Dynamic adsorption behavior of methylene blue onto oil palm shell granular activated carbon prepared by microwave heating

Chemical Engineering Journal 203 (2012) 81–87

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Dynamic adsorption behavior of methylene blue onto oil palm shell granular activated carbon prepared by microwave heating K.Y. Foo, B.H. Hameed ⇑ School of Chemical Engineering, Engineering Campus, University Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia

h i g h l i g h t s " Highlight the renewable use of oil palm solid residue (PS). " Examine the dynamic adsorption behavior of PS granular activated carbon. " Short activation time of 10 min. 2

" High BET and Langmuir surface area of 895 and 1347 m /g. " Dynamic adsorption capacity of 133.13 mg/g.

a r t i c l e

i n f o

Article history: Received 9 March 2012 Received in revised form 15 June 2012 Accepted 18 June 2012 Available online 26 June 2012 Keywords: Activated carbon Adsorption Isotherm Methylene blue Microwave Oil palm shell

a b s t r a c t In this work, the potential of oil palm solid residue, oil palm shell for preparation of granular activated carbon (PSAC) by microwave induced KOH activation has been attempted. PSAC was examined by pore structural analysis and Fourier transform infra-red spectroscopy. A series of column tests were performed to determine the breakthrough characteristics by varying the operational parameters, bed heights (3–9 cm), hydraulic loading rate (10–30 mL/min) and feed concentrates (100–200 mg/L). Results illustrates an encouraging performance towards the removal of methylene blue (MB), with the highest bed capacity of 133.13 mg/g at 6 cm of adsorbent bed height, hydraulic loading rate of 20 mL/min and feed concentration of 150 mg/L. The dynamic adsorption behavior was favorably described by the Thomas and Yoon–Nelson models, with the coefficient of determination, R2 > 0.99 at different operating conditions. The successful adsorptive removal of MB in the continuous adsorption system has demonstrated the suitability of PSAC as an effective alternative solution for the treatment of contaminated wastewaters. Ó 2012 Elsevier B.V. All rights reserved.

1. Introduction For the past two decades, a huge evolution has been undergone by the oil palm industry. From a humble source of the edible oil, today oil palm has demonstrated a variety of implications, almost every part in the world [1]. During the 1950s, the expansion of palm oil industry started as part of the government’s diversified cautious policy from rubber to oil palm, in raising the socioeconomic status of the expanding population. Today, its growth has been phenomenal in Malaysia, replacing Nigeria as the chief producer since 1971 [2]. In the world trade market, Malaysia is presently the major key player, accounting approximately 50% and 58%, the leading producer and exporter of the palm oil. Simultaneously, from merely 54,000 hectares in the early of 1960s, the oil palm plantation area has gradually increased, representing 56% of the total ⇑ Corresponding author. Tel.: +60 45996422; fax: +60 45941013. E-mail address: [email protected] (B.H. Hameed). 1385-8947/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2012.06.073

agricultural land and 11.75% of the country’s total land area [3]. By 2020, the figures are expected to be further expanded, occupying 5.1 million hectares of estates around the Peninsular Malaysia and the east states of Sabah and Sarawak [4]. In step with the projected growth of the cultivation of oil palm, the supply of the world oil palm biomass and its processing by-products are found to be 7 times of the availability of natural timber, generating more than 184.6 million tons of biomass per year [5]. In the formal practice, some quantity of these residues is used as boiler fuel for power generation (heat and electricity), where a larger proportion is discarded by open burning [6]. It is an added advantage to the oil palm industry if the excess biomass can be turned into useful and valuable products [7]. A promising option is converting them into a prospective precursor for the preparation of activated carbon. Although batch laboratory adsorption studies provide useful information on the application of adsorption to the removal of specific waste constituents, continuous column studies provide the most practical application of this process in wastewater treatment [8].

