Preparation and characterization of activated carbon from reedy grass leaves by chemical activation with H3PO4

Accepted Manuscript Title: Preparation and characterization of activated carbon from reedy grass leaves by chemical activation with H3 PO4 Author: Jianzhong Xu Lingzhi Chen Hongqiang Qu Yunhong Jiao Jixing Xie Guangen Xing PII: DOI: Reference:

S0169-4332(14)01956-4 http://dx.doi.org/doi:10.1016/j.apsusc.2014.08.178 APSUSC 28633

To appear in:

APSUSC

Received date: Revised date: Accepted date:

24-5-2014 29-8-2014 29-8-2014

Please cite this article as: J. Xu, L. Chen, H. Qu, Y. Jiao, J. Xie, G. Xing, Preparation and characterization of activated carbon from reedy grass leaves by chemical activation with H3 PO4 , Applied Surface Science (2014), http://dx.doi.org/10.1016/j.apsusc.2014.08.178 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Highlights. 1, Activated carbons were produced from reedy grass leaves by activation with phosphoric acid. the

activated

carbons

have

a

large

number

oxygen-

and

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phosphorus-containing surface groups

of

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2.

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3. the structure of activated carbons were bight fibers features on the surface and the external surface of the activated carbons was slightly corrugated and abundant

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pores.

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Preparation and characterization of activated carbon from reedy grass leaves by chemical activation with H3PO4 ，

Department of Applied Chemistry，Hengshui University，Hengshui 053000， Hebei, China

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b

College of Chemistry and Environmental Science, Hebei University, Baoding 071002, Hebei, China

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a

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Jixing Xiea, Guangen Xingb

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Jianzhong Xua,, Lingzhi Chena b, Hongqiang Qua, Yunhong Jiao a,

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ABSTRACT

Activated carbons were produced from reedy grass leaves by chemical activation

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with H3PO4 in N2 atmosphere and their characteristics were investigated. The effects

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of activation temperature and time were examined. Adsorption capacity was

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demonstrated with BET and iodine number. Micropore volume and pore size distribution of activated carbons were characterized by N2 adsorption isotherms. The

surface area and iodine number of the activated carbons produced at 500°C for 2h were 1474 m2/g and 1128 mg/g, respectively . Thermal decomposition of pure reedy grass leaves and H3PO4-impregnated reedy grass leaves have been investigated with

thermogravimetric/mass spectroscopy (TG–MS) technique. It was found that the temperature and intensity of maximum evolution of H2O and CO2 of



Corresponding Author. Tel.: +86-0312-5079482.

Fax: +86-0312-5079482.

E-mail: [email protected]. 2

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H3PO4-impregnated reedy grass leaves were lower than that of pure reedy grass leaves. This implies that H3PO4 as an activating reagent changed the thermal degradation of the reedy grass leaves, stabilized the cellulose structure, leading to a subsequent

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change in the evolution of porosity. The results of X-ray Photoelectron Spectroscopy

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and Fourier - Infrared Spectroscopy analysis indicate that the produced activated carbons have rich functional groups on surface

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Keywords: Activated carbons; Reedy grass leaves; H3PO4; Surface chemistry

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1. Introduction

Activated carbons (AC) are materials containing large surface area,

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well-developed porosity and rich surface groups. Therefore it has been widely used for the separation of gases, the recovery of solvents, the removal of organic pollutants

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from drinking water, as a catalyst support, supercapacitors electrodes, gas storage, and so on[1–4]. Nowadays, activated carbon can be produced from a large number of

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abundant and low-cost materials such as agricultural products[5]. In recent years, a lot of researches have been reported on activated carbons from agricultural wastes, such as cherry stones[6,7], vine shoots[8], spirit lees[9], coconut shells[10], bamboos[11], corncob[12,13], candlenut shell[14], Palm shells[15], acorn shell[16,17], pecan

shells[18] and lotus stalks[19]. et al. Reedy grass is a kind of plant growing abundantly in Northern China’s Hebei province. Reedy grass leaves have little economic value, and incineration may cause environmental pollution problems. The aim of this work is to study the ability of reedy grass leaves to serve as a precursor for an efficient activated carbon. These

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applications would add value to reedy grass leaves, decrease the waste disposal cost and environmental pollution, and provide an alternative source of commercial carbons.

