Determination of isotherm parameters for the adsorption of Rhodamine B dye onto activated carbon prepared from Ziziphus  jujuba seeds

 

Sivarajan, A^1*, Shanmugapriya, V. ²

¹Department of Chemistry, M.R.G College, Mannargudi – 614 001.

²Department of Chemistry, Government Arts college, Thuvakudi Malai, Tiruchirappalli - 620 022.

*Corresponding Author E-mail: vnchem14@gmail.com

The adsorption of Rhodamine B dye from aqueous solution onto activated carbon prepared from Ziziphus  jujuba seed by zinc chloride activation (ZAC) was studied in a batch system with respect to contact time, pH, and temperature. Solution pH 4 was favorable for the adsorption of this dye. Equilibrium isotherms were analysed by Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherms. The adsorption capacity was found to be 142.9 mg/g by Langmuir isotherm. The Temkin  and Dubiniin - Raduskevich isotherm constants suggested that physisorption might be the major mode of the adsorption process. Thermodynamic parameters like ∆G^◦, ∆H^◦ and ∆S^◦ were calculated. These values inferred the spontaneous adsorption with  increased randomness at the solid-liquid interface and endothermic behavior.

 

 

 

INTRODUCTION:

Development of science and technology enhanced the life style of human considerably and so has the degradation of ecological systems. Such development use dyes in various fields of textiles, food, cosmetics, paper, paints, pharmaceuticals and several other industries. Effluent containing dyes prove toxic to the aquatic ecosystem. Dyes and pigments are widely used, mostly in leathers, textiles, paper mill, additives, foodstuff and cosmetics industry to color products. Today, they are considered as a kind of extremely important pollutant in environment due to their complex composition, high toxicity, poor degradability and great solubility in water [1]

 

Rhodamine B is one among the most commonly used dyes. Rhodamine B is a chemical dye with IUPAC name [9- (2 - carboxyphenyl) - 6 - diethylamino-3-xanthenylidene] - diethyl ammonium  chloride (Fig 1) often used as a tracer within water and possess remarkable fluorescence property due which it finds application in biotechnological techniques.

 

Fig 1 Rhodamine B dye structure

 

Several physical or chemical processes are used to treat dye-laden wastewaters. However, these processes are costly and cannot be used effectively to treat the wide range of dye-laden wastewater. Each method has its own advantages and disadvantages [2]

 

The adsorption process is one of the efficient methods to remove dyes from effluent and has an advantage over the other methods due to the excellent adsorption efficiency of activated carbon (powdered or granular) for organic compounds even from dilute solutions, but commercially available activated carbons are very expensive. Various carbonaceous materials, such as coal, lignite, coconut shells, wood and peat are used in the production of commercial activated carbons [3]

 

However, the abundance and availability of agricultural by-products make them good sources of raw materials for activated carbons. Agricultural by-products [4] are renewable sources of raw materials for activated carbon production because the development of methods to reuse waste materials is greatly desired. Disposal of agricultural by-products is currently a major economic and ecological issue, and the conversion of by-products to adsorbents, such as activated carbon, represents a possible outlet. A number of agricultural waste materials such as Maize cob, Coconut shell, groundnut shell, Silk, cotton hull, coconut tree sawdust, Rice husk, Orange peel , Coir pith , Banana and orange peels , Banana pith ,Groundnut shell powder ,Wheat straw, corncob, bark husk are being studied for the removal of different dyes from aqueous solutions at different operating conditions [5]. In this article, the feasibility of agricultural waste, Zizupus jujuba seed has been attempted to prepare activated carbon. Agricultural wastes are of low economic value, so inexpensive and abundantly available, mainly composed of cellulose, hemicelluloses and lignin which make them effective adsorbents for a wide range of pollutants. Adsorbing potential and behavior of the prepared activated carbon is evaluated using Rhodamine B dye.

 

Table 1 Symbols

 

 

Table 2 Isotherm equations

 

 

 

MATERIALS AND METHODS:

Chemicals

Rhodamine B (C.I. 45170) used in this study was purchased from BDH, England. All other chemicals and reagents were procured from Merck, Germany.

