International Research Journal of Management Science & Technology ISSN 2250 – 1959(0nline) 2348 – 9367 (Print) A REFEREED JOURNAL OF
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IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
Removal of heavy metal ions from laboratory effluents by Phytoremediation Jasleen Kaur, Navneet Manav* and A.K. Bhagi Email:
[email protected]; Dyal Singh College, University Of Delhi, Lodhi Road, New Delhi 110003. Abstract The laboratory effluents contain toxic pollutantswhich are normally discharged into the drains without any treatment. These organic pollutants and inorganic pollutants are serious threat to ecosystems.Toxic metal ions in the effluents due to their persistant and bioaccumulating nature are harmful to all living beings even if present in trace amount.Phytoremediation is an economical, environmental friendly technique applicable to a broad range of contaminant . In the present study two aquatic plants Eichhornia crassipes and Salvinia minimaare used to remove lead,copper and chromium ions from laboratory waste water.Biosorption of these ions from aqueous solutions was studied in a batch adsorption system to know the effect of pH and contact time. It was observed that the percentage removal of metal ions increases with increasing the contact time initially and after certain time it becomes constant (84.52% of Pb(II) by Eichhornia and 82.14% by Salvinia,14% of Cu(II) by Eichhornia and 21.56% by Salvinia,70.96% of Cr(VI) by Eichhornia and 75.30% by Salvinia).Adsorption data was described by pseudo first order kinetics model.Langmuir isotherm model have been studied for monocomponent adsorption of metal ions by phytoremediation. Free energy change for sorption is also calculated.Various physical parameters of laboratory effluent water were compared before and after the adsorption. Introduction Elements with an atomic density greater than 6g/cm3 are called heavy metals which are the most common pollutant in the waste water and laboratory effluents[1]. Arsenic, lead, mercury, cadmium, cobalt, chromium, copper, nickel, silver and zinc are persistent heavy metal contaminants in laboratory effluents. These heavy metals are persistent in laboratory effluents as they are toxic in nature. Thus these pollutants have a detrimental effect on plants, animal and human health[2]. Some of the negative impacts of heavy metals on plants include decrease of amylaseenzyme activity and plant growth by chromium, the inhibition of photosynthesis by copper and the reduction of chlorophyll production and plant growth by lead[3]. The impact of these metals on animals include reduced growth and development, cancer, organ damage, nervous system damage and in extreme cases, death. The ultimate goal of laboratory effluents management is to protect the environment in a manner which is in line with public health and socio-economic concerns. Also there are strict laws for disposal of wastes in water bodies making waste water treatment an important environmental issue[4,5].
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Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
The conventional methods are costly, clumsy and degrade the surrounding environment[6]. Moreover, they are developed for industrial effluents to treat larger quantities of wastewater. In view of these disadvantages a search was initiated for alternative remediation techniques[7]. Bioremediation, showed competent ability to degrade and detoxify certain organic contaminants,but have limited application to remediate metal ion polluted environment.In contrast, plants are known to sequester certain metal elements in their tissues and may prove best candidate in the removal of metal ions from contaminated soils[8]. Thus, the focus was diverted in developing technologies such as phytoremediation, which use plant for