PREPARATION OF ACTIVATED CARBON FROM PALM OIL SHELL BY CHEMICAL ACTIVATION WITH Na2CO3 AND ZnCl2 AS IMPRENATED AGENTS FOR H2S ADSORPTION

Hydrogen Sulfide (H2S, rotten-egg) is one of the major environmental po l utants having its sources in natural and anthropogenic activities. It’s had smel l gas produced by anaerobic digestion in acid condition from organic and inorganic compounds cont aining sulphur, presents dual problems of its toxicity and foul ordour. One of methods of its rem oval is adsorption. Activated carbon is a widely used adsorbent in the treatment of air pollution. A dsorption type and capacity are primarily based on the physical properties of pores, namely the surfac e rea. Convetionnally, activated carbon is produce from biomass residues, wood coal and agricultural r esiduces. Today, one promising approach for the production of cheap and efficient activated carbon is used of waste from palm oil mill industries, which is palm oil shell. Palm oil shell is availabl e in large quantities of approximately 0.53 million tonnes annually in Thailand. Palm oil shell is a by -products of the palm oil industry and was used as a raw material in this study due to its high carbon c tent, high density and low ash content. Normally, H2S in biogas, which is found the range between as lo w as about 50-10,000 ppm depending on the feed material composition to prodction, can cause corros ion to engine and metal substance via of SO 2 from combustion. H2S must be removed from biogas product prior to furt her utilization. Therefore, in these research the usage of palm oil shell is especially mportant due to its high value added for produced activated carbon adsorbent for H 2S adsorption in biogas product. In this study, fixe d bed reactor (stainless steel with 54.1 mm internal diameter and 320 mm length) was studied to observe the effect of char product: Chemical agent ratio (Na 2CO3 and ZnCl 2, 1:1 to 1:3), which there are activated at 700°C activation temperature for 2 h on the chemical an d physical properties, BET surface area, the pore volume, micropore volume and hydrogen sulfide adsorption. The result showed that the BET surface area, BET surface area, the pore volume and micropore volume increased progressively with increasing the char product: Chemical agent ratio. The value of maen total pore volume of activated carbon increased with an increased char product: Ch emical impregnation agent ratio (Na 2CO3 and ZnCl2) as is a 1:1 to 1:3, from 0.3743 to 0.4181 cc/g an d 0.2877 to 0.3137 cc/g, respectively. The average micropore volume were 0.2224, 0.2411, 0.227 0, 0.1721, 0.1686 and 0.1546 cc/g of AC_Na13, AC_Na12, AC_Na11, AC_Z13, AC_Z12 and AC_Z11, respec tiv ly. The results of yield, it was found that that the activated carbon for Na 2CO3 agent is higher than activated carbon for ZnCl 2 agent. The highest of yield was 32.3% for AC_Na13. Moreover, t he maximum BET surface area and H 2S adsorption was 743.71 m /g and 247.33 ppm was obtained on AC_Na13. This gav e H2S adsorption more than commercial activated carbon (1%). Guideli ne for evaluation chemically activated carbon for potential application were suggestd. The conclusion showed that AC_Na13 has good chemical and physical properties scuh as chemical content and su rface area, which showed that the highest H 2S adsorption (247.33 ppm). The carbon content and BET surface area of AC_Na13 were 78.76 (wt%) Kanokorn Hussaro / American Journal of Environmenta l Sciences 10 (4): 336-346, 2014 337 Science Publications AJES and 743.71 m/g, respectively. Thus, chemical agent (Na 2CO3) can be used effectively as an operating strategy to optimize surface area. The synthetices activated carbon with suggested BET surface area were is good agreement with those obtained with che mical activation by Na 2CO3 impregnation. Moreover, activated carbon was used to the H 2S removal, it is also for environment benefit in wh ich air pollution by H2S emission and impact on human health could be pote ntially reduced.


