My Community, Our Earth Geographic Learning for Sustainable Development Philippine Science High School Southern Mindanao Campus

ACTIVATED CARBON FROM Durio zibethinus L. (DURIAN) RIND

Joram Ner L. Combatir

Dominic Angelo V. Echavez

Al Sean A. Sala Jr.

Green Science Camp Project

Research Adviser

Michael Casas

My Community, Our Earth Geographic Learning for Sustainable Development Philippine Science High School Southern Mindanao Campus

ABSTRACT

Durio zibethinus (durian) rind is considered as waste here in Mindanao and is still not tested for its ability to produce activated carbon. The study aimed to produce activated carbon from Durio zibethinus (durian) rind at 700-800oC and compare its physical and adsorptive properties with a commercially available activated carbon. The durian rind was oven-dried for 24 hours and was converted to charcoal. The produced charcoal was processed into activated carbon through steam pyrolysis at a temperature setting of 700-800oC in a small rotary kiln. The results showed an average yield of 40.03%. The activated carbon samples were tested for its bulk density, apparent density, moisture content, benzene adsorption, and carbon tetrachloride (CTC) activity. The average values of these parameters are: 0.124 g/cm3(apparent density), 0.319 g/cm3(bulk density), 4.7% (moisture content), 10.6% (benzene adsorption), and 11.6% (CTC activity). These values were compared to the respective qualities of the commercial activated carbon (CAC). The bulk and apparent densities of the durian activated carbon (DAC) were not significantly different to the CAC but the moisture content and adsorptive properties, benzene adsorption and CTC activity, was significantly different to the CAC. The activated carbon prepared from Durio zibethinus (durian) rind is comparable to the commercial activated carbon in terms of its adsorption per unit volume, determined by its bulk and apparent densities. However, the prepared activated carbon’s moisture content and pore volume, determined by its benzene adsorption and CTC activity, is not comparable to that of the commercial activated carbon. These findings open to more researches looking at waste materials as main components in product development. This research promotes solid waste minimization in Davao City, provides an alternative remedy to air pollution and a possible source of income for locals in the city.

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INTRODUCTION

Background of the Study Air pollution is contamination of the atmosphere by any chemical, physical or biological agent that changes the natural characteristics of the atmosphere and makes it harmful to organisms. Pollutants of major public health concerns include particulate matter, carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide (WHO, 2012). The increasing concentration of these pollutants has been one of the causes to many respiratory diseases. However, various sectors and organizations continuously pour their efforts to address these concerns and decrease air pollution. At present, biofilters, acid gas control, and wet and dry scrubbers are widely used to remove air pollutants from industrial exhaust. The use of biofilters is a bioremediation process for it makes use of microorganisms that naturally degrades pollutants. The disadvantage of this method is that is requires a large amount of physical space. Acid gas control removes of acid gases from the air through adsorption in a dryer. Finally, wet and dry scrubbers involves the injection of an alkaline into a gas stream which causes a reaction that creates solid salts which can be easily removed (Enviro-news, 2009). However, these methods are expensive, and not readily available for developing countries. A different solution to trap and remove air pollutants is through the use of activated carbon filters. Activated carbon filters use activated carbon placed in exhausts to filter pollutants and prevent them from contaminating the air. Activated carbon is a highly adsorbent material which makes it efficient in removing particulate matter and other minute substances. It is prepared by carbonization and chemical or physical activation. Carbonaceous materials are usually used to prepare activated carbon. The durian rind is plentiful around Davao, especially in big market areas in the city such as Bankerohan, Agdao and Matina. Since the insides are the only edible parts, the rind is not consumed. It was observed that the durian rind accumulates in stores and fruit stalls. The rind is considered a waste and is therefore thrown away. These wastes add up to the overall solid wastes of the city contributing to pollution. Thus, it would be beneficial to make use of these wastes. In this study, durian rind was used as a material in producing activated carbon to provide a cheap alternative air filter and at the same time maximizing the use of durian rind which is considered a waste in the city.