remediation,and are cost effective, low-impact, have aesthetic value, and environment friendly[9].Phytoremediation is efficient in removing lead and zinc from polluted water. Also uptake of nickel and cadmium by floating aquatic plants[10,11] was reported. Laboratory effluents contain considerable heavy toxic metal ions, which could endanger environment and public health if discharged without treatment. The scale and type of pollutants are different in laboratory wastes as compared to industrial waste hence techniques which can help removal of these pollutants over wide range of pH are required[12].In this paper the aim of the study was to observe the efficiency of removal of Cu(II),Cr(VI) and Pb(II) ions from the laboratory effluents using two floating aquatic plants Eichhornia crassipes and Salvinia minima focusing on the potential of these plants in accumulating heavy metals ,the effect of pH on metals adsorption in aqueous solution andthe kinetics and sorption isotherms of phytoremediation of these metal ions were also studied. Methods And Materials The aquatic plants (E.crassipes and S.minima) were collected from a pond in Botany Department, University of Delhi.All the reagents used were of analytical grade. Stock solutions ofmetal ions each for different pH range were prepared in distilled water with analytical grade Pb(NO3)2,CuSO4 and K2 Cr2O7.Two medium size Eichhornia plants were placed in 2 liter plastic tanks containing stock solutions of metal salts and placed under natural sunlight. The total volume of the solution was kept constant by adding deionised water to compensate for the water loss through evaporation, sampling and plants transpiration. Samples of solutions undergoing phytoremediation were taken at regular intervals. All absorbance measurements were made with UVVisible spectrometer (Systronics Pc Based Double Beam Spectrometer 2202). Absorbance values were recorded at the wavelength for maximum absorbance (λ max) corresponding to each metal ions solutions. These solutions were initially calibrated for concentration in terms of absorbance units. Same procedure was adopted to study phytoremediation by Salvinia plants. The physical parameters such as pH, TDS, EC were recorded before and after treatment for metal ion solutions and its mixture by using water analyzer (ELICO) (Table I). Table I:- Physical parameters of the solution before and after phytoremediation Physical
Cu(II)
Cr(VI)
55
Pb(II)
Laboratory Effluents
IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
Parameters
Before treatment
After treatment
Before treatment
After treatment
Before treatment
After treatment
Before
pH
5.396
6.218
5.28
6.28
4.93
5.46
5.07
9.31
EC (µS)
647.3
107.1
658.2
119.0
730.6
85.58
497.5
88.88
TDS (ppm)
350.80
57.80
358.30
63.97
390.10
45.28
247.5
45.54
After treatment treatment
Effect of pH These two aquatic plants were able to tolerate pH values from 4 to 10 and maximum removal of metal ions was observed in neutral medium. Metal removal efficiency The concentrations of dissolved metals in test solutions significantly decreased with increase in exposure time and became constant after few days. Metal removal efficiency by aquatic plants from the effluents were calculated as per given formula (Table 2).
Table 2:Metal Removal Efficiency
Metal ions
Aquatic plant
% removal of metal ions
Pb(II)
Cu(II)
Salvinia minima
Eichhornia Salvinia
84.5%
82.1%
Eichhornia
minima
Cr(VI)
Salvinia minima
crassipes
crassipes
14%
Batch mode adsorption studies 56
21.5%
Eichhornia crassipes
75.3%
70.9%
IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
