tan lean seey

Tan Lean Seey and Mohd Jain Noordin Mohd Kassim, 2012. Characterization of Mangrove Bark Adsorbent and Its

Application in the Removal of Textile Dyes from Aqueous Solutions.

Journal of Applied Phytotechnology in Environmental Sanitation, 1 (3): 121-130.

121

Research Paper

CHARACTERIZATION OF MANGROVE BARK ADSORBENT AND ITS

APPLICATION IN THE REMOVAL OF TEXTILE DYES FROM AQUEOUS SOLUTIONS

TAN LEAN SEEY* and MOHD JAIN NOORDIN MOHD KASSIM

Material Chemistry and Corrosion Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, 11800, Pulau Pinang Malaysia.

*Corresponding Author: Phone: +6012-428 5432; Fax: +604-658 9666; E-mail: [email protected]

Received: 28th February 2012; Revised: 2nd April 2011; Accepted: 13th

April 2012

Abstract: Mangrove bark, a natural, low-cost agricultural waste in Malaysia has been studied for its potential application as an adsorbent in its modified form. Adsorbent was prepared by pre-treating the mangrove bark with formaldehyde. The adsorbent was characterized before applied as an adsorbent to adsorb textile dyes. In this study, the removal of a reactive (Reactive Black 5) and a basic (Malachite Green) dye from aqueous solutions were investigated. Batch experiments were carried out in this study to investigate the feasibility of using mangrove bark for dye removal from aqueous solutions under different process conditions. It was found that the extent of dye adsorption by treated mangrove bark increased with initial dye concentration, contact time, and pH of the system. Keywords: Adsorption, characterization, mangrove bark, reactive dye, basic dye

INTRODUCTION

Textile dyeing is a major industry in Malaysia and consumes large quantity of water and

produces large volumes of wastewater from different steps in the dyeing and finishing processes [1]. The total dye consumption of the textile industry worldwide is more than 107 kg every year, and it is estimated that 10–15% of the dye is lost during the dyeing process and released with the effluent [2]. Considering both volume and composition, effluent from the textile industry was declared as one of the major sources of wastewater in ASEAN countries [3]. Dyes can be classified as: anionic (direct, acid and reactive dyes), cationic (basic dyes) and non-ionic (dispersive dyes) [4]. Water pollution by dyes is a world-wide problem, particularly in the textile

ISSN 2088-6586

V o l u m e 1 , N u m b e r 3 : 1 2 1 - 1 3 0 , A p r i l , 2 0 1 2 © T2012 Department of Environmental Engineering S e p u l u h N o p e m b e r I n s t i t u t e o f T e c h n o l o g y , S u r a b a y a & Indonesian Society of Sanitary and Environmental Engineers, Jakarta O p e n A c c e s s h t t p : / / w w w . t r i s a n i t a . o r g / j a p e s

This work is licensed under the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

International peer-reviewed journal




122

industry. They are aesthetically and environmentally unacceptable due to the strong persistent colour and high BOD (biochemical oxygen demand) loading [5]. Most of these dye wastes are toxic and may be carcinogenic. The formation of carcinogenic aromatic amine o-tolidine from the dye Direct Blue 14 by skin bacteria has been established [6]. Adsorption is a mass transfer process by which a substance is transferred from the liquid phase to the surface of a solid, and becomes bound by physical and/or chemical interactions. Many efforts, however, have been made to investigate the use of various low cot organic adsorbents.

Mangrove trees also called “Kayu Tangar” in Malay. Rhizophora species are medicinal plants of eastern and southeast Asia. The most common representatives are Rhizophora mucronata, Rhizophora mangle and Rhizophora apiculata. The mangrove timbers are used for the production of charcoal, firewood and woodchips. Choice of mangrove barks is justified by the large availability of this material, as charcoal industry waste. The raw material is harmless, cheaper, and plentiful. This industrial residue simply thrown away on landscapes and has not been found any high value application. The use of agriculture waste as an adsorbent for dyes has a double purposes. MATERIALS AND METHODS Preparation of Adsorbent (TBB)

The mangrove barks were obtained from the charcoal factory as waste products in Kuala Sepetang, Perak, Malaysia. The collected barks were extensively washed with distilled water to remove adhering dirt and soluble impurities and air-dried to near-equilibrium humidity. Air dried bark was crushed to small pieces and ground in a mortar to a fine powder. After grinding, the bark powder was sieved using U.S.A Standard Testing Sieve A.S.T.M. E-11 No. 60 of 250 microns. The ground powder of mangrove bark was treated with 37 % formaldehyde in the ratio of 2:5 (bark: formaldehyde, w/v) at room temperature for 24 hours. Formaldehyde act as a cross linking agent to immobilize the water soluble substances of bark. The mixture was filtered and repeatedly washed with distilled water to remove free formaldehyde. The residue obtained was kept in hot air oven at 50 ◦

