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Biosorption of Eriochrome Black T and Astrazon FGGL blue using Almond and Cotton seed Oil Cake Biomass in a Batch Mode.

Byline: Yusra Safa

Summary: In the present research study the biosorption of Eriochrome Black T (EBT) and Astrazon FGGL blue (A-FGGL) onto novel biomasses Almond (Prunus dulcis) oil cake and Cotton seed oil cake respectively was investigated in the batch mode using different process parameters like pH particle size biosorbent dose initial dye concentration contact time and temperature. Maximum biosorption capacity was observed at pH 3 for EBT onto almond oil cake and pH2 for Astrazon FGGL blue onto cotton seed oil cake.The biosorption capacity was efficient at the smallest particle size of biosorbent. The amount of dye sorbed (mg/g) decreased with the decrease in biosorbent dose and increased with increase in initial dye concentration and temperature. Optimum contact time for equilibrium to achieve was found to be 120 and 180 minutes for EBT and A-FGGL blue respectively. The Langmuir isotherm model was best fitted to experimental data.

The biosorption followed the pseudo-second order kinetic model suggesting a chemisorption mechanism. The positive value of H showed the endothermic nature of the process. In this research the influence of electrolytes heavy metals and surfactants on the removal of dyes was also examined.

Key Words:- Biosorption; Almond oil cake; cotton seed oil cake; acid dyes; modeling.


Pigments and dyes are extensively used in the textile paper and leather dyeing printing pharmaceutical and cosmetic industries. About 10000 different dyes are produced annually for various industrial processes 10-15% of them are discharged by the textile industry and cause pollution [1].

Textile wastes have complex composition with variety of dyes surfactants bleaching agents and ionic impurities. A large amount of these dyes go into the effluent during the dyeing process as they are highly soluble in water. Most of them are toxic or even carcinogenic. Discharge of these toxic substances into water stream pollute the water and make it unfit for aquatic life. Most of the dyes are harmful to marine flora and fauna. Further the dyes affecting the possibility for aquatic plants to perform photosynthesis. A majority of these dyes are stable to light and oxidation. Many physio-chemical methods such as adsorption coagulation precipitation filtration and oxidation have been used for the treatment of effluent containing dyes. The adsorption process has been found to be the most effective. Dyes usually have complex aromatic molecular structures. Dyes can be classified as follows: Anionic (acid direct and reactive dyes)

Cationic (basic dyes) and Nonionic (disperse dyes) dyes [2 3].

Generally dyes are not degraded easily. Many treatment processes have been used for the removal of dyes from waste water such as physical chemical and biological methods. Adsorption chemical precipitation coagulation chemical oxidation ultra-filtration reverse osmosis photo- catalysis dilution ion-exchange and membrane filtration etc are incorporated in the physical and chemical treatment methods. But these methods have many disadvantages such as ineffective dye removal costly sludge formation and not applicable to the wide range of dye wastewaters [4 5].

But biosorption is more promising method among all these due to its effectiveness less costly capacity and capability to remove dyes from industrial wastewaters on the extensive scale [6 7].

Eriochrome Black T (EBT) and Astrazon FGGL blue are acidic dyes. EBT is poison causes severe eye irritation or blindness. It is flammable liquid and its vapors are harmful if inhaled. Target organs in human body are kidneys central nervous system liver cardiovascular system eyes. EBT solution may be absorbed in harmful amounts through intact skin and causes skin irritation. It causes liver damage. Advanced stages may cause collapse unconsciousness coma and possible death due to respiratory failure. It can also cause kidney failure vascular collapse and damage. A-FGGL blue is also toxi it can cause necrosis blood congestion and inflammation of skin.

The idea of using biomass in environmental cleanup has been come since the early 1900's when Arden and Lockett discovered certain types of living bacteria cultures were capable of recovering nitrogen and phosphorus from raw sewage when it was mixed in an aeration tank. There are various low cost adsorbents which are used in the biosorption process such as wheat straw [3] cotton waste rice husk [8] maize cob treated parthenium biomass Almond oil cake [9].

In the present research project Almond oil cake and cotton seed oil cake are used for removal of acid dyes (EBT) and A-FGGL bluerespectively from aqueous solution. Influence of different parameters on biosorption capacity is studied.