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In static mode studies, the same solution remains in contact with a given quantity of adsorbent, where the adsorption process continues till equilibrium between the solute concentration and the solute adsorbed per unit weight of adsorbent is reached. This equilibrium established is static in nature, as it does not change further with time [9]. In dynamic adsorption, solution continuously enters and leaves the column, where the complete equilibrium is never established at any stage between the solute in solution and the amount adsorbed. Equilibrium has to be continuously established, as it meets with the fresh concentrations. The equilibrium in column mode studies is termed as dynamic equilibrium [10]. The present work was undertaken to examine the potential of oil palm shell as an efficient feedstock for preparation of granular activated carbon (PSAC) by microwave induced KOH activation. The dynamic adsorption behavior of methylene blue onto PSAC was investigated in an effort to seek for an effective remediation of contaminated wastewaters. Textural, functional and surface chemistry of the prepared adsorbent was performed. Moreover, the dynamic adsorption models were elucidated. 2. Materials and methods 2.1. Adsorbate Methylene blue (MB), a cationic pollutant difficult to be degraded in natural environment was selected as the model adsorbate in the present study. A standard stock solution was prepared by dissolving an appropriate quantity of MB in double distilled water. Working solutions of desired concentrations were prepared by successive dilution. 2.2. Preparation of activated carbon Oil palm shells used as raw materials in this study were collected from the local oil palm mill, Nibong Tebal, Malaysia. The raw precursors were manually chosen, cleaned, dried, crushed and sieved to obtain the particle size fraction of 1–2 mm. The carbonization process was performed by loading 500 g of dried precursor into a vertical furnace, and heated up to a carbonization temperature of 700 °C under purified N2 flow (150 mL/min). The char produced was mixed in potassium hydroxide solution with a char/KOH impregnation ratio of 1:1.75 (wt.%) with occasional stirring. The activation step was conducted in a tubular glass reactor fixed in the chamber of commercial microwave oven [11] with a microwave input power of 600 W and irradiation time of 10 min. Nitrogen gas at a pre-set flow rate of 300 mL/min was used to purge air in the reactor before the start of microwave heating and it continued to flow during the cooling intervals. The resultant activated carbon was washed with 0.1 M hydrochloric acid and rinsed repeatedly with hot and cold distilled water until the filtrate reached to neutral pH. 2.3. Characterization of activated carbon The pore structure characteristics were determined by nitrogen adsorption–desorption isotherm at 77 K using an automatic Micromeritics ASAP-2020 volumetric adsorption analyzer. Chemical characterization of surface functional groups was detected using the pressed potassium bromide (KBr) pellets containing 5% of carbon sample by Fourier transform infrared spectrometer (FTIR-2000, Perkin Elmer) in the scanning range of 4000–400 cm1.

temperature control, with an inner diameter of 1.2 cm and 19.5 cm in height. A known quantity of PSAC was packed in the column to the desired bed height of 3, 6 and 9 cm (equivalent to 2.00, 3.99 and 5.99 g of activated carbon). At the bottom of the column, a stainless steel sieve was attached follow by a layer of glass wool. To avoid air entrapment, the column was filled with deionized water and the slurry of adsorbent was introduced carefully, which was slowly settled down by displacing the heel of water. The MB solution was pumped upward using a peristaltic pump (Masterflex, Cole-Parmer Instrument Co.) where the solution flow rate was measured periodically to maintain the desire flow rate of solution along the experiment. The tank was placed on a magnetic plate stirrer to ensure consistent inlet concentrations of the stock solutions. The MB solutions were collected at prescribed time intervals and the concentration was measured using a double beam UV–visible spectrophotometer (Shimadzu-1601, Japan). The effect of MB inlet concentration on the column performance was performed by varying the inlet concentrations from 100 to 200 mg/L for MB solution, with the PSAC bed height of 6 cm and feed flow rate of 20 mL/min. To evaluate the effect of feed flow rate, the adsorption studies were carried out at the MB feed flow rate of 10–30 mL/min, with the adsorbent bed height of 6 cm and inlet concentration of 150 mg/L. The effect of bed height was examined by varying the PSAC bed height from 3 to 9 cm, with the MB feed flow rate of 20 mL/min and inlet concentration of 150 mg/L. All the experiments were conducted at 30 °C. 2.5. Dynamic adsorption analysis The performance of fixed-bed adsorption is often complemented by dynamic column studies to determine the system size requirements, contact time and carbon usage which can be deduced from the concept of breakthrough curve. The breakthrough curves show the loading behavior of dye to be removed and is usually expressed in terms of adsorbed dye concentration (Cad), inlet concentration (C0), outlet concentration (Ct) or normalized concentration defined as the ratio of outlet concentration to inlet concentration (Ct/C0) as a function of time or volume of effluent for a given bed height. The desired breakthrough concentration was determined at 10% of the inlet concentrations, and the time required to reach to the breakthrough point is known as the breakthrough time. The flow through the tested column was continued until the concentration of adsorbate effluent approached 1.0 Ct/ C0, which indicated the exhaustion point [12]. The area under the breakthrough curve (Ac) obtained by integrating the adsorbed concentration, Cad versus time, t plot, can be used to determine the quantity adsorbed, qtotal (mg/g) for a given inlet concentration and flow rate given by:

qtotal ¼

QAc Q ¼ 1000 1000

Z

t¼t total

C ad dt

ð1Þ

t¼0

where Q is the volumetric flow rate (mL/min) and ttotal is the total flow time (min). Meanwhile, the equilibrium uptake/maximum column capacity (qeq) is derived as the quantity adsorbed ðqtotal Þ per weight of adsorbent (W) [12]:

qeq ¼

qtotal W

ð2Þ

3. Results and discussion 3.1. Characterization of activated carbon

2.4. Dynamic adsorption studies The dynamic adsorption studies were carried out at 30 °C in a Pyrex glass adsorption column equipped with a water jacket for

The surface physical parameters of PSAC were deduced from the nitrogen adsorption isotherms. The BET surface area, Langmuir surface area and total pore volume of PSAC were identified to be

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895.16 m2/g, 1346.51 m2/g and 0.491 cm3/g, respectively (compared with 61.14 m2/g, 90.95 m2/g 0.033 cm3/g for char), implying pore development and widening of the existing pores during the microwave irradiation stage. The Fourier Transformed Infra-red (FTIR) spectra of PSAC was demonstrated in Fig. 1. The region between 3840 cm1 is related to the –OH (hydroxyl) groups, and the broad band at 3233 cm1 is assigned to the N–H derivatives. The presence of –COOH dimmer shows an intensity at 2343 cm1. The transmittance at 1424 cm1 are associated with the CH2 (alkyl) groups, where the sharp peak at 1053 cm1 is corresponded to the C–O (anhydrides) and C–H functionalities.

other words, the diffusion process is concentration dependent. Initial concentration provides an essential driving force for alleviating the mass transfer resistance between the aqueous phase and the solid medium. As the feed concentration increases, the MB loading rate increases, which lead to a decrease in the adsorption zone [15].

3.2.2. Effect of feed flow rate The effect of feed flow rate was investigated at the constant PSAC bed height of 6 cm, feed concentration of 150 mg/L, and with the hydraulic loading rate ranging from 10 to 30 mL/min. From Fig. 2b, an earlier breakthrough and exhaustion time were observed as the feed flow rate increased from 10 to 30 mL/min. The column was found to perform better at lower feed flow rate, which resulted in a longer breakthrough and exhaustive time. The greatest adsorption uptake (qtotal) and equilibrium capacity (qeq) was observed at the lowest flow rate of 10 mL/min. Increasing hydraulic loading rate from 10 to 30 mL/min illustrated a steadily increase of adsorption zone speed, resulting in a significant decrease of breakthrough time, saturation time and column capacity by 81%, 75% and 65%, respectively. The variation of trend of the saturation rate and adsorption column capacity may be explained on the basis of mass transfer fundamentals. This behavior is primarily associated with the insufficient residence time for the MB solution within the bed and the diffusion limitations of MB into the pores of PSAC at higher feed flow rates [16]. Moreover, the higher turbulence at higher feed flow rates could lead to a weaker interaction and intraparticle mass transfer between the adsorbate molecules and adsorbent for the adsorption to be taken place [17].

3.2. Dynamic adsorption studies 3.2.1. Effect of inlet concentrations The variation of inlet MB concentration to the breakthrough characteristics was performed at the adsorbent bed height of 6 cm and feed flow rate of 20 mL/min, as depicted in Fig. 2a and Table 1. Initially, the adsorption process increased rapidly due to the availability of readily accessible surface sites to capture the dye molecules. As the dye solution continued to flow, the uptake became less effective and, therefore, the outlet concentration started to rise until the saturation points were reached. Generally, the breakthrough curves display a typical S-shape and relatively sharp curve, indicative of shortened mass transfer zone, where the axial dispersion is insignificant at the studied concentrations [13]. An inverse relationship between the initial dye concentrations and the breakthrough time and volume of treated solution was observed. It is clearly shown that increasing initial concentration from 100 to 200 mg/L illustrated a gradually decrease of breakthrough time from 195 to 120 min. A decrease in inlet concentration gave an extended breakthrough curve, indicating a higher volume of solution could be treated. This was ascribed to a lower concentration gradient which reduces the diffusion or mass transfer coefficient [14]. The larger the initial feed concentrations, the steeper the slope of the breakthrough curves and the lower the breakthrough time. These results demonstrated that changes in initial concentration could modify the adsorption rate and breakthrough time, or in

