INTRODUCTION:

Enhanced industrial activity after the industrial revolution has led to the discharge of chemicals, which causes environmental and public health problems. The presence of heavy metals in the environment is of major concern because of their extreme toxicity and tendency for bioaccumulation in the food chain even in relatively low concentrations [1,2]. Water has the central role in mediating global-scale ecosystem processes, linking atmosphere, lithosphere and biosphere by moving substances between them and enabling chemical reactions to occur. Heavy metals of concern include cobalt, lead, chromium, mercury, uranium, selenium, arsenic, cadmium, silver, gold, nickel etc.

Due to their mobility in natural water ecosystems and their toxicity to higher life forms, heavy metal ions in surface and ground water supplies have been prioritized as major inorganic contaminants in the environment. Heavy metal pollution in the aquatic system has become a serious threat today and of great environmental concern as they are non-biodegradable and thus persistent. To avoid health hazards, it is essential to remove these toxic heavy metals from waste water before its disposal. Hence, the government has imposed several stringent environmental protection rules. This has forced the scientific and industrial community to work towards decontamination of the effluents. Among all the effluents treatment of toxic metal bearing wastewater needs special attention owing to its non-biodegradable nature when compared to other organic pollutants. The studies made on investigation of economic and effective methods for the removal of heavy metals have resulted in the development of new separation technologies. Biological treatment, ion exchange, coagulation, electrochemical operation and filtration are commonly applied to the treatment of industrial effluents [3,4,5]. However technical and economic factors limit sometimes the feasibility of such processes. Then the search for new technologies has directed the attention towards biosorption. The main advantages of this method are of being effectiveness in the reduction of the concentration of heavy metal ions to permissible levels using low cost biomass materials, low operating cost, minimal volume of chemical disposable, regeneration of the biosorbent and biological sludge and high detoxifying efficiency of very dilute effluents [6].

RESULTS AND DISCUSSION:

In the present investigation, the potential of dry Ipomea palmata leaves powder as biosorbent for biosorption of nickel metal present in an aqueous solution is investigated. The effects of various parameters on biosorption of nickel are studied. The measured data consist of initial and final concentration of nickel in the aqueous solution, agitation time, biosorbent size, biosorbent dosage, pH of the aqueous solution and temperature of the aqueous solution. The experimental data are obtained by conducting batch experiments.

Effect of agitation time:

Duration of equilibrium biosorption is defined as the time required for heavy metal concentration to reach a constant value during biosorption. The equilibrium agitation time is determined by plotting the % biosorption of nickel against agitation time as shown fig.1. for the interaction time intervals between 1 to 180 min. For 53 μm size of 10 g/L biosorbent dosage, 36 % (0.72 mg/g) of nickel is biosorbed in the first 5 min. The % biosorption is increased briskly up to 30 min reaching 62 % (1.24 mg/g). Beyond 30 min, the % biosorption is constant indicating the attainment of equilibrium conditions [7,8,9,10].

Fig.1. Effect of agitation time on % biosorption of nickel

Effect of biosorbent size:

The variations in % biosorption of nickel from the aqueous solution with biosorbent size are obtained. The results are drawn in fig.2. with percentage biosorption of nickel as a function of biosorbent size. The percentage biosorption is increased from 50 (1.0 mg/g) to 62 % (1.24 mg/g) as the biosorbent size decreases from 150 to 53 μm. This phenomenon is expected, as the size of the particle decreases, surface area of the biosorbent increases; thereby the numbers of active sites on the biosorbent are better exposed to the biosorbate.

Fig 2. Effect of biosorbent size on % biosorption of nickel

Effect of pH:

pH controls biosorption by influencing the surface change of the biosorbent, the degree of ionization and the species of biosorbate. In the present investigation, nickel biosorption data are obtained in the pH range of 2 to 8 of the aqueous solution (C₀ = 20 mg/L) using 10 g/L of 53 μm size biosorbent. The effect of pH of aqueous solution on % biosorption of nickel is shown in fig.3. The % biosorption of nickel is increased from 59 % (1.18 mg/g) to 74 % (1.48 mg/g) as pH is increased from 2 to 5 and decreased beyond the pH value of 5 [9,10,11]. % biosorption is decreased from pH 5 to 8 reaching 59 % (1.18 mg/g) from 74 % (1.48 mg/g). Low pH depresses biosorption due to competition with H⁺ions for appropriate sites on the biosorbent surface. However, with increasing pH, this competition weakens and Nickel ions replace H⁺ ions bound to the biosorbent [12,13,14].