INTRODUCTION
In Thailand, palm oil is one of primary agricultural products and it generates a large volume of residues. Every year about 0.53 million tons of palm oil shell are produced as by product and inadequely disposed. Only a portion of this residues is used for limites practical applications, such as raw material for the production of fuel and feed stock for obtaining chemical compounds. Palm oil residues results in palm oil mill industry. It is an environmental problem that has been frequently discussed by several sectors of the society. One alternative to attach this problem is by using adsorbents to remove pollutants from several effluents. This, has generated an increasing interest in the search for effiecient and low cost materials to be used as adsorbents for the elimination of air pollutants.
Activated Carbons (AC) as microporous materials are of the most important adsorbents, which have been extensively used as adsorbents, catalyst and catalyst supports in a variety of industrial and environmental applications. AC is an extremely versatile material as a effective adsorbent with its high adsorptive capacity and high surface area (Şahin and Saka, 2013). AC has been considered for the capture and eventual recovery of metal ions in aqueous industrial discharges for many years and indeed has enjoyed some commercial application. Metal plating and fabrication industries stand to benefit from a fast and robust method of sizing activated carbon adsorption columns for pollution mitigation and/or metals recovery (Banjonglaiad et al., 2008). Among the factors making the activated carbon application attractive are availability, environmentally friendly material, safe and very low cost of the staring materials coupled with its high surface area (Diya'uddeen et al., 2013).
Production of activated carbon can either be through physical or chemical activation. The former involves primary carbonization of raw material (below 700°C) followed by controlled gasification at higher temperatures (>850°C) (Yorgun et al., 2009). Physical activation of AC consists of two steps (i) the first step is the elimination of most of the hydrogen and oxygen contents by pyrolysis of carbonaceous material at high temperature and inert atmosphere and (ii) the second step is to activate the chars at high temperature and in presence of steam or carbon dioxide as oxidizing gases. Carbon atoms are extracted by these agents from the structure of the porous carbon according to the following endothermic reactions (Arami-Niya et al., 2011): (1) Chemical activation is inpregnated with an activation reagent and heated in an inert atmosphere. The carbonization step and the activation step proceed simultaeously. By dehydration and oxidation reactions of the chemicals, pore are developed. Produced char then washed to rid it from residual impurities (Kılıç et al., 2012). Chemical activation is the process that normally takes place at lower temperature and shorter time than those used in physical activation (Yorgun et al., 2009). Moreover, the advanges of chemical activation are: Its low enery and operating cost, higher carbon yields ad large surface areas when compared with physical activation. Chemical activation also has better development of porous structure. Knowledge of different variables during the activation process is very important in developing porosoty of carbon which is sought for give applications. Chemical activation is held in the presence of dehydrating reagents such as KOH, K 2 CO 3 , NaOH, ZnCl 2 , H 3 PO 4 and H 2 SO 4 which influence pyrolytic decomposition and inhibit tar formation. These reagents can improve the pore distribution and increase the surface area of adsorbents (Kılıç et al., 2012).
Activated carbons are produced from variety of organic materials rich in carbon contents like coal, lignite, wood and somm types of polymers. Due to increasing usage of AC, exploring the economial Science Publications AJES supplies for production of AC is necessary. Although coal and wood are mostly used as precursor, agricultural waste products would be a better choice in some applications (Arami-Niya et al., 2011). Due to high carbon and low ash contents, many of agricultural byproducts are appopriate for use as precursors for AC production it is accepted that the differences in material composition, such as lignin, cellulose and holocellulose influence the pore structure and pore size distribution of AC (Arami-Niya et al., 2010).
Hydrogen Sulfide (H 2 S) is an extremely toxic and malodorous gas, which is harmful to human health and has detrimental effects on many industrial catalysts, as well as a major source of acid rain when oxidized to sufur oxide. Many efforts have been focused on H 2 S removal from gas as the restrictive emission standards are worldwide enacted. One of the major challenges for natural gas purification is the removal of H 2 S. Amine scrubbing along with the Claus process is a dominant tecnology currently used in industry for H 2 S removal in natural gas, especially for high concentration of H 2 S removal. But this method loses its efficiency and economic advantage for low concentration of H 2 S removal. Alkali-impregnated activated carbons are usually used as low concentration of H 2 S oxidation catalysts, due to their high activity and fast kinetics of reaction (Chen et al., 2011).
In this research, palm oil shell as by product palm oil mill industries, was used as a raw material for the production of activated carbon by chemical activation. Palm oil shell is a cheap and abudant agricutural solid waste in tropical countries (Thailand). Palm oil shells have been successfully converted into well-developed activated carbons used for removal of various gaseous pollutants (Guo et al., 2007). On the other hand, they have been done on the utilization of palm oil shell as a raw material of AC production and it was reported that due to its high density, high carbon contents and low ash, this material can be used for the production of good quality AC (Arami-Niya et al., 2010).
This research focuses on different impregnation agents and the ratio of impregnated agent as controlling for activated carbon production and also on its pore volume and removal of H 2 S for biogas purification. The aim of this study to achieving the following: (i) Production of activated carbon by chemical activation with Na 2 CO 3 and ZnCl 2 as impregnation agent using palm oil shell as a raw material, (ii) analysis of chemical and physical properties for activated carbon product is performed by ultimate analysis, proximate analysis and surface area, (iii) Hydrogen Sulfide (H 2 S) adsorption test.

