EFFECTIVE METHOD FOR PREPARATION OF ACTIVATED CARBON FROM COMBRETUM NIOROENSE (GEZA) TARGETED TOWARDS HIGHER YIELD AND ADSORPTION CAPACITY
Table of contents
CHAPTER ONE 11.0 INTRODUCTION AND LITERATURE REVIEW 11.1 INTRODUCTION 11.1.2 Preparation of activated carbon 11.2 LITERATURE REVIEW 21.2.1Granular activated carbon (GAC) 61.2.2 Extruded activated carbon (EAC) 71.2.3 Impregnated carbon 71.2.4 Polymer coated carbon 81.2.5 Properties of activated carbon 81.2.6 Applications of activated carbon 91.2 Aims and Objectives 11CHAPTER TWO 122.0MATERIALS AND METHODS 122.1 MATERIALS 122.1.1 Collection of sample 122.1.2 Chemicals used 122.1.3 Equipments used 122.2 METHODS 132.2.1 Preparation of sample 13CHAPTER THREE 153.0 RESULT AND DISCUSSION 153.1 RESULT 153.2 DISCUSSION 16CHAPTER FOUR 174.0 CONLUSION AND RECOMMENDATIONSthat the chemical method of preparation was said to be more effective method compared to other methods employed in the present research work.
INTRODUCTION AND LITERATURE REVIEW1.1 I
carbon, also widely known as activated charcoal or activated coal is a form of carbon which has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions. The word active is sometimes used in place of activated. Due to such high degree of micro porosity , just 1 gram of activated carbon has a surface area in excess of 500m 2 (about one tenth the size of an American football field), as typically determined by nitrogen gas adsorption. Sufficient activation for useful applications may come solely from the high surface area, though further chemical treatment generally enhances the adsorbing properties of the material.
Activation carbon is most commonly derived from charcoal.1.1.2 Preparation of activated carbon Activated carbon is nothing but carbon produced from carbonaceous source materials like nutshells, peat, wood, coir, lignite, coal and petroleum pitch. It can be produced by any one of the following described processes: a) Physical reactivation: by this process precursor is developed into activated carbons using gases.
This is generally done by using one or a combination of the following processes: Carbonization: Material having appreciable carbon content is pyrolyzed at temperature ranging between 600–900 °C, in the absence of oxygen (usually in inert atmosphere with gases like argon or nitrogen) Activation/Oxidation: in this process raw material or carbonized material is exposed to oxidizing atmospheres (carbon monoxide, oxygen, or steam) at temperatures above 250 °C, usually in the temperature range of 600–1200 °C.b) Chemical activation: Before carbonization, the raw material can be impregnated with certain chemicals. The chemical needs to be typically an acid, strong base, or a salt (phosphoric acid, potassium hydroxide, sodium hydroxide, zinc chloride, respectively).
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After impregnation, the raw material needs to be carbonized at lower temperatures (450–900 °C). It is believed that the carbonization / activation step proceeds simultaneously with the chemical activation. Chemical activation is preferred over physical activation owing to the lower temperatures and shorter time needed for activating material
1.2 LITERATURE REVIEW
Activated carbons are carbonaceous materials that can be distinguished from elemental carbon by the oxidation of the carbon atoms found on the outer and inner surfaces. (Mattson and Mark 1971) These materials are characterized by their extraordinary large specific surface areas, well-developed porosity and tunable surface-containing functional groups (Barker et al., 1992). For these reasons, activated carbons are widely used as adsorbents for the removal of organic chemicals and metal ions of environmental or economic concern from air, gases, potable water and wastewater.(EL-Hendwy., 2003) The surface oxygen functional groups can be easily introduced to the carbon by different activation methods including dry and wet oxidizing agents.
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Dry oxidation methods involve the reaction with hot oxidizing gas such as steam and CO2 at temperatures above 700℃. (Smisek and Cerney., 1970) Wet oxidation methods involve the reaction between the carbon surface and solutions of oxidizing agents such as phosphoric acid H3PO4, nitric acid HNO3, hydrogen peroxide H2O2, zinc chloride ZnCl2, potassium permanganate KMnO4, ammonium persulphate (NH4)2SO8, potassium hydroxide KOH, etc. From the above oxidizing agents, phosphoric acid and zinc chloride are usually used for the activation of lignocellulosic materials, which have not been carbonized before. (Puziy et al., 2002) On the other hand, potassium hydroxide is usually used to activate coal or chars precursors. It has been reported that zinc chloride produces activated carbon with higher specific area than that produced by using phosphoric acid. (Thomas and Thomas., 1997) However, phosphoric acid activation is widely preferred over zinc chloride because ZnCl2 has bad environmental impact and the activated carbon produced when using it cannot be used in the food and pharmaceutical industries. (Srinivasakannan and Abu Barker., 2006) Activated carbon usually increases the cost of the treatment process. Its economical drawback has stimulated the interest to utilize cheaper raw materials for the production of activated carbon.