Effect of initial concentration of nickel:

The effect of initial concentration of nickel in the aqueous solution on the percentage biosorption of nickel is shown in fig.4. The percentage biosorption of nickel is decreased from 74 % (1.48 mg/g) to 57.5 % (9.2 mg/g) with an increase [15,16,17] in C₀ from 20 mg/L to 160 mg/L. Such behavior can be attributed to the increase in the amount of biosorbate to the unchanging number of available active sites on the biosorbent.

Fig. 3 Effect of pH on % biosorption of nickel

Fig.4 Effect of initial concentration for the biosorption of nickel

Effect of biosorbent dosage:

The percentage biosorption of nickel is drawn against biosorbent dosage for 53 μm size biosorbent in fig.5. The biosorption of nickel increased from 74 % (1.48 mg/g) to 90 % (0.5142 mg/g) with an increase in biosorbent dosage from 10 to 35 g/L. Such behavior is obvious because with an increase in biosorbent dosage, the number of active sites available for nickel biosorption would be more. The change in percentage biosorption of nickel is marginal from 90 % (0.5142 mg/g) to 92.5 % (0.3083 mg/g) when ‘w’ is increased from 35 to 60 g/L. Hence all other experiments are conducted at 35 g/L dosage [18-22].

Fig. 5. Effect of biosorbent dosage on % biosorption of nickel

Effect of Temperature:

The effect of temperature on the equilibrium metal uptake was significant. The effect of changes in the temperature on the nickel uptake is shown in Fig.6. When temperature was lower than 303 K, Nickel uptake increased with increasing temperature, but when temperature was over 303 K, the results were on the contrary. This response suggested a different interaction between the ligands on the cell wall and the metal. Below 303 K, chemical biosorption mechanisms played a dominant role in the whole biosorption process, biosorption was expected to increase by increase in the temperature [23-26] while at higher temperature, the plant powder were in a nonliving state, and physical biosorption became the main process. Physical biosorption reactions were normally exothermic, thus the extent of biosorption generally is constant with further increasing temperature.

Langmuir isotherm:

Irving Langmuir [27-29] developed an isotherm named Langmuir isotherm. It is the most widely used simple two- parameter equation

(C_e/q_e) = 1/(bq_m) + C_e/q_m

From the plots between (C_e/q_e) and C_e, the slope {1/ (bq_m)} and the intercept (1/b) are calculated.

The equation obtained ‘n’ C_e/q_e = 0.061 C_e + 3.413 with a good linearity (correlation coefficient, R²~0.981) indicating strong binding of nickel ions to the surface of Ipomea palmata leaves powder.

Fig.6 Effect of temperature for the biosorption of nickel

Fig. 7 Langmuir isotherm for biosorption of nickel Freundlich isotherm:

Freundlich [30,31,32] presented an empirical biosorption isotherm equation, that can be applied in case of low and intermediate concentration ranges. It is easier to handle mathematically in more complex calculations.

The Freundlich isotherm is given by

ln q_e = ln K_f+ n ln C_e

Fig.8 Freundlich isotherm for biosorption of nickel

Freundlich isotherm is drawn between ln C_eand ln q_e resulting equation is ln q_e = 0.709ln C_e - 0.746; is presented in Fig.5.8 for the present data. The resulting equation has a correlation coefficient of 0.996.

Temkin isotherm:

Temkin and Pyzhev [33,34,35,36] isotherm equation describes the behavior of many biosorption systems on the heterogeneous surface and it is based on the following equation

q_e= RT ln(A_TC_e)/b_T

The linear form of Temkin isotherm can be expressed as

q_e= (RT/ b_T ) ln(A_T) + (RT/b_T) ln(C_e)

The best fit model is determined based on the linear regression correlation coefficient (R). it is found that biosorption data are well represented by Freundlich isotherm with higher correlation coefficient of 0.996, followed by Langmuir and Temkin isotherms with correlation coefficients of 0.981 and 0.963 respectively.