Results and Discussion

Influence of pH

Dye biosorption is a pH dependent process. The pH of the solution influences the properties of biomass affects the adsorption mechanisms and dissociation of the dye molecules. The effects of pH on the biosorption of EBT and A-FGGL dye on the almond and cotton seed oil biomass were studied in the pH ranging from 1-10. The results showed that the maximum biosorption of EBT and A-FGGL dyes were observed at the pH 3.0 and 2.0 respectively. At higher pH values the biosorption of dye was not effective.

A maximum uptake value of 4.846 mg/g was observed for EBT at the optimum pH 3.0. The biosorption capacity of A-FGGL dye was 3.012mg/g at pH 2.The results are depicted in Fig. 1. The pH value of the dye solution is the most important controlling factor that should not be neglected during the biosorption process. At lower pH the biosorbent surface turned out to be positively charged and electrostatic attraction develops between the positively charged biomass and negatively charged anionic dyes. At high pH value electrostatic repulsion appears due to the number of negatively charged sites on the biosorbent [10]. A similar behavior was observed earlier for the biosorption of acidic dyes by Paenibacillus macerans [11] and direct azo dyes by Spirogyra sp.I02 [12].

Ardijani et al. [9] examined the effect of initial pH on the adsorption of direct Red 80 from aqueous solution onto almond shells. As pH increased from 2 to 12 the adsorption capacity decreased from 20.5 to 18.8 mg/g. Maximum uptake of dye was observed at pH 2.0.

Similarly Dulman and Cucu-Man [13] also investigated the pH effect on the uptake of dyes by the beech wood sawdust. A maximum removal of 98.6% and 94.4% was observed for Direct Brown 2 and Direct Brown at pH 3.0 respectively.

Influence of Biosorbent Dose

The effect of biosorbent dose on the biosorption of EBT and A-FGGL dyes on the Almond and cotton seed oil cakes was evaluated by varying the biosorbent dose and results are reported in Fig. 2.

The quantity of dye adsorbed decreased due to the decrease in biosorbent dose.. The maximum biosorption occurred in the present investigation at0.3g of biosorbent dose.

Several reasons are given that the adsorption is maximum at high biosorbent dose due to the large surface area and an increase in the number of available binding sites [14]. Similar behavior regarding the biosorption of anionic dye on the Peanut hull was observed by Gong et al. [15]. Akhtar et al. [16] investigated the effect of biosorbent dose on the uptake of 24- dyechlorophenol. By increasing the biosorbent dose from 0.025 0.1g the percentage adsorption increased fastly up to 66% and then remained constant.

Mohan et al. [12] reported that the adsorbent dose imparted great influence on the biosorption of direct azo dye from the aqueous media and maximum dye removal (85%) was observed with 0.5g dose. Colak et al. [11] also reported that biosorption of Acid Blue 225 and the Acid Blue 062 increased with an increase in the biosorbent concentration. This is due to the availability of the binding site for dyes.

Influence of Biosorbent Particle Size

The particle size of biosorbent is very important factor. The rate of dye removal increases as the particle size decreases. So in present case adsorption occurred at smallest biosorbent particle size. Fig. 3 represents the amount of dyes adsorbed by oil cakes at different mesh sizes.

The results showed that the biosorption capacity of biosorbents increased with the decrease in the particle size. The maximum biosorption capacity (4.42 mg/g) was recorded at the smallest particle size (60 mesh size) for almond oil cake and (2.004mg/g) for cotton seed oil cake.

Influence of Initial Dye Concentration

The effect of initial dye concentration of two dyes onto the biosorption capacity of the Almond and cotton seed oil cake biomasses was investigated by varying the initial concentration of dyes at the optimum biosrbent dose and other parameters. The results regarding the effect of initial concentration of dyes on the biosorption capacity of oil cake biomasses are given in the Fig. 4.