(Rengarag et al., 2002)Consequently, a wide variety of agricultural by-products and wastes has been investigated as cellulosic precursors for the production of activated carbon in addition to hard wood and bituminous coal. These precursors include coconut shell and wood (Laine et al 1989), Olive stones (Rodriguez-Reinoso et al., 2001), (Elsheikh et al., 2003) pecan shells (Rengarag et al., 2002), palm seed, (Garcia et al., 2003) apple pulp, (Rengarag et al., 1996) rubber seeds (Legrouri et al 2005) and molasses. (Khalili et al., 2000) Commercial activated carbons are commonly produced from naturally occurring carbonaceous materials such as coal, wood and peat. (Rodaza et al., 2003) Due to the growing need for activated carbons in our society and the high cost of raw materials and production, many researchers have attempted various wastes such as tires, (Mui et al., 2004) resins, (Yue et al., 2006) agricultural byproducts(Lee et al., 2003); (Cha’vez-gouerror et al., 2008)], [Kalderis et al., 2008) and dried sewage sludge (Zhang et al., 2005), (Rio, et al., 2006) as raw materials and proposed new production methods (Mane’ndez et al., 2005), (Wang et al., 2008) for activated carbons with potential applications in pollution control. Furthermore, more interest has been devoted to utilize some wastes of carbonaceous materials such as paper mill sludge (Kalili et al., 2000), old newspapers (Otowa et al., 1990) and waste tires (Rozada et al., 2005). Recently, activated sludge has been produced as a result of wastewater treatment activities and has emerged as an interesting option for the production of activated carbon. (Jeyaseelan and Lu., 1999) (Tay et al., 2001) The results reported in these studies indicate that chemical activation of the sewage sludge with ZnCl2 and H2SO4 produced activated carbon of high adsorption capacity comparable with that of commercial activated carbon. In addition, the choice of a cheap precursor for the production of activated carbon means both considerable savings in the production cost and a way of making use of a waste material, thus reducing its disposal problem. (Rozada et al., 2003).
The sewage sludge used in the previous investigations is characterized by its carbonaceous nature and its high content of volatile compound. However, this sludge seems to contain appreciable quantities of inorganic impurities as it comes from urban treatment plants. Therefore sulphuric acid seems to be suitable as a chemical activation agent because it is able to dissolve the majority of inorganic impurities found in the sludge. Activated carbons are increasingly used as an economic and stable mass separation agent for the removal of surfactants to raise the final product quality in many industrial processes.
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Activated carbons also play an important role in many areas of modern science and technology such as purification of liquids and gases, separation of mixtures, and catalysis. (Kenneth et al., 2002) Adsorption of activated carbon is governed by the chemical nature of the aqueous phase, the solid phase, and the chemical nature of the adsorbing organic.( Bilal et al., 1996) According to Torregrosa-Macia et al.( Torregrosa-Macia et al., 1997) for a given industrial application, a solid adsorbent with a relatively wide pore size distribution can be obtained solely through a chemical activation process.
Physical activation can further enhance the adsorbent‘s pore structure due to a partial oxidation of the carbonized material by gases such as CO/CO2 or steam. (Molina-Sabio et al., 1996),(Rodriguez-Reinoso et al., 1995), Analysis of the surface physical properties of the carbon includes determination of the total surface area, extent of microporosity, and characterization of the pore size distribution. Nitrogen adsorption isotherms are commonly used for these types of surface analyses. (Carrott et al., 1987), (Mikhail et al., 1968), (Harkins and Jura., 1964) and (Aranovich and Donohue, 1998) The measured relative pressure and adsorbed volume of nitrogen gas are commonly used in various mathematical models (i.e. BET model) to calculate the monolayer coverage of nitrogen adsorbed on the adsorbent surface, while the characteristics of the pore structure and pore distribution can be identified from comparative plots such as ‗t‘ and ‗αs‘-plots . (Lippens and de Boer., 1965).(Gregg and Sing., 1982),( Barret et al., 1951) and (Sing et al., 1985) The extent of the microporosity is commonly evaluated by applying low-pressure isotherm data to the Dubinin– Radushkevich (DR) equation.(Lippens and de Boer., 1965),(Warhurst et al., 1997,) The pore size distribution and the corresponding surface areas of the mesoporous adsorbents are traditionally calculated from the hysteresis loop according to the BJH theory, which is based on the Kelvin equation. (Barret et al., 1951), (Sing et al., 1985) 2.1
Classification: Activated carbons are complex products which are difficult to classify on the basis of their behaviour, surface characteristics and preparation methods. However, some broad classification is made for general purpose based on their physical characteristics. Powdered activated carbon (PAC) A micrograph of activated charcoal under bright field illumination on a light microscope. Notice the fractal-like shape of the particles hinting at their enormous surface area.