Fig. 9 Temkin isotherm for biosorption of nickel

Table – 1-Isotherms constants

Langmuir	Freundlich	Temkin
q_m = 16.39344	k_f = 0.45113	A_T = 0.260375
b = 0.017873	n = 0.600508	b_T = 852.7901
R² =0.981	R² =0.996	R² =0.963

Kinetics of biosorption:

The order of biosorbate – biosorbent interactions have been described using kinetic model. Traditionally, the first order model of Lagergren [37,38] finds wide application. In the case of biosorption preceded by diffusion through a boundary, the kinetics in most cases follows the first order rate equation of Lagrangen:

(dq_t/dt)= K_ad (q_e – q_t)

where q_e and q_t are the amounts adsorbed at t, min and equilibrium time and K_ad is the rate constant of the pseudo first order biosorption [39,40].

The above equation can be presented as

∫ (dq_t/(q_e – q_t) )= ∫ K_ad dt

Applying the initial condition q_t= 0 at t = 0, we get

log (q_e – q_t) = log q_e– (K_ad/2.303) t

log (q_e – q_t) = 0.2023t + 0.6497

Plot of log (q_e–q_t) versus ‘t’ gives a straight line for first order kinetics, facilitating the computation of adsorption rate constant (K_ad)_.If the experimental results do not follow the above equation, they differ in two important aspects:

i) K_ad (q_e – q_t) does not represent the number of available biosorption sites and

ii) log q_e is not equal to the intercept.

In such cases, pseudo second order kinetic equation: (dq_t/dt)₌ K (q_e – q_t)² is applicable, where

‘K’ is the second order rate constant.

The other form of the above equation is: (dq_t/(q_e–q_t)²)= Kdt

let q_e – q_t= x

dq_t = dx

1/ x = K x + C

C = 1/ q_e at t = 0 and x = q_e

Substituting these values in above equation, we obtain:

1/( q_e – q_t) = Kt + (1/q_e)

Rearranging the terms, we get the linear form as:

(t/q_t) = (1/ Kq_e² ) + (1/q_e ) t.

(t/q_t) = 0.638 t + 0.9521.

The pseudo second order model [41] based on above equation, considers the rate -limiting step as the formation of chemisorptive bond involving sharing or exchange of electrons between the biosorbate and biosorbent. If the pseudo second order kinetics is applicable, the plot of (t/q_t) versus ‘t’ gives a linear relationship that allows computation of q_e and K.

In the present study, the kinetics are investigated with 50 mL of aqueous solution (C₀= 20 mg/L) at 303 K with the interaction time intervals of 1 min to 180 min. Lagragen plots of log (q_e-q_t) versus agitation time (t) for biosorption of nickel the biosorbent size (53 μm) of Ipomea Palmata leaves powder in the interaction time intervals of 1 to 180 min are drawn in figs.10 and 11.

Fig.10 First order kinetics for biosorption of nickel

Fig.11 Second order Kinetics for biosorption of nickel

Table.2-Equations and rate constants

Order	Equation	Rate constants	R²
Lagergren first order	log (q_e-q_t)=–0.032 t–0.120	0.073696 min^-1	0.953
Pseudo second order	t/q_t=0.833 t+2.243	0.309358 g/(mg-min)	0.980

As the correlation coefficient value for the pseudo second order kinetics is 0.980, we can say that the pseudo second order kinetics describes the mechanism of nickle – Ipomea palmata leaves powder interactions better.

Thermodynamics of biosorption:

Biosorption is temperature dependant. In general, the temperature dependence is associated with three thermodynamic parameters namely change in enthalpy of biosorption ((∆H), change in entropy of biosorption (∆S) and change in Gibbs free energy (∆G) [42,43,44,45,46].

