Adsorption of Natural Aluminium Dye Complex from Silk-Dyeing Effluent Using Eucalyptus Wood Activated Carbon

Saowanee Chuyingsakuntip, Chaiyot Tangsathitkulchai

School of Chemical Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima, Thailand.

DOI: 10.4236/ajac.2013.48048                

Abstract

Two activated carbons with controlled pore size were prepared from Eucalyptus wood by physical activation with carbon dioxide, giving the BET surface area and pore volume of738 m²/g and0.39 cm³/g, and921 m²/g and0.53 cm³/g for the carbon sample AC1 and AC2, respectively. These activated carbons were then used to remove the residual dye left after the silk-dyeing process. The dye solution used for adsorption study was a cationic aluminium dye complex of [Al(brazilein)₂]⁺ derived from a mixture of alum and extract of the heartwood of Ceasalpinia sappan Linn., with initial dye concentration of 220 mg/l. Effects of adsorbent dosage, adsorption time and temperature in the range of 25℃40℃ on dye adsorption were investigated. It was found that the adsorption kinetics of this dye complex was best described by the pseudo-second order model. Adsorption isotherms of this dye complex were well fitted by Langmuir isotherm equation. The adsorption capacities for the uptake of this dye complex at 25℃, 30℃ and 40℃ were 718.7, 1240.4 and 1139.5 mg/g and 1010.5, 1586.1 and 1659.0 mg/g for carbon sample AC1 and AC2, respectively. From these results, it can be concluded that activated carbon containing a higher proportion of mesopores gave better dye removal efficiency, emphasizing the fact that a proper pore size distribution of carbon adsorbent is crucial for the effecttive removal of relatively large size of the dye molecules. Thermodynamic parameters, including free energy, enthalpy and entropy of adsorption, were also determined. The adsorption enthalpies for the removal of this dye complex of AC1 and AC2 were 105.3 and 55.6 kJ/mol, respectively, indicating that the adsorption is an endothermic process. It was found that the adsorption of this dye complex is spontaneous at the temperatures under investigation.

Keywords

Adsorption; Activated Carbon; Dyeing Effluent; Eucalyptus Wood

1. Introduction

The aqueous extract from the heartwood of Ceasalpinia. Sappan Linn. is traditionally used for the dyeing of silk by villagers in the northeast of Thailand. The extracted dye, which consists mainly of brazilein (see Figure 1(a)), imparts a beautiful red or pink color to the silk [1]. An alum mordant is generally added to the dye solution to form a cationic dye complex of [Al(brazilein)₂]⁺ (see Figure 1(b)) which helps improve the fastness property of dye onto silk. The effluent left from the silk dyeing exhibits high color and the discharge can cause a serious problem and concern to the environment. There are various methods available for treating dyeing effluents such as membrane separation [2], eletrochemical method [3], coagulation/flocculation [4], and biological processes [5-7] etc., with each method having its own limitation in terms of cost and effectiveness. Of these treatment processes, adsorption is an attractive separation process for removing a number of pollutant species from wastewater, due to its process simplicity, low energy operation and capability of adsorbent regeneration [8,9]. Among commercial adsorbents, activated carbon is most widely used for liquid-phase adsorption because of its many advantages such as low cost, large internal area (typically 1000 m²/g) and the required pore size distribution can be easily achieved by controlling the preparation conditions [10-12].

(a)(b)

Figure 1. Chemical structure of (a) Brazilein and (b) [Al(brazilein)₂]⁺ complex.

In this study, activated carbons prepared from eucalyptus wood by physical activation with carbon dioxide were used to remove residual cationic dye of [Al(brazilein)₂]⁺ from real silk-dyeing effluent. The effect of carbon porous structure on the kinetics, equilibrium, and thermodynamics of dye adsorption was investigated.

2. Materials and Methods

2.1. Activated Carbon Preparation and Characterization

Eucalyptus wood (Eucalyptus camaldulensis Dehn.) in the form of shaving was milled and sieved to obtain a size fraction of 20 × 30 mesh (0.714 mm average size). The wood sample was then dried in an oven at 110˚C for 24 h to remove excess moisture. Next, about 7 g of the dried sample was placed in a ceramic boat and carbonized in a tube furnace (Carbolite, UK) at 400˚C under the flow of N₂ (100 cm³/min) for 60 min. The derived char was further activated with carbon dioxide at a rate of 100 cm³/min in a stainless steel packed-bed reactor (2.5 cm I.D. and 10 cm long) inserted in a tube furnace. Two activation conditions, 800˚C for 60 min and 900˚C for 90 min, were employed to produce activated carbon with different porous structure and the resulting carbons were designated as AC1 and AC2, respectively.