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Activated carbons can be produced basically by two methods: Physical or

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chemical activation. In the chemical activation method, the dehydrating effect of used

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active agents inhibits the formation of tar which helps to enhance the yield of porous carbon and to decrease the activation temperature and activation time compared with

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the physical activation method[20,21]. H3PO4 acts as catalyst on the one hand promoting bond cleavage reactions, on the other hand facilitating crosslinking via

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cyclization, condensation, and forming a layer of linkage such as phosphate and polyphosphate esters, which could protect the internal pore structure and thus prevent

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the adsorbent from excessive burn-off[15,22]. In addition, H3PO4 is eco-friendly as it is non-polluting, easy to recover by simply dissolving the salts of H3PO4 in water and

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can be recycled back into the process. The phosphorus-containing group is the most important one for the adsorption of heavy metal ions from acidic solutions. Thus, carbons activated with H3PO4 may be regarded as prospective cation-exchangers for the removal of heavy metal cations from water solutions[23]. In this study, activated carbons were prepared from reedy grass leaves by chemical activation with H3PO4 as

one of the effective procedure for preparation of highly porous carbons having rich surface chemistry. 2. Experimental 2.1. Preparation of activated carbon

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Reedy grass leaves from Hengshui Lake (HeBei province) were washed with hot distilled water to remove the impurities (dust and water soluble substances) and dried at 110°Cfor 24 h, and sieved to obtain particles size lower than 80 mesh prior to their

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activations.10g of sieved reedy grass leaves was mixed with H3PO4 (60%) at an

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impregnation ratio (grams of 100% H3PO4/gram of dried precursor) of 0.88:1, and

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impregnation time for 4h, The resulting activated carbons were then chemically activated at 400, 500, 600,700, and 800°C for 1,2,3 and 4h under nitrogen (N2)

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atmosphere (flow rate= 100 mL min-1). The heating rate was 5°C min-1. After activation, the carbonized sample was washed with hot distilled water in a Soxhlet

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extractor until a neutral pH. Finally, the sample was dried in a vacuum oven at 105°C

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2.2. Iodine test

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for 10h.

The iodine number indicates the porosity of the activated carbon and it is defined

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as the amount of iodine adsorbed by 1g of carbon at the mg level. 2.3. N2 adsorption–desorption at −196°C Characterization of obtained activated carbons was determined by N2 adsorption

at −196°C with surface area and pore size analyzer (TriStar II 3020, Micromeritics). Before analysis, all of the obtained ACs was evacuated under vacuum condition at 150°C over night in order to clean all the pores. The BET surface area is calculated from the isotherms using the Brunauer–Emmett–Teller (BET) equation[24]. The Dubinin–Radushkevich (DR) method is used to calculate the micropore volume[25]. The pore size distribution is as certained by Non-local Density Functional Theory

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(NLDFT)[26]. 2.4. X-ray diffraction (XRD) analysis The products were characterized by X-ray diffraction (XRD) in reflection mode

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2.5. thermogravimetric/mass spectroscopy (TG–MS)

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rate of 0.01°/sec, typically in the angle range between 10° and 90°.