The uptake capacity of biomass increased from 4.7 9.8 mg/g (for EBT) and from 1.212- 2.97mg/g (for A-FGGL) with increase in the initial dye concentration while % sorption shows the opposite trend. In the biosorption mechanism in the start the dye molecules adsorbed externally and the bioorption rate increased rapidly. When the external surface became saturated the dye molecules adsorbed into the porous structure of the biomass [11]. The initial concentration of dyes provides an important driving force to overcome the mass transfer resistance of all molecules between the aqueous and the solid phases. Bulut et al. [4] observed that the amount of dye sorbed per unit mass of biosorbent increased with an increase in the initial dye concentration from 50-250 mg/l. It is estimated that the binding sites of the biosorbent stays unsaturated during the biosorption .

Khaled et al. [14] investigated the effect of initial concentration of Direct N Blue-106 on the biosorption of orange peel carbon. The amount of dye adsorbed q increased with increase in the dye concentration.

Tune et al. [17] explained the decrease in percentage uptake of Ramazol Black B reactive dye due to the saturation of exchanging sites at higher dye concentration using cotton plant waste. The decrease in the biosorption capacity of biomass may be attributed to the hindrance in movement of dye molecules into the biosorbant Vijayaraghavan et al [18] Another reason of unavailability of binding sites of the biosorbant is due to the shielding of gell matrix [19].

Influence of Contact Time

The biosorption efficiency was evaluated as a function of time and the results are depicted in Fig. 5.

The amount biosorbed (mg/g) by the biosorbent increased rapidly with the increase in the contact time. When the agitation time was further increased there was no drastic increase in the biosorption capacity of biosorbent. This increase was fast in the beginning and then slow removal was observed till equilibrium. The equilibrium was attained after 120 minutes for EBT dye and 180 minutes for A-FGGL dye.

It was generally observed that the biosorption capacity increased with time and after certain time reached to equilibrium. In the beginning the fast biosorption may be attributed to the presence of positive charged sites on the almond waste biosorbent surface which developed an interaction with negetively charged dye molecules. Then the biosorption began to slow down due to the slow movement of dye molecules into the interior of the bulk of the biosobent [10]. Another reason was large number of exchanging sites helped the biosorption process and then saturation occurred [20].

In another study Ahmad et al. [21] observed the effect of contact time on the direct dye biosorption onto palm ash. The biosorption capacity increased steadily in the beginning and the equilibrium was attained after 129 minutes. Similarly Akar et al. [22] investigated the effect of agitation time on the removal of a reactive dye from the aqueous solution. The results showed that the dye removal density (mg/g) increased with increase in time. The equilibrium was established after 40 minutes of agitation time.

Influence of Temperature

Wastewater from textile industry is discharged into the water stream at comparatively higher temperature. So temperature is a vital issue to study. The results in the Fig. 6 showed that the biosorption capacity of both oil cake biosorbents increased with increase in temperature from 30 oC 60 oC. High temperature favored the biosorption of anionic dyes by oil cakes.

The biosorption capacity of oil cake biomasses increased with increase in temperature ranging from 30o 70o C indicating the endothermic nature of the process. This might be due to the increase in the number of molecules attaining the sufficient energy to undergo the chemical reaction with the biosorbent [12].

Another reason was the increase in the pore size on the biomass surface at high temperatures. The elevated temperature reduced the thickness of the outer surface of the biosorbent and increased the kinetic energy of the dye molecules as a result the dye molecules biosorbed easily into the surface of biomass [23].

The biosorption mechanism was affected in two ways. First of all the rate of diffusion of dye molecules into the pores of biosorbent increases with the increase in temperature. Secondly the elevated temperature modified the biosorption capacity of biosorbent for the dye molecules [24]. The motion of dye molecules also increased with increase in the temperature [25]. Akar et al. [22] reported the effect of temperature on the removal of basic dye from aqueous solution onto Pyracantha coccinea berries using four different temperatures (15 25 35 and 45oC).

Preparation of Aqueous Dye Solutions

In the present investigation both dyes were used without any further purification. Stock solutions of dyes were prepared by dissolving 0.1g of dye in 100ml of double distilled water. The experimental solutions of different concentrations from 25 to 150 mg/l were made by further dilution of stock solution. Standard curve was developed through the measurement of the dye solution absorbance by UV- Visible Spectrophotometer. The general characteristics of dyes are shown in Table-1.

Table-1: General characteristics of dyes.