The eucalyptus wood was characterized for proximate analysis and lignocellulosic compositions using the procedures outlined by Tangsathitkulchai et al. [13]. Specific surface area and pore volume of activated carbon were determined from nitrogen adsorption isotherms obtained at −196˚C provided by an automated adsorption apparatus (Micromeritics ASAP2010). Adsorption theories and models required for calculating porous properties of activated carbon from isotherm data are well documented by Rouquerol et al. [14].

2.2. Preparation of Dye-Complex Solution

The heartwood of Ceasalpinia sappan Linn. was collected from plantation areas in Nakhon Ratchasima province, Thailand. The wood was reduced into small sizes (~0.3 cm × 3 cm) and boiled in deionized water, using the ratio of 1 g wood per 100 ml water, for 2 h at 80˚C - 90˚C. The aqueous extract was filtered and dewatered by a rotary evaporator (R-210, Buchi), followed by drying in a vacuum freeze dryer (DW3 Drywinner, Hito) to give the extract in powder form.

Next, the alum-dye complex solution for silk dyeing was prepared by mixing the stock solution of dye powder (5 × 10^{−4 M, 100 mL) with alum [KAl(SO}₄) 12.H₂O] (5 × 10^{−4 M, 200 mL), giving alum-to-dye mole ratio of 2:1. The dye complex formed is present in the dye bath as a cationic complex, [Al(brazilein)}₂]⁺ or [Al(C₁₆H₁₄O₅)₂]⁺, which has a molar mass of 599 g/mol [1]. The existence of this aluminium dye complex in the dye solution was ascertained by the application of electrospray ionization mass spectrometry (ESI-MS); the details of measurement and results can be found elsewhere [15]. The dyeing was performed by mixing 5 g of silk yarn with 50 mL of the prepared dye-complex solution and shaken in a water-bath shaker at room temperature for 2 h. The dye solution left after the dyeing process was further diluted with water to obtain the dye solution with initial concentration of 220 mg of dye/L solution and was used for the subsequent adsorption experiments.

2.3. Adsorption Experiments

Tests were carried out to obtain adsorption isotherms of the dye complex by AC1 and AC2 as follows. For each run, 25 mL of dye solution (220 mg/L) was mixed with a fixed amount of activated carbon and shaken at a set temperature (25˚C, 30˚C and 40˚C) in a thermostat shaking bath until the equilibrium was reached (~72 h). The amount of carbon used was varied from 0.005 - 0.025 g. The equilibrium concentration of dye in the solution was determined from a calibration curve constructed based on the measured absorbance of standard dye solutions, using a UV-visible spectrophotometer (model 8453, Agilent) run at the wavelength (λ_max) of 509 nm. The amount of dye adsorbed can be calculated from the following equation.

(1)

where q_e is the amount of dye adsorbed at equilibrium (mg/g carbon), C_o and C_e are the dye concentration (mg/L) at time t = 0 and at equilibrium, respectively, V is the solution volume (L) and W is the amount of carbon used (g). Experiments were also performed to study the effect of time (adsorption kinetics), carbon dosage, and temperature on the adsorption of this Al-dye complex from aqueous solution. Since the primary purpose of this work was to study the effect of pore texture of activated carbon on dye adsorption but not the effect of surface chemistry, no attempt was made at this stage to investigate the influence of solution pH on the dye removal. Therefore, dye solution with the initial natural pH of 4.0 was used throughout the adsorption experiments.

3. Results and Discussion

3.1. Material Characterization

Table 1 shows the proximate analysis and lignocellulosic composition of eucalyptus wood studied in this work. The results indicate that eucalyptus wood contains a high proportion of volatile matters but with relatively low ash content. The fixed carbon content is comparable to other biomass materials used for the production of activated carbon, for example, corn cob (16.1%) [16], coconut shell (18.6%) [17], and pistachio nut shell (21.6%) [18]. Eucalyptus wood studied in the present work is classified as hard wood type, based on the following range of lignocellulosic contents for hard wood: cellulose (57% - 62%), hemicellulose (12% - 16%) and lignin (25%) [19].

The porous properties of prepared activated carbons are listed in Table 2. It is observed that sample AC2 has

Table 1. Chemical analysis of eucalyptus wood.

Table 2. The porous properties of activated carbon.

larger average pore size, higher surface area and pore volume and contains greater mesopore volume than those of sample AC1. Figure 2 shows the nitrogen adsorption isotherms of the two carbons used for the pore characterization. As seen, the isotherm of sample AC1 shows Type I isotherm, typical of microporous adsorbent, while AC2 displays Type II isotherm with small hysteresis loop which is indicative of a mesoporous adsorbent. It has been reported that the pore structure of activated carbon plays a significant role in determining its adsorbed capacity and the transport of adsorbate molecules within the pores can be strongly limited by the steric effect due to the molecular size and shape of adsorbate relative to the pore size [20].