Each particle in this image, despite being only around 0.1 mm wide, has a surface area of several square metres. This image of activated charcoal in water is at a scale of 6.236 pixels/μm, the entire image covers a region of approximately 1.1 by 0.7mm. Traditionally, active carbons are made in particulate form as powders or fine granules less than 1.0 mm in size with an average diameter between .15 and .25 mm.(http://en.mimi.hu/astronomy/granule.html) Thus they present a large surface to volume ratio with a small diffusion distance. PAC is made up of crushed or ground carbon particles, 95–100% of which will pass through a designated mesh sieve or sieve. Granular activated carbon is defined as the activated carbon being retained on a 50-mesh sieve (0.297 mm) and PAC material as finer material, while ASTM classifies particle sizes corresponding to an 80-mesh sieve (0.177 mm) and smaller as PAC. PAC is not commonly used in a dedicated vessel, owing to the high head loss that would occur. PAC is generally added directly to other process units, such as raw water intakes, rapid mix basins, clarifiers, and gravity filters.1.2.1Granular activated carbon (GAC) Granular activated carbon has a relatively larger particle size compared to powdered activated 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 as their rate of diffusion are faster. Granulated carbons are used for water treatment, deodorization and separation of components of flow system. GAC can be either in the granular form or extruded. GAC is designated by sizes such as 8×20, 20×40, or 8×30 for liquid phase applications and 4×6, 4×8 or 4×10 for vapor phase applications. A 20×40 carbon is made of particles that will pass through a U.S. Standard Mesh Size No. 20 sieve (0.84 mm) (generally specified as 85% passing) but be retained on a U.S. Standard Mesh Size No. 40 sieve (0.42 mm) (generally specified as 95% retained). AWWA (1992) B604 uses the 50-mesh sieve (0.297 mm) as the minimum GAC size. The most popular aqueous phase carbons are the 12×40 and 8×30 sizes because they have a good balance of size, surface area, and head loss characteristics.1.2.2 Extruded activated carbon (EAC) Extruded activated carbon combines powdered activated carbon with a binder, which are fused together and extruded into a cylindrical shaped activated carbon block with diameters from 0.8 to 130 mm. These are mainly used for gas phase applications because of their low pressure drop, high mechanical strength and low dust content.1.2.3 Impregnated carbon Porous carbons containing several types of inorganic impregnant such as iodine, silver, cations such as Al, Mn, Zn, Fe, Li, Ca have also been prepared for specific application in air pollution control especially in museums and galleries. Due to antimicrobial/antiseptic properties, silver loaded activated carbon is used as an adsorbent for purification of domestic water. Drinking water can be obtained from natural water by treating the natural water with a mixture of activated carbon and Al(OH)3, a flocculating agent. Impregnated carbons are also used for the adsorption of H2S and thiols. Adsorption rates for H2S as high as 50% by weight have been reported.1.2.4 Polymer coated carbon This is a process by which a porous carbon can be coated with a biocompatible polymer to give a smooth and permeable coat without blocking the pores. The resulting carbon is useful for hemoperfusion. Hemoperfusion is a treatment technique in which large volumes of the patient’s blood are passed over an adsorbent substance in order to remove toxic substances from the bloodOther:Activated carbon is also available in special forms such as cloths and fibres. The “carbon cloth” for instance is used in personnel protection for the military1.2.5 Properties of activated carbon A gram of activated carbon can have a surface area in excess of 500 m 2 , with 1500 m2 being readily achievable. Carbon aerogels, while more expensive, have even higher surface areas, and are used in special applications. Under an electron microscope, the high surface-area structures of activated carbon are revealed. Individual particles are intensely convoluted and display various kinds of porosity; there may be many areas where flat surfaces of graphite-like material run parallel to each other, separated by only a few nanometers or so. These micropores provide superb conditions for adsorption to occur, since adsorbing material can interact with many surfaces simultaneously. Tests of adsorption behaviour are usually done with nitrogen gas at 77 K under high vacuum, but in everyday terms activated carbon is perfectly capable of producing the equivalent, by adsorption from its environment, liquid water from steam at 100 °C and a pressure of 1/10,000 of an atmosphere. James Dewar, the scientist after whom the Dewar (vacuum flask) is named, spent much time studying activated carbon and published a paper regarding its absorption capacity with regard to gases.