INTRODUCTION:

Industrial and mining waste water is the major source of pollution of heavy metals. Furthermore in the developing countries like India, many industries are operated at small or medium scale or even a family business within the residential premises of owner. These smaller units can generate a considerable pollution load which in many cases is discharge directly into the environment without any waste water treatment. This is because capital investment, turnover and profit for these industries are also small. In India, such a situation exists and the discharge of waste water containing chemicals and metallic ions into nearby water sources.

In recent years increasing awareness of the environmental impact of heavy metals has prompted a demand for the purification of industrial waste water prior to discharge into natural water¹. Conventional methods like Ion-exchange, chemical precipitation, ultra-filtration of electro-chemical deposition do not seem to be economically feasible for such industries because of their relatively high cost. Therefore, there is a need to look into alternatives to investigate a low cost method which is effective, economic and can be used by such industries.

In recent past development of efficient and eco-friendly methods for removal of heavy metals are receiving attention by agro waste as adsorbent by various researchers^2-7.

Literature survey reveals that no work has been reported on thermodynamic and kinetic study by using Kammoni Leaf Powder (KLP) as an adsorbent for removal of Nickel, Copper and Iron from aqueous solution. In the present work an attempt has been made to study the feasibility of KLP, a cheap, locally and easily available for the adsorption of metal ions. The optimum temperature (range 30 to 45°C), pH (range 3 to 7), contact time (60 minutes) for the present study were selected by carrying trial experiments and was found to be maximum removal of metal ions by KLP in this range. The batch adsorptions kinetics was carried for the first order reversible reaction.

EXPERIMENTAL:

Adsorbent:

The adsorbent used in the present investigation were leaves of Kammoni Plants collected from Ahmednagar District of Maharashtra State (India). The leaves of Kammoni were dried in shadow avoiding direct sunlight on them. The dried plant leaves were grinded into powder and were boiled in distilled water to remove the suspended and dust for one hour and filtered. The residue left was treated with formaldehyde and finally with very dilute solution of sulphuric acid, stirred for 30 minutes vigorously using mechanical stirrer at room temperature, it was filtered and washed with distilled water repeatedly to remove free acid. After chemical treatment residue was dried first in air and finally in oven at 90-100°C for 8-10 hours and powdered using electric grinder. The homogeneous powder was then passed through mesh for desired particle size (9.8 - 41.8 micron). The adsorbent once prepared were used throughout the experimental work. The particle size selected for these experiments were on the basis of their settlement at the bottom of the system, so that the portion of the solution could be taken out conveniently from the supernatant liquid.

FT - IR Spectrum of Kammoni Leaf Powder (KLP):

The surface chemistry of KLP was determined by the type quantity and bonding of oxygen containing functional groups such as hydroxyl, carbonyl, carboxyl, nitro groups^8-9.

The FT - IR spectrum of KLP adsorbent can be summarized from the bands observed as:

(1) Medium based overlapping bands at 3310.21cm^-1 may be attributed to -OH group stretching present in secondary alcohol of KLP.

(2) The bands at 2917.77cm^-1 indicates C-H stretching assigned to secondary asymmetric carbon.

(3) The bands at 1730.8 cm^-1 indicates C=O stretching in a - b unsaturated Ketones.

(4) The bands range of 668.21cm^-1 ascribed to N-H deformation (out of plane band) in primary, secondary amines of KLP.

Preparation of Adsorbate Solution:

Nickel, Copper and Iron were the metal ions selected for the present investigation. The chemicals used were of A.R. grade and used without further purifications. The solutions were prepared in doubly distilled water. A distilled water prepared by using first metal distillation unit and then all quick fit glass assembly in permangantic condition, wherever necessary the prepared solutions were standardized as per literature¹⁰. All the metals were estimated following a suitable colorimetric method. Nickel was estimated by the dimethylglyoxime method¹¹, Copper and Iron by the thiocyanate methods^12-13.

Batch Adsorption experiments:

Each batch adsorption study was carried out by contacting the Kammoni leaf powder (KLP) with the metal ions Ni (II), Cu (II) and Fe (III) under different conditions for 60 minutes in a glass tube. Study was conducted in a thermostated water bath and the residual metal ions were analyzed. The amount of metal ions adsorbed from solution was determined by difference¹⁴. The pH range for adsorption study was kept in range of 3.5 to 7.2 and the temperature was maintained at 30°C to examine the effect of initial solution pH on the adsorption of metals by contacting 0.9 g of the KLP with 100 ml. of Ni (II), Cu (II) and Fe (III) solutions in different glass tube. The pH of each solution was adjusted to the desired value with 0.1 M NaOH and / or 0.1 HCl (HNO₃).