Eriochrome Black T###Black###400###Anionic

AstrazonFGGL blue###Blue###404###Anioinc

Batch Biosorption Experimental Studies

Biosorption experiments were conducted in batch mode to investigate the effects of different process parameters such as pH biosorbent dose particle size initial dye concentration contact time and temperature on the biosorption of dyes.Effect of salts surfactants and heavy metals on the biosorption capacity were also studied.

The amount of biosorbed dye was calculated using the following equation:

q= (Co Ce) V/W

where q is the amount of dye biosorbed on the biosorbent (mg/g) Co and Ce are the initial and equilibrium concentration of dye solution respectively. V is the volume of the dye solution (ml)

Adsorption Isotherm Studies

The equilibrium data commonly known as adsorption isotherms are basic requirements for the design of adsorption systems. Two most commonly employed adsorption isotherm models were applied in this present investigation viz. the Langmuir [27] and Freundlich [28] isotherm models. Analysis of adsorption data is necessary for the development of biosorption isotherms and biosorption kinetics models. These models are used for optimization of design parameters. The interaction between biosorbent and sorbate can be determined by biosorption isotherm models. There are different isotherms which are used to describe the biosoption equilibrium data. In this present study two isotherms named as Langmuir and Freundlich isotherm models were investigated.

Langmuir Isotherm

The Langmuir adsorption isotherm is frequently applied for the biosorption of organic and inorganic pollutants from aqueous solution. This model suggests that the biosorption onto the adsorbent surface is homogenous in nature. According to Langmuir isotherm the biosorption of solute from aqueous solution onto the biosorbent surface is occurred as monolayer biosorption on the homogeneous number of exchanging sites. This phenomenon describes the uniform biosorption energy on the biosorbent surface [29].

where Kf is the Freundlich isotherm constant related to the bonding energy. Kf is defined as the distribution coefficient and suggests the amount of dye sorbed on the biosorbent for unit equilibrium concentration. qe is the amount adsorbed per unit mass of adsorbent (mg/g) and Ce is the equilibrium concentration of adsorbate (mg/l). The value of n indicates whether the biosorption process is favorable or not. The value of n for favorable adsorption should be greater than 1 [30] The values of Freundlich constants are given in Table-2. From the values given in Table-2 it can be concluded that the biosorption of Eriochrome Black-T and A-FGGL dye is best fitted to the Langmuir isotherm model with R2 value of 0.9082 and respectively

Table-2: Comparison of the isotherm parameters for the biosorption of EBT and A-FGGL dyes onto almond and cotton seed oil cake biomasses.

Isotherm models###EBT dye###A-FGGL dye









Adsorption Kinetics Studies

The transient behavior of dyes onto the Almond and cotton seed oil cake biomass was analyzed using the pseudo-first order [31] and pseudo second order [32] kinetic models. Kinetic studies are necessary to optimize different operating conditions for the biosorption. The rate of biosorption process depends upon the physical and chemical properties of the biosorbent material and the mass transfer mechanism. Various kinetic models have been suggested for explaining the order of reaction.

In this study Pseudo-first-order and Pseudo-

The values of qe experimental qe calculated R2 and K1 of both dyes are given in Table-3.

Table-3: Comparison of the kinetic parameters for the biosorption of EBT and A-FGGL dyes onto almond and cotton seed oil cake biomasses.

Kinetic models###EBT dye###A-FGGL dye###adsorption of Methylene Blue using wheat shells and


###K1 (1/min)###0.00737###0.00691###they found that the values of constants for the

###qe (experimental)###7.131###1.985###pseudo-first order and pseudo-second order models

###qe (calculated)###2.128###7.107


###were increased with increasing temperature and the

###Pseudo-second-order###R2 value for the pseudo-second order model was

###K2 (g/mg min) 10-3###4.543###0.031###greater than 0.999 indicating the second order nature

###qe (experimental)###7.131###1.985

###qe (calculated)###8.403###5.672###of adsorption process.


Ozacar and Sengil [36] suggested that the removal of reactive dyes onto calicinated alunite obeyed the second order kinetic model. Ncibi et al. [1] and Acemioglu [37] reported that the removal of textile metal complexed dye by Posidonia oceanica (L) leaf sheaths and uptake of Congo red fro aqueous solution by calcium rich fly ash followed pseudo- second order kinetics.