3.2.3. Effect of bed height The breakthrough behavior for different bed heights of 3, 6 and 9 cm were conducted at the constant feed concentration of 150 mg/L and the hydraulic loading rate of 20 mL/min. Comparison between the plotted curves (Fig. 2c) indicates that increasing the PSAC bed heights caused a reduction in breakthrough and exhaustive time. The increase in adsorbent mass in higher bed depth would signify a greater service area and more fixation binding sites for the adsorbate molecules to be adsorbed. Increasing PSAC bed

13.0 12.0

% Transmittance

11.0 10.0 9.0 3840 8.0

2343 3233

7.0

1424

6.0 1053 5.0

4.0 4000

3600

3200

2800

2400

2000

1800

1600

1400

Wavenumber cm-1 Fig. 1. FT-IR spectra of PSAC.

1200

1000

800

600

400

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3.3. Dynamic adsorption models

1.2

Successful design of a dynamic adsorption process requires the prediction of concentration–time profile or breakthrough curve which describes the specific relation or mobility of solute substances onto a solid adsorbent [19]. Typically, the mathematical correlation provides an insight into the adsorption mechanisms, surface properties as well as the degree of affinity of the adsorbents. In the present investigation, the dynamic adsorption behavior was examined using the Adam’s–Bohart, Yoon–Nelson and Thomas models.

1

C/C0

0.8

0.6

100 mg/L 150 mg/L

0.4

200 mg/L

0.2

0 0

100

200

300

400

500

Time (min)

(a) 1.2

1

ln

C/C0

0.8

10 mL/min

0.6

20 mL/min 0.4

30 mL/min

0.2

0 0

100

200

300

400

500

Time (min)

(b) 1.2 1 0.8

C/C0

3.3.1. Adam’s–Bohart model It is generally accepted that the bed depth service time (BDST) model offers the simplest approach and rapid prediction of adsorber design and performance. The basic relation that relating C0/Ct and column service time (t) for purification in a flowing system was originally proposed by Bohart and Adam [20]. The simplified equation of Bohart and Adam’s model is presented as:

Ct Z ¼ kAB C 0 t  kAB N0 F C0

where C0 and Ct (mg/L) are the inlet and effluent dye concentrations, kAB (L/mg min) is the adsorption rate constant, F (cm/min) is the linear velocity determined by dividing the flow rate (mL/min) by the column sectional area (cm2), N0 (mg/L) is the saturation concentration, t is the flow time (min), and Z (cm) is the adsorbent bed depth. This model assumes that the adsorption rate is proportional to both residual capacity of the adsorbent and the concentration of the adsorbing species. To examine the applicability of Bohart and Adam’s model, a linear plot of ln CC0t against service time, t with a slope kAB C 0 and the intercept kAB N 0 ZF was established (figure not shown). For the breakthrough curves, the coefficient of determination (R2) together with the detailed parameters under the applied experimental variables were determined and listed in Table 2. The validity of the models to fit the data was justified by average relative errors (ARE), the commonly used statistical tool measuring the predictive power of a model derived as:

Pn

0.6

ARE ¼

3 cm 0.4

6 cm 9 cm

0.2 0 0

100

200

300

400

500

Time (min)

(c) Fig. 2. Breakthrough curves for the adsorption of MB onto PSAC at different (a) initial MB concentrations (PSAC bed height = 6 cm, feed flow rate = 20 mL/min), (b) feed flow rate (initial MB concentrations = 150 mg/L, PSAC bed height = 6 cm) and (c) PSAC bed height (initial MB concentrations = 150 mg/L, feed flow rate = 20 mL/ min) at 30 °C.

heights from 3 to 9 cm indicated a dramatic increase of adsorption uptake and in the volume of MB solution to be treated. The slope of the breakthrough curve decreased with increasing the PSAC bed height, which resulted in a broadened mass transfer zone. At lower adsorbent bed height, axial dispersion phenomenon predominated and reduced the diffusion of MB adsorbate [18]. Consequently, the solute molecules had insufficient time to diffuse into the pores of the adsorbent.