 

Preparation of Adsorbent

The Zizupus jujuba seed were collected from mannargudi, Tiruvarur Dt., S. India and washed with distilled water to remove the surface adhered particles, dried in sun light for 8 hours, chopped into small pieces and powdered in a pulveriser. 50g of the powder was mixed with 100ml of 60% ZnCl₂ solution. The slurry was kept at room temperature for 24 hours, to ensure the complete access of the ZnCl₂ to the seed powder. Excess liquid in the slurry was decanted and heated in a muffle furnace at 723 K  for 3 hours. Thus obtained carbon was washed with 0.5 M HCl followed with distilled water until the washings reach pH 7.0. Then it was dried in a hot air oven at 383 K for 1 hour. The dried material was grounded and sieved to get particle size between 75 and 105 µm which was stored in an air tight container. It was designated as Zizupus Jujube Activated carbon (ZAC) [6]

 

Preparation of dye solution and estimation

Stock solutions (1000 mg/l) of Rhodamine B (RDB) was prepared in deionized and double distilled water and diluted to get the desired concentration of the dyes. Calibration curves for the dyes were prepared by measuring the absorbance of different concentrations of the dyes at λ _max 554 nm using Systronics Double Beam UV-visible Spectrophotometer-2202. The dye concentrations in the experimental samples were evaluated from the calibration curves.

 

Adsorption experiments

Adsorption experiments were conducted with 50 mL of dye solution of known concentration at desired pH with known mass of ZAC in 250-ml Erlenmeyer flask. The mixture was agitated (130 rpm) at specific temperature for pre-determined time. Desired pH of the solution was brought by adding either 1N HCl or 1N NaOH solution of necessary quantity. At the end of incubation, ZAC was separated from the solution by centrifugation at 1000 rpm for 10 minutes and the concentration of the dye in the solution was determined as described above. Amount of dye uptake, q (mg/g) and the percentage of removal were calculated using the following equations

                     q = (C_i − C_f) V/ 1000W

% of Removal = (C_i − C_f) 100/ C_i

 

where, C_i (mg/l) is the initial dye concentration, C_f (mg/L) is the final dye concentration after adsorption ,  W (g) is the amount of adsorbent and V (L) is the volume of the solution

 

RESULTS AND DISCUSSION:

Effect of pH

pH is one of the most important parameters controlling the adsorption process [7]. The influence of hydrogen ion concentration on the adsorption process was studied by adding 30 mg of ZAC in 50 mL of dye solution (50 mg/L) over a pH range of 2.0–11.0. The result is shown in Fig. 2.

 

Fig 2 Effect of pH

[C_i : 50 mg/L;  Dose: 30 mg/ 50 mL;  Time: 160 min; Temp : 305 K]

 

The percentage of removal of RDB dye at pH 7 was the minimum, and a maximum percentage of removal was obtained at pH 4. When the pH of the solution was increased more than pH 7, the percentage of removal of RDB dye was increased.

 

This result may be attributed to the formation of different ionic species of RDB dye and different carbon surface charge. At pH values lower than 4, the RDB dye ions are cationic and monomeric molecular forms [8]. The monomeric form of  RDB ions at lower pH easily enter into the pore structure. At a pH value higher than 4, RDB becomes zwitter ion and gets aggregated due to dipolar nature .The bigger molecular form (dimer) cannot easily enter into the pores of the carbon. Ghanadzadeh et al. [9]. The greater aggregation of the zwitter ionic form is due to the attractive electrostatic interactions between the carboxyl and xanthene groups of the monomers [10]. At a pH value higher than 8, the preponderance of OH^- decrease the aggregation of RDB by intervening the attraction between positive charge on the nitrogen and negative charge of the carboxylate ion which increases in the adsorption of RDB ions on the carbon surface. [11].

 

Effect of sorbent amount

The effect of adsorbent dosage on the uptake of RDB dye solution was studied in the range of 5 mg to 50 mg  for 50 mL of dye solution (50 mg/L) at 305 K temperature. The uptake of RDB increased as the adsorbent dose increased as shown in the Fig 3.This is due to the large number of adsorption sites on the surface of adsorbent.