RESULTS AND DISCUSSION:

Effect of pH:

The effect of pH on the adsorption of Ni (II), Cu (II) and Fe (III) carried out within the range that would not influenced by the metal precipitation¹⁵. The solution pH plays a vital role in the removal of heavy metals as the acidity of solution pH is one of the most important factors for controlling the uptake of heavy metals from wastewater and aqueous solution¹⁶. The maximum adsorption of Nickel, Copper and Iron on to the surface of KLP adsorbent was found to be at pH 3.5 which was rather acidic. Our findings have been supported by the earlier reported work¹⁷. The adsorption in acidic media may be attributed to link H⁺ion which are released from active sites and enhances the adsorption capacities as the surface oxide functions as ligands for the metal ions on to the surface of KLP, it is in good agreement with the findings of Devaprasath et al and others^18-19.

In the present investigation with increase in pH from 3.5 to 7.2 the degree of protonation of adsorbent functional group decreased gradually and hence the removal decreased as shown in figure 1 and The order of adsorption of metal ions on to the surface of KLP was found to be Ni > Cu > Fe.

Figure 1- Effect of pH on removal of metal ions.

Effect of adsorbent dose:

The present study reveals that as the adsorbent dose increased from 0.5 gms to 0.8 gms there was increase in the adsorption of metal ions on to the surface of KLP, as in figure 2. This is in good agreement with the earlier reported work²⁰. The increase in adsorption with increase in KLP dose may be attributed to the increase in the availability of active sites, increase in the effective surface area²¹.

Figure 2- Effect of adsorbent dose on removal of metal ions.

Effect of Initial Concentration of metal ions:

The feasibility and efficiency of a adsorption process not only depends on the properties of the adsorbents but also on the concentration of the metal ion solution the initial metal concentration provides an important driving force to overcome all the mass transfer resistances of the metal between aqueous and solid phase²². In the present investigation the removal of metal ions from the aqueous with variation in the initial concentration showed no regular trend and removals of metal ions found to be random as in figure 3. The decline in the adsorption capacity of KLP with increase in the concentration of metal ion (adsorbate) may be attributed to the availability of smaller number of surface sites on the adsorbents (KLP) for a relatively larger number of adsorbing species at higher concentration. The increase in metal concentration, also increases electrostatic interaction between the metal ion and KLP adsorbent active sites and can be explained by the fact that more adsorption sites were covered as the metal ion increases²³.

Figure 3- Effect of initial concentration on removal of metal ions.

Figure 4- Effect of temperature on removal of metal ions.

Effect of Temperature:

Temperature has two major effects on the adsorption process increases the rate of adsorbate diffusion across the external boundary layer and in the internal pores of the adsorbate particles due to decrease in liquid viscosity at higher temperature and the other effects is the equilibrium capacity of the adsorbate depending on nature of the process i.e. exothermic or endothermic²⁴. The effect of temperature on adsorption of metal ion on KLP is given in figure 4. The increased adsorption at higher temperature with some exception during the present investigation may be attributed to acceleration of some originally slow step, creation of new activation sites on adsorbent surface decrease in the size of adsorbing species, this could well occur due to progressive dissolution of the metal ion as the solution temperature increases. Our findings are in good agreement with the findings of different researchers²⁵.

Adsorption Isotherms:

The capacity of adsorption isotherm provides a panorama of the course taken by the system under study in a concise form, indicating how efficiently an adsorbent will adsorb and allows an estimate of the economic viability of the adsorbents commercial applications for the specified solute. The Langmuir and Freundlich models are the most widely used models, in case of adsorption of metal ions by adsorbents even though the metal uptake may not exactly follows the monolayer adsorption mechanism. The Freundlich model²⁶ is perhaps the most popular adsorption model for a single solute system and is an empirical relation equation based on the distribution of solute between the solid phase and the aqueous phase at equilibrium.

In the present study the Freundlich model is found to be linear the coefficient of correlation value (r²) was maximum. It is in good agreement with the findings of Shilpi et al²⁷. A smaller value of 1/n indicates better adsorption mechanism and formation of relating strong bond between adsorbate and adsorbent. The rate of attachment to the surface should be proportional to a driving force times on area. The affinity between the adsorbent and the different metals can be quantified by fitting the obtained adsorption values to the Langmuir Isotherm²⁸. The Langmuir equation and Freundlich model describes the isotherm of Ni (II), Cu (II) and Fe (III) adsorption with high correlation coefficient (r² = 0.99). In our present findings isotherm data reveals that the adsorption process follows both Freundlich and Langmuir isotherm and suggest favorable adsorption. The dimensionless equilibrium parameter R_L also known as separation factor was defined by Hall et al.²⁹ and given by the equation,

Where 'b' is Langmuir constant (1/mg) and C₀ is the initial concentration (mg/L). In the present investigation the values of R_L for Nickel (0.0102), Copper (0.0100) and Iron (0.0102) which lies in the range between 0 to 1 and shows favorable adsorption. Our findings are good agreement with the findings reported by Patil et al and others³⁰.