Enthalpy is the most commonly used thermodynamic function due to its practical significance. The negative value of ∆H will indicate the exothermic/endothermic nature of biosorption and the physical/chemical in nature of sorption. It can be easily reversed by supplying the heat equal to calculated ∆H.

The ∆H is related to ∆G and ∆S as

∆G = ∆H – T ∆S

∆S < 1 indicates that biosorption is impossible whereas ∆S > 1 indicates that the biosorption is possible. ∆G < 1 indicates the feasibility of sorption.

The Vant Hoff’s equation is

log (q_e /C_e) = ∆H/(2.303 RT) + (∆S/2.303 R)

log (q_e /C_e) = – 0.695 (1 / T) + 1.747

Where (q_e/C_e) is called the biosorption affinity.

If the value of ∆S is less than zero, it indicates that the process is highly reversible. If ∆S is more than or equal to zero, it indicates the reversibility of process. The negative value for ∆G indicates the spontaneity of biosorption. Whereas the positive value indication is non spontaneity of sorption.

Experiments are conducted to understand the biosorption behavior varying the temperature from 283 to 323 K. The Vant Hoff’s plot for the biosorption data obtained is shown in fig.12

Fig.12 Vant Hoff’s plot for biosorption

In the present investigation, DH = 13.30726 J/mole, DS = 32.68417 J/mole-K and DG = –9890 J/mole. ∆H is positive indicating that the biosorption is endothermic. The negative value of DG indicates the spontaneity of biosorption. As ∆S is more than zero, it indicates the irreversibility of biosorption.

CONCLUSIONS:

In this review expulsion of Nickel on IP leaves powder has been explored. The Nickel expulsion process is fundamentally influenced by different process parameters, specifically, pH, adsorbent measurement, metal particle fixation and contact time. Greatest evacuation of Nickel on IP leaves powder was at pH 5.0. Nickel sorption concurs Freundlich display and took after the Langmuir, Temkin models. Pseudo second request show has clarified the Nickel sorption more successfully than first request.

REFERENCES:

1. P. Malakul, K. R. Srinivasan, H. Y. Wang, ”Metal biosorptionand desorption characteristics of surfactant modified clay complexes, Ind. Eng. Chem. Res. 37 (1998) 4296-4301.

2. D. Mohan, K.P. Singh, “Single and multi-component biosorptionof cadmium and zinc using activated carbon derived from bagasse -an agricultural waste, Water Res.36(2002)2304-2318.

3. A.Sari, M. Tuzen, M. Soylak, “Biosorption of Pb(II) and Cr(II) from aqueous solution on Celtek clay, J. hazard. Mater. B 141 (2007) 258-263.

4. P. Xiangliang, W. Jianlong, Z. Daoyong, “ Biosorption of Pb(II) by pleurotus ostreatus immobilized in calcium alginate gel, Process Biochem. 40 (2005) 2799-2803.

5. K Kumaraswamy, BV Dhananjaneyulu, P Vijetha and Y Prasanna Kumar, “Kinetic and Equilibrium Studies For the Removal of Chromium Using Eggshell Powder”, Research Journal of Pharmaceutical, Biological and Chemical Sciences, January - February 2015 RJPBCS 6(1) Page No. 529–536.

6. Kratochvil D., volesky, B., 1998. “Advances in biosoption of heavy metals “,Trends Biotechnol. 16,291-300.

7. Kadirvelu, K., K. Thamaraiselvi, and C. Namasivayam. "Adsorption of nickel (II) from aqueous solution onto activated carbon prepared from coirpith."Separation and purification Technology 24.3 (2001): 497-505.

8. Popuri, Srinivasa R., et al. "Adsorptive removal of copper and nickel ions from water using chitosan coated PVC beads." Bioresource Technology 100.1 (2009): 194-199.

9. Kadirvelu, K., et al. "Utilization of various agricultural wastes for activated carbon preparation and application for the removal of dyes and metal ions from aqueous solutions." Bioresource technology 87.1 (2003): 129-132.

10. Kalyani, S., P. Srinivasa Rao, and A. Krishnaiah. "Removal of nickel (II) from aqueous solutions using marine macroalgae as the sorbing biomass."Chemosphere 57.9 (2004): 1225-1229.