 

Fig 3 Effect of dose

[C_i : 50 mg/50 mL;  pH : 4;  Time : 160 min;  Temp : 305 K]

 

 

Effect of initial concentration

The study on the effect of initial concentration showed that the time to attain equilibrium increased from 60 minutes to 120 minutes when the initial concentrations were increased from 15 mg/L to 95 mg/L. This is because extra time is required for the large number of adsorbates to access into the interior pores of the sorbent. Percentage of removal of dyes at equilibrium decreased with the increase of initial concentrations of dye solution as given in Table 3. This is due to the decrease in the ratio between available adsorption sites and the concentration of solute in the solution [12, 13].

However amount of dye adsorbed by the adsorbent, increased with the increase of initial concentrations of the dye. This may be attributed to the increased driving force. This kind of results are reported in earlier literatures [14,15,16].

 

Table 3:   Effect of initial concentration

[Dose: 30 mg/ 50 mL;   pH : 4]

 

Isotherms

Adsorption isotherms are prerequisites to understand the nature of the interaction between adsorbate and the adsorbent used for the removal of organic pollutants [17].

 

Analysis of the results obtained from the equilibrium isotherm studies is fundamental to evaluate the affinity of the adsorbent for a particular adsorbate. Equilibrium studies are described by a sorption isotherm characterized by certain constants whose values express the surface properties and affinity of the adsorbent.

 

In the present study, the adsorption of Rhodamine B shows that the adsorption of the dyes increases with increase in dye concentration and tends to attain saturation at higher concentrations as shown in Table 4.The experimental data were analyzed by well-known adsorption isotherm models such as  Langmuir, Freundlich, Temkin and Dubinin – Raduskevich isotherms

 

Table 4: Equilibrium data at different temperatures

[Dose: 30 mg/ 50 mL;   pH: 4;   Time: 180 min;]

 

 

 

Langmuir isotherm

The monolayer coverage of the adsorbate on the adsorbent surface at constant temperature is represented by the Langmuir isotherm. The Langmuir isotherm hints towards surface homogeneity. [18, 19]

 

Fig. 4 shows Langmuir isotherm model for the t adsorption of RDB dyes on ZAC that fits well to the with a regression coefficient ranging from 0.98 to 0.99 supporting monolayer coverage of the adsorbate on the surface of adsorbent. The theoretical monolayer saturation capacities of ZAC was found to be in between 142.9 -181.8 mg/g for the studied temperature as given in Table 5.This value is moderate when compared other adsorbents (Table 6)

 

Langmuir equation can also be used to obtain, R_L, the dimensionless equilibrium parameter or the separation factor. R_L  values of present investigation are in between 0 and 1indicating that the adsorption process is favourable.

 

Fig 4 Langmuir isotherm

 

Table 5 Langmuir isotherm parameters

[pH: 4;  Dose : 30 mg/ 50 mL; Time :160 min;]

 

Table 6 Langmuir monolayer adsorption capacity of other adsorbents for RDB dye

 

Freundlich isotherm

Freundlich isotherm is an empirical equation. It is the most popular model for a single solute system based on the distribution of solute between the solid phase and aqueous phase at equilibrium. It also suggests that sorption energy exponentially decreases on completion of the sorptional centres of an adsorbent.  The Freundlich model describes the adsorption within a restricted range only. It is capable of describing the adsorption of organic and inorganic compounds on a wide variety of adsorbents [34].

 

Fig 5 shows that Freundlich model. The regression coefficient (R²) for Freundlich isotherms are 0.99 and 0.98 for all the studied adsorbates which indicate that the experimental data fit well into Freundlich model. Freundlich constant K_f (mg/g) values for adsorption of RDB are ranged from 11.3 to 17.3. Further it is noticed that the adsorption capacity increased with the increase of temperature as shown in Table 7

 

Table 7 Freundlich isotherms for RDB dye onto ZAC

[Dose: 30 mg/ 50 mL;  pH : 4;  Time :160 min;]

Fig 5 Freundlich isotherm

 

 

Temkin isotherm

The Temkin isotherm assumes that the heat of sorption in the layer would decrease linearly with coverage due to sorbate - sorbent interactions. Further the fall in the heat of adsorption is not logarithmic as stated in Freundlich expression [35, 36].