Thermodynamic Parameters:

Thermodynamic Parameters evaluates the nature of adsorption of adsorbate and its magnitude during adsorption process. The change in Gibbs free energy (DG), enthalpy changes (DH) and entropy change (DS) were calculated and are summarized in the tabular form in Table 1. According to Laura³¹(i) DG upto -15KJ/mole is connected with the physical interaction between adsorption site and metal ions (physical adsorption), (ii) DG when more than -30KJ/mole involves charge transfer from adsorbent surface to the metal ion to form a co-ordination bond. In the present investigation DG values for Nickel (II), Copper (II) and Iron (III) are below -15KJ/mole indicates adsorption mechanism as the physical interaction between adsorption sites and metal ion (physical adsorption). The negative value of DH shows the exothermic nature of adsorption of metal ions on to the surface of KLP. Our observations are supported by the work carried by Soon-Yong et al³².

Table 1- Thermodynamic Parameters at different temperature.

Adsorbate	Temperature (K)	-DG (KJ)	-DH (KJ)	DS (J)
Nickel	308 313 318	3.936 3.812 3.358	21.790	57.790
Copper	308 313 318	3.808 3.543 2.752	36.409	105.564
Iron	308 313 318	3.164 3.679 3.421	14.596	25.618

Furthermore before adsorption process takes place the adsorbate ions are heavily solvated (the system is more ordered) and this order may be lost when the ions are adsorbed on the surface, due to the release of solvated water molecules.

CONCLUSION:

The experimental data generated by the present investigation shows that acid treated KLP is an efficient adsorbent for the removal of Ni (II), Cu (II) and Fe (III) from solution. The important advantage of using KLP as an adsorbent creates no effluent problem and easily biodegradable. Metal ion adsorption is a reasonably fast process on to the surface of KLP as more than 50% of metal ion is adsorbed within 20-30 minutes. The Langmuir and Freundlich isotherms are found to be applicable in the present metal ion adsorption, which may be attributed to the formation of monolayer on the surface of the adsorbent. The values of thermodynamic parameters DG, DH, DS are indicative of spontaneous process. The plant material such as KLP will open new area of using various abundantly available plant materials as adsorbent in the removal of toxic effluents.

REFERENCES:

1. Quek S, Wase D and Forster C F. The use of sago waste for the sorption of lead and copper. Water S.A. 1998; 24: 251-256.

2. Edwin A, Vasu E. Surface Modification of Activated Carbon for Enhancement of Nickel (II.) Adsorption J. Chem. 2008; 5 (1): 1-9.

3. Adesola Babarinde N A, Oyebamiji Babalola J, Kehinde A A. Kinetic, Isotherm and Thermodynamic Studies of the Biosorption of Cadmium (II) by Snail (Lymnaea ufescens) Shell. J. Appl. Sci. Research, 2008; 4(11):1420-1427.

4. Vinod V, Anirudhan T, Sorption of tannic acid by zirconium pillared clay. J. Chem. Technol Biotechnol. 2002; 77: 92-101.

5. Abia A, Horsfall M, Jnr.O Didi. The use of chemically modified and unmodified cassava waste for the removal of Cd, Cu and Zn ions from aqueous solution. J. Bioresource Technol. 2003; 37: 4913-4923.

6. Randall J, Hautala E, Waiss A, Removal and recycling of heavy metal ions from agricultural by products. Proc. 4th mineral waste utilization symp. Chicago II, USA; 1974.

7. Torresdey G, Gonzalez J, Tiemann J, Rodrignuez K, Gomez O, Alfalfa G. Phytofiltration of Hazardous cadmium, chromium, lead and zinc ions by biomass of edicago sativa (Alfalfa). J. Hazard. Mater. 1998; 48: 191-206.

8. Wang S, Zhu Z H, Coomes A, Haghsereshi F, Lu G Q. The physical and surface chemical characteristics of activated carbons and the adsorption of methylene blue from wastewater. J. Colloid and Interface Sci., 2005,; 284: 440-446.

9. Collin G J, Awang B, Duduku K, Kok Onn. Sorption studies of methylene blue from Guava seeds (Psidium guajaval). .J. Mater. Science. 2007; 13(1):83-87.