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(Cu Kα radiation) on a Bruker D8 diffractometer. Scans were recorded with a scanning

Thermogravimetric analyzer (TG) coupled with mass spectrometer (MS) system

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has been used to study the evolved gaseous compounds generated during pyrolysis experiments. The pyrolysis tests were performed in a Netzsch Sta 449 C

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thermogravimetric analyzer. The samples were placed in a platinum crucible. About 10 mg of each sample was heated under nitrogen flow rate of 100 mL min−1 and a

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heating rate of 5◦C min−1 from 35 to 800◦C. 2.6. Fourier - Infrared Spectroscopy (FT-IR)

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Infrared transmittance measurements of the activated carbons were carried out on a

Varian 640 FT-IR spectrometer at room temperature in the 4000–400cm−1 wavenumber range. The pellet for infrared studies was prepared by mixing a given sample with KBr crystals and pressed into a pellet. 2.7. X-ray Photoelectron Spectroscopy (XPS) The XPS measurements were performed on PHI 5300 ESCA system (perkin-Elmer) using monochromated Al-Ka excitation source. XPS provided the elemental composition of carbons within 10nm of the sample’s surface. 2.8. Scanning electron microscopy (SEM)

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The surface physical morphoiogy was identified by using scanning electron microscopy (SEM) technique. SEM (TM3000, Japan) instrument with a 15 kV accelerating voltage was used to characterize the morphology of activated carbons,

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which was dried overnight at approximately 105◦C under vacuum before SEM

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analysis.

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3. Results and discussion 3.1. Effect of activating temperature and activating time

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Activating temperature plays an important role in the pyrolysis of the precursors, so it is a key parameter for the surface area and the micropore volume of the AC. The

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effects of activating temperature on the BET surface area, micropore volumes, iodine number of the ACs are shown in Table 1. BET surface areas, micropore volume and

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iodine number gradually increased at first and then decreased with the increase of activating temperature. These facts indicate that the development of microporosity

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below 500°C involves principally the creation of new micropores (ultramicropores), whereas micropore widening prevails at higher temperatures. It may be connected with the fact that phosphorus species present in the impregnated reedy grass leaves under such heating conditions tend to boil and this causes a structural expansion in the product that is being carbonized. The BET surface area, micropore volume and iodine number at 500°C is found to be appropriate to reach the maximum of 1474 m2/g,

0.560 cm3/g, and 1128 mg/g respectively. From the data in Table 1, it is obvious that the activation time is essential to the activated carbon. Increasing the activation duration from 1 to 2h leads to the

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increasing of BET surface area, micropore volume and iodine number. However, the increase of the activation duration from 2 to 5h results in a lower BET, micropore volume and iodine number. It may be that longer duration of activation time caused

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some of the pores to enlarge or even collapse.

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Comparison of activated carbons of present work with other literature data under

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optimum conditions is presented in Table 2.

Fig. 1 shows the Pore size distribution( PSDs) obtained by the NLDFT method for

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activated carbon prepared from reedy grass leaves at the activation temperature of 500°C under N2 atmosphere for 2h of duration. The curve exhibit systematically a

assumptions[27].

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minimum around 1 nm, which is well known to be an artifact introduced by modeling The PSDs exhibit two maxima at 0.6 and 1.1 nm, as well as

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another small shoulder at 2–4 nm, where the pore sizes become predominantly micro and mesoporous. The pore size distribution shows a twin peak in the micropore region,

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contributing nearly to 50% of total pore volume. 3.2. XRD analysis

The activated carbons produced from reedy grass leaves at activation temperature

of 500°C, under N2 atmosphere for 2h of duration can be crystallographically characterized by means of X-ray diffraction (Fig. 2). Overall two broad peaks around 26o and 44o related to (002) and (10) Bragg reflections are noted signifying the amorphous nature of activated carbons[28]. The diffraction pattern is characterized by very broad (002) lines due to the small number of stacked layers. Unsymmetrical (10) lines due to random turbostratic stacking of layers. In addition, in the case of sample,

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which exhibits certain sharp peaks, the existence of those sharp peaks may be attributed to the existence of residual ash in the carbon. 3.3. Thermogravimetric analysis (TGA)

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Fig. 3 shows the results from TGA carried out on pure reedy grass leaves and

