 4. Effect of pH on desorption of Pb(I1).
-0 Fe(lll)l Cr ( I l l ) hydroxide Concentration (g/L)
Figure 5. Effect of adsorbent dose on Pb(I1)removal from radiator manufacturing industry wastewater. Table 4. Characteristics of Radiator Manufacturing Industry Wastewater parameter PH total solids, mgL COD, m g L chloride, m g L sulfate, mgL Na, m g L Ca, m g L Pb(II), mgL
3.5 5930.0 312.8 1957.0 302.0 350.0 160.0 24.0
of PWII) by Fe(III)/Cr(III) hydroxide (Periyasamy and Namasivayam, 1994). 3.6. Test with Lead-ContainingRadiator Manufacturing Industry Wastewater. The characteristics of radiator manufacturing industry wastewater are shown in Table 4. Increase in adsorbent dose increased the lead removal and complete removal of Pb(I1) from 50 mL of wastewater at pH 3.5 occurred at an adsorbent dose of 4.0 g/L (Figure 5). 4. Conclusions
Waste Fe(III)/Cr(III) hydroxide is an effective adsorbent for the removal of Pb(I1) from aqueous solutions. Adsorption was endothermic in nature and followed a Langmuir adsorption isotherm. Quantitative removal of Pb(I1) a t 24 mg/L from 50 mL of radiator manufacturing industry wastewater required 200 mg of adsorbent. As the adsorbent is disposed as waste in fertilizer industries, the treatment method is expected to be economical.
Acknowledgment The authors gratefully acknowledge Dr. R. M. Krishnan, Chief Manager, R & D Centre, Southern Petrochemical Industries Corp. Ltd. (SPIC), Tuticorin for
Agelidis, T.; Fytianos, K.; Vasilikiotis, G. Lead Recovery from Aqueous Solution and Wastewater by Cementation Utilizing an Iron Rotating Disc. Resour., Conserv. Recycl. 1989,2,131-138. APHAs. Standard Methods for the Examination of Water and Wastewater;American Public Health Association: Washington DC, 1980. Aualiitia, T. U.; Pickering, W. F. The Specific Sorption of Trace Amounts of Cu, Pb and Cd by Inorganic Particulates. Water, Air Soil Pollut. 1987, 35, 171-185. Balistrieri, L. S.;Murray, J . W. The adsorption of Cu, Pb, Zn and Cd on Goethite from Major Ion Sea Water. Geochim. Cosmochim. Acta 1982,46, 1253-1265. Farrah, H.; Pickering, W. F. Influence of Clay-solute Interactions on Aqueous heavy metal ion levels. Water,Air Soil Pollut. 1977, 8 , 189-197. Farrah, H.; Halton, D.; Pickering, W. F. The Affinity of Metal Ions for Clay Surfaces. Chem. Geol. 1980,28, 55-68. Giles, C. H.; Smith, D.; Huitson, A. J. J . Colloid Interface Sci. 1974, 47, 755. Gray, M. J.; Malati, M. A. Adsorption from Aqueous Solution by Manganese dioxide. I1 Adsorption of some Heavy Metal Cations. J . Chem. Tech. Biotechnol. 1979, 29, 135-144. Groffman, A,; Peterson, S.; Brookins, D. Removing Lead from Wastewater Using Zeolite. Water Environ., Technol. 1992, 4, 54-59. Haggerty, G. M.; Bowman, R. S. Sorption of chromate and other inorganic anions by organo-zeolite. Environ. Sci. Technol. 1994, 28, 452-458. ISI. Tolerance limits for industrial emuents prescribed by Indian Standards Institution, IS:2490 (Part I), 1982. (Address: Bureau of Indian Standards, Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 100 002, India). ISI. Drinking Water Specification, 1991, IS:10500. Kaur, A.; Malik, A. K.; Varma N.; Rao, A. L. J. Removal of Copper and Lead from Wastewater by Adsorption on Bottom Ash. Indian J . Environ. Protection 1991, 11,433-435. Kinniburg, D. G.; Jackson, M. L.; Syers, J. K. Adsorption of Alkaline earth, Transition and Heavy Metal Cations by Hydrous oxide gels of Iron and Aluminium. Soil Sci. SOC.Am. J . 