Objectives of the Study This study aimed to prepare activated carbon from Durio zibethinus (durian) rind. Specifically, it aimed to: 1. determine the percent yield of activated carbon from the charcoal prepared from Durio zibethinus (Durian) rind at 700-800° C; 2. determine the bulk density, apparent density, benzene adsorption, and CTC activity of the activated carbon produced from the charcoal prepared from D. zibethinus rind; and My Community, Our Earth Geographic Learning for Sustainable Development Philippine Science High School Southern Mindanao Campus

3. compare the physical and adsorptive properties of the activated carbon from D. zibethinus rind with the commercial activated carbon produced by PJAC.

Significance of the Study This research explored a new source of activated carbon which can be used in air filtering processes. This study will have an impact to the Philippine economy because a new source of activated carbon, from durian peels which are abundant wastes in the Philippines specifically Mindanao, can lead to increased income and employment in the country. Moreover, this study will benefit the environment because the raw materials that will be used are wastes and the prepared activated carbon can be used to prevent air contaminants escaping the earth’s atmosphere.

Scope and Limitations of the Study This study focused in producing activated carbon from Durio zibethinus (Durian) rind. The durian rind was made into using a drum and the charcoal was activated at PJAC using a rotary kiln with the temperature setting of 700-800° C. The produced AC was also tested for its apparent and bulk densities in PSHS-SMC Research Lab and its benzene adsorption, moisture content, and CTC activity were evaluated in Philippine- Japan Activated Carbon (PJAC). The results obtained from such tests were compared to the corresponding physical and adsorptive qualities of the AC manufactured by PJAC.

Figure 1. Philippine-Japan Activated Carbon Production Plant (A) which is the production site of the activated carbon is 13.5 km from Ramon Magsaysay Park (B) which is the source of durian peels in the research.

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METHODOLOGY

Gathering and Preparation of Materials Ten (10) kilograms of Durian rind were obtained from Matina, Davao City. Ten (10)test tubes, one graduated cylinder, one weighing scale, and one mortar and pestle were borrowed from Philippine Science High School Southern Mindanao Campus Research Laboratory. Ten (10) sealable plastic bags were bought from HB1, Mintal. The durian rind was oven-dried in the PSHS-SMC Laboratory for twenty-four (24) hours to prepare for charcoal processing.

Processing of D. zibethinus Rind into Charcoal Three (3) kilograms of dried durian rind was placed inside a twenty (20) liters capacity drum. A separate pile of wood was also placed inside to act as the fuel to burn the rind. It was burned and tightly sealed inside the drum. When the drum has cooled, the produced charcoal was taken out of the drum. After twenty four hours of charring, the durian charcoal was obtained and separated from the ash.

Production of Activated Carbon The rotary kiln was set at 700-800oC activation temperature. A 200-gram sample of the durian charcoal was placed inside the rotary kiln. When the rotary kiln reached 700oC, the peristaltic pump which supplies water which serves as steam for the activation of the carbonized rind was switched on and water was pumped into the rotary kiln at a rate of 14mL/min. After fifteen (15) minutes of pyrolysis, the process was stopped and the activated carbon was collected. The process was done thrice to represent three replicates. The activated carbon gathered was weighed and stored in sealed plastic bags. The percent yield of the activated carbon is determined as: Mass of Activated Carbon % yield= X 100% Mass of Durian Charcoal

Apparent Density and Bulk Density Twenty (20) grams of the sample was ground using a mortar and pestle and measured for its volume. The quotient of its mass and volume is equal to its apparent density. Mass of Grinded Sample Apparent Density= Volume of Grinded Sample

The 20-gram samples were pressed and made compact in a graduated cylinder. The volumes of the samples were determined. The quotient of its mass and volume corresponds toits bulk density. Mass of Compacted Sample Bulk Density = Volume of Compacted Sample

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Benzene Adsorption and CTC Activity The samples were weighed and placed in a cylindrical tube. Benzene was introduced at a flow rate of 20mL/min and made to pass through the activated carbon. The change in the weight of the activated carbon is the total weight of benzene it adsorbed. The CTC activity was derived from the benzene adsorption measurements.

Statistical Analysis The data gathered were analyzed statistically using t-test and at 5% level significance.