C for drying. The resulting material was sieved and stored in air tight container for further use. TBB was analysed by the FTIR spectrometer with a universal ATR sampling accessory with MIR detector from Perkin Elmer to determine functional groups. The surface morphological structure of TBB was analyzed by Leo Supra 50VP Field Emission Scanning Electron Microscope. The Brunauer- Emmett- Teller (BET) method as applied for the determination of the surface area of TBB.

Adsorbate The specifications of selected dyes were illustrated in Table 1. These dyes were purchased

from Merck Chemicals and were used as commercial salts without purification. Stock solution of 1000 mg/L of dye was prepared by dissolving an accurately weighed amount (1000 mg) of dye in a liter of distilled water. Experimental solutions of desired concentration were prepared by successive dilutions of stock solutions. The pH of the solutions was adjusted by addition of either 0.1 mol/L HCl or 0.1 mol/L NaOH solutions respectively. The supernatants at fixed time intervals were analysed for residual dye concentration using UV/Visible spectrophotometer with 1 cm path length quartz cell at λmax of selected dyes. Calibration curve was plotted between adsorbance and concentration of the dye solution to obtain absorbance-concentration profile. All the experiments are triplicate. Only the mean values are reported in this paper. The maximum deviation observed is less than 5 %.




123

Table 1: Specification of two selected dyes for this research.

Dye

chemical structure

Colour Index No.

Empirical formula

Formula Weight, (g/mol)

UV wavelength

(lambda max), nm

Malachite green

42000 C23H25N2 365 Cl 616

Reactive Black 5

20505 C26H21N5Na

4O19S 991.82 6 597

RESULTS AND DISCUSSION Fourier Transform Infrared (FTIR) analysis

FTIR analysis was carried out in order to identify the functional groups that might be involved in the binding of dye ions. The infrared adsorption spectrums of raw and chemically modified bark are shown in Figure 1. There are few peaks in the infrared absorption spectrum might be explained by the functional groups of the bark are shown in Table 2. . The cell walls of the barks consist mainly of cellulose and lignin. Numerous hydroxyl groups in the molecules of these compounds represent main active sites for binding of ionic compounds, usually by an ion-exchange mechanism. However, some other binding mechanisms may occur on the bark sorbents, such as hydrogen bonding or hydrophobic interactions on the non-polar moieties of the bark matrix. It was also found that the spectrum of treated bark does not differ significantly from the spectrum of the ‘‘parent” (untreated) material, suggesting that the treatment procedures did not change substantially the bark structure.




124

Fig.1: FTIR spectrum of raw bark and TBB Table 2: Assignment of the IR bands of functional groups

Band position (cm-1 Functional group ) 3450-3400 O-H alcohol 2930-2890 C-H methyl and methylene groups 1740-1730 C=O carbonyls 1640-1618 C=C alkene 1527-1500 C=C aromatic 1462-1425 CH2 1384-1346

cellulose, lignin C-H cellulose, hemicellulose

1264-1109 O-H phenolic 910-740 C-H phenolic

Surface area, total pore volume and pore size distribution

Physical characteristics of the raw bark and bark adsorbent, including specific surface area, pore volume distribution, and pore diameter, were measured via N2 (g) adsorption in an ASAP 2010 micropore analyzer at 77 K in liquid N2

Table 3 shows the physical characteristics of raw bark and TBB. Results suggest that the mesopore-dominant TBB is suitable for dye adsorption. Modification caused specific surface area to decrease and the average pore diameter of the adsorbent to increase [8]. It is generally held that one should use the adsorbent with the highest surface area for adsorption. However, Abraham [9] has pointed out the danger in relying upon high surface area (as measured by BET) in comparing phenol-formaldehyde resins with inorganic or charcoal adsorbents. From his founding, a resin with a surface of only 1.4 m

. Porosity is one of the factors which influence the chemical reactivity of solids and the physical interaction of adsorbents with dyes. Since adsorption occurs on the surface of the adsorbent, the total surface area is an important parameter. Surface area was calculated by the BET method [7].