Materials
Palm oil shell was used as raw material in this research study. Palm oil shell was colected from Suratthani provice, southen Thailand. This raw material was dried at 110°C for 24 h and then crushed with a cutting mill and sieved to a particle size in the range from 1-2 mm. was used for preparation of activated carbon by chemical activation. The standard activated carbon (Comercial grade; code No.CGC-11A) was supplied from C. Gigantic Carbon Co. Ltd. Zinc Chloride (ZnCl 2 ) and Sodium Carbonate (Na 2 CO 3 ) were dissolved in distilled water to prepare a saturated solution.

Experimental Method
The preparations of the activated carbon were divided into two steps. The steps are as follows: (i) Carbonization process and (ii) impregnation process. The first step, carbonization process was the first step of the experiment. Palm oil shell was set in a reactor, which had fixed bed design of stainless steel with 54.1 mm internal diameter and 320 mm length, as shown in Fig. 1. This process was carried out under constant nitrogen flow (150 cm 3 /min) at a heating rate of 10°C/min up to 600 ˚C for 1 h. The second step, char product was directly impregnated with chemical agents, using Zinc Chloride (ZnCl 2 ) and Sodium Carbonate (Na 2 CO 3 ) solution in three different weight as 1:1, 1:2 and 1:3 of char product: Chemical agent ratio (w/w) and were kept at 80°C for 10 h. The experimental design was reported in Table 1. The temperature of activation was raised at 4°C /min up to 700°C, which was maintained for 2 h. After activation, the excess of chemical agent (ZnCl 2 and Na 2 CO 3 ) was removed with a 0.1 M solution of hydrochloric acid. Finally, the sample was then washed to remove excess reagent until there were pH about 6-7 and dried at 110°C for 3 h to obtain the final activated carbons. The samples were classified as AC_Z and AC_Na. The first two characters, AC, represents activated carbon and the third characters, Z and Na, represents ZnCl 2 and Na 2 CO 3 impregnation, respectively. The experimental design was operated following condition in Table 1.

Characterization of Impregnated Samples and Standard Activated Carbon
An elemental analysis was carried out using a CHNS/O ANALYZER (PE2400 SeriesII). Gaseous products were freed by pyrolysis in high-purity oxygen and were chromatographically separated by frontal analysis with quantitatively detected by thermal conductivity detector. Proximate analysis was conducted according to the American Society for Test in and Materials (1997) and the results were expressed in terms of moisture, volatile matter, ash and fixed carbon content. The surface areas of various samples were determined by gas adsorption and desorption (ICG, 2010). The specific surface areas of the samples were calculated using the Brunauer-Emmett-Teller (BET) single-point method. Approximately 0.01-0.03 g of the sample was placed in the sample cell, heated to 623 K and held at that temperature for 6 h under a N 2 /He flow. The sample was then cooled to room temperature and dipped into liquid nitrogen. After the adsorption of nitrogen reached equilibrium, the sample cell was then dipped into a water bath at room temperature. The amount of nitrogen desorped was measured by a gas chromatograph (Hussar et al., 2011). The specific surface area of the prepared activated carbons was estimated by the BET method using N 2 adsorption isotherm data.