Influence of electrolytes on the biosorption of acid dyes

Industrial water contains various salts/electrolytes which significantly affect the dye biosorption. The effect of ionic strength of NaCl and NaOH was investigated in this study. The salt concentrations range from 0.1 1.0 was used to investigate the effect on the dye removal. Fig. 7 8 shows that the amount of dye sorbed of EBT and A- FGGL onto almond and cotton seed oil cake biomasses decreased with increase in the concentration of electrolytes.

Janos et al. [39] investigated that the biosorption of acidic dye increased with increase in the concentration of salts by using wood shaving biomass. At low concentration of salts the amount of dye sorbed (mg/g) decreased. This was due to screening effect of salt which decrease the electrostatic interactions between dye molecule and biosorbent surface [40].

Influence of heavy metals on the biosorption of acid dyes

In this research influence of heavy metals (Hg2+ and Pb2+) on acid dyes biosorption was studied and depicted in Figs. 910.

The biosorption capacity of dyes enhanced in case of Hg2+and Pb2. Increase in the biosorption capacity of dyes with addition of metals may be due to complex formation between metal ions and dyes and binding to the surface of the biosorbent [41]. Other reason is the addition of metals produced the aggregation and flocculation of biomass and increased the biosorption capacity. Pb2+ caused great aggregation than any other metal [42].

The biosorption capacity of dyes decreased by adding anionic surfactant SDS (sodium dodecylsulfate). The reduction of biosorption capacity may be due to repulsive interactions between anionic surfactant and anionic dye molecules. The solubility of anionic dyes is less in SDS micelles than in the aqueous phase [44].


The results obtained from investigation indicated that the Almond and cotton seed oil cakes are very efficient and promising biosorbents for the removal of EBT and A-FGGL dyes from aqueous solution. The biosorption was influenced by the dye solution pH biosorbent particle size biosorbent dose initial dye concentration contact time and temperature. Adsorption capacity of biomass was found to decrease with increase in pH. The adsorption of present acidic dyes is primarily influenced by the surface charge of the adsorbent particles which in turn is influenced by the solution pH. The availability of positively charged groups at the adsorbent surface is necessary for the adsorption of anionic dye. As pH increased more negatively charged surface was available which decreased the availability of positively charged sites which in turn hindered the adsorption of dye. The biosorption capacity was found to be increase with decrease in the biosorbent particle size. The maximum biosorption

capacity was recorded at the smallest particle size (60 Mesh Size). The increase in biosorption capacity may be attributed to the large surface area of the smallest particle size of biosorbent and large number of exchanging sites. The quantity of dye adsorbed decreased with the decrease in biosorbent dose. Maximum biosorption occurred at

0.3g of biosorbent dose. This is due to increase in the number of available binding sites. The uptake capacity of biomass increased with increase in the initial dye concentration. It suggests that the available sites on the biosorbent are the limiting factor for the dye removal. Optimum contact time for equilibrium to achieve was found to be 120 and 180 minutes for EBT and A-FGGL dyes. The amount of dye biosorbed increased rapidly with increase in contact time but there was no drastic increase in biosorption capacity with further increase in agitation time. It is due to the slow movement of dye molecules into the

interior of the bulk of the biosorbent after the saturation of exterior exchanging sites. Biosorption of dyes is best fitted to the Langmuir Isotherm and pseudo-second order kinetic models.


1. M. C. Ncibi B. Mahjoub A. M. Ben Hamissa R. Ben Mansour and M. Seffen Desalination 243 109 (2009).

2. G. Mishra and M. Tripathy Colourage 40 35 (1933).

3. T. Robinson T. B. Chandran and P. Nigam Water Resource 36 2824 (2002).

4. Y. Bulut N. Gozubenli and H. Aydin Journal of Hazardous Material 144 300 (2007).

5. G. Crini Bioresource Technology 97 1061 (2006).6. Z. Aksu Z and S. Tezer Journal of Process Biochemistry 40 1347 (2005).

