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One of the most important food crops in many regions of the world can be classified as rice. Globally, majority of the rice production is grown in Asia which is roughly about 550 million ton/year. Asian countries are the main production countries because rice is the main food for Asian. Rice is commercially plant in Malaysia because of the temperature regime and the rainfall distribution is suitable for year round cultivation of rice (Chong, 2009). About 300500 hectares on Malaysia Peninsular and 190000 hectares on Borneo Islands are allocated to rice production. It is also reported that rice production is estimated to grow from year to year due to global demand. Rice as the essential primary processed product is obtained from paddy and it is further processed for completes various secondary and tertiary products. There are several manufacturing processes for rice production which is cleaning, de-husker (milling), polished and packaging.
Rice milling or de-husking is the process of removal of husk and bran to obtain the ripe section for consumption. Rice milling will produce about 22% of byproduct known as rice husk (Fig 1.1). Rice husk (RH) is hard and it is used as the protecting shell to cover the grain (Johnson et al., 2009). It is contains 35% cellulose, 25% of hemicellulose, 20% of lignin, 17% of ash and others chemical is 3%. (Hattotuwa et al., 2002). Rice husk also contains about 75% of organic volatile matter and the others from it will be converted into ash during the firing process. By having the lignocellulosic materials, rice husk can be converted to different types of fuels and chemical feedstock through a variety of thermo chemical conversion process.
Figure 1.1: Rice Husk
Fourier Transformed Infrared Spectroscopy (FTIR) is used as one of the main methods to notice and investigate the changes or variations of any compositions. It is also can identify the unknown materials, establish the quality or consistency of a sample and determine the amount of components in a mixture. An infrared spectrum is corresponding to fingerprint of a sample with absorption peaks which represent the frequencies of vibrations between the bonds of the atoms making up the material. Similar to fingerprint, no two unique molecular structures produce the equal infrared spectrum (Thermo Nicolet, 2001). Therefore, it makes the FTIR valuable for several types of analysis. The physical principle of the FTIR including the molecular bonds is vibrating at various frequencies depending on the elements and the type of bonds. For any given bond, there are several specific frequencies at which it can vibrate. Based on the quantum mechanics, these frequencies are related to the ground state which is the lowest frequency and also excited states which is the higher frequencies. In order to cause the frequency of a molecular vibration to increase is to excite the bond by absorbing light energy.
Figure 1.2: Fourier Transformed Infrared Spectroscopy
There are some advantages of using FTIR over the dispersive technique such as:
It is a non-destructive technique
It provides a precise measurement method which requires no external calibration because it is self-calibrating and never need to be calibrated by the user.
It can increase speed because all of the frequencies are measured simultaneously. Therefore, most measurements by FTIR are made in a matter of seconds rather than several minutes.
Sensitivity is significantly improved because the detectors employed are much more sensitive; the optical throughput is much higher which results in much lower noise levels.
It is mechanically simple with only one moving part
It has greater optical throughput
Majority of the rice millers and farmers believe that RH is the most unwanted rice by-product. The disposal of these agricultural by-products has become a problem because open burning is harmful to the environment and also human health. RH disposal has become a problem especially to millers who leave and burn these by-products along the roadsides. This is because the smoke disturbs the motorists, commuters, and the community resident (Philippine Rice Research Institute, 2005).
1. Analyze the change in the chemical bond of functional group of treated rice husk with the untreated by using FTIR.
2. Optimize the treatment condition (sulphuric acid concentration and particle size of RH) by using Design of Experiment (DOE).
Rational of the Research
In this current research, analytical models are developed by using FTIR that has the potential to study the functional group of the treated RH. Moreover, the level of the composition of lignocellulosic material in treated RH also can be identified. Therefore, to achieve the purpose of this current research, the essential parameters are necessary to be estimated through analytical specification of lignocellulosic material. FTIR also has the potential and can be used successfully to study the chemical structure and spatial distribution of cellulose, hemicelluloses and lignin in various agricultural materials (Adapa et al., 2009).
FTIR analysis in this current research is used to analyze the treatment of the lignocellulosic materials. During treatment process, the bonds connecting lignin, cellulose and hemicelluloses were break apart. Treatment methods typically use chemical, physical, mechanical or biological techniques to break down lignocellulose (Hector et al., 2008). Physical treatment usually involved the breakdown of lignocellulosic size and crystallinity in order to increase the mass transfer characteristic. While for the chemical treatment, it will modify the crystal structure of cellulose and hemicelluloses. Some of the chemical treatment method removed the composition of lignin and hemicelluloses in order to yield enriched cellulose.
Globally, the concern over the fossil oil prices, the security of the oil supply and the negative impact of fossil fuels on the environment has growing increasingly. Therefore, the conversion of lignocellulosic material to the biofuels has become important since it provides the best economically reasonable and conflict-free second generation alternatives (Rubin, 2008). Significant advances have been made towards bioconversion of plant wastes into bioethanol, biodiesel, biohydrogen and also biogas (methane). Nowadays, the technology development has focusing on the utilization of residual lignocellulosic materials rather than the production of ethanol (Howard et al., 2003). This is because, the production of ethanol by using sugar or starch from sugarcane and cereals are more expensive compared to the production of fossil fuel from residual of plant.
Currently, research and development of saccharification and fermentation technologies that convert lignocellulosic to reducing sugars and finally to ethanol, respectively, in eco-friendly and beneficial approach have picked tempo with step forward results being reported (Lin et al., 2006; Prasad et al., 2007; Patel et al., 2007; Pasha et al., 2007; Tahezaden et al. , 2007 and; SÃÂ¡nchez et al., 2008).