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Yield is usually defined as final weight of activated carbon produced after impregnation, washing and drying, divided by initial weight of raw material. The following relationship is used for calculating the yield of activated carbons (Kılıç et al., 2012): Where: W i = Mass of impregnated sample W AC = Mass of the dried carbon after washing

Hydrogen Sulfide (H 2 S) Adsorption Test
Activated carbon with different microporous and mesoporous structure were presented and then impregnated with different content of ZnCl 2 and Na 2 CO 3 to remove H 2 S in the biogas product at low temperature of ambient temperature (about 30°C). The H 2 S adsorption using small column test equipment was conducted on the adsorbents of the activated carbon product. Adsorbent (20 g) of the impregnated activated carbon was placed in a glass column 5 cm diameter, using biogas product (Saitawee et al., 2014) as test gas with the total flow rate 15 cm 3 min −1 . Biogas detector was used to analyze the concentration of H 2 S in the inlet and outlet gases, as shown

Characteristics of Raw Material
The results of component characteristics of raw materials fed to reactor are summarized in Table 2. The ultimate proximate analyses of palm oil shell were as follows (dry wt basis%): Fixed carbon 24.1, moisture 4.2, ash 2.3, volatile 69.4, C 49.90, H 6.37 and N 0.46. A high carbon and low ash content of palm oil shell indicates that the precursor is suitable for activated carbon production. After carbonization process with the temperature of 600°C for 1 h, the volatile content of the chars decreased from 69.4 to 24.34% whilst the fixed carbon content increased from 24.1 to 70.65%. This phenomena was due to the release of volatile matter during physical process (with N 2 inlet during activation process), which subsequently caused an increase in carbon content.