(Michael et al., 2004) In this paper, he discovered that cooling the carbon to liquid nitrogen temperatures allowed it to absorb significant quantities of numerous air gases, among others, that could then be recollected by simply allowing the carbon to warm again and that coconut based carbon was superior for the effect. He uses oxygen as an example, wherein the activated carbon would typically absorb the atmospheric concentration (21%) under standard conditions, but release over 80% oxygen if the carbon was first cooled to low temperatures. Physically, activated carbon binds materials by van der Waals force or London dispersion force. Activated carbon does not bind well to certain chemicals, including alcohols, glycols, strong acids and bases, metals and most inorganics, such as lithium, sodium, iron, lead, arsenic, fluorine, and boric acid. Activated carbon does adsorb iodine very well and in fact the iodine number, mg/g, (ASTM D28 Standard Method test) is used as an indication of total surface area.1.2.6 Applications of activated carbon Activated carbon is used in gas purification, gold purification, metal extraction, water purification, medicine, sewage treatment, air filters in gas masks and respirators, filters in compressed air and many other applications. Recently Activated Carbon filters have gained popularity among recreational users of Cannabis, and other smoking herbs for their use in effectively filtering out “Tar” from the smoke. They are becoming quick competition for Vapourizers as they are only a fraction of the cost and achieve nearly the same thing. One major industrial application involves use of activated carbon in the metal finishing field. It is very widely employed for purification of electroplating solutions. For example, it is a main purification technique for removing organic impurities from bright nickel plating solutions. A variety of organic chemicals are added to plating solutions for improving their deposit qualities and for enhancing properties like brightness, smoothness, ductility, etc. Due to passage of direct current and electrolytic reactions of anodic oxidation and cathodic reduction, organic additives generate unwanted break down products in solution. Their excessive build up can adversely affect the plating quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level. Activated carbon, in 50% w/w combination with celite, is used as stationary phase in lowpressure chromatographic separation of carbohydrates (mono-, di- trisacchardes) using ethanol solutions (5–50%) as mobile phase in analytical or preparative protocols.In environment field activated carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as spill cleanup, Groundwater remediation , Drinking water filtration , Air purification , Volatile organic compounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes. In medical applications activated carbon is used to treat poisonings and overdoses following oral ingestion. It is thought to bind to poison and prevent its absorption by the gastrointestinal tract. In cases of suspected poisoning, medical personnel administer activated charcoal on the scene or at a hospital’s emergency department. Dosing is usually empirical at 1 gram/kg of body mass (for adolescents or adults, give 50–100 g), usually given only once, but depending on the drug taken, it may be given more than once.(Michael et al., 2004) In rare situations activated charcoal is used in Intensive Care to filter out harmful drugs from the blood stream of poisoned patients. Activated charcoal has become the treatment of choice for many poisonings, and other decontamination methods such as ipecac-induced emesis or stomach pumping are now used rarely. 1.2 Aim and Objectives Aim of this research is to test for the Effective methods for the preparation of activated carbon from Combretum nioroense (Geza). The objectives of this research are;To study the methods of activated carbon preparation.To study the adsorption properties of activated carbon.To prepare activated carbon from Combretum nioroense.To prepare an adsorbent.