10. Jeffery G H, Bassett Mendnam J, Denny R C, Vogels Text book of Quantitative Chemical Analysis. 5th Edition ELBS with Longman Group U.K. 1999.

11. Manivasakam N, Physico chemical Examination of Water, Sewage Industrial Effluents. Pragati Prakashan, India, 1984; 161.

12. Mendham V J, Denny R C, Barnes J D,. Thomas M J K. Vogels Textbook of Quantitative Chemical Analysis, 6th Ed. Pearson Education (Singapore) 2002, 668.

13. Snell F D, Snell C T, Snell C A, Colorimetric Methods of Analysis, Vol. II A, D Van Nostrand Company Inc Princeton, New Jersey, 1959; 67.

14. Barros A J M, Prasad S, Leite V D, Souza A G. Biosorption of heavy metals in upflow sludge columns. Bioresour. Technol., 2007; 98: 1418-1425.

15. Pavasant P, Apiratikul R, Sungkhum V, Suthiparinyanont P, Wattanachira S, Marhaba T F. Removal of methylene blue by invasive marine seaweed: Caulerpa racemosa var. cylindracea. Bioresur. Technol., 2006; 97: 2321-2329.

16. Tumin N D, Chauah A L, Zawani Z, Rashid S A. Asorption of copper from aqueous solution by Elais guineensis kernel activated carbon. J. Engg. Sci. and Tech., 2008; 3 (2): 180-189.

17. Kongsuwan A, Patnarkao P. Proceed: Second Joint International Conference on "Sustainable Energy and Environment 21-23 Nov., Bangkok (Thailand) 2006.

18. Devaprasath P M, Solomon J S, Thomas B V. Removal of Cr(VI) from aqueous solution using natural plant material. J. Appl. Sci. Environt. Sanit., 2007; 2 (3): 77-83.

19. Jambulingam M, Rehugadevi N, Karthikeyan S, Kiruthika Patabhi J. Adsorption of Cr (VI) from Aqueous Solution using Low Cost Activated Carbon. Ind. J. Environ. Prot. 2005; 25 (5): 458-463.

20. Oboh O J., Aluyog E O. The removal of heavy metal ions from aqueous solutions using sour sop seeds as biosorbent. Afric. J. Biotech. 2008; 7 (24): 4508-4511.

21. Farooqui M, Maqdoom Farooqui, Quadri S H. Adsorption studies of heavy metal ion by low cost agricultural by-products Bajra powder. Ind. J. Chem. Technol. 2004; 2: 190-193.

22. Larous S, Meniai A H, Bencheikh Lehocine M. Removal of copper from aqueous solution by Retama raetam, Forssk.growing in Algerian Sahara. Desalination. 2005; 185: 483-490.

23. Abdel - Ghani N T, Hefny M, Chaghaby E G. Removal of lead from aqueous solution using low-cost abundantly available adsorbents. Indian J. Environ. Sci. Technol. 2007; 4 (1): 67-73.

24. Al Qodah Z. Biosorption of heavy metal ions from aqueous solutions by activated sludge. Desalination, 2006; 196:164-176.

25. Addagalla V A, Darwish N A, Hilal N. Experimental Investigation on the Removal of Toner Particles from Laser-Printed Office Waste Papers. World Appl. Sci. J., 2009; 5: 32.

26. Freundlich I H. A theory of surface tension of binary solutions: Binary liquid mixtures of organic compounds. Colloid Capil. Chem, New York; 1928.

27. Shilpi K, Suparna S, Padmaja P. Equilibrium, Kinetics and Thermodynamic Studies for Adsorption of Hg (II) on Palm Shell Powder. Proc. of World Academy of Science, Engg. Technol. 2008; 43: 600-606.

28. Langmuir I. The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc, 1918; 40: 1361-1403.

29. Hall K R. Removal of health hazards causing acidic dyes from aqueous solutions by the process of adsorption. Indian Engg. Chem. Fundam. 1966; 5: 212-223.

30. Patil S J, Bhole A G, Natarajan G S. Scavenging of Ni(II) metal ions by adsorption on PAC and babhul bark. J. Environ. Sci. Engg. 2006; 48(3): 203-208.

31. Laura B, Mioura R, Dumitra B, Matei M. Equilibrium study of Pb(II) and Hg(II) sorption from aqueous solutions by moss peat. Environ. Engg. Mang. J. 2008; 7 (5): 511-516.

32. Jeong S Y, Lee J M. Removal of heavy metal ions from aqueous solutions by adsorption on magadiite. Bull. Korean Chem. Soc. 1998; 19: 218-222.

Received on 04.08.2010 Modified on 22.08.2010

Asian J. Research Chem. 4(1): January 2011; Page 100-103