ð3Þ

i¼1 jððC t =C 0 Þexp

 ðC t =C 0 Þcal Þ=ðC t =C 0 Þexp j  100% n

ð4Þ

where n is the number of measurements, and (Ct/C0)exp and (Ct/ C0)cal are the experimental and theoretical normalized concentrations, respectively. ARE (%) explains the variation and average squared distance of the experimental data points from the fitted line, where the lower the ARE value, the better the estimated model performs. Although the Adam’s–Bohart model provides a simple and comprehensive approach for evaluating the adsorption-column tests, its validity is limited to the range of conditions used. There is a good agreement between the experimental data and predicted values for the relative concentration region up to 0.6. Large discrepancies can be found between the experimental and predicted curves above this value. From Table 2, the predicted values of Adam’s–Bohart rate constant, kAB decreased with increasing the PSAC bed heights, but it increased with increasing the initial MB concentration and feed flow rate, which showed that the dynamic adsorption system was governed by external mass transfer in the initial stage of the adsorption process [21]. 3.3.2. Yoon–Nelson model A relatively simple model addressing the breakthrough behavior was developed by Yoon and Nelson in 1981 [22]. The model is based on the assumption that the rate of decrease in

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K.Y. Foo, B.H. Hameed / Chemical Engineering Journal 203 (2012) 81–87 Table 1 Fixed-bed adsorption parameters for the adsorption of MB onto PSAC at 30 °C. Initial MB concentration, C0 (mg/L)

PSAC bed height, (cm)

MB feed flowrate, Q (mL/ min)

Breakthrough time, tb (min)

Bed exhausted time, te (min)

Bed capacity, qe,exp (mg/g)

100 150 200 150 150 150 150

6 6 6 6 6 3 9

20 20 20 10 30 20 20

195 145 120 345 65 55 330

420 210 165 445 110 105 430

63.31 75.14 95.29 111.08 39.09 38.22 133.13

Table 2 Adam’s–Bohart fitting parameters for the adsorption of MB onto PSAC at 30 °C. Initial MB concentration, C0 (mg/L)

PSAC bed height, (cm)

MB feed flowrate, Q (mL/min)

Adam’s–Bohart rate constant, kAB (L/ mg min) (1000)

Saturation concentration, N0 (mg/L)

R2

ARE (%)

100 150 200 150 150 150 150

6 6 6 6 6 3 9

20 20 20 10 30 20 20

0.062 0.099 0.170 0.057 0.139 0.107 0.046

101,479 100,156 100,670 95,737 93,175 111,432 129,491

0.626 0.661 0.741 0.836 0.533 0.517 0.785

34.7 44.9 42.6 17.3 24.3 30.2 28.6

R2

ARE (%)

0.997 0.996 0.998 0.998 0.996 0.997 0.998

1.5 2.6 1.3 0.2 1.9 5.3 1.4

Table 3 Yoon–Nelson fitting parameters for the adsorption of MB onto PSAC at 30 °C. Initial MB concentration, C0 (mg/L)

PSAC bed height, (cm)

MB feed flowrate, Q (mL/min)

Yoon–Nelson velocity rate constant, kYN (L/mg min)

s, time (min) for 50 % of adsorbate

100 150 200 150 150 150 150

6 6 6 6 6 3 9

20 20 20 10 30 20 20

0.032 0.056 0.090 0.040 0.075 0.077 0.036

125.27 100.38 94.43 294.53 34.19 23.99 269.31

breakthrough

Table 4 Thomas fitting parameters for the adsorption of MB onto PSAC at 30 °C. Initial MB concentration, C0 (mg/L)

PSAC bed height, (cm)

MB feed flowrate, Q (mL/ min)

Thomas rate constant, kTh (L/ min mg)

Thomas equilibrium uptake, qTh (mg/g)

R2

ARE (%)

100 150 200 150 150 150 150

6 6 6 6 6 3 9

20 20 20 10 30 20 20

0.447 0.379 0.315 0.267 0.501 0.512 0.246

62.79 75.26 94.81 109.49 38.54 36.08 133.49

0.998 0.997 0.999 0.999 0.996 0.997 0.998

0.6 0.4 0.1 0.2 1.9 2.1 1.3

Table 5 Comparison of dynamic adsorption capacities for MB with the literature. Precursor