Figure 3 shows SEM images of carbon samples AC1 and AC2. Visually, sample AC2 possesses larger pore size as compared with AC1, in accord with the pore texture results reported in Table 2.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	K. Wongsooksin, S. Rattanaphani, M. Tangsathtikulchai, V. Rattanaphani and J. Bremner, “Study of an Al(III) Complex with the Plant Dye Brazilein from Ceasalpinia sappan Linn.,” Suranaree Journal of Science and Technology, Vol. 15, No. 2, 2008, pp. 159-165.
[2]	G. Ciardelli, L. Corsi and M. Marcucci, “Membrane Separation for Wastewater Reuse in the Textile Industry,” Resources, Conservation and Recycling, Vol. 31, No. 2, 2001, pp. 189-197. doi:10.1016/S0921-3449(00)00079-3
[3]	G. R. P. Malpass, D. W. Miwa, S. A. S. Machado and A. J. Motheo, “Decolourisation of Real Textile Waste using Electrochemical Techniques: Effect of Electrode Composition,” Journal of Hazardous Materials, Vol. 156, No. 1-3, 2008, pp. 170-177. doi:10.1016/j.jhazmat.2007.12.017
[4]	A. Alinsafi, M. Khemis, M. N. Pons, J. P. Leclerc, A. Yaacoubi, A. Benhammou and A. Nejmeddine, “Electro-Coagulation of Reactive Textile Dyes and Textile Wastewater,” Chemical Engineering and Processing: Process Intensification, Vol. 44, No. 4, 2005, pp. 461-470. doi:10.1016/j.cep.2004.06.010
[5]	K. Kumari and T. E. Abraham, “Biosorption of Anionic Textile Dyes by Nonviable Biomass of Fungi and Yeast,” Bioresource Technology, Vol. 98, No. 9, 2007, pp. 1704-1710. doi:10.1016/j.biortech.2006.07.030
[6]	T. Akar, A. S. Ozcan, S. Tunali and A.Ozcan, “Biosorption of a Textile Dye (Acid Blue 40) by Cone Biomass of Thuja orientalis: Estimation of Equilibrium, Thermodynamic and Kinetic Parameters,” Bioresource Technology, Vol. 99, No. 8, 2008, pp. 3057-3065. doi:10.1016/j.biortech.2007.06.029
[7]	A. R. Khataee, F. Vafaei and M. Jannatkhah, “Biosorption of Three Textile Dyes from Contaminated Water by Filamentous Green Algal Spirogyra sp.: Kinetic, Isotherm and Thermodynamic Studies,” International Biodeterioration & Biodegradation, Vol. 83, 2013, pp. 33-40. doi:10.1016/j.ibiod.2013.04.004
[8]	P. S. Kumar, S. Ramalingam, C. Senthamarai, M. Niranjanaa, P. Vijayalakshmi and S. Sivanesan, “Adsorption of Dye from Aqueous Solution by Cashew Nut Shell: Studies on Equilibrium Isotherm, Kinetics and Thermodynamics of Interactions,” Desalination, Vol. 261, No. 1-2, 2010, pp. 52-60. doi:10.1016/j.desal.2010.05.032
[9]	N. M. Mahmoodi, B. Hayati, M. Arami and C. Lan, “Adsorption of Textile Dyes on Pine Cone from Colored Wastewater: Kinetic, Equilibrium and Thermodynamic Studies,” Desalination, Vol. 268, No. 1-3, 2011, pp. 117-125. doi:10.1016/j.desal.2010.10.007
[10]	C. Pelekani and V. L. Snoeyink, “Competitive Adsorption between Atrazine and Methylene Blue on Activated Carbon: The Importance of Pore Size Distribution,” Carbon, Vol. 38, No. 10, 2000, pp. 1423-1436. doi:10.1016/S0008-6223(99)00261-4
[11]	Y. Guo, S. Yang, W. Fu, J. Qi, R. Li, Z. Wang and H. Xu, “Adsorption of Malachite Green on Micro- and Mesoporous Rice Husk-based Active Carbon,” Dyes and Pigments, Vol. 56, No. 3, 2003, pp. 219-229. doi:10.1016/S0143-7208(02)00160-2
[12]	R. L. Tseng and S. K. Tseng, “Pore Structure and Adsorption Performance of the KOH-Activated Carbons Prepared from Corncob,” Journal of Colloid and Interface Science, Vol. 287, No. 2, 2005, pp. 428-437. doi:10.1016/j.jcis.2005.02.033
[13]	C. Tangsathitkulchai, Y. Ngernyen and M. Tangsathitkulchai, “Surface Modification and Adsorption of Eucalyptus Wood-based Activated Carbon: Effects of Oxidation Treatment, Carbon Porous Structure and Activation Method,” Korean Journal of Chemical Engineering, Vol. 26, No. 5, 2009, pp. 1341-1352. doi:10.1007/s11814-009-0197-4