Effect of Impregnated Ratio on Activated Carbon Product
The results of standard activated carbon and activated carbon product (AC, AC_Z11, AC_Z12, AC_Z13, AC_Na11, AC_Na12 and AC_Na13) samples characterization are presented in Table 3. The elemental analysis shows that the nitrogen and hydrogen contents are low. The impregnation process of char produces an increment in the carbon. The carbon content was increased with in increasing impregnate ratio of reagent. The high char product: Chemical agent ratio (1:3) in the AC_Na13 and AC_Z13 samples indicates a degree of aromaticity and suggests that during heating a polymerization takes place. It can be inferred that impregnation process of palm oil shell activated with Na 2 CO 3 had carbon content higher than that of palm oil shell activated with ZnCl 2 . The impregnation ratio plays an important role on the yield of activated carbon, as seen in Fig. 3, which the yield percentage had been calculated from Equation 1-3. The yields of activated carbons were in the range of 32.3-19.1% for Na 2 CO 3 and 25.1-15.2% for ZnCl 2 impregnated samples. It is shown that yield of carbon decreased as the impregnation ratio increases, due to promoting the gasification of char and increasing the total weight by excess chemicals (Kılıç et al., 2012). Moreover, it is observed that the activated carbon for Na 2 CO 3 agent is higher than activated carbon for ZnCl 2 agent. The activating agent in the interior of particles produces a dehydrating effect on the already transformed components during the heat treatment (700°C). It is very possible that cross-linking reactions are predominant in this step with the subsequent reduction in the exit of volatile matter and tars, leading to high active carbon yield observed (Yorgun et al., 2009). The surface area of powdered or porous solid can be calculated from the volume of gas absorbed onto the surface of the solid. In general, solids adsorb gases weakly bound due to Van der Waal's forces only, to cause sufficient gas to be absorbed for surface area measurement. The volume of gas absorbed increases with increasing pressure. The physical absorption of gases by solids increases with decreasing temperature and with increasing pressure. The process is exothermic, i.e., energy is released. The investigative procedure has first to establish what is known as an absorption (or desorption) isotherm. This, quite simply, is a measure of the molar quantity of gas n (or standard volume V a , or general quantity q) taken up, or released, at a constant temperature usually T by an initially clean solid surface as a function of gas pressure P. Most frequently the test is conducted at a low temperature, usually that of Liquid Nitrogen (LN2) at one atmosphere pressure) (Hussar et al., 2011). Convention has established that the quantity of gas adsorbed is expressed as its volume at standard conditions of temperature and pressure (0°C and 760 torr and signified by STP) while the pressure is expressed as a relative pressure which is the actual gas pressure P divided by the vapor pressure P 0 of adsorbing gas (called the adsorptive prior to adsorption and adsorbate afterward) at the temperature at which the test is conducted. Regardless of how the data are obtained and how manipulated thereafter, all analyses first must establish information in the form of quantity adsorbed (or desorbed) versus pressure; therefore the requirement that these measurements be of the highest quality cannot be overemphasized. These data, having been gathered at one temperature, constitute the adsorption (desorption) isotherm for the material in question. Plots of V a as the Science Publications AJES ordinate against P/P 0 as the abscissa reveal much about the structure of the adsorbing material (called adsorbent) simply from their shape. N 2 -adsorption/desorption isotherms was using the adsorption process, as shown in Table 4 and Fig. 4; the Brunauer, Deming, Deming and Teller (BDDT) theory, the basis of modern IUPAC classification, was used in this research to characterize the N2-adsorption isotherms. As can be seen from Fig. 4 had very silimar shapes. The nitrogen uptake was significate only in the low pressure where P/P0<0.2. At the higher relative pressure (P/P0>0.2) had a nearly horizontal plateau, which no futher adsorption was observed and the adsorption curve reached equilibrium at P/P0 about 0.2. This results indicating type I of isotherm based on the classification of IUPAC, which is characteristic of adsorbents having extremely small pores. On the other hand, in these material, the limiting uptake is controlled by accessible micropore volume rather than by the internal surface area (Diya'uddeen et al., 2013).

Table 4. Adsorption/desorption isotherms of N2 at 77 K on activated carbon product AC_Na13
AC_Na12 Volume ( The adsorption curve of Fig. 4 has rises more rapidly in the intermediate zone and shown a wide hysteresis loop instead of nearly retracing the adsorption curve. This behavior is typical of mesoporous and macroporous materials, such as, those that have pores with openings greater than 2 nm (20 Å) and 50 nm (500 Å), respectively. Therefore, pore are likely to have a wide range of sizes and shapes. There were closed in the pressure region near saturation. This shaps reveals that the adsorbing solid contains mesopores with an upper size restriction. For ease of comparison, activated carbon obtained at three different values of char product/chemical agent ratio (1:1, 1:2 and 1:3), when the char to agent ratio was increased by a factor of agent in the range of 1-3, it was found that a volume of N2 gas adsorption increasing with increased char product: Chemical agent ratio. Frome above results, it was found that the highest volume of nitrogen gas adsorption of AC_Na13>AC_Na12>AC_Na11>AC_Z13>AC_Z12>AC _Z11 were 274. 676, 267.5799, 246.6837, 205.6472, 197.4784 and 197.2957 cc/g, respectively. Which, the AC_Na13 and AC_Na12 had the highest volume of nitrogen gas adsorption more than standard activated carbon (AC, 254.7467 cc/g).
The results of mean the BET surface area, total pore volume and micropore volume from three methods are reported in Table 5. By obtaining triple measurements under the same experimental conditions, the experimental reponds are randomized. Mean surface area analysis was obtianed from BET method, which this results shown that AC_Na13 had the highest mean BET surface area, as shown in Table 5. The mean surface area of AC_Na12>AC_Na11>AC_Z13> AC_Z12>AC_Z11 were 725.66, 671.31, 551.05, 533.68 and 523.05 m 2 /g, respectively. The data show that surface area of activated carbons increased from 671.31 to 742.34 m 2 /g when the char product: Na 2 CO 3 ratio increased from 1 to 3; this is different from that char activated with ZnCl2, which the mean BET surface area of standard activated carbon (comercial graded) is lower AC_Na13 and AC_Na12. However, investigating the activation mechanism and understanding this phenomenon are quite meaningful. The value of maen total pore volume of activated carbon increased with an increased char product: Chemical impregnation agent ratio (Na 2 CO 3 and ZnCl 2 ) as is a 1:1 to 1:3, from 0.3743 to 0.4181 cc/g and 0.2877 to 0.3137 cc/g, respectively. The average micropore volume were 0.2224, 0.2411, 0.2270, 0.1721, 0.1686 and 0.1546 cc/g of AC_Na13, AC_Na12, AC_Na11, AC_Z13, AC_Z12 and AC_Z11, respectively.  The normality of the respond data is assumed. There were analyzed by using statistical software. The results of appying the analysis of variance are shown in Table  6, which it was found that a significant interaction the char product: Chemical agent ratio on BET surface area, total pore volume and micropore volume (Sig. <0.05).

