SEMINAR ON ACTIVATED CARBON
TABLE OF CONTENTS
Introduction – – – – – – – – – – 1Activated Carbon – – – – – – – – – 1-2Uses of Activated carbon – – – – – – – – 2Applications of Activated carbon in various fields – – – – 2-3Classification of Activated carbon – – – – – – – 3Powdered Activated carbon – – – – – – – 3Granular Activated carbon – – – – – – – – 3-4Methods of Activated carbon generation – – – – – – 4-5Factors affecting Activated carbon production conclusion – – – 5-6Conclusion – – – – – – – – – – 7References – – – – – – – – – – 8SUMMARY
Activated carbon or porous carbon materials are characterized by their highly developed internal surface area and porosity. Development of micro and mesopores are of great importance because it allows the carbon to adsorb, in large amounts, various types of gaseous or liquid medium. Various method of activation used to obtain activated carbon with high surface area and porosity involve physical and chemical activation method. Chemical activation involve the addition of compound such as znd2 and H3 PO4 to the precursor prior to carbonization, physical activation refers to gasification of the carbon by oxidizing gases such as CO2. Activated carbon can be prepared in the form of powder, granular, and pallets form depending on the area of application
INTRODUCTION Activated carbon, also called activated charcoal is a form of carbon that has been processed to make it extremely porous and thus, to have a large surface area available for adsorption of chemicals, heavy metals, toxic chemicals, separation of gases, recovery of solvents, removal of organic pollutants, petrochemicals etc. (Jyotsna et al., 2005). Activated carbon is well known for its porosity and adsorption capacity, thus, it is used in different industries of a vast varities of application. Activated carbon has exceptional adsorption properties because of their high surface area. The properties of activated carbons depend on the activation process and nature of the source materials, moreover, in both physical and chemical activation process, knowledge of different variables is very important in developing the porosity of the carbon (Lozano-Castello et al 2001).Although, activated carbon was first recognized adsorbent and it is still widely used in industry, and understanding of their porous structures still continues. The advantage of using the agricultural activation carbon is that, these raw materials are renewable and potentially less expensive to produce. However, the abundance and availability of area of Northern Nigeria make then god source of row materials for activated carbon production. (Tsai et al, 2001).Activated carbon can be prepared either by physical or chemical means using a variety of starting materials such as rice husk, coal, sawdust, tropical wood, palm shells, corn cobs, coconut shells and many more (Gimba et al. 2004)
ACTIVATED CARBON
is solid, tasteless and black carbonaceous materials having complete porous structure (USDA 2002). Their structural heterogeneity is as result of existence of microspores, mesopores, and macrospores of different size and shapes. These properties make activated carbon most important due to its high degree of microporosity, just one excess of 500m2, some have surface area as high 5000m2/g (Baker et al., 1992, cited in USDA, 2002).An activated carbon level sufficient for useful application, may be obtained slowly from high surface area, further chemical treatment often enhance adsoption properties (CCI, 2006)
USES OF ACTIVATED CARBON
Activated carbon is used in methane and hydrogen storage, air purification, decaffeination, metal extraction, water purification, medicine, sewage treatment, filters in compressed air, teeth whitening, and many other applications (Salvador f and Sanchez, 1999)
APPLICATION OF ACTIVATED CARBON IN VARIOUS FIELD
Some of its application in various fields is discussed below:In industry, the major application involves the use of activated carbon in metal finishing for purification of electroplating solution. A variety of organic chemicals are added to plating solution for improving their deposit qualities and enhancing properties like brightness, smoothness, duchlity etc (Elliot et al., 1989).In medicine, activated carbon is used to treat poisoning and overdoses ingestion.