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H3PO4- impregnated reedy grass leaves. The decomposition of reedy grass leaves

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takes place in three stages. The first stage that obtained at 35 to 200°C indicates the loss of adsorbed water was about 2.01%. In the second stage, sharp weight loss of the

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raw material was about 72.0% at 200 -400°C in which carbonisation process begins and mainly hemicellulose and cellulose fractions decompose. Finally, consolidation of

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the char structure at 400–800°C resulted in a small weight loss. The mass loss at 800°C is close to 80%, and confirms that the pyrolysis of the precursor without

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impregnation is not interesting in term of carbon production yield. By contrast, the plot of mass loss of the impregnated reedy grass leaves is shifted to higher

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temperatures.

This TGA curve of H3PO4- impregnated reedy grass leaves shows an important

mass loss up to 300°C, then a slower and progressive mass loss in the range 300–450°C and a third one in the range 450–650°C. During the first stage, only a slight weight loss was observed which was mainly due to the evaporation of water. Water comes from the H3PO4 solution, the moisture in samples and from reactions of

samples and H3PO4 at low temperature[29]. Volatile components and light gases such as CO and CO2 may also be released at this stage for the weight loss of the sample is higher than the moisture content of the raw reedy grass. During the second stage

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corresponding to the formation of micropores and mesopores by reaction of the H3PO4 with biopolymer (lignin, hemicellulose, and cellulose) to form crosslinked biopolymer fragments connected with phosphate and polyphosphate bridges (expansion of the

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materials), The third mass loss may be assigned to the ultimate oxidation of the

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carbon material after reaction with H3PO4, the third stage due to the decomposition of

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the phosphate bridges (accompanied by a volumic contraction of the material and a decrease of the microporous volume) [30]. The TGA plot of the impregnated material

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shows that activation temperature at 500°C corresponds to a 39.6% mass burn off which can be attributed essentially to the reedy grass leaves mass loss due to the

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activation reaction with H3PO4. This means that less than 76.4% of the reedy grass leaves precursor is burn off by the activation reaction.

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3.4. Evolved gas analysis with TG-MS MS coupled with TG system has been used to study volatile species of thermal

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decomposition of pure reedy grass leaves and H3PO4-impregnated reedy grass leaves.

The following m/z ratio (mass-to-charge ratio) analyses were obtained from TG-MS to better understand the decomposition mechanisms of reedy grass leaves. Fig. 4-6 present the evolution curves of H2O (m/z=18), CO2 (m/z=44) and C3H3O+ (m/z=55)

during pyrolysis of the samples. For the evolution curve of H2O, the lowest temperature (below 100°C) peak produced comes from the moisture in the samples. As can be seen from Fig. 4-5, H2O and CO2 are formed from the pyrolyzing processes of all samples, but the temperatures at which the evolution peaks reach their values are different. For pure reedy grass leaves, the temperatures of maximum evolution of

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H2O and CO2 are 345°C and 340°C, respectively. With the incorporation of H3PO4, The temperature of maximum evolution of H2O and CO2 decreases to 142°C and 148°C. The low temperature evolution of CO2 was produced by esters and carboxylic

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acid groups in the reedy grass leaves (mostly present in hemicellulose and lignin). It

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appears that H3PO4 first attacks hemicellulose and lignin. Effects of acid attack are to

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hydrolyze glycosidic linkages in the hemicellulose and cellulose and to cleave arylether bonds in the lignin. Further, the acid-catalyzed hydrolysis of ether linkages

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in lignin leads to the formation of ketones. And H3PO4 can be combined with organic species to form phosphate and polyphosphate bridges that connect and cross-link

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biopolymer fragments [31].

Analyses of evolved gases show that the effect of H 3PO 4 is to promote

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d

dehydration of reedy grass leaves at low temperature. Thus, the H3PO4-impregnated reedy grass leaves decompose early in comparison with pure reedy grass leaves.