11. Zafar, Muhammad Nadeem, Raziya Nadeem, and Muhammad Asif Hanif. "Biosorption of nickel from protonated rice bran." Journal of Hazardous Materials 143.1 (2007): 478-485.

12. Gupta, Vinod K., Arshi Rastogi, and Arunima Nayak. "Biosorption of nickel onto treated alga (Oedogonium hatei): application of isotherm and kinetic models." Journal of Colloid and Interface Science 342.2 (2010): 533-539.

13. Vijaya, Y., et al. "Modified chitosan and calcium alginate biopolymer sorbents for removal of nickel (II) through adsorption." Carbohydrate polymers 72.2 (2008): 261-271.

14. Sheng, Ping Xin, et al. "Sorption of lead, copper, cadmium, zinc, and nickel by marine algal biomass: characterization of biosorptive capacity and investigation of mechanisms." Journal of Colloid and Interface Science 275.1 (2004): 131-141.

15. Chen, Zhen, Wei Ma, and Mei Han. "Biosorption of nickel and copper onto treated alga (Undaria pinnatifida): application of isotherm and kinetic models."Journal of hazardous materials 155.1 (2008): 327-333.

16. Akhtar, N., J. Iqbal, and M. Iqbal. "Removal and recovery of nickel (II) from aqueous solution by loofa sponge-immobilized biomass of Chlorella sorokiniana: characterization studies." Journal of hazardous materials 108.1 (2004): 85-94.

17. Williams, C. J., D. Aderhold, and R. G. J. Edyvean. "Comparison between biosorbents for the removal of metal ions from aqueous solutions." Water Research 32.1 (1998): 216-224.

18. Popuri, Srinivasa R., et al. "Adsorptive removal of copper and nickel ions from water using chitosan coated PVC beads." Bioresource Technology 100.1 (2009): 194-199.

19. Yang, Fan, et al. "Preparation and characterization of chitosan encapsulated Sargassum sp. biosorbent for nickel ions sorption." Bioresource technology102.3 (2011): 2821-2828.

20. Ho, Yuh-Shan, and Gordon McKay. "Pseudo-second order model for sorption processes." Process biochemistry 34.5 (1999): 451-465.

21. Oliveira, E. A., et al. "Equilibrium studies for the sorption of chromium and nickel from aqueous solutions using raw rice bran." Process Biochemistry40.11 (2005): 3485-3490.

22. Al-Rub, FA Abu, et al. "Biosorption of nickel on blank alginate beads, free and immobilized algal cells." Process Biochemistry 39.11 (2004): 1767-1773.

23. Panda, G. C., et al. "Adsorption of nickel on husk of Lathyrus sativus: Behavior and binding mechanism." Colloids and Surfaces B: Biointerfaces57.2 (2007): 135-142.

24. Pavan, Flávio A., et al. "Use of Ponkan mandarin peels as biosorbent for toxic metals uptake from aqueous solutions." Journal of hazardous materials 137.1 (2006): 527-533.

25. Holan, Z. R., and B. Volesky. "Biosorption of lead and nickel by biomass of marine algae." Biotechnology and Bioengineering 43.11 (1994): 1001-1009.

26. Can, Mevra Yalvac, Yusuf Kaya, and O. Faruk Algur. "Response surface optimization of the removal of nickel from aqueous solution by cone biomass of Pinus sylvestris." Bioresource technology 97.14 (2006): 1761-1765.

27. Vijayaraghavan, K., et al. "Biosorption of nickel (II) ions onto Sargassum wightii: application of two-parameter and three-parameter isotherm models."Journal of hazardous materials 133.1 (2006): 304-308.

28. Ngomsik, Audrey-Flore, et al. "Nickel adsorption by magnetic alginate microcapsules containing an extractant." Water research 40.9 (2006): 1848-1856.

29. Akar, Tamer, et al. "Enhanced biosorption of nickel (II) ions by silica-gel-immobilized waste biomass: biosorption characteristics in batch and dynamic flow mode." Journal of Hazardous Materials 163.2 (2009): 1134-1141.