[14]	F. Rouquerol, J. Rouquerol and K. Sing, “Adsorption by Powders and Porous Solids: Principles, Methodology and Applications,” Academic Press, San Diego, 1999.
[15]	K. Wongsooksin, “Adsorption of Homoisoflavonoid and Extracted Dye from Heartwood of Ceasalpinia sappan Linn. On Silk Fibers and Treatment of Dye Effluent by Activated Carbons,” Ph.D. Thesis, Suranaree University of Technology, 2008.
[16]	C. F. Chang, C. Y. Chang and W. T. Tsai, “Effects of Burn-Off and Activation Temperature on Preparation of Activated Carbon from Corn Cob Agrowaste by CO2 and Steam,” Journal of Colloid and Interface Science, Vol. 232, No. 1, 2000, pp. 45-49. doi:10.1006/jcis.2000.7171
[17]	W. M. A. W. Daud and W. S. W. Ali, “Comparison on Pore Development of Activated Carbon Produced from Palm Shell and Coconut Shell,” Bioresource Technology, Vol. 93, No. 1, 2004, pp. 63-69. doi:10.1016/j.biortech.2003.09.015
[18]	T. Yang and A. C. Lua, “Characteristics of Activated Carbons Prepared from Pistachio-Nut Shells by Physical Activation,” Journal of Colloid and Interface Science, Vol. 267, No. 2, 2003, pp. 408-417. doi:10.1016/S0021-9797(03)00689-1
[19]	J. Colman, “Acacia-Wattle,” 2001. http://www.janinesgarden.com/plants/A/acacia.html
[20]	M. Valix, W. H. Cheung and G. McKay, “Preparation of Activated Carbon using Low Temperature Carbonisation and Physical Activation of High Ash Raw Bagasse for Acid Dye Adsorption,” Chemosphere, Vol. 56, No. 5, 2004, pp. 493-501. doi:10.1016/j.chemosphere.2004.04.004
[21]	D. Suteu and T. Malutan, “Industrial Cellolignin Wastes as Adsorbent for Removal of Methylene Blue Dye from Aqueous Solutions,” BioResources, Vol. 8, No. 1, 2013, pp. 427-446.
[22]	Y. S. Ho and G. McKay, “Kinetic Models for the Sorption of Dye from Aqueous Solution by Wood,” Process Safety and Environmental Protection, Vol. 76, No. 2, 1998, pp. 183-191. doi:10.1205/095758298529326
[23]	Y. S. Ho and G. McKay, “Pseudo-Second Order Model for Sorption Processes,” Process Biochemistry, Vol. 34, No. 5, 1999, pp. 451-465. doi:10.1016/S0032-9592(98)00112-5
[24]	D. D. Do, “Analysis of Adsorption Kinetics in a Single Homogeneous Particle,” In: D. D. Do, Ed., Adsorption Analysis: Equilibria and Kinetics, Imperial College Press, 1998, pp. 521-545.
[25]	M. Tangsathitkulchai, C. Tangsathitkulchai, K. Wongsooksin and S. Chuyingsakuntip, “Removal of Residual Aluminium-Dye Complex and Aluminium Ion from Spent Natural-Dye Solution Using Activated Carbons,” Engineering Journal, Vol. 16, No. 5, 2012, pp. 29-44. doi:10.4186/ej.2012.16.5.29
[26]	I. Langmuir, “Adsorption of Gases on Plain Surfaces of Glass Mica Platinum,” Journal of American Chemical Society, Vol. 40, No. 9, 1918, pp. 1361-1403. doi:10.1021/ja02242a004
[27]	H. Freundlich, “Adsorption Solution,” Zeitschrift für Physikalische Chemie, Vol. 57, 1906, pp. 384-470.
[28]	M. F. R. Pereira, S. F. Soares, J. J. M. Orfao and J. L. Figueiredo, “Adsorption of Dyes on Activated Carbons: Influence of Surface Chemical Groups,” Carbon, Vol. 41, No. 4, 2003 pp. 811-821. doi:10.1016/S0008-6223(02)00406-2
[29]	A. A. Attia, W. E. Rashwan and S. A. Khedr, “Capacity of Activated Carbon in the Removal of Acid Dyes Subsequent to Its Thermal Treatment,” Dyes and Pigments, Vol. 69, No. 3, 2006, pp. 128-136. doi:10.1016/j.dyepig.2004.07.009
[30]	K. Li, Z. Zheng, X. Huang, G. Zhao, J. Feng and J. Zhang, “Equilibrium, Kinetic and Thermodynamic Studies on the Adsorption of 2-Nitroaniline onto Activated Carbon Prepared from Cotton Stalk Fibre,” Journal of Hazardous Materials, Vol. 166, No. 1, 2009, pp. 213-220. doi:10.1016/j.jhazmat.2008.11.007