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Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, ingestion and flahilence. However, it is insufficient for a number of poisoning including strong acids or alkali, cyanides, iron arsence etc. incorrect application results in pulmonary aspiration which sometimes be fatal if immediate medical treatment is not inhated. (Bae W et al., 2014).In analytical chemistry, activated carbon in 50% combination with celite, is used as stationary phase in low pressure chromatographic separation of carbohydrate using ethanol solution as mobile phase in analytical or preparative protocols. (AOAC, 1990).In the environment (i.e environmental application), activated carbon has numerals application in removing pollutants from air or water streams both in the field and industrial processes such as air purification, drinking water filtration etc.s (Saueprasearsit 2011).In agriculture, activated charcoal is an allowed substance used by organic farmers in both livestock production and wine. In livestock production, it is used as a pesticide, feed additive, processing and non-agricultural ingredients and disinfectants (USDA, 2002)
CLASSIFICATION OF ACTIVATED CARBONActivated carbons are complex products which are difficult to classify on the basis of their behavior surface characteristics and preparation methods. The types of activated carbon available in the current market are powder, granular and pellet. It is classified according to its particle sizes and shapes, and each type has its specific application. However, some broad classification is made for general purpose based on their physical characteristics (Rotich and Lemaro 2007)
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POWDERED ACTIVATED CARBON (PAC)The particle size of powdered activated carbon is less than 100Um in size with an average diameter between 15 and 25Um. Thus, they present a large internal surface with a small diffusion distance. Powdered activated carbon is made up of crushed or ground carbon particles, 95-100% if which will pass through a designated sieve. Powdered activated carbons are mainly used in liquid phase adsorption and flue gas treatment. In waste water treatment, the most commonly used of powdered activated carbon is in the secondary treatment called powdered activated carbon treatment process (Rotich and Lemaro, 2007)
GRANULAR ACTIVATED CARBON (GAC)Granular activated carbon has a relatively large particles size compared to powdered activate carbon and consequently, presents a smaller external surface. Diffusion of the adsorbate is thus an important factor. These carbons are therefore preferred for all adsorption of gases and vapors and their rate of diffusion are faster. Granulated carbons are used for water treatment, deodorization and separation of components of flow systems. GAC can be either in the granular form or extruded. They have the advantages of being harder and longer lasting than powdered activated carbons, clean to handle, purity large volumes of gas or liquids of a consistent quality and can be reactivated and reused many times (Rolich and Lemaro, 2007)
METHODS OF ACTIVATED CARBON GENERATIONG of activated carbon reported by many researchers were classified into three main processes which are pyrolysis process (Zhu J, et al., 2009), physical and chemical activation process (Bae W et al., 2014).The physical activation includes carbonization and activation step whereby steam and CO2 are the most broadly used reagents, significantly influencing the porosity of the Activated carbon, the Activated carbon generation using chemical activation entails a single step whereby chemical reagents like potassium hydroxide, phosphoric acid zine chloride can simply be used at room temperature. (Bae W et al., 2014)
PYROLYSIS PROCESS
Thermochemical conversion of organic biomass into gaseous or/and liquid fields at extremely high temperature in the absence of halogen (mainly oxygen) is termed as pyrolysis. Pyrolysis is a simultaneous process that changes both the chemical composition and physical phase of materials and is irreversible. Pyrolysis process is mostly observed when materials are exposed to higher temperature (Zhu J et al., 2009). Some features of pyrolysis such as temperature has the most significant effect and then followed by retention time, heating rate and nitrogen flow rate.
Normally, when the reaction temperature increased, causes reduction in both AC and char production, while at the same time increasing the pyrolysis temperature leads to a drop off of solid yield and an increase in both gases and liquid percentage yield. On the other hand, raising the temperature leads to raised ash and Activated carbon percentage, whereas the volatile matter gets reduced. Therefore, Activated carbon with greater quality is obtained at a higher temperature (Ioannidou O and Zabaniotou A, 2007)
PHYSICAL ACTIVATION PROCESS.
Physical activation is a two-step process carbonization of carbonaceous materials comes first, then activation of the resulting char at high temperatures in the presence of CO2, steam, air or the mixture serving as oxidizing gases. The CO2 is usually used as activated gas being easy to handle, clean and possesses a slow reaction rate at a temperature around 80000C, which facilitates control of the activation process. A temperature range of 4000C and 8500C was found to be the carbonization temperature, though it may sometimes reach up to 10000C while activation temperature between 6000C and 9000C the activated carbon produced using physical activation method is somehow deficient in some qualities, which makes them unsuitable to be use as filters or as adsorbents. It worth mentioning that physical activation can be performed using various agricultural biomass residues such as mango pits, rice husk, rice hull, sawdust, sunflower shells, corncobs, olive pits, pine cone, wood waste, corn-hulls, cotton residues, oak, tobacco stems, corn Stover, coconut coipeth. Almond shells and peanut hulls (Bae W et al., 2014)
CHEMICAL ACTIVATION PROCESSIn the chemical activation process, involves multiple two steps occurring simultaneously, with the chemical activating agents mixing with the precursor, as oxidants and dehydrates. Performing activation and carbonization simultaneously during the chemical activation process at lower temperature results in having better porous structure of Activated carbon, even though, concern about environmental protection may limit the use of chemical agents for activation. Moreover, some chemicals that are widely used as activating agents are Zinc chloride (Znd2), potassium hydroxide (KOH), phosphoric acid (H3PO4) and potassium carbonate (K2CO3). Where the agriculture wastes are being reduced with the earlier mentioned chemicals consist of; olive seed, apricot stones macadama, pecan-shells, peanut-hulls nut-shells almond shells, corn-cob, hazelnut shells, rice husks, rise straw and cassava peel (Ioannidou O and Zabaniotou A, 2007)
FACTORS AFFECTING ACTIVATED CARBON PRODUCTIONRaw MaterialsMost organic substances with high carbon content are potentially raw materials for Activated carbon production. To produce a porous carbon structure, the under listed factors can be considered.High carbon contentLow in organic content (i.e. low ash)Potential extent of activationLow degradation upon storageHigh density and sufficient volatile contentStability of supply in the countriesInexpensive materialsLignocellulosic materials were generally accepted as precursor for Activated carbon production and constitute about 45% of the total raw materials used. To produce Activated carbon with low ash content, it is important to get materials with low in organic content (Zarifah MS, 2010).T
TEMPERATURE the Activated carbon production, the activation temperature plays a vital role in affecting the characteristics of the Activated carbon produced. As for commercial purposes Activated carbon, it is normally carried out in a mixture of steam and CO2 at a temperature above 8000C. Several studies have been reported which indicated that activation temperature has great influence surface area and production yield of activated carbon (Foo KY and Hameed BH, 2011).