30. Malkoc, Emine, and Yasar Nuhoglu. "Investigations of nickel (II) removal from aqueous solutions using tea factory waste." Journal of Hazardous Materials127.1 (2005): 120-128.

31. Vijayaraghavan, K., et al. "Removal of nickel (II) ions from aqueous solution using crab shell particles in a packed bed up-flow column." Journal of hazardous materials 113.1 (2004): 223-230.

32. Öztürk, Ayten, Tuba Artan, and Ahmet Ayar. "Biosorption of nickel (II) and copper (II) ions from aqueous solution by Streptomyces coelicolor A3 (2)."Colloids and Surfaces B: Biointerfaces 34.2 (2004): 105-111.

33. Puranik, P. R., J. M. Modak, and K. M. Paknikar. "A comparative study of the mass transfer kinetics of metal biosorption by microbial biomass."Hydrometallurgy 52.2 (1999): 189-197.

34. Padmavathy, V., P. Vasudevan, and S. C. Dhingra. "Biosorption of nickel (II) ions on Baker's yeast." Process Biochemistry 38.10 (2003): 1389-1395.

35. Öztürk, Ayten. "Removal of nickel from aqueous solution by the bacterium Bacillus thuringiensis." Journal of Hazardous Materials 147.1 (2007): 518-523.

36. Wang, Xue‐Song, Yong Qin, and Zhuang‐Fu Li. "Biosorption of zinc from aqueous solutions by rice bran: kinetics and equilibrium studies." Separation science and technology 41.4 (2006): 747-756.

37. Hawari, Alaa H., and Catherine N. Mulligan. "Biosorption of lead (II), cadmium (II), copper (II) and nickel (II) by anaerobic granular biomass." Bioresource Technology 97.4 (2006): 692-700.

38. Gabr, R. M., S. H. A. Hassan, and A. A. M. Shoreit. "Biosorption of lead and nickel by living and non-living cells of Pseudomonas aeruginosa ASU 6a."International Biodeterioration and Biodegradation 62.2 (2008): 195-203.

39. Chubar, Natalia, Jorge R. Carvalho, and M. Joana Neiva Correia. "Cork biomass as biosorbent for Cu (II), Zn (II) and Ni (II)." Colloids and Surfaces A: Physicochemical and Engineering Aspects 230.1 (2003): 57-65.

40. Özer, Ayla, et al. "Investigation of nickel (II) biosorption on Enteromorpha prolifera: optimization using response surface analysis." Journal of hazardous materials 152.2 (2008): 778-788.

41. Thevannan, Ayyasamy, Rubeena Mungroo, and Catherine Hui Niu. "Biosorption of nickel with barley straw." Bioresource technology 101.6 (2010): 1776-1780.

42. Nuhoglu, Yasar, and Emine Malkoc. "Thermodynamic and kinetic studies for environmentaly friendly Ni (II) biosorption using waste pomace of olive oil factory." Bioresource Technology 100.8 (2009): 2375-2380.

43. Sala Cossich, Eneida, Célia Regina Granhen Tavares, and Teresa Massako Kakuta Ravagnani. "Biosorption of chromium (III) by Sargassum sp. biomass." Electronic Journal of Biotechnology 5.2 (2002): 6-7.

44. Kalyani, S., et al. "Removal of copper and nickel from aqueous solutions using chitosan coated on perlite as biosorbent." Separation Science and Technology 40.7 (2005): 1483-1495.

45. Ho, Y. S., J. C. Y. Ng, and G. McKay. "Kinetics of pollutant sorption by biosorbents: review." Separation and Purification Reviews 29.2 (2000): 189-232.

46. Vijayaraghavan, K., et al. "Biosorption of copper, cobalt and nickel by marine green alga Ulva reticulata in a packed column." Chemosphere 60.3 (2005): 419-426.

Received on 27.05.2017 Modified on 29.06.2017

Research J. Pharm. and Tech. 2017; 10(9): 3029-3034.

DOI: 10.5958/0974-360X.2017.00538.8