2

4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 400.010.0

15

20

25

30

35

40

45

50

55

60.0

cm-1

%T

BARK

TBB

3421 1619

15271447

13181060

780 649 516

29291367

1158

1110

8783426

1618

1449

1317

1112

781 660 515

29181524 1379

1158

1054

883

/g had the highest relative adsorption. It is because




125

the resin swells in water to form an open-lattice which readily allows diffusion of the organic impurities from the water into the particle for adsorption. Table 3: Physical characteristics of raw bark and TBB adsorbent

Properties Raw Bark TBB BET surface area (m2g-1 121.489 ) 48.307 Micropore area (m2g-1 0.000 ) 0.000 Mesopore area (external surface area) (m2g-1 121.489 ) 48.307 Total pore volume, Vtot (cm3 g-1 1.110 x 10) 5.255 x 10-1 Total micropore volume, V

-2 mic (cm3 g-1 0.000 ) 0.000

Total mesopore volume, Vmeso (cm3 g-1 1.110 x 10) 5.255 x 10-1 Average pore diameter, Å

-2 36.56 43.52

Thermogravimetric Analysis (TGA)

Proximate analysis was carried out by a thermogravimetric analyser (TA-50, Shimadzu). The decomposition profiles of TBB under oxygen atmosphere up to 850°C are shown in Fig. 2. Bark is a complex material and its decomposition products contain numerous compounds At temperatures above 100 ºC, chemical bonds begin to break. The rate at which the bonds are broken increases as the temperature increases. The weight loss from room temperature to 130 oC corresponds to release of water vapour. Upon rapid heating, the carbohydrates (cellulose and hemicellulose) break down to provide low molecular weight volatile products. The main DTG peak is dominated by the decomposition of cellulose, while the shoulder at lower temperature (around 300 oC) can be attributed mainly to hemicellulose decomposition. The lignin decomposes at a lower rate in a wide temperature range (200–600 oC) [10]. The lignin is charred to a carbonaceous residue. Lignin is the least reactive component of biomass; higher temperatures are necessary for the pyrolysis of most lignin. Pyrolysis of lignin yields phenols from cleavage of ether and carbon–carbon linkages. The weight loss executed between 630 and 900 o

C can be attributed to the carbonate decomposition [11].

Fig. 2: TGA and DTG curves of TBB

Step -10.4195 % -1.1045 mgResidue 30.9674 % 3.2825 mgLeft Limit 630.49 °CRight Limit 894.16 °C





%

30

40

50

60

70

80

90

100

min

°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850

0 5 10 15 20 25 30 35 40

1/min

-0.06

-0.05

-0.04

-0.03

-0.02

-0.01

0.00

TBB 11.08.2011 08:43:20

STARe SW 9.20Lab: METTLER




126

Effect of initial pH Adsorption responses of MG and RB at various pHs is shown in Fig. 3. pH value of the

solution will determine the surface charge of the adsorbent which will affect the interaction between the adsorbate and adsorbent. The pHzpc is a point at which the surface functional groups no longer contribute to the pH value of the solution. The pHzpc value of TBB was found to be around 4.5. It can be concluded that chemical modification with formaldehyde yielded acidic surface since pH values of point of zero charge for TBB is at a lower pH range. Cations adsorption will be favourable at pH value higher than pHPZC, and anions adsorption at pH values lower than pHZPC. The OH-

The increase in MG removal as the pH increases can be explained on the basis of a decrease in competition between protons (H

group on the bark is chiefly responsible for dyes adsorption.

+) and positively charged MG ions at the surface sites and by a decrease in positive charge, which results in a lower repulsion of the adsorbing MG ions. At lower pH a possible protonation of OH- occurs, precluding the electrostatic attraction with the MG dye, decreasing the adsorbate uptake. The optimum pH for the removal of MG for both adsorbents was pH 8. This can explained with the percentage dye removal remained almost constant from pH 8 to 10. Similar results were reported in the literature [12]. The adsorption of RB 5 on TBB shows that the best adsorption may be obtained at acidic pH as the affinity of anionic dye to treated bark decreased with increasing pH. At very low pH, the surface of TBB becomes positively charges enhanced the interaction of H+

ions with the dye anion causing increase in the amount of dye adsorbed. Hence, the adsorption is favored at low pH. A significantly high electrostatic attraction exists between the positively charged surfaces of the adsorbent, due to the ionization of functional groups of adsorbent and negatively charged anionic dyes. As the pH of the system increases, the numbers of negatively charged sites are increased. A negatively charged site on the adsorbent does not favor the adsorption of anionic dyes due to the electrostatic repulsion.