 

The results obtained from Temkin model for the removal of RDB, are collected in Table 8. Concerned isotherm plots were shown in Fig 6. The regression coefficient (R²) values ranged from 0.96 to 0.99 for the studied temperatures .These results show the best fitting of the equilibrium data with Temkin isotherm. Equilibrium binding constant ‘a_T’ values (L/g) are ranged from 0.62 to 1.05. The Temkin constant related to heat of sorption, b_T values (kJ/mg) are ranged from 77.3 to 83.6. Low values of heat of adsorption, supports the physisorption mechanism [37]

 

 

 

Table 8 Temkin isotherms results

[pH : 4; Dose : 30 mg/ 50 mL; Agitation time :160 min;]

 

Fig 6 Temkin isotherm

 

D-R isotherm

Dubinin–Radushkevich isotherm is generally applied to express the adsorption mechanism with a Gaussian energy distribution onto a heterogeneous surface [38, 39]. The model has often successfully fitted high solute activities and the intermediate range of concentrations data well.

 

The constants q_D and B were calculated from the slope and intercept of straight line obtained from the plot of ln q_e versus ε² (Fig 7). The mean free energy of adsorption E calculated from B [40]. E per molecule of adsorbate (for removing a molecule from its location in the sorption space to the infinity can be computed. The low values of mean free energy (Table 9) indicate the physisorption process [41] and the R² value express the moderate fitting of the equilibrium data with this isotherm model.

 

Table 9 D-R isotherm results

[Dose: 30 mg/ 50 mL; pH : 4; Time :160 min;]

…

Fig 7 D-R Isotherm

 

CONCLUSION:

Investigation of the equilibrium sorption was carried out at different temperature (305,315, 325 and 335 K) and pH between 2 and 10. Four adsorption isotherm models were studied. The sorption data fitted into Langmuir, Freundlich, Temkin and Dubunin – Radushkevich isotherms. Values obtained for isotherm constants inferred that this sorption was favourable with physisorption mechanism. It could be concluded that the carbon prepared from Zizupus jujube seed is a potential and active adsorbent for removal of Rhodamine B dyes from aqueous solution.

 

REFERENCES:

1.          García-Montano, J., Xavier Domènech, X., García-Hortal, J.A., Torrades, F., Peral, J. ,The testing of several biological and chemical coupled treatments for Cibacron Red FN-R azo dye removal, J. Hazard. Mater. 154 (2008) 484–490

2.          Robinson, T., McMullan, G., Marchant, R., Nigam, P., Remediation of dyes in textile effluent: A critical review on current treatment technologies with a proposed alternative, Bioresour. Technol. 77 (2001) 247–255

3.          Bansode, R.R., Losso, J.N., Marshall, W.E., Rao, R.M., Portier, R.J., Adsorption of metal ions by pecan shell based granular activated carbons, Bioresour. Technol. 89 (2003) 115–119

4.          Ankur, K., Collin, G., Faujan, J., Ahmad, B.H. , Zulkarnian, Z. Hussain, Z.M., Abdullah, H.A., Preparation and characterization of activated carbon from Resak wood (Vatika hulletti), Res. J. Chem. Environ. 5 (3) (2001) 21–24.

5.          Malik, R., Ramteke, D.S., Wate, S.R., Adsorption of malachite green on groundnut shell waste based powdered activated carbon, Waste Management 27 (9) (2007) 1129–1138.

6.          Namasivayam C., Sangeetha D., Equilibrium and kinetic studies of adsorption of phosphate onto ZnCl₂ activated coir pith carbon, J. Colloid and Interface Science, 280 (2004) 359-365

7.          Marzal P, Seco A, Gabaldon C., Cadmium and zinc adsorption onto activated carbon: Influence of temperature, pH and metal/carbon ratio. J Chem. Technol. Biotechnol,66 (3), (1996)279-85.

8.          Deshpande AV, Kumar U., Effect of method of preparation on photo physical properties of Rh-B impregnated sol-gel hosts. J Non-Cryst Solids,306 (2),( 2002)149-59.