After a constant interval of time, the samples were separated from solutions centrifuged and filtered by using whatman filter paper and residual concentration of metal ions were determined spectrophotometrically.The equilibrium adsorption amount(qe) is calculated using the equation: qe={(C0-Ce)/m}V where C0 is the initial metal concentration (mgL -1), Ce is the metal ion concentration at equilibrium time in solution (mgL-1), qe is the amount of metal ion, V is the volume of metal ion solutions and m is the mass of the adsorbent. Equillibrium Sorption Study Sorption Isotherm is the common representation of adsorbate concentration and quantity of material adsorbed i.e. graph of amount adsorbed against equilibrium concentration at specific temperature [13]. Langmuir Isotherm Model Langmuir Adsorption isotherm has found successful application in monolayer adsorption. It is based on the assumption that intermolecular forces decrease rapidly with distance and adsorption takes place at specific homogeneous sites within the adsorbent. It also considers all the adsorption sites of homogeneous adsorbent are identical and equivalent energetically and after saturation no further adsorption can takes place. Langmuir isotherm for sorption of metal ions by aquatic plants was developed based on the assumption that only a definite number of homogenous binding sites are present on the plant surface having affinity for metal ions [14]. Initial concentration of the metal was taken as concentration added and concentration of residual metal left after the time when no more metal ions were adsorbed by the plants or residual concentration of the metal ion in solution became constant was considered as metal ion concentration at equilibrium. The Langmuir Isotherm model can be presented by well known equation: Ce/qe=Ce/qm+1/qmkl Where Ce is the metal ions concentration at equilibrium (mgL -1), qe is the amount of the metal ions adsorbed at equilibrium (mgL-1), qm is maximum adsorption capacity (mg/g) and kl is the Langmuir isotherm constant relatedto free energy of adsorption (Lmg -1).Ce/qe Vs Ce plot was made which give an intercept of 1/qmkl and a slope of 1/qm. Langmuir plots for adsorption of Cu(II) ions: Adsorption of Cu (II) on Eichhornia 100
0.600 0.400
Ce/qe
Ce/qe
Adsorption of Cu(II) on Salvinia
50
0.200 0.000
0 0
1000
Ce
2000
3000
85
57
90
95
Ce
100
IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print) 10
40
5
Adsorption of Cr(VI) ion Eichhornia
20 0 -20 0
20
40
Ce/qe
Ce/qe
60
0
60
80
-5 0
Adsorption of Cr(VI) on Salvinia 20
40
60
Ce
Ce Adsorption of Pb(II) on Eichhornia
Adsorption of Pb(II) on Salvinia
niaWaste
5
0 0.2
0.4
Ce/qe
Ce/qe
5 iaEEEEEEEEEEEEEEEEEEEEeSalvi 10
0
80
0.6
0.8
0 0
-5
0.2
0.4
0.6
Ce
0.8
Ce
Table III:- Langmuir Isotherms Adsorbent
Heavy Metals
qm
KL
R2
Eichhornia
Cu(II)
0.4593
0.1274
0.7529
Salvinia
Cu(II)
0.2177
1.1858
0.9854
Eichhornia
Cr(VI)
1.058
0.2518
0.9842
Salvinia
Cr(VI)
1.885
0.2108
0.9776
Eichhornia
Pb(II)
2.1261
0.6552
0.9818
Salvinia
Pb(II)
1.995
0.7680
0.9809
Adsorption Kinetic Study The adsorption of metal ions was studied by using two kinetic models which are, pseudo first order kinetic model and pseudo second orderkinetic model[15]. On the basis of correlation coefficient (R2) from linear regression, the best fit model was selected, which told how much the predicted value from a forecast model match with the experimental data(Table IV). Pseudo First Order Kinetic Model: The pseudo-first order equation in linear form was expressed in equation: Log (qe-qt) = log qe – k1t/2.303 Where k1 is first order constant (min-1). The plot of log (qe-qt) Vs t gave the intercept of log q e& slope k1. Pseudo first order kinetic model tells about the rate of adsorption[16]. 58
IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
Pseudo Second-Order Kinetic Model: The pseudo second order is based on the exchange of electron between heavy metal ions and adsorbate in the rate limiting step. Equation of Pseudo-second order is: 1/qt = 1/tk2qe2 + 1/qe . where k2 is the rate constant of second order. This model predicts theoverall behaviour of whole range of adsorption [17].