The activation temperature is between 200 to 11000C. therefore, increasing activation temperature always results in the reduction of Activated carbon yield during production, which at the same time results in increasing the volume of volatile substances released. Generally it is inappropriate to prepare Activated carbon at a temperature above 8000C. This goes along with an increase of fixed carbon and ash content, which may be ascribed to the removal of volatile matter in the material during carbonization process. (Abdullah AH et al., 2001).
ACTIVATED TIME The activation time also has a greater influence on both the carbonization process and properties of Activated carbon in addition to the activation temperature. It is observed that as excessive activation time occurs, it causes the reduction in product yield. (Zarifah MS, 2010).CONCLUSIONConclusively, it is seen from the findings that, the importance and advantages of Activated carbon can’t be overestimate as it almost fulfills the needs in every sector that need adsorbent for purification of liquid, gas and solid matters consequently, there is a great obligation from the authorities to assist (physically and economically) researchers in finding easy and viable ways to boost the production of Activated carbon at best possible quality.REFERENCESAbdullah AH, Kassim A, ZaindZ, Hussein MZ, Kuang D, Wooi OS. Preparation and characterization of activated carbon from Gelam wood bark (Malaleuca Cayuput). Malaysian J. Anal. Sci. 2001;7 (1): 65-68.AOAC, (1990). “Associatio of official analytical chemistry official method of analysis” 15th Washington D.C, 147-158.Bae W, KM J, Chung J. production of granular activated carbon from food-processing wastes (wal-nut, shells and Jujbe seeds) and its adsorptive properties. J. Air Waste Manage. Assoc. 2014; 64 (8): 879-886.Baker, F, Miller A, and tolles D (1992). “Activated carbon” kirkothmer encyclopedia of chemical technology 4(1): 1015-1037.Cameron Carbon Incorporated (CCI). Activated carbon: manufacture, structure and properties. Activated carbon & related technology, USA; 2006.Elliot C, Colby adsorption of GAC, BAC and bio filter diffuse pollution difference, Dulbin.Foo ky, Hamed Bh. The environmental applicators of actuated carbon /zeo lite composite materials. Adv. Colloid interface sci. 2011: 162 (1-2) : 22-28Gimba C. Ocholi O, Nok A, (2004). “Preparation of activated carbon from agricultural /coasters. Cyanide binding with activated carbon matrix from ground nut shell”. Nig. Journal of science research 4 (2): 106-110Jyotsna G, Krishna K, Chitra R, Vinod K.G, (2005), “Removal of lead (11) by adsorption using treated granular accurate carbon: Batch and column shi dies” journal of Hazardous materials. Volume 125, issue 13,17, 99,211-220.Loanindou O, Zabaniobu A. agricultural residues as precursors for actuated carbon production: a review renew sustain energy rev. 2007; 11 (9): 1966-2005 Lozano-castello D, Lillo-Rodenas, MA, cazorta – amorros D, and linares – Solano A, (2001) “preparation of actuated carbon from Spanish anthracite I activated carbon by KOH”. Carbon 39: 741 – 749.Rotiah Bk, Lemaro F.A, (2012) “preparation and characterization of activated carbon from locally available materials, v12 coconut shells” project research, university of Nairobi, Kenya.Salvador F, Sanchez-Jiminez C. Effect of regeneration treatment with liquid water at high pressure and temperature on the characteristics of three commercial activated carbons. Carbon 1999; 37:577-583.Saueprasearsit P. Adsoption of chromium (vi) using durian peel. Intl conf Biotechnology and environment management, Singapore; 2011; 18:33-38.Tsai W.T Chang C.Y, Lin M.C Chen S.f, sun H.F and Hsieh, M.F., (2001) “Adsorption of acid dye on to Activated carbons prepared from Agricultural waste baggase by ZhCl2”. Chemosphere 45, 51-58.USDA, (2002),
“Activated carbon processing review by national organic standard board panel” pp-1-23.Zarifah MS. To produce the activated carbon from matured palm kernel shell. Bachelor thesis, faculty of Chemed and natural resources engineering university Malaysia Pahang, Malaysia; 2010.Zhu j, Sh B, Zhu J, Chen L. production, characterization and properness of chloridized mesoporous activated carbon from waste tyres. Waste managers 2009; 27:553-560.