9.          Ghanadzadeh A, Zanjanchi MA, Tirbandpay R., The role of host  environment on the aggregative properties of some ionic dye materials. J Mol Struct, 616(1e3),( 2002)167-74.

10.       Lopez Arbeloa I, Ruiz Ojeda P., Dimeric states of rhodamine B.Chem Phys Lett 1982; 87(6):556-60.,

11.       Yupeng Guo, Jingzhe Zhao, Hui Zhang, Shaofeng Yang, Jurui Qi, Zichen Wang, Hongding Xu, Use of rice husk-based porous carbon for adsorption of Rhodamine B from aqueous solutions, Dyes and Pigments 66 (2005) 123-128.

12.       Abechi, E.S., Gimba, C.E., Uzairu, A., Kagbu, J.A., Kinetics of adsorption of methylene blue onto activated carbon prepared from palm kernel shell. Arch. Appl. Sci. Res. 3 (1),(2011) 154- 164

13.       Arivoli, S., Nandhakumar, V., Saravanan, S., Sulochana Nadarajan, Adsorption Dynamics of Copper ion by Low Cost Activated Carbon, The Arabian J. Sci. Engineer. Volume 34, Number 1A, January.( 2009. ) 1-12

14.       Nandhakumar, V., Roopa1, V., Ramesh, K. Rajappa, A., Equilibrium and isotherm studies on the adsorption of Rhodamine B onto activated carbon prepared from bark of Erythrina  Indica, Int. J. Curr. Res. Chem. Pharma. Sci.1(2), (2014) 23-29

15.       Nandhakumar, V., Rajappa, A., Ramesh, K., Adsorption of Bismarck Brown R Dye from Aqueous Solution onto Activated Carbon Prepared from  Pods shell (Flame Tree), International Journal of Chemistry and Pharmaceutical Sciences, Vol.2(9),(2014)1032-1041.

16.       Gupta, V.K, Suhas, A.I, Saini, V.K, Removal of Rhodamine B, fast green and methylene blue from wastewater using red mud an aluminum industry waste. Ind. Eng. Chem. Res., 43, (2004) 1740–1747.

17.       Aksu, Z., Application of biosorption for the removal of organic pollutants: a review, Process Biochem. 40 (2005) 997–1026.

18.       Oladoja, N.A., Asia, I.O. , Aboluwoye, C.O., Oladimeji, Y.B., Ashogbon, A.O., Studies on the sorption of basic dye by rubber (Hevea brasiliensis) seed shell, Turk. J.Eng. Env. Sci. 32 (2008) 1–10.

19.       Langmuir, The adsorption of gases on plane surfaces of glass, mica, and platinum J. Am. Chem. Soc., 40 (1918),1361–1403.

20.       Ramuthai,S.,Nandhakumar,V.,Thiruchelvi,M.,Arivoli,S.,Vijayakumaran, V., Rhodamine B:AdsorptionKinetic,Mechanistic and Thermodynamic Studies, E-Journal of Chemistry, Vol.  6 (S1), (2009), S363-S373

21.       Santhi, T., Ashly Leena Prasad , Manonmani, S., A comparative study of microwave and chemically treated Acacia nilotica leaf as an eco-friendly adsorbent for the removal of Rhodamine B dye from aqueous solution, Arab. J. Chem.,7, 4 (2014) 494 -503

22.       Sureshkumar, M.V., Namasivayam, C., Adsorption behavior of direct red 12B and  Rhodamine B from water unto surfactant modified coconut coir pith, Colloid Surfaces A: Physic. Chem. Eng. Aspects, 317(1–3), (2008) 277–283.

23.       Mohammadine El Haddad, Rachid Mamouni, Nabil Saffaj , Saïd Lazar, Adsorptive Removal of Basic Dye Rhodamine B from Aquoeus Media onto Animal Bone Meal as New Low Cost Adsorbent ,Global Journal of human social science Geography and Environmental Geo Sciences Volume 12 Issue 10 ( 2012), 19 -30

24.       Anandkumar, J., Mandal, B., Adsorption of Chromium (VI) and Rhodamine B by surface modified tannery waste: kinetics, mechanistic and thermodynamics, J. Hazard. Mater. 186 (2-3), (2011) 1088–1096.