Activation method

Activation time (min)

Bed capacity (mg/g)

Reference

Oil palm shell Sludge Coal (Commercial) Oil palm shell Peach stones

Microwave heating Conventional heating – Conventional heating Conventional heating

10 40 – 120 120

133.13 103.58 12.06 40.86 71.80

Present study [24] [24] [25] [26]

the probability of adsorption for each adsorbate molecule is proportional to the probability of adsorbate adsorption and the adsorbate breakthrough on the adsorbent. The linear form of the Yoon–Nelson model for a singlecomponent system is expressed as:

 ln

Ct Co  Ct



¼ kYN t  skYN

ð5Þ

where kYN is the Yoon–Nelson velocity rate constant (1/min) and s is the time (min) required for 50% of adsorbate breakthrough.

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The model parameters for the  Yoon–Nelson were predicted t against the sampling time, t. from the linear plot of ln C oCC t Similar to the Adam’s–Bohart model, the Yoon–Nelson velocity rate constant, kYN decreased with increasing the PSAC bed height, and increased with increasing the inlet dye concentration and feed flow rate. A comparison between the coefficient of determination, R2, ARE and the predicted values summarized in Table 3 indicated a good agreement between the experimental data and the predicted normalized concentration. The result suggested that the Yoon– Nelson model which neglects the effect of axial dispersion is suitable for representing the dynamic adsorption process. 3.3.3. Thomas model The Thomas model [23] is one of the most widely used theoretical methods to describe the column performance. The model assumes plug flow with no axial dispersion in the bed, and derived with the assumption that the rate driving force obeys Langmuir isotherm and second-order reversible reaction kinetics. The linerized form of the Thomas model is given by:

ln

  C0 kTh qTh W  kTh C 0 t 1 ¼ Q Ct

ð6Þ

where kTh (mL/min mg) is the Thomas rate constant, qTh (mg/g) is the predicted bed capacity, W (g) the mass of adsorbent and Q (mL/min) is the feed flow rate. This model is suitable for adsorption processes where the external and internal diffusion limitations are absent. The Thomas rate constant, KTh and the equilibrium uptake, qo   were determined from the linear regression analysis of ln CC0t  1 against t. As expected, the bed capacity, qTh increased with increasing the inlet concentrations and bed height and decreased with increasing the feed flowrate. Inspection of the regressed lines indicated that the model gave a good fit to the experimental data at all bed heights, flow rates, and initial MB concentrations, with the lowest ARE and coefficient of determination, R2 in the range of 0.996–0.999 (Table 4). It is also observed that the calculated theoretical qTh values are in high agreement with the corresponding data obtained experimentally. A comparison of the dynamic adsorption capacity of PSAC for MB with the literature [24–26] was summarized in Table 5. It can be concluded that the activated carbon prepared in this work showed relatively high adsorption capacity of 133.13 mg/g. The activation time due to present work is much shorter owing to the thermal efficiency of microwave heating system. The tremendous thermal gradient of internal and volumetric heating allows microwave-induced activation to react more effectively at lower bulk temperature, resulting in energy savings and shortening of the processing time [27]. This irradiation promoted the release of volatiles from the char surface widening the porosity in the original carbon network [28]. 4. Conclusion This investigation identified the feasibility of oil palm shell as a suitable candidate for preparation of high quality granular activated carbon. The dynamic adsorption was dependent on the initial MB concentration, feed flow rate and the adsorbent bed height. Increasing initial MB concentration and hydraulic loading rate illustrated a gradually decrease of exhaustive and breakthrough time, but increasing the adsorbent bed height indicated an opposite trend. Comparison of breakthrough points showed good agreement with the predicted results estimated by the Thomas and Yoon–Nelson models (R2 > 0.99), which proved the versatility of the models for scale up calculations. The prepared adsorbent exhibited a relatively high dynamic adsorption capacity

of 133.13 mg/g, implying the great potential for wastewater treatment processes.

Acknowledgements The authors acknowledge the financial support provided by Universiti Sains Malaysia under the Research University (RU) Scheme (Project No. 1001/PJKIMIA/814072) and RU-PRGS grant scheme (Project 465 No. 8043030).

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