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外文翻译(英文)蓝色膨润土经微波和酸处理后作为吸附剂从模拟染料废水吸附甲基蓝

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Bull Eng Geol Env (2007) 66: 53–58 DOI 10.1007/s10064-006-0054-1

ORIGINAL PAPER

F. S. S. S.

Banat Al-Asheh Al-Anbar Al-Refaie

Microwave- and acid-treated bentonite as adsorbents of methylene blue from a simulated dye wastewater

Received: 9 February 2006 Accepted: 28 April 2006 Published online: 10 June 2006 ? Springer-Verlag 2006

Abstract Batch adsorption tests for removal of methylene blue dye (MBD) from aqueous solutions onto bentonite was investigated using natural chemically treated (sulphuric acid) and physically treated (microwaved) bentonite. In batch sorption tests for MBD removal by the developed sorbents, the time needed to reach equilibrium was less than 30 min. The uptake of MBD by the microwave-treated bentonite was the highest, followed by the acid-treated and ?nally the untreated bentonite. The uptake of MBD increased with an increase in the dye concentration or the solution temperature. Three kinetic models were used for elucidation of the probable mechanisms of MBD uptake by the three sorbents. The rates of MBD uptake followed the pseudo second-order model with a high correlation. Intraparticle di?usion was involved in the sorption process but was not the rate-controlling factor. The Freundlich and Langmuir isotherm models were employed and well represented the experimental data. Keywords Bentonite ? Adsorption ? MBD ? Microwave ? Natural ? Kinetics ? Isotherm ? ? Resume Des tests d’adsorption en ? ? ` serie, destines a enlever des colora? ` tions au bleu de methylene (MBD)

F. Banat ? S. Al-Anbar ? S. Al-Refaie Department of Chemical Engineering, Jordan University of Science and Technology, Irbid 22110, Jordan S. Al-Asheh (&) Department of Chemical Engineering, University of Qatar, Doha, Qatar E-mail: alasheh@qu.edu.qa

` de solutions aqueuses, a l’aide de ? ? ? ? bentonite, ont ete realises. La ben? ? ? tonite utilisee etait naturelle, traitee ` chimiquement a l’acide sulfurique ? ou traitee physiquement par microondes. Dans les tests d’adsorption ` pour enlevement de MBD par les agents de sorption mis en oeuvre, le ? temps necessaire pour atteindre ? ? ` l’equilibre est inferieur a 30 mn. Le ? ` prelevement de MBD par la ben? ? ? tonite traitee par micro-ondes a ete le plus important, suivi par la ben? ` tonite traitee a l’acide et ?nalement ? ` la bentonite naturelle. Le prelevement de MBD augmente avec la concentration du colorant ainsi ? qu’avec la temperature de la solu` ? tion. Trois modeles cinetiques ont ? ? ? ? ete consideres pour comprendre les ? ` processus vraisemblables de prelevement de MBD par les trois agents ? ` de sorption. Les taux de preleve` ment de MBD suivent un modele de ` ` second ordre, de tres pres. La diffusion intra-particulaire est con? cernee par le processus de sorption, mais n’est pas le facteur controlant ? ? ` ` le taux de prelevement. Les modeles des isothermes de Freundlich et de Langmuir rendent bien compte des ? ? donnees experimentales. ? Mots cles Bentonite ? Adsorption ? MBD ? Micro-ondes ? Naturel ? ? Cinetique ? Isotherme