25.       Zhang, Z., O’Hara, I.M., Kent, G.A., Doherty, W.O.S., Comparative study on adsorption of two cationic dyes by milled sugarcane bagasse, Indust. Crops Products, 42, (2013) 41–49.

26.       Shanmugam Arivoli, M. Thenkuzhali, P. Martin Deva Prasath, Adsorption of Rhodamine B by acid activated carbon-Kinetic, thermodynamic and equilibrium studies, Orbital , 1 (2), (2009)138-155

27.       Zamouche, M., Hamdaoui, O., Sorption of Rhodamine B by cedar cone: effect of pH and ionic strength, Energy Procedia, 18, (2012)1228–1239.

28.       Yu, J., Li, B. , Sun, X. , Jun, Y., Chi, R., Adsorption of methylene blue and Rhodamine B on baker’s yeast and photo catalytic regeneration of the biosorbent, BioChem. Eng. J., 45,( 2009) 145–151.

29.       Gad H M H, El-Sayed, A. , Activated carbon from agricultural by-products for the removal of Rhodamine-B from aqueous solution. Journal of Hazardous Materials, 168 (2-3), (2009) 1070–1081.

 

30.       Khan, T.A., Dahiya, S. Ali, I., Use of kaolinite as adsorbent: Equilibrium, dynamics and thermodynamic studies on the adsorption of Rhodamine B from aqueous solution. Appl. Clay Sci., 69(2012) 58–66

31.       Panda, G.C. , Das, S.K., Guha, A.K., Jute sticks powder as a potential biomass for the removal of Congo red and Rhodamine B from their aqueous solution, J. Hazard. Mater., 164 (2009) 374–379.

32.       Chang, S., Wang, K., Li, H., Wey, M. Chou, J., Enhancement of Rhodamine B removal by low-cost fly ash sorption with Fenton pre-oxidation. J. Hazard. Mater. 172 (2009) 1131–1136.

33.       Adejumoke A.Inyinbor, Folahan A. Adekolab, Gabriel A. Olatunji, Adsorption of Rhodamine B Dye from Aqueous Solution on Irvingia gabonensis Biomass: Kinetics and Thermodynamics Studies, S. Afr. J. Chem.,68(2015)  115–125,

34.       Freundlich, H.Z., Over the adsorption in solution J. Phys. Chem., 57 (1906) 385–470.

35.       Temkin, M.,Pyzhev, V. Kinetics of Ammonia Synthesis on Promoted Iron Catalysts. Acta Physicochimica URSS, 12 ((1940) 217-222.

36.       Bansode, R.R., Losso, J.N., Marshall, W.E., Rao, R.M., Portier, R.J., Adsorption of metal ions by pecan shell based granular activated carbons, Bioresour. Technol. 89 (2003) 115–119.

37.       Naushad, Mu., Zeid Abdullah AL Othman, Md. Rabiul Awual, Sulaiman M. Alfadul, Tansir Ahamad, Adsorption of rose Bengal dye from aqueous solution by amberlite Ira-938 resin: kinetics, isotherms, and thermodynamic studies, Desalination and Water treatment , Volume 57, (2016)  013527–13533

38.       Gunay, A., Arslankaya, E., Tosun, I., Lead removal from aqueous solution by natural and pretreated clinoptilolite: adsorption equilibrium and kinetics, J. Hazard. Mater. 146 (2007) 362–371.

39.       Dabrowski, A., Adsorption—from theory to practice, Adv. Colloid Interface Sci.93 (2001) 135–224.

40.       Dubinin, M.M., The potential theory of adsorption of gases and vapors for adsorbents with energetically non-uniform surface, Chem. Rev. 60 (1960) 235–266.

41.       Hobson, J.P., Physical adsorption isotherms extending from ultra-high vacuum to vapor pressure, J. Phys. Chem. 73 (1969) 2720 – 2727.

 

 

 

Received on 19.05.2017         Modified on 29.05.2017

Accepted on 05.06.2017         © AJRC All right reserved