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RESULTS AND DISCUSSION The study evaluated the use of Durio zibethinus (Durian)rind as an alternative source of activated carbon. The activated carbon produced from Durian rind was subjected to different tests to identify its physical and adsorptive qualities. The average percent yield of the durian activated carbon (DAC) is 40.03%. The apparent density of the DAC, which is 0.124, is not significantly different to that of the commercial activated carbon (CAC), which is 0.480. Moreover, the bulk densities of the DAC, which is 0.319, and the CAC, which is 0.481, are not significantly different. The moisture content of DAC is 4.70% and is significantly different of the moisture content of the CAC, which is 2.30%. The benzene adsorption of DAC is 10.6% and the benzene adsorption of the CAC which is 34.3%, are significantly different. Finally, the Carbon Tetrachloride (CTC) Activity of the DAC is 11.6% whereas the CTC activity of the CAC which is 63.5% and these values are significantly different (Table 1).

Table 1. Percent Yield, Physical and Adsorptive Qualities of Activated Carbon produced from D. zibethinus charcoal at 700-800oC Commercial D. zibethinus Activated Parameter Activated Carbon Carbon (DAC) (CAC) Percent Yield (%) 40.03 n/a Apparent Density (g/cm3) 0.124a 0.480a Physical Bulk Density (g/cm3) 0.319b 0.481b Properties Moisture Content (%) 4.70c 2.30d Benzene Adsorption (%) 10.6e 34.3f Adsorptive Carbon Tetrachloride Properties 11.6g 63.5h Activity (%) *Values with different superscripts are significantly different to each other. The percent yield of activated carbon from the charcoal shows how much activated carbon can be obtained given a certain amount of charcoal. A higher percent yield would mean that the particular source of the activated carbon is an ideal source because producing activated carbon form it will be less expensive since a smaller amount of source is used compared to a source that has a lower percent yield of activated carbon. Based from the table, the percentage of activated carbon that can be produced from durian rind is 40.03% of the original mass which is an average percent yield of activated carbon. The percent yield of activated carbon from the charcoal shows much activated carbon can be obtained given a certain amount of charcoal. A high percent yield would mean that the source is ideal because it maximizes the product produces and can be translated to increased profit for manufacturing industries using such raw material. Up to 40.03% of activated carbon can be produced from durian rind charcoal. This yield is higher compared to peanut hulls which have activated carbon percent yield of 22-36% but lower compared to olive seeds which have a percent yield of 59-76% (Ioannidou and My Community, Our Earth Geographic Learning for Sustainable Development Philippine Science High School Southern Mindanao Campus

Zabaniotou, 2007). Meanwhile, cattle bone and wood carbon yields 41.1% and 36.3% activated carbon respectively (Yusufu, Ariahu and Igbabul, 2012). The peanut hulls have asmall yield compared to others since it is softer and less dense than the other sources. However, olive seeds have a large yield since it is a hard and very compact seed. When olive seeds are converted into activated carbon, less amount of carbon will be removed from the material thus having a large percent yield since the molecules are more compact. The relatively high percent yield of durian rind is attributed to the temperature used in the research. The higher the temperature, the lower the percent yield of activated carbon results (Jabit, 2007). Apparent density is the density of the activated carbon including the pores. Bulk density, on the other hand is the density of the activated carbon (AC) while being compressed which excludes the pores. The bulk and apparent densities help determine the adsorption per unit volume of the AC, or how much volume of AC is used in a filter to reach desirable adsorption quality. This means that the produced AC can be used for the same applications of the CAC using same containers for filters. The apparent density of AC from palm kernel is 0.65 g/cm3 while the AC from bamboo has 0.42 g/cm3 (Inegbenebor I., Inegbenebor O. and Boyo, 2012). Bulk densities also differ. AC from bone usually has a bulk density of 0.78-0.79 g/cm3 whereas AC from wood has a bulk density of 0.40-0.48 g/cm3 (Yusufu, Ariahu, and Igbabul, 2012). The structure of the source also affects the density of the activated carbon. When the source is hard and compact, it tends to have an activated carbon with a high density, and when the source is rather soft, it will yield an activated carbon with a lower density. The density of the activated carbon affects how it is used and applied in containers and filters. Since the densities of the DAC and CAC have no significant difference, this means that the durian is as hard as the coconut to produce similar densities with their activated carbon. Thus, both DAC and CAC could be used for the same application and filters. Moisture is the amount of water that is bound to the AC pores. Since moisture content shows how much water is already adsorbed in the pores of the AC, it denotes its capacity to adsorb more particles. The higher the moisture content is, the fewer additional molecules the activated carbon can accommodate. The produced DAC has significantly different moisture content with the commercial activated carbon. This means that the commercial activated carbon. The reason for the higher moisture content of the DAC may be caused by the conventional techniques employed in the conversion of the durian rind to charcoal and the temperature used in the conversion of the charcoal to activated carbon. These factors may have caused the moisture to remain within the pores of the DAC thus explaining its higher moisture content compared to CAC. Also, moisture content affects the adsorption of the activated carbon. This pre-existing moisture in the AC takes the place in the pores where other molecules will bind to the activated carbon reducing the adsorption capacity of the AC (Abiko, Furuse, and Takano, 2010).The DAC has higher moisture content than the CAC which also means that the DAC has a more reduced adsorption capacity than the CAC. Activated carbons may have three different types of pores that determines the particle size which it is most suitable in adsorbing, namely the macropore which is the My Community, Our Earth Geographic Learning for Sustainable Development Philippine Science High School Southern Mindanao Campus