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Introduction
Textile processing requires the use of vast amounts of water. Often the wastewater of this industry contains dyeing materials. In addition to the colour problem associated with wastewater containing dyes, they also have hazardous e?ects on human health. The potential for toxic e?ects on the environment and humans resulting from exposure to dyes and dye metabolites is not a new concern. As early as 1895 increased rates in bladder cancer were observed in workers involved in dye manufacturing. Since that time, many studies have been conducted showing the toxic potential of azo dyes. A complete review of these studies is beyond the scope of this paper; however, a broader understanding of the problem can be found in the works of Brown and DeVito (1993). Removal of dyes from wastewater e?uents is an important issue in environmental engineering. In many cases, destruction of these wastes is not feasible for economic, technical or political reasons. Chemical treatment is one of the techniques used by textile companies to remove excess colour from wastewater. For example, the coagulation–?occulation process was employed for the treatment of reactive dye wastewater, using ferric chloride as a coagulant (Papic et al. 2000). Dyes can also be removed by biological processes using anaerobic digestion (Talarposhti et al. 2001; Sirianuntapiboon and Saengow 2004). Membrane separation and ion exchange processes are also used for the removal of colour from dye wastewater. The cost and/or ine?ectiveness is the main drawback of these techniques (Mishra and Tripathy 1993). Adsorption is one of the most e?ective methods of decolourization of wastewater (McKay 1980; Yeh et al. 1993; McKay and Al-Duri 1990). In adsorption, activated carbon is the most commonly used adsorbent (McKay and Al-Duri 1990), however, other materials such as activated clay, wood and di?erent types of cellulose-based materials have also been used (Yeh et al. 1993; Nassar and Geundi 1990; Yeh and Thomas 1995). Fly ash (Viraraghavan and Ramakrishna 1999) and low-cost adsorbents, such as shells of almond and hazelnut, and poplar and walnut sawdust (Aydin et al. 2004) have also been investigated as potential adsorbents for removing dyes from textile water. The use of di?erent natural clays for the removal of toxic and other organic materials from wastewaters has been increasing lately (Boyd et al. 1988). One of these clay minerals is bentonite, which previously been used for removal of basic red dye (Hu et al. 2005). Al-Asheh et al. (2003) tried to enhance the adsorption capacity for methylene blue (MB) by placing a suitable surfactant on bentonite or by thermal treatment in an oven at 850°C. They found the capacity of bentonite to absorb MB was signi?cantly improved.

In this work, natural, acid-treated and microwavetreated bentonite are used for the removal of methylene blue dye (MBD) from aqueous solutions. The main objectives of this work are: (1) to determine the ability of physically and chemically treated bentonite to adsorb dye, (2) to compare the adsorption capacity of treated bentonite with that of natural (untreated) bentonite and (3) to study the e?ect of di?erent parameters such as temperature, concentration and contact time on the adsorption process.

Materials and methods
Materials The pure powder form of bentonite was obtained from Suppilco Chemicals (England). The mesh size, average particle diameter, total surface area and cation exchange capacity of this material were 200–300, 40 lm, 400 m2/g and 90 mequiv/100 g, respectively. MB powder and distilled water were used for the preparation of the stock solution. For acid treatment, sulphuric acid (H2SO4) 50/ 50 (v/v), of analytical grade was used (Aldrich Company, Milwaukee, WI, USA). Acid-treated bentonite Fifteen grams of natural bentonite were activated by re?uxing, using 50/50 (v/v) H2SO4 solution at 60°C for 2 h in a round-bottom ?ask. The suspension was left to cool in air. Bentonite was then separated from the suspension by sedimentation, washed several times with distilled water and placed in an oven at 120°C until dry. The dried bentonite was in the form of clumps, thus crushing by mortar and pestle was required before the sample was passed through a 0.125 mm mesh analysis. Microwave-treated bentonite Ten grams of natural bentonite were placed in a porcelain dish which was placed in a microwave oven for 3 h. The samples were then kept in dark closed bottles for storage. Batch sorption test Sorption tests on the treated and untreated bentonite were performed in order to determine the time needed to reach equilibrium and the pattern of the kinetics. For this purpose, samples of 0.15 g of natural, or acidtreated or heat-treated bentonite were transferred into dark bottles containing 30 mL of 100-ppm MBD

Treated bentonite as adsorbents of Methylene Blue

55

solution. The bottles were placed in a temperaturecontrolled shaker (GFL, Hanover, Germany) to agitate the mixture at 30°C. Samples from the solution were taken at pre-determined time intervals. The sorbent was separated from the samples by centrifugation (300 g, 10 min) and the supernatant was analysed spectrophotometrically at a wavelength of 610 nm (Al-Asheh et al. 2003) for the residual concentration of MBD. Distilled water was used as a control. Another set of tests were performed to study the effect of temperature on the sorption of MBD. For this purpose, thermally (microwave) treated bentonite was used as a model sorbent. The procedure was similar to that mentioned above but in this case, the MBD solution concentrations employed were in the range of 60– 1,000 mg/L. The temperature-controlled shaker was used to agitate the mixture at the desired temperatures, namely 25, 30 and 40°C. In this case, the bottles were left in the shaker till equilibrium, without any sampling during the course of the experiment.