7. H. N. Bhatti and Y. Safa Desalination and Water Treatment 48 267 (2012).

8. Y. Safa and H. N.Bhatti African Journal of Biotechnology 10 3128 (2011).

9. F. D. Ardejani K. Badii N. Y. Limaee S. Z. Shafaei and A. R. Mirhabibi Journal of Hazardous Material 151 730 (2008).

10. A. El-Nemr O. Abdelwahab A. El-Sikaily and A Khaled Journal of Hazardous Material 161 102 (2009).

11. F. Colak N. Atar and A. Olgum Journal of Chemical Engineering 150 120 (2009).

12. S. V. Mohan S. V. Ramanaiah and P. N. Sarma Journal of Chemical Engineering 38 61 (2008).

13. V. Dulman and S. M. Cucu-Man Journal of Hazardous Material 162 1457 (2009).

14. A. Khaled A. El-Nemr A. EI-Sikaily and O. Abdelwahab Journal of Hazardous Material 165 100 (2009).

15. R. Gong Y. Ding M. L. I. C. Yang H. Liu and Y. Sun Dyes Pigments 64 187 (2005).

16. M. Akhtar M. I. Bhanger S. Iqbal and S. M. Hasany Journal of Hazardous Material 128 44 (2006).

17. O. Tune H. Tanaei and Z. Aksu Journal of Hazardous Material 163 187 (2009).

18. K. Vijayaraghavan M. H. Han S. C. Choi and Y. S. Yun Chemosphere 68 1838 (2007).

19. R. Gourdon E. Rus S. Bhende and S. S. Sofer Journal of Environmental Science and Health 25 1019 (1990).

20. V. Vadivelan and K. V. Kumar Journal of Colloid and Interface Science 286 90 (2005).

21. A. A. Ahmad B. H. Hameed and N. Aziz Journal of Hazardous Material 141 70 (2007).22. T. Akar B. Anilan A. Gorgulu and S. T. Akar Journal of Hazardous Material 168 1302 (2009).

23. Z. Aksu A. I. Tatli and O.Tnc Journal of Chemical Engineering 142 23 (2008).

24. N. Cancer I. Kiran S. Ilhan and C.F. Iscen Journal of Hazardous Material 165 279 (2009).

25. G. Bayramoglu and M. Y. Arica Journal of Hazardous Material 143 135 (2007).

26. Z. Aksu and S. Tezer Journal of Process Biochemistry 36 431 (2000).27. T. Langmuir Journal of American Society for Chemistry 38 2221 (2000).]

28. H. M. F. Freundlich Journal of Physical Chemistry 57 385 (1906).

29. M. Dogan M. Alkan and Y. Onganer Water Ai Soil and Pollution 120 229 (2000).

30. O. Anjaneya M. Santoshkumar S. N. Anand and T. B. Karegoudar International Biodeterioration and Biodegradation 63 782 (2009).

31. S. Lagergren Handlingar 24 1 (1898).

32. Y. S. Ho G. McKay D. A. J. Wase and C. F. Foster Adsorption Science Technology 18 639 (2000).

33. Z Aksu and D. Donmez Chemosphere 50 1075 (2003).

34. Y. Bulut and H. Aydin Desalination 194 259 (2006).35. V. Ponnusami S. Vikram and S. N. Srivastavam Journal of Hazardous Material 152 276 (2008).

36. M. Ozacar and I. A. Sengil Journal of Hazardous Material 40 1 (2003).

37. B. Acemioglu. Journal of Colloid and Interface Science 274 371 (2004).

38. Q. H. Tao and H. X. Tang Journal of Environental Science China 24 3890 (2004).

39. P. Janos S. Coskun V. Pilarova and J. Rejnek Bioresour Technology 100 1450 (2009).

40. E. L. Grabowska and G. Gryglewicz Dyes and Pigments 74 34 (2007).

41. Z. Aksu S. Ertugrul and G. Donmez Journal of Hazardous Materials 168 310 (2009).

42. R. X. Liu X. M. Liu and H. X. Tang Journal of Colloidal and Interface Science 239 475 (2001).43. B. C. Oei S. Ibrahim S. Wang and H. M. Ang Bioresour.Technology 100 4292 (2009).

44. C. Kartal and H. Akbas Dyes Pigments 65 191 (2005).
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Date:Aug 31, 2014
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