Fig. 3: Effect of pH on the percentage removal (initial concentration of solution = 100 mgL-1

, contact time = 360 min, agitation speed = 150 rpm)

0 10 20 30 40 50 60 70 80 90

100

0 2 4 6 8 10 12

Perce

ntage

remo

val (%

)

pH

MG RB




127

Effect of adsorbent dosage Figure 4 shows the plots of percentage dye removal against the adsorbent dosage. As seen

that the percentage of dye removal is increased with increase in adsorbent dosage of TBB. According to [13], the increase in the percentage removal of dye with an increase in adsorbent dosage can be attributed to the increase of surface area and the availability of more adsorption sites. A similar observation was previously reported for removal of malachite green dye from aqueous solution by bagasse fly ash and activated carbon.

Fig.4. Effect of adsorbent dosage on percentage removal (initial concentration of solution = 100 mgL-1

, contact time = 240 min, agitation speed = 150 rpm)

Effect of contact time and initial concentration Figure 5 shows the effect of contact time with 50 mg/L and 100 mg/L dye concentration

for the removal of dyes by TBB at room temperature. The period of contact time required for attaining equilibrium may be a result of diffusion processes of the dye into the pores structure of the adsorbent. The plots are smooth and continuous suggesting the possible monolayer adsorption of dye on the surface of adsorbents. The effect of contact time on the removal of MGand RB 5 by the TBB showed rapid adsorption of dye in the first 30 min. Such short times coupled with high removals indicate a high degree of affinity for the dye groups pointing towards chemisorption. During the initial stage of adsorption process occurred, a large number of vacant adsorption sites is available on the adsorbent surface. However, after a lapse of time the available adsorption sites is reduced and the occupied adsorption sites become saturated. At higher concentration, lower adsorption yields were observed because of the saturation of the adsorption sites.

0

20

40

60

80

100

120

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

perce

ntage

remo

val (%

)

adsorbent mass (g)

MG RB




128

Fig.5. Effect of initial concentration and contact time on percentage removal Proposed sorption mechanisms

There are two possible mechanisms for the effect of pH on adsorption of dyes on any adsorbent: (a) electrostatic interaction between the protonated or deprotonated groups of adsorbents with dyes, and (b) the chemical reaction between the adsorbate and the adsorbent [14]. The bark consists mainly of cellulose and lignin. Numerous hydroxyl groups in the molecules of these compounds represent main active sites for binding of ionic compounds [15].

For anionic dyes (RB 5), main mechanism is surface association between the acidic phenolic hydroxyl (+OH2At low pH, we have

) groups in adsobents and the dye anion.

Sur–OH + H3O+→Sur–OH2 ++ H2where Sur denotes the surface of adsorbent. The association of positively charged surface of adsorbent and anionic dye may be expressed as

O (1)

Sur–OH2++ Dye−→Sur–OH2+ Dye−

As the pH increases, the positive charge on adsorbent is decreased and the anionic dye must be in competition with the hydroxyl groups (OH

(2)

−

At high pH, we have

). Thus, a significant decrease in dye adsorption occurs at higher pH.

Sur–OH+ HO−→Sur–O−+ H2The repulsion between the negatively charged surface of adsorbent and anionic dye may be expressed as

O (3)

Sur–O−+ Dye−→Sur–O−/Dye−

For cationic dye (MG) adsorption on TBB, the hydroxyl groups are protonated in acidic pH values which render the sorbent positively charged. Due to the positively charge of the basic dye, strong coulombic repulsions are developed between them. However, bark still adsorbs cationic dye molecules at pH 2–5, but in lower percentages. This fact occurs through a combination of other

(4)

0

20

40

60

80

100

120

0 100 200 300 400

perce

ntage

remo

val (%

)

contact time, t (min)

MG-50 mg/L RB-50 mg/L MG-100 mg/L RB-100 mg/L




129

interactions, as Van der Waals forces and hydrogen bonding. The repulsion between the positively charged surface of adsorbent and cationic dye may be expressed as

Sur–OH

2+Dye+→ Sur–OH2+/Dye+

Increasing the pH of the solution the repulsive forces weaken since the hydroxyl groups of sorbent are deprotonated. Bark becomes strongly anionic with increasing the pH of solution, deprotonation of bark is realized and strong attractive forces, between the positive charged dye and negatively charged bark, result in high uptakes as follows:

(5)

Sur-O− + Dye+ → Sur-O−Dye+

The uptake of RB 5, as a kind of vinyl sulfone, decreased with increasing the pH and reached a minimum at pH 7. At pH > 7, the uptake of RB 5 increase slightly. The trend was similarly mentioned by Sung and Min [16]. RB 5 has a sulphatoethylsulfone as a reactive group, which can be hydrolyzed during the dyeing process. Especially, under strongly alkaline conditions, this undesired reaction may be expedited. The sulphatoethylsulfone group of RB 5 can be converted into an activated vinyl sulfone group, or even completely hydrolyzed, under alkaline condition [16]. Therefore, the observed RB 5 adsorption onto the protonated TBB under strong alkaline conditions can be explained due to the hydroxyl group of the adsorbent reacting with the vinyl sulfone group of RB 5.