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The results of gas adsorption studies conducted utilizing a gas biogas on samples were shown in Table 6. Hydrogen Sulfide (H 2 S) adsorption for AC_Na13 and AC_Z13 showed that the amount of H 2 S adsorbed increased progressively with Na 2 CO 3 impregnation. The total amount of H 2 S adsorbed followed the order of AC_Na13>AC>AC_Z13. The average capacity of H 2 S adsorbed by AC_Z13 was 241.67 ppm. While that of AC_Na13 was 247.33 ppm, which was better agreed with AC (245 ppm) as compared with other sample (as can seen in Table 7). These results show that the activated carbon could absorb the H 2 S, but the adsorption capacity of impregnation ratio these result confirmed by pore volume analysis, showing the increase pore volume with increased char product: Chemical agent ratio.

DISCUSSION
The results of this research showed that palm oil shell can be successfully converted into activated carbon with surface area properties. It was found that the amount of Na 2 CO 3 and ZnCl 2 used for chemical activation controls the characteristics of the carbon contents including BET surface area, total por volume, micro pore volume and H 2 S adsorption. Increasing the amount of chemical agent (Na 2 CO 3 and ZnCl 2 ) used for chemical activation; char product: Na 2 CO 3 and char product: ZnCl 2 ratio from 1:1 to 1:3 resulted in 9.69 and 5.07%, respectively, increase in the BET surface area. These findings are in agreement with the few reports in the orther hand that have addressed the possibility of using ZnCl 2 activation (Yorgun et al., 2009). In particular, Arami-Niya et al. (2010) reported activation of palm oil shell with ZnCl 2 , which chemically activated samples without extra heat treatment showed an increase in the surface area and pore volume with the increase in the mass ratio of ZnCl 2 , methan adsortion did not improve at any ratio (less than 13 cm 3 /g). There are various methods of determing surface are of an adorbent which include water and gas adsorption, inverse of iodine value and BET machine (Diya'uddeen et al., 2013). The most reliable and recognized internationally results are those obtained from BET machines.
Moreover, Arami-Niya et al. (2011) was presented chemically ACs from palm oil shell as a precusor have been prepared using low concetration of zinc chloride or phosphoric acid as activating agent, which combined physical and chemical activation of palm shell revealed that H 3 PO 4 impregnated samples attained better activation rates than those prepared using ZnCl 2 or physically samples.
Experimental results indicate that the suitable impregnated agent was Na 2 CO 3 to prepare activated carbon. Which chemical activation is widely employed, mainly using the reagents ZnCl 2 or Na 2 CO 3 as activating agents. Although the Na 2 CO 3 has cation similar characteristics to ZnCl 2 , in aqueous solution the Sodium cation (Na + ) is bigger than the Zinc cation (Zn 2+ ), which it is 99 and 83 pm, respectively. And this opens up the possibility of producing activated carbon with higher pore volume upon their activation. On the other hand, the zinc cation present in aqueous solution is a well-known pollutant (Oliveira et al., 2009). As indicated by Table 6 there were different the value of H 2 S adsorption, due to different chemical impregnated char product. The different impregnated agent on char product for H 2 S adsoprtion of AC_Na13 and AC_Z13 were the results of the distinguishably different of the surafce area. For the AC and AC_Z13 the activities of H 2 S dissolve abd dissociation are refrained, which slows down the removal rate, due to the hydrophobic property of the carbon surface water film is difficult to be formed when the relative pressure of water is low. While, AC_Na13 an additional factor that Na 2 CO 3 easily absorbs water should be considered. A basic solution film in formed on the surface of the AC_Na13, which promotes the dissociation. The present results in practice suggest that activated carbon production can be optimized if a impregnated with charproduct: Na 2 CO 3 (1:3) can be used effectively as a means of higher surface area and H 2 S adsorption.