largest at 25nm or greater radius. The macropore is usually the one directly on the surface of the AC. Second is the mesopore, which is usually 1-25nm in radius. This pore is the one that connects the macropores to the third type of pore, which are the micropores (Indo German Carbon Limited, n.d). Both the size and distribution of micropores, mesopores and macropores determine the adsorptive properties of ACs. For instance, small pore size will not trap large adsorbate molecules and large pores may not be able to retain small adsorbates, whether they are charged, polar molecules or uncharged, non- polar compounds. Therefore, most of the benzene would be adsorbed by the mesopores (Ioannidou and Zabaniotou, 2007). In other words, if the benzene adsorption of an AC is high, then most probably, the number of mesopores the AC contains is large. The DAC’s benzene adsorption is significantly different from the CAC which means that the DAC has lesser mesopores than the CAC. The amount of mesopores greatly affects the capacity of the AC to adsorb benzene. Carbon tetrachloride or CCl4 is a small molecule that was made to be adsorbed into the AC. The ratio change in weight of the AC and the weight of the AC is its CTC Activity. Since CCl4 is a small molecule, the most suitable pore that can adsorb it is the micropore. The CTC activity of the DAC is significantly different from the CTC activity of the CAC which means CAC have more micropores to accommodate carbon tetrachloride molecules than the DAC. More pores in the AC contribute to better adsorption of molecules. In other words, DAC does not efficiently adsorb CTC compared to CAC because of the lesser content of micropores. The DAC is less effective as a filter than that of the CAC because of its low pore volume for adsorption. However, each material has its own degree of porosity. Coconut shell-based activated carbon is rich in micropores where 95% of its surface is accounted for micropores. Wood and peat based activated carbon are dominant of mesopores and macropores which is suitable for adsorbing large molecules (Cameron Carbon, 2006). Durian may not be rich with micropores and mesopores but it could have a large amount of macropores which may be studied by future researches.

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CONCLUSIONS Based on the results of the experiment, the following conclusions are drawn: 1. The mean percent yield of the activated carbon produced from Durio zibethinus (durian) rind at a temperature setting of 700-800oC is 40.03%. 2. The apparent density, bulk density, moisture content, benzene adsorption, and carbon tetrachloride activity of the activated carbon produced from Durio zibethinus (durian) rind are 0.123 g/cm3, 0.319g/cm3, 4.70%, 10.6%, and 11.6%, respectively. 3. The activated carbon from Durio zibethinu s(Durian) rind is not effective source of activated carbon because its moisture content, benzene adsorption and CTC activity is not comparable to the commercialized activated carbon based on the statistical analysis made but its bulk density and apparent density are comparable to that of the commercial activated carbon.

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