Aquatic Plants
Concentration of metal ions
Pseudo First Order
Pseudo Second Order
K1
R2
K2
R2
Eichhornia
CuSO4
0.1192
0.9849
0.0105
0.8933
Salvinia
CuSO4
0.0055
0.9890
0.0682
0.8607
Eichhornia
K2Cr2O7
0.4524
0.9855
0.0169
0.9087
Salvinia
K2Cr2O7
0.26413
0.9976
3.5024
0.9851
Eichhornia
Pb(NO3)2
273.2707
0.9824
0.0774
0.9751
Salvinia
Pb(NO3)2
311.2274
0.9828
0.0581
0.9623
Table IV:- Kinetic study data
(1) Kinetic Data Plot For Cu(II) ion (Eichhornia) : Pseudo First Order Kinetic Model -1.7 20
40
60
80
Second
Order
Kinetic
0.015 0.01 0.005 0
1/qt
Log(qeqt)
-1.8 0
Pseudo
-1.9 -2
0
-2.1
Time
0.02
0.04
1/t
(2) Kinetic Data Plot For Cu(II) ion (Salvinia) :
59
0.06
Model
IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
Pseudo First Order Kinetic Model
Pseudo Second Order Kinetic Model
-1.85 50
100
0.012 0.0115 0.011 0.0105 0.01
1/qt
Log(qeqt)
-1.9
0
-1.95 -2
0
0.02
0.04
Time
0.06
1/t
(3) Kinetic Data Plot For Cr(VI) ion (Eichhornia) : Pseudo First Order Kinetic Model
Pseudo
0
Order
Kinetic
0.06 50
100
150
0.04
1/qt
-0.5 0
Log(qeqt)
Second
-1
0.02
-1.5
0
-2
0
0.05
0.1
Time
0.15
0.2
1/t
(4) Kinetic Data Plot For Cr(VI) ion (Salvinia) : Pseudo First Order Kinetic Model
Pseudo Second Order Kinetic Model 0.06 0.04
0
-50
0
50
100
150
1/qt
Log(qeqt)
50
0.02
0
-100
0
0.01
Time
0.02
0.03
0.04
0.05
1/t
(5) Kinetic Data Plot For Pb(II)ion (Eichhornia) : Pseudo First Order Kinetic Model
Pseudo Second Order Kinetic Model 10
1
-1
5 0
20
40
60
1/qt
Log(qeqt)
0 80
0
-2
Time
0
0.02
0.04
1/t 60
0.06
Model
IRJMST
Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
(6) Kinetic Data Plot For Pb(II)ion (Salvinia) : Pseudo First Order Kinetic Model
Log(qeqt)
0.5
5
0 20
40
60
80
-1
1/qt
10
1
-0.5 0
Pseudo second Order Kinetic Model
0 0
0.02
Time
0.04
0.06
1/t
Pseudo first order gave better R2 values confirming sorption of metal ions by aquatic plants. CALCULATION OF ΔG0 The percentage adsorption of the metal ions on the adsorbent decreased with increase in temperature. The adsorption processs is exothermic in nature. The increases in the temperature of the system affects the solubility and particularly the chemical potential of the adsorbate metal ions which is known to be a controlling factor in the process of adsorption. The equilibrium constant was calculated with the help of equation: K = CAe/Ce Where CAe is solid phase concentration (mg/L) and Ce is the equilibrium concentration of the metal ions in the solution.The calculated free energy change (ΔG 0) was calculated by using equation: ΔG0 = -RT lnK Where R is the gas constant and K is the equilibrium constant and T is absolutetemperature (303K) . The negative values of ΔG0 indicate that the adsorption ofmetal ions on Eichhornia and Salvinia is a spontaneous process(Table V). Table V : Gibb’s free energy data Aquatic plants
Metal ions
K
ΔG (kJ/moL-1)
Eichhornia
Cu2+
1.25
-0.562
Eichhornia
Cr6+
3.378
-3.066
Eichhornia
Pb2+
4.6
-3.844
Salvinia
Cu2+
1.145
-0.341
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Vol 8 Issue 11 [Year 2017]
ISSN 2250 – 1959 (0nline) 2348 – 9367 (Print)
Salvinia
Cr6+
3.609
-3.231
Salvinia
Pb2+
5.807
-4.431 Conclusion:
Aquatic plants were able to significantly remove Pb(II)and Cr(VI) ions from laboratory effluent , but were of little value in case of Cu(II) .Eichhornia was more efficient in removal of Pb(II) ions whereas Salvinia removed Cr(VI) ions more efficiently .It is concluded that both these plants were not effective in removal of Cu(II) ions.Kinetic, equilibrium and thermodynamic results indicate that metal ion removal from aqueous solutions by adsorption proceeded through chemisorption and physiosorption mechanisms.The negative value of ΔG0 suggest the sorption of metal ions on these aquatic plants is a spontaneous process. Reference: 1. Arpor, O B., Ohibor, G. O., Olaolu, T. D. 2014. Heavy metal pollutants in wastewater effluents: Sources, effects and remediation. Advances in Bioscience and Bioengineering 2 (4): 37-43. 2. Lone, M. I., He, Z., Stofella, P. And Yang, X. 2008. Phytoremediation of heavy metal polluted soils and water: progresses and perspective. J Zhejiang Univ. Sci. B 9 (3): 210-220. 3. Gardea-Torresdey,JI,Peralta-Videa,JR,Rosa,GD and Parsons, jg(2005).Phytoremediation of heavy metals and study of the metal coordination by X-ray absorption spectroscopy,249(17-18):1797-1810. 4. Dixit, A., Dixit, S., and Goswami, C.S. 2011. Process and Plants for waste water remediation; A review. Sci Revs. Chem. Commun 1 (1): 71-77. 5. Turkar et al, S.S., Bharti, D.B., and Gaikwad, G.S., 2011. Various methods involved in waste water treatment to control water pollution. J. Chem. Pharm. Res 3(2): 58-65. 6. Cunningham, S.D., and D.W. Ow. 1996. Promises and prospects of phytoremediation. Plant Physiol. 110:715-719. 7. Manav N, Bhagi AK, Kaur J and Bhandari N. 2015. A study of removal of toxic metal ions (Cu 2+, Cd2+, Pb2+ ) from laboratory effluents by adsorption on Agricultural Waste. In proceedings of International conference on climate change and the developing world CCDW, Kottayam, Pg 258266. 8. Chaney, R.L. 1983. Plant uptake of inorganic waste constitutes. P. 50-76. In J.F. Parr, P.B. Marsh, and J.M. Kla (ed). Land treatment of hazardous wastes. Noyes Data Corp., Park Ridge, NJ. 9. Cunningham, S.D., J.R. Shann, D.E. Crowley, and T.A. Anderson.1997. Phytoremediation of contaminated water and soil. P. 2-19. In E.L. Kruger, T.A. Anderson, and J.R. Coats (ed.) Phytoremediation of soil and water contaminants. ACS symposium series 664. American Chemical Society, Washington, DC. 10. Wolverton, B C. A.1975. Water Hyacinth for Removal of Phenols from Polluted Waters, NASA Tech. Memo., (TM-X-72722), 18p, Issued also in Sci. Tech. Aerospace Rep, 13(7), 11. Buddhavarapu, L R and Hancock, S J. 1991. Advanced Treatment for Lagoons using Duckweed, Water Environ. Technol., 3, 41-44. 12. Manav N, Jain C, Kumar A, Bhagi A.K.2016.Adsorption of toxic metal ions from laboratory effluents by agricultural waste.Journal of Integrated Science and Technology.4(2),70-75.
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13. Surchi Shareef K.M.(2011). Agricultural Wastes as Low Cost Adsorbents for Pb Removal: Kinetics, Equilibrium And Thermodynamics. InternationalJournal Of Chemistry Vol. 3(3). 14. Verma VK, Gupta RK and Rai JPN. 2005. Biosorption of Pb and Zn from pulp and paper industry effluent by water hyacinth (Eichhornia Crassipes). Journal of Scientific and Industrial Research Vol. 64, pp. 778-781. 15. Ho YS, Mckay G(2000). The Kinetics Of Sorption Of Divalent Metal Ions Onto Sphagnum Moss Peat. Water Res 34(3):735-742. 16. Mashhadi somaye, Ghasemi Maryam, Mirali Sara, Ghasemi Nahid(2012).Adsorption Isotherms And Kinetics for Removal of Pb(II) from Aqueous SolutionsUsing Low Cost Adsorbent. International Conference On Environmental Science And Engineering Vol. 32. 17. Ossman M.E. And Mansour M.S.(2013). Removal Of Cd(II) Ion from Wastewater By Adsorption Onto Treated old Newspaper: Kinetic Modelling And Isotherm Studies. International Journal Of Industrial Science , 4-7 .
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