rate of MBD on the three used sorbents shows that the MBD adsorption on microwave-treated bentonite is much faster than on acid-treated bentonite followed by natural bentonite. Such behaviour can be attributed to the treatment of bentonite in the microwave which takes place at a high temperature, thus volatile matter could have been released in a larger fraction than the acid-treated bentonite, hence creating more porous sites. The kinetic data for the three tested sorbents indicate that the initial decrease in the concentration of dye with time is governed by di?usion in the boundary, and the remainder of the curve where the rate of adsorption is diminished has an in?uence on internal di?usion. The ?rst mechanism is relatively fast, followed by di?usion of dye in the pores and capillaries of the structure of the bentonite (Banerjee et al. 1997; McKay et al. 1980). To verify the possible controlling mechanism during this sorption process by the di?erent sorbents, the following kinetic models were used and applied on the experimental data in Fig. 1: (1) Lagergren pseudo ?rst-order model: log?qe ? qt ? ? log qe ? k1 t 2:303 ?1?

Results and discussion
Kinetics of the adsorption process The e?ect of contact time on the uptake of MBD by natural bentonite, chemically and thermally treated bentonite has been considered using 100 mg/L initial dye concentration. The results (Fig. 1) showed that all three types of bentonite have the ability to adsorb MB from aqueous solution. It can also be seen from the results in Fig. 1 that the time needed to reach equilibrium does not exceed 30 min, although to ensure that equilibrium was reached experiments were carried out for 60 min. A comparison between the adsorption

where k1 is the ?rst-order rate constant, qt and qe (mg MBD/g bentonite) represent the amount of dye adsorbed at time t (min) and equilibrium time, respectively. (2) The pseudo second-order model: t 1 t ? ? qt k2 qe qe ?2?

where k2 is the rate constant of the pseudo second-order adsorption. (3) Weber and Morris intraparticle di?usion model: qt ? kd t1=2 ? c ?3?

20.00

MBD uptake (mg/g)

19.95 19.90 19.85 19.80 19.75 19.70
Natural Bentonite Acid-Treated Bentonite Microwave-Treated Bentonite

where kd is the intraparticle di?usion rate constant and c is an empirical constant; c=0 if intraparticle di?usion is the rate-controlling step. The validity of the above-mentioned three models was checked using linear plots of log(qe - qt) versus t, t/qt versus t and qt versus t1/2, respectively. Best linearity of the plots indicates the applicability of the models to the experimental data. Such plots (not shown) showed that the adsorption kinetics data for the three sorbents used in this work obey the pseudo second-order model. It was also found that intraparticle di?usion is obvious in the adsorption process but it is not the rate-controlling step (i.e. c ? 0). Table 1 displays the rate constant for the pseudo second-order model and the correlation coe?cients (R2) for the three kinetic models applied to the three types of bentonite considered in this work.

0

10

20

30

40

50

60

70

Time (min)

Fig. 1 Kinetics of the MBD sorption by natural and treated bentonite. Initial MBD concentration—100 mg/L; bentonite concentration—5 mg/L

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F. Banat et al.

Table 1 Rate constant for the pseudo second-order model and R2 values for other models Adsorbent k2 (min)1) R2 pseudo ?rst-order kinetic model 0.9664 0.9954 0.9932 R2 pseudo second-order kinetic model 1.00 1.00 1.00 R2 intraparticle di?usion model 0.8268 0.9476 0.7548

di?erent temperatures. The experimental data were well represented by the linearized forms of the Langmuir and the Freundlich isotherm models. One of its linearized forms, the Langmuir model can be expressed as: Ce Ce 1 ? ? qe qmax kl qmax ?4?