1976, 40, 796-799. Langmuir, I. J . Am. Chem SOC,1918, 40, 1361. Larsen, V. J.; Schierup, H. H. The use of Straw for Removal of Heavy Metals from Wastewater. J . Environ. Qual. 1981, 10, 188-193. Latif, P. A.; Jaafar, N. Adsorption of Cu(II), Zn(II), and Pb(I1) by Selected Agricultural Wastes. Pertanika 1989, 12, 193-200. Manahan, S. Environmental Chemistry;Brooks/Cole: California, 1984; Chapter 7. Mathur, A.; Rupainwar, D. C. Removal of Lead from Polluted Waters by Adsorption on Fly Ash. Asian Environ. 1988,10,1925. McKay, G.; Blair, H. S.; Gardner, J. R. Adsorption of Dyes on Chitin. 1. Equilibrium studies. J. Appl. Polym. Sci. 1982, 27, 3043-3057. Namasivayam, C. Application of Fe(III)/Cr(III) Hydroxide as FlocculanffSettling Agent. Indian J . Enuiron. Protection 1989, 9, 734-736. Namasivayam, C. Adsorbents for the treatment of wastewaters. In: Encyclopedia of Environmetal Pollution and Control;Trivedy, R. K., Ed.; Enviro Media: Karad, India, 1994. Namasivayam, C.; Chandrasekaren, B. Treatment of Dyeing Industry Wastewater Using Fe(III)/Cr(III)Sludge and Red Mud. J . Indian Assoc. Environ. Management 1991, 18, 93-99. Namasivayam, C.; Kanagarathinam, A. Distillery Wastewater Treatment Using Fe(III)/Cr(III) Hydroxide Sludge and Polymer Flocculants. J . Enuiron. Sci. Health 1992, A27, 1721-1737. Namasivayam, C.; Ranganathan, K. Waste Fe(III)/Cr(III)Sludge as Flocculant for the Treatment of Dairy Wastewater. Bioresource Technol. 1992, 40, 209-213. Namasivayam, C.; Ranganathan, K. Waste Fe(III)/Cr(III) Hydroxide as Adsorbent for the removal of Cr(V1) from Aqueous
Ind. Eng. Chem. Res., Vol. 34, No. 3, 1995 873 Solution and Chromium Plating Industry Wastewater. Environ. Pollut. 1993, 82 , 255-261. Nandita, S.; Pandey, G. S. Charred Waste of Oxalic Acid Plant as an Adsorbent of Toxic Ions and Dyes. Biol. Wastes 1990, 32, 145-148. Netzer, A,; Hughes, D. E. Adsorption of Copper, Lead and Cobalt by Activated Carbon. Water Res. 1984, 18, 927-933. Orhan, Y.; Bugukgungor, H. The removal of heavy metals by using agricultural wastes. Water Sci. Technol. 1993,28, 247, 255. Periyasamy, K.; Namasivayam, C. Process development for removal and recovery of cadmium from wastewater by a low-cost adsorbent Adsorption rates and equilibrium studies. Ind. Eng. Chem Res. 1994,33, 317-320. Pollard, F. H.; Hanson, P.; Geary, W. J. 4-(2-pyridylazo resorcinol) as a Possible Analytical Reagent for the Colorimetric Estimation of Cobalt, Lead and Uranium. Anal. Chim. Acta 1959,20,2631. Ramakrishnan, S. R.; Subramanian, G. A Continuous Process for the Purification of Cooling Tower Blowdown-Water or the Effluent Containing Hexavalent Chromium. Indian Patent 158019, 1987.
Singh, A. K.; Singh, D. B.; Panday, K. K.; Singh, V. N. Wollastonite as adsorbent for removal of Fe(I1) from water. J . Chem. Technol. Biotechnol 1988,42, 39-49. Vishwakarma, P. P.; Yadava, K. P.; Singh, V. N. Nickel(I1) Removal from Aqueous Solutions by Adsorption on Fly ash. Pertanika 1989,12,357-366. Yadava, K. P.; v a g i , B. S.; Singh, V. N. Effect of Temperature on the Removal of Lead(I1) by Adsorption on China clay and Wollastonite. J . Chem. Technol. Biotechnol. 1991, 51, 47-60. Yenkie, M. K. N.; Natarajan, G. S. Adsorption equilibrium studies of some aqueous aromatic pollutants on granular activated carbon samples. Sep. Sci. Technol. 1991,26, 651-674.
Received for review April 28, 1994 Revised manuscript received October 20, 1994 Accepted November 2, 1994@ I39402729 Abstract published in Advance ACS Abstracts, January 15, 1995. @