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The ion m/z=55 can be attributed to the fragment C3H3O+ derived from small molecule aldehydes. In Fig. 6, the maxima intensities of fragment C3H3O+ released

from pure reedy grass leaves was exhibited at around 286°C, With the incorporation of H3PO4, The maxima intensities of fragment C3H3O+ increases to 410°C. That can be seen, as the temperature is increased, a contraction of the structure of activated carbon was caused by the scission of P-O-C bonds. The reduction in cross-link density allows the growth and alignment of polyaromatic clusters, producing a more densely packed structure with some reduction in porosity.The above phenomena can be explained that H3PO4 is a dehydrating compound, which will increase the yield but

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will also change the thermal degradation of the precursor, leading to a subsequent change in the evolution of porosity. Interestingly, for most of gas products, their evolution intensity from pure reedy

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grass leaves is higher than that from H3PO4-impregnated reedy grass leaves, that may

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be explained reaction with H3PO4 can stabilizes the cellulose structure by inhibiting

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the formation of levo-glucosan which otherwise offers a route to the substantial degradation of cellulose through its decomposition to volatile products. That can be

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clearly seen that the formation of most of gas products is well accompanied by the sharp decomposition of samples shown in the TG curves.

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3.5. Functional groups of reedy grass leave activated carbon

The FT-IR spectra of reedy grass leaves activated carbon prepared based on the

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activation temperature (500°C) and activation time (2h) are shown in Fig.7. The broad

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absorption band at 3600–3200 cm-1 with a maximum at about 3420 cm-1 is

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characteristic of the stretching vibration of hydrogen-bonded hydroxyl groups from carboxyls, phenols or alcohols, and water adsorbed in the activated carbons. The band at 2800–3000 cm−1 indicates the presence of an aliphatic–CH stretching. The spectra shows a pronounced band at 1630 cm-1, that can be assigned to the C=C stretching

vibration in the structure of the activated carbon. The band at 1000 –1300 cm− 1 is usually found with oxidized carbons and has been assigned to C-O stretching in acids, alcohols, phenols, ethers, and/or esters groups[30]. Nevertheless, it is also characteristic of phosphorus and phosphocarbonaceous compounds present in H3PO4 activated carbons. The peak at 1163cm-1 can be assigned

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to the stretching mode of hydrogen-bonded P=OOH groups from phosphates or polyphosphates, to the O–C stretching vibration in the P–O–C (aromatic) linkage. The band at 1080-1065cm-1 could be due to P+–O- in acid phosphate esters and to the

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symmetrical vibration in polyphosphate chain P–O–P[32]. The FT-IR spectroscopy

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result indicates that the produced carbons are rich in surface functional groups.

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Fig. 8-10 shows the XPS analysis results for the reedy grass leaves activated carbon prepared based on the activation temperature (500°C) and activation time (2h).

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XPS spectra of C1s excitation showed complicated envelope that indicated several carbon species at the carbons’ surface (Fig. 8). The characteristic bands for carbon

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occuring in: graphite (284.2–284.9ev), carbon species in alcohol, phenols, ether groups, and/or C-O-P linkage (285.4–286.3ev), carbon in carbonyl groups

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(287.2–287.9 eV), carboxylic groups or esters (288.7–289.3 eV) can be found[33]. The contribution of (285.8ev) peak is higher than (287.9ev) peak, so there is a

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significant presence of C-O-P and/or C-O-C bonds. Fig. 9 shows the XPS spectra of O1s excitation. The O1s spectra of activated

carbon was fitted to four peaks according to the literatures[34], which include oxygen in carbonylic groups(C=O) and non-bridging oxygen in the phosphate group (P=O)(531.2–531.6 eV), oxygen in phenolic, lactonein and C-O-P groups (532.7–533.0 eV), noncarbonyl oxygen in carboxylic groups (533.8–534.4 eV) and oxygen in H2O (535.5– 536.3 eV) [33]. In the O1s spectrum it can be seen a small con- tribution of OH groups. The P2p peak was deconvoluted into three different components (Fig. 10). Peak