(6)

CONCLUSIONS

The study presented revealed that mangrove bark could be effectively used to remove MG, SY, DR 23, and RB 5 dye from an aqueous solution. The utilization of mangrove bark for the production of adsorbent can provide an excellent disposal option for charcoal; industry and at the same time would provide a cheap and valuable adsorbent. The effect of initial pH, kinetic and isotherm parameters demonstrated that the selected dyes were probably adsorbed onto bark mainly by chemical adsorption. It was found that the adsorption process by mangrove bark adsorbent could be well described by the Langmuir isotherm. Furthermore, a pseudo-second order kinetics showed to be well-suited with the rate of sorption. Moreover, the rate of dye removal from the aqueous solutions is sensitive to the initial concentration of dye in solution phase. References 1. Hameed, B.H., 2009. Spent tea leaves: A new non-conventional and low-cost adsorbent for removal

of basic dye from aqueous solutions. Journal of Hazardous Materials, 161, 753–759. 2. Tan, L. S., Jain, K., Rozaini, C.A., 2010. Adsorption of textile dye from aqueous solution on pretreated

mangrove bark, an agricultural waste: equilibrium and kinetic studies. Journal of applied sciences in environmental sanitation, 5, 283-294.

3. Vaidya, A.A., and Datye, K.V., 1982. Environmental pollution during chemical processing of synthetic fibers. Colourate, 14, 3-10.

4. Zollinger, H., 1987. Syntheses, properties and applications of organic dyes and pigments. New York: Colour chemistry: VCH Publishers.

5. Gupta, V. K., Ali, I., Saini, V. K., Gerven, T. V., Bart, V. D. B., Carlo, V., 2005. Removal of dyes from wastewater using bottom ash. Ind. Eng. Chem. Res., 44, 3655-3664.

6. Platzek, T., Lang, C., Grohmann, G., Gi, U-S, Baltes, 1999. W. Hum. Exp. Toxicol., 18, 552-559. 7. Gregg, S.J. and Sing, K.S.W.,1982. Adsorption, Surface Area and Porosity, p. 303 Academic Press,

London.




130

8. Gaballah, I., Kilbertus, G., 1998. Recovery of heavy metals ions through decontamination of synthetics solutions and industrial effluents using modified barks. J. Geochem. Explor. 62, 241–286.

9. Abraham, E.P., Newton, G.G.F., Hale, C.W., 1965. U.S. Patent No. 3,184,454. 10. Mészáros, E. Jakab, G. Várhegyi, P. Szepesváry, B. Marosvölgyi, 2004. Comparative study of the

thermal behavior of wood and bark of young shoots obtained from an energy plantation, Journal of Analytical and Applied Pyrolysis, Volume 72, Issue 2, Pages 317-328.

11. Ayari,F., Srasra,E., Trabelsi-Ayadi,M., 2005. Characterization of bentonitic clays and their use as adsorbent, Desalination, Volume 185, Issues 1-3, 1, Pages 391-397.

12. Low, K.S., Lee, C.K., Tan, B.F., 2000. Quarternized wood as sorbent for reactive dyes. Appl. Biochem. Biotech. 87, 233–245.

13. Van der Zee,E. P., Villaverde,S.,2005. Combined anaerobic-aerobic treatment of azo dyes—a short review of bioreactor studies, Water Res. 39, 1425–1440.

14. Namasivayam C, Kavitha D., 2002. Removal of Congo red from water by adsorption onto activated carbon prepared from coir pith, J. Dyes Pigments, 54: 47-58.

15. Shukla A, Zhang Y.H, Dubey P,2002 Margrave JL. The role of sawdust in the removal of unwanted materials from water, J. Hazard. Mater, B95:137–152

16. Son, Y.-A., Hong, J.-P., Lim, H.-T., Kim, T.-K., 2005. A study of heterobifunctional reactive dyes on nylon fibers: dyeing properties, dye moiety analysis and wash fastness. Dyes Pigments 66 (3), 231–239

tan lean seey

Documents