Microwave- 3.13 treated bentonite Acid-treated 4.18 bentonite Natural 2.23 bentonite

E?ect of temperature: equilibrium isotherms The experiments were performed to measure the isotherms of adsorption of MBD on microwave-activated bentonite at 25, 30 and 40°C. The increase in temperature led to an increase in MB uptake (Fig. 2). This indicates that adsorption of MBD on bentonite is an endothermic process. This trend has been reported by some authors when studying the adsorption of di?erent types of dyes and other organic compounds on several adsorbents (McKay et al. 1980, 1982; Nakhla et al. 1994; Asfour et al. 1985; Gayle 1994). It has been suggested (McKay et al. 1980) that this behaviour is due to the possibility of an increase in the porosity and in the total pore volume of the adsorbent with the increase of the temperature. Achife and Ibemesi (1989) also suggested the possibility of the increase in the number of active sites for the adsorption with the increase of the temperature. The equilibrium isotherms for the adsorption of MBD by microwave-treated bentonite were obtained at

where qe is the equilibrium dye concentration on the adsorbent (mg/g), Ce is the equilibrium dye concentration in the solution (mg/L), qmax is the monolayer capacity of the adsorbent (mg/g) and kl is the Langmuir adsorption constant (L/mg MBD). The linearized form of the Freundlich model is normally expressed as: 1 ln qe ? ln kf ? ln Cf n ?5?

where kf is the Freundlich constant related to the sorption capacity and 1/n is the other Freundlich constant which is called heterogeneity factor. The Langmuir and Freundlich isotherm representation of the equilibrium experimental data obtained from this work are shown in Figs. 3 and 4, respectively. Both models ?t the data very well; however, the Langmuir model showed a better ?t of the data than the Freundlich model. The maximum adsorption capacity of microwave-treated bentonite for MBD at di?erent temperatures, qmax as obtained from the Langmuir model is given in Table 2, as well as values of the same parameter for the other adsorbents. It is seen that the adsorption capacity, at di?erent temperatures, of the microwave-treated sorbent for MBD developed in this work is much higher than the other potential sorbents.

120

10

100

8

MBD uptake (mg/g)

80

6

Ce/qe

60
40οC 30οC 25οC

4
40οC

40

2

30οC 25οC

20

0

0

0

100

200

300

400

500

600

700

0

200

400

600

Equilibrium MBD concentration, Ce (mg/L)

Equilibrium MBD concentration, Ce (mg/L)

Fig. 2 E?ect of temperature and MBD concentration on the uptake of MBD by microwave-activated bentonite. Bentonite concentration—5 mg/L

Fig. 3 Langmuir isotherms at di?erent temperatures for sorption of MBD by microwave-treated bentonite. Bentonite concentration—5 mg/L

Treated bentonite as adsorbents of Methylene Blue

57

5.0 4.8 4.6 4.4

Table 2 Adsorption capacity of potential sorbents for MB Adsorbent Sorption capacity (mg/g) 84 24 130 80 18.6 80.3 12.9 111 92.6 75.2 Reference

ln(qe)

4.2 4.0 3.8 3.6 2 3 4 5 6 7
40οC 30οC 25οC

Wood Cotton waste Activated tyres Pyrolysed furniture Orange peel Raw date pits Activated date pits Microwave-treated bentonite (40°C) Microwave-treated bentonite (30°C) Microwave-treated bentonite (25°C)

McKay and Poots (1986) McKay and Poots (1986) Saniz-Diaz and Gri?ths (2000) Saniz-Diaz and Gri?ths (2000) Annadurai et al. (2002) Banat et al. (2003) Banat et al. (2003) This work This work This work

ln(Ce)

Fig. 4 Freundlich isotherms at di?erent temperatures for sorption of MBD by microwave-treated bentonite. Bentonite concentration—5 mg/L

Conclusions
Natural bentonite, acid-treated bentonite and microwave heat-treated bentonite remove appreciable amounts of MBD from aqueous solutions. The level of uptake of MBD by these three potential sorbents follows the following ranking: microwave-treated bentonite > acid-treated bentonite > natural bentonite. The kinetics studies showed that the uptake of MBD by the

three sorbents increases with time up to 30 min, after which no more uptake was observed. The kinetic data are best accommodated by the pseudo second-order model. The intraparticle di?usion was involved in the adsorption of MBD but was not the rate-controlling step. The uptake of heat-treated bentonite increased with increasing temperature and initial concentration of MBD. The Langmuir and the Freundlich isotherm models followed the experimental data reasonably, but the Langmuir model gave the better representation.