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(131.9–132.7 eV) was attributed to the formation of phosphates and polyphosphates (likely pyrophosphates). Peak (133.3–134.9 eV) comes from metaphosphates[35]. Peak (129.6 eV) comes from elemental phosphorus. It may appear that the existence

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of elemental phosphorus in carbons chemically activated with H3PO4. The XPS

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analysis result indicates that the produced carbons are rich in surface functional

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groups, supporting FT-IR spectra the findings, and as observed by TG-MS. 3.6. Textural characterization by SEM

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SEM images of the reedy grass leaves activated carbon prepared based on the activation temperature(500°C) and activation time (2h) are shown in Fig. 11(a–c), It

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can be seen from the micrographs( Fig. 11a) that the activated carbons have relatively heterogeneous and highly porous surface. Fig. 11b shows the structure of activated

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carbon was bight fibers features on the surface. Fibers had been contacted each other and made network structures. When reedy grass leaves were subjected to activation,

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most of the organic volatiles were evolved, leaving behind the ruptured surface of activated carbon with a small number of pores[36]. Fig. 11c shows the external surface of the AC was slightly corrugated and abundant pores, fairly uniformly distributed were gradually formed during activation. These pores are the exterior pores that serve as the main channels that connect to the micropores on the inner surface of the carbon. This observation is supported by the BET surface area and Pore size distribution of the activated carbon. 4. Conclusions In the present study, Activated carbons were produced from reedy grass leaves by

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chemical activation with H3PO4 in N2 atmosphere. With the increase of activation temperature and activation time, BET surface areas, iodine number, and micropore volume of produced activated carbon were gradually increased at first and then

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decreased. The optimal conditions for the activation of reedy grass leaves AC are

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estimated to be activation temperature of 500°C, activation time of 2 h, giving the

BET surface area and iodine number of 1474 m2/g and 1128 mg/g respectively. The

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micropore volume of obtained activated carbon has 0.560cm3/g.

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The various characterization methods used in this study show that H3PO4 acts as an activating reagents, which will increase the yield but will also change the thermal

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degradation of the precursor, leading to a subsequent change in the evolution of porosity. And the reedy grass leaves activated carbons have a large number of oxygen-

te

d

and phosphorus-containing surface groups. The amorphous structure of reedy grass leaves activated carbons were bight fibers features on the surface and the external

Ac ce p

surface of the activated carbons was slightly corrugated with abundant pores. Therefore, reedy grass leaves might be a potential raw precursor for preparation of high quality activated carbon.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (21276059), Program of Hebei Science and Technology Commission (13211402D), Natural Science Foundation of Hebei Province (B2014201101). References

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Wei Li, Jinhui Peng, Libo Zhang, Hongying Xia, Ning Li, Investigations on carbonization

cr

[29]

ip t

2857–2868.

processes of plain tobacco stems and H3PO4-impregnated tobacco stems used for the

us

preparation of activated carbons with H3PO4 activation, Industrial Crops and Products 28 (2008) 73–80. [30]

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an

Methylene Blue adsorption of phosphoric acid activated carbons from globe artichoke leaves, Fuel Processing Technology 92 (2011) 1203–1212.

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M

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te

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d

Tascón, Oxygen and phosphorus enriched carbons from lignocellulosic material, Carbon 45

Ac ce p

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Table 1 Effect of activation temperature, activation time on the BET surface area of activated carbons, yield and iodine numbers.

18

Page 18 of 33

Table 2 Comparison of activated carbons of present work with other literature data under optimum conditions.

ip t

Fig. 1. Pore size distribution of produced activated carbon from reedy grass leaves (the activation

cr

temperature (500◦C) and activation time (2 h)).