CONCLUSION
The experimental study two contributions. First, it provides the palm oil shell from palm oil mill: As raw material in producing activated carbon by chemical activation. Activated carbon was prepared from char product of palm oil shell using Na 2 CO 3 and ZnCl 2 impregnated for 1:1 -1:3 of char product: Chemical agent and there was activated at 700°C activation temperature for 2 h. Second, it is indicated that the activated carbon performace for removal Hydrogen Sulfilde (H 2 S). The results of these research showed that palm oil shell can be successfully converted into activated carbon with BET surface area, total pore volume and micropore volume. It was found that BET surface area, total pore volume and micropore volume were increasing with increased the char product: Chemical agent ratio (1:1 to 1:3). Moreover, AC_Na13 has good chemical and physical properties scuh as chemical content and surface area, which showed that the highest H 2 S adsorption (247.33 ppm). The carbon content of AC_Na13 and AC (Standard activated carbon) were 78.76 (wt%) and 72.56 (wt%), respectively. The BET surface area of AC_Na13 and AC mearsured by N 2 adsorption at 77.4 K were found 743.71 and 707.10 m 2 /g, respectively. It indicated the activated carbon produced from palm oil shell lies in the range of commercial activated carbon. The impregnation with Na 2 CO 3 results in the high concentration of Hydrosulfide Ion (HS¯) and enhances the oxidation of H 2 S (Xiao et al., 2008). The high catalytic activity allows the pores to be fully utilized, which is the reason for the high sulfur capacity of AC_Na13. It had H 2 S adsorption more than commercial Science Publications AJES activated carbon (1%). However, the extra installation costs and process complexity in biogas purification system concept should be evaluated with the economic gain achieved due to extra biogas produced. Accordingly, the activated carbon produced from palm oil shell can be used as adsorbents for various environmental application including removing H 2 S compound from industrial production, which this is the developing research in the future for developed purify system. Therefore, Na 2 CO 3 was found more effective than the other agents as chemical reagent under same conditions in terms of high BET surface area, total pore volume, micropore volume and H 2 S adsortion. In these case, H 2 S adsorption was operated on lab-scale, due to there were used in biogas production on lab-scale. In future research, other impregnants and activated carbons will be used in studies similar to those described in this reseach. Morover, H 2 S adsorption will be operate in large scale for adsortion from source of biogas production on industrial.

ACKNOWLEDGMENT
The gratefully acknowledge the provision of Scientific and Technological Research Equipment, Chulalongkorn University researchers gratefully acknowledge the provision of Scientific and Technological Research Equipment, Chulalongkorn University and King's Mongkut University of Technology Thonburi.