References
Achife E, Ibemesi JA (1989) Applicability of the Freundlich and Langmuir adsorption-isotherms in the bleaching of rubber and melon seed oils. J Am Oil Chem Soc 66:247–252 Al-Asheh S, Banat F, Abu-Aitah L (2003) The removal of methylene blue dye from aqueous solutions using activated and non-activated bentonite. Adsorption Sci Technol 21:451–462 Annadurai G, Juang R, Lee D (2002) Use of cellulose-based wastes for adsorption of dyes from aqueous solutions. J Hazard Mater B92:263–274 Asfour HM, Fadali OA, Nassar MN, ElGeundi MS (1985) Equilibrium studies on adsorption of basic dyes on hardwood. J Chem Technol Biotechnol 35A:21–27 Aydin AH, Bulut Y, Yavuz O (2004) Acid dyes removal using low cost adsorbents. Int J Environ Pollut 21:97–104 Banat F, Al-Asheh S, Al-Makhadmeh (2003) Evaluation of the use of raw and activated date pits as potential adsorbents for dye containing waters. Process Biochem 39:193–202 Banerjee K, Cheremisino? PN, Cheng SL (1997) Adsorption kinetics of xylene by ?yash. Water Res 31:249–261 Boyd S, Shaobia S, Lee J, Mortland M (1988) Pentachlorophenol sorption by organo clay. Clay Clay Miner 35:125– 130 Brown MA, DeVito SC (1993) Predicting azo dye toxicity. Crit Rev Environ Sci Technol 23:249–324 Gayle N (1994) Activated carbon and soluble humic substances: adsorption, desorption and surface charge e?ects. J Colloid Interface Sci 164:452–462 Hu QH, Qiao SZ, Haghseresht F, Wilson MA, Lu GQ (2005) Adsorption study for removal of basic dye using bentonite. Ind Eng Chem Res 102:885–889 McKay G (1980) Color removal by adsorption, American Dye-Stu? Reports, March 38 McKay G, Al-Duri B (1990) Comparison of theory and application of several mathematics models to predict kinetics of single component batch adsorption systems. Trans IChemE 68B:255–264 McKay G, Poots V (1986) Kinetics and di?usion processes in color removal from e?uent using wood. J Chem Technol Biotechnol 30:279–282 McKay G, Otterburn MS, Sweeney AG (1980) The removal of colour from e?uent using various adsorbents—IV silica equilibria and column studies. Water Res 14:21–27 McKay G, Blair HS, Gardner JR (1982) Adsorption of dyes on chitin. I. Equilibrium studies. J Appl Polym Sci 27:3043–3057 Mishra G, Tripathy M (1993) A critical review of the treatments for decolourization of textile e?uent. Colourage 40:35–38

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Nakhla Abuzaid N, Garooq S (1994) Activated carbon adsorption of phenolics in oxic systems: e?ect of pH and temperature variations. Water Environ Res 66:842–850 Nassar MN, Geundi MS (1990) Comparative cost of colour removal from textile e?uents using natural adsorbents. J Chem Biotechnol 50:257–263 Papic S, Koprivanac N, Loncaric Bozic A (2000) Removal of reactive dyes from wastewater using Fe(III) coagulant. Coloration Technol 116:352–358

Saniz-Diaz C, Gri?ths A (2000) Activated carbon from solid wastes using a pilotscale batch ?aming pyrolyser. Fuel 79:1863–1871 Sirianuntapiboon S, Saengow W (2004) Removal of vat dyes from textile wastewater using biosludge. Water Qual Res J Can 39:278–284 Talarposhti M, Donnelly T, Anderson GK (2001) Colour removal from a simulated dyes wastewater using a two-phase anaerobic packed bed reactor. Water Res 35:425–432 Viraraghavan T, Ramakrishna KR (1999) Fly ash for colour removal from synthetic dye solution. Water Qual Res J Canada 34:505–517

Yeh R, Thomas A (1995) Color di?erence measurement and color removal from dye wastewater using di?erent adsorbents. J Chem Technol Biotechnol 63:55–71 Yeh RL, Liu R, Chiu HM, Hung YT (1993) Comparative study of adsorption capacity of various adsorbents for treating dye wastewater. Int J Environ Stud Sect B: Environ Sci Technol 44:259–268



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