Fig. 2. X-ray diffraction pattern of produced activated carbon from reedy grass leaves (the activation

us

temperature (500◦C) and activation time (2 h)).

an

Fig. 3. TG analysis curves of pure reedy grass leaves (A) and H3PO4-impregnated (H3PO4-to-precursor

M

ratio 0.88:1) reedy grass leaves (B)

Fig. 4. Ion current curves of m/z = 18 during thermal degradation of pure reedy grass leaves (A) and

te

d

H3PO4-impregnated (H3PO4-to-precursor ratio 0.88:1) reedy grass leaves (B)

Fig. 5. Ion current curves of m/z = 44 during thermal degradation of pure reedy grass leaves (A) and

Ac ce p

H3PO4-impregnated (H3PO4-to-precursor ratio 0.88:1) reedy grass leaves (B)

Fig. 6. Ion current curves of m/z = 55 during thermal degradation of pure reedy grass leaves (A) and H3PO4-impregnated (H3PO4-to-precursor ratio 0.88:1) reedy grass leaves (B)

Fig. 7. FTIR spectra of produced activated carbon from reedy grass leaves (the activation temperature (500◦C) and activation time (2 h)).

Fig. 8. XPS spectra of the C1s region for produced activated carbon from reedy grass leaves (the activation temperature (500◦C) and activation time (2 h)).

19

Page 19 of 33

Fig. 9. XPS spectra of the O1s region for produced activated carbon from reedy grass leaves (the activation temperature (500◦C) and activation time (2 h)).

cr

activation temperature (500◦C) and activation time (2 h)).

ip t

Fig. 10. XPS spectra of the P2p region for produced activated carbon from reedy grass leaves (the

Fig. 11. (a–c) Scanning electron micrographs of produced activated carbon from reedy grass leaves

Ac ce p

te

d

M

an

us

(the activation temperature (500◦C) and activation time (2 h)).

20

Page 20 of 33

Table 1 Effect of activation temperature, activation time on the BET surface area of activated carbons, yield and iodine numbers. BET Surface Micropore

time(h)

area (m2/g)

number

(cm3/g)

(mg/g)

us

(◦C)

volume

Iodine

ip t

temperature

Activation

cr

sample Activation

455

1223

0.541

1082

1102

0.453

1079

1178

0.526

1104

1320

0.556

1109

3

1376

0.558

1117

4

1298

0.547

1100

5

1107

0.456

1070

400

2

690

II

500

2

1474

III

600

2

IV

700

2

V

800

2

VI

500

1

VII

500

VIII

500

VIIII

500

0.274

0.560

1128

Ac ce p

te

d

M

an

I

21

Page 21 of 33

Table 2 Comparision of activated carbons of present work with other literature data under optimum conditions. Activation Chemical

Activation

treatment

Iodine

References

Surface number

cr

temperature(◦C) time(h)

BET

ip t

Raw material

area

(mg/g)

us

(m2/g)

2

Corncob

400

1

Palm shells

420

0.5

Acorn shell

600

d

1600

665

[12]

H3PO4

2081

711

[13]

H3PO4

1109

1035

[15]

ZnCl2

1289

1209

[16]

644

-

[19]

trimethyl

1

phosphate

450

1

H3PO4

1179

-

[19]

240

3

ZnCl2

697

1009

[20]

500

2

H3PO4

1474

1128

This study

Ac ce p

Lotus stalks

450

0.5

te

Lotus stalks

KOH

an

800

M

Corncob

Biomass(Elaeagnus angustifolia seeds)

Reedy grass leaves

22

Page 22 of 33

Ac

ce

pt

ed

M

an

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cr

i

Figure

Page 23 of 33

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ce

pt

ed

M

an

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cr

i

Figure

Page 24 of 33

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ce

pt

ed

M

an

us

cr

i

Figure

Page 25 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 26 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 27 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 28 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 29 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 30 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 31 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 32 of 33

Ac

ce

pt

ed

M

an

us

cr

i

Figure

Page 33 of 33