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MATERIALS AND METHODS 2.1
Collection of sampleThe Combretum nioroense used in this experiment was obtained from Aliero local government, of Kebbi state, Nigeria 2.1.2 Chemicals used The chemicals used in this project are as follows: Sulphuric acid H2SO4Distilled water Sodium hydroxide NaOH2.1.3 Equipments used The equipments used in this project are as follows:BeakersVolumetric flaskMeasuring cylinderStop watchFilter papersSeparating FunnelOvenConical flaskMuffle furnace 2.2 METHODS2.2.1 Preparation of sampleThe sample was air dried for about 3 days, The died sample was grinded using pulverizer and then sieved to mesh size of about 0.3-0.4mm.
i. CARBONIZATIIONThe carbonization was done for physical, physiochemical and chemical activations in which the powdered sample was carbonized in a stainless steel, The carbonized sample was put into crucible and then placed in a muffle furnace at 400℃ for 2 hrs.ii.
ii. SINGLE STEP ACTIVATION METHODS 10g 0f powdered sample was put into stainless steel for carbonization until the sample was turn to black, and then the sample was kept at room temperature to cooled, the carbonized sample was also placed into crucible and take to muffle furnace for activation for 30mins at 200℃. The activated sample was also washed with distilled and filtered until the filtrates reaches about PH of 7
iii. DOUBLE STEP ACTIVATION METHODS The sieved combretum nioroense leaves (CNL) were then carbonized in a stainless steel, The carbonized sample was put into crucible and then placed in a muffle furnace. The temperature of the furnace was ramped from room temperature of 400℃ at heating rate of 10mins. The produced from carbonization process in physical activation subsequently impregnated with 10% w/v of NaOH with 3g of carbonized sample. The impregnated char filtered and dried in an oven for 1hr, and then cooled at room temperature and thereafter washed with distilled water to the PH of the filtrate to about 7. (Salman and Hameed., 2010)
iv. IMPREGNATION METHOD OF ACTIVATION
Activated carbon of the leaves powder with concentrated sulphuric acid (H2SO4) in a weight ratio of 1:3. The resulting blank product was kept in an air free oven maintained at 166℃ for 6hrs followed by washing with distilled water until free excess acid, and then dried in an oven at 105℃ for 1hr.(Singanan et al., 2007)v
ADSORPTION EXPERIMENT0.2g of activated carbon were weighed into a different beakers and 25ml of 100ppm of Cr6+ ion was added to the same beakers and then shake with an orbital shaker at 300rpm for 30min and then filtered, The filtrate was analysed by the AAS to determine the adsorption capacity of each generated carbon. And the amount adsorbed by each carbon were calculated byWhere, qe = the amount adsorbedV= Volume of metal ionCi= initial concentrationCf= final concentrationm = mass of adsorbentCHAPTER THREE3.0 RESULT AND DISCUSSION3.1 RESULTTable 3.1 shows the average amount of Cr ions removed The result is expressed as mean of triplicate analysis Figure 3.1 Amount of Cr ions removed 3.2 DISCUSSIONFrom the result obtained as shown in fig. 3.1 as well as in Table 3.1 it shows that about 30.26 of the Chromium ion was removed from aqueous solution by the adsorbent prepared using physiochemical method of preparation whereas that of physical method was found to be 32.90 and that of chemical method which is also known as single step method was 34.78, this implies that the chemical method of preparation was said to be more effective method compared to other methods employed in the present research work
.CHAPTER FOUR4.0 CONLUSION AND RECOMMENDATIONS
4.1 CONCLUSIONThe Combretum nioroense was employed for the study of effective method of the preparation of the activated carbon in the research work; three methods of preparation were used to ascertain the level of adsorption capacity of the activated carbon generated the methods are physical activation, chemical activation and physiochemical activation methods. The Combretum nioroense can be used for industrial purposes because of its ability to remove the selected metal.
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Simler to study should be carried out for other heavy metals such Pb, Cd, Zn, etc.Because the Combretum nioroense is in abundance if its employed and controlled with no doubt it will provide source of adsorbent materialThe Combretum nioroense should be characterized using different techniques so that to have a clear understanding of other application of the leaves.References “Properties of Activated Carbon”, CPL Caron Link, accessed 2008-05-02 . http://en.mimi.hu/astronomy/granule.html Baker F. S., Miller C. E., Repic A. J. and Tolles E. D., Activated carbon. Kirk-Othmer Encycolpedia of Chemical Technology, 4, 1015-1037 (1992). El-Hendawy A. A., Influence of HNO3 oxidation on the structured and adsorptive properties of corncob activated carbon. Carbon, 41, 713-722 (2003). Elsheikh A., Newman A., Al-Daffaee H., Phull S. and Crosswell N., Characterization of activated carbon prepared from a single cultivar of Jordanian olive stones by chemical and physicochemical techniques. J. Anal. 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