Advantages and Important of the Research
FTIR was generally used to study the functional group of lignocellulosic material and the changes caused due to different treatment. The qualitative and semi-quantitative information is recommended by this spectrum in order to study the presence and absence of lignocellulosic compositions and also to investigate whether the intensity of an absorption band has changed after treatment (Li et al. 2010). This technique is well known for its simplicity in sample preparation and speed of analysis (Davis et al., 2010). Moreover, bands corresponding mainly to cellulose, hemicelluloses and lignin were measured to identify changes due to different treatments. FTIR have recently replaced dispersive instruments for most appliances due to their advanced speed and sensitivity. They have greatly extended the capabilities of infrared spectroscopy and have been applied to many areas that are very difficult or nearly impossible to analyze by dispersive instruments. Instead of viewing each component frequency in sequence, all frequencies are examined simultaneously by using FTIR.
Scope of the Study
Lignocellulosic from the forestry, agricultural and agro-industrial wastes are abundant, renewable and economical organic sources (Ang et al., 2011). Lignocellulose wastes are collected every year in large quantities, causing environmental problems. On the other hand, due to their chemical composition based on sugars and other compounds of interest, they can be consume for the production of a number of value added products, such as ethanol, food additives, organic acids, enzymes, and others. Thus, besides the environmental problems caused by their increasing in the nature, the non-use of these materials constitute a loss of potentially valuable sources. These materials are mainly composed of three groups of polymers, namely cellulose, hemicellulose, and lignin which are strongly bonded by non-covalent cross linkages. The composition of lignocellulosic material varies considerably by type of species and includes approximately 30-50 % of cellulose, 20-30 % hemicelluloses and also 10-25 % of lignin (Sanchez, 2009). On the whole, cellulose forms a skeleton which is surrounded by hemicellulose and lignin.
Figure 4.1: Structure of Lignocellulosic
Cellulose is a polysaccharide made up of glucose monomers, and is the most abundant organic polymer on Earth (Zhu et al. 2006). Polysaccharides are synthesized by plants, animals, and humans to be stored for food, structural support, or metabolized for energy. Cellulose is the major structural component of the rigid plant cell wall and offers strength to the plant. Cellulose is strong, crystalline, resistant to hydrolysis and is water insoluble (Habibi, 2010).
Hemicellulose was classified as a heterogeneous polysaccharide which is an amorphous polymer that mainly includes five different sugar groups (Sjostrom, 1981). Hemicellulose chains were shorter than the chains in simpler cellulose, can be branched, and often have side groups, such as monosaccharides and acetyl groups (Mai et al., 2004). Hemicellulose is also a much more complex structure than cellulose which composed of several different monomers. In the primary cell wall, hemicellulose interacts with other polymers to maintain the physical properties of the wall. In many types of plants, hemicellulose can also act as a seed storage carbohydrate. Hemicellulose strengthens the secondary cell wall and facilitates transport of water to the plant (Scheller et al., 2010 and Dashtban et al. 2009).
Lignin is a very complex molecule constructed of phenyl propane units linked in a large three-dimensional structure. Due to its complex structure, lignin is the most recalcitrant component of lignocellulose followed by cellulose due to its highly crystalline structure and then hemicelluloses. Lignin is closely bound to cellulose and hemicellulose and its function is to provide rigidity and cohesion to the material cell wall, to present the water impermeability to xylem vessels, and to form a physicochemical barrier against microbial attack (Amanda, 2010). Due to its molecular configuration, lignins are extremely resistant to chemical and enzymatic degradation.
Tretment of Lignocellulosic Material
Treatment of RH is essential to modify the structure of cellulosic material in order to make cellulose more available to the enzymes which convert the cellulose into fermentable sugars. It is the method to break apart the bond that connects lignin, cellulose and hemicelluloses. Treatment also has a great potential for improvement of efficiency and lowering of cost through research and development (Lynd et al., 1996; Lee et al., 1994; Kohlman et al., 1995 and; Mosier et al., 2003). Several treatment approaches have been developed to improve the reactivity of cellulose and to enhance the yield of fermentable sugars.
Usually, the principle of treatment consist of production of highly digestible solids that enhances sugar yields during enzyme hydrolysis, avoiding the degradation of sugars including those derived from hemicelluloses, minimizing the formation of inhibitors for subsequent fermentation steps, recovery of lignin for conversion into valuable co-products and to be cost effective by operating in reactors of moderate size and by minimizing heat and power requirements. The treatment methods that normally used were chemical, physical, and biological techniques, which all aim to break down the lignocellulose (Hector et al. 2008).
Figure 4.2: Schematic of goals of treatment on lignocellulosic material (adapted from Hsu et al., 1980)
Physical treatment involved the breakdown of cellulosic size and crystallinity by grinding process. Due to the reduction in crystallinity and particle size of the material, the hydrolysis result and mass transfer characteristic can be improved. This treatment also increases the surface area for enzyme attack by breaking down the lignocelluloses and reduces the particle size. They also decrease the crystallinity of cellulose, which is resistant to enzyme attack, and reduce the degree of polymerization. The energy requirements for physical treatments are dependent on the final particle size and reduction in crystallinity of the lignocellulosic material.
Acid treatment involves the use of concentrated and diluted acids to break the rigid structure of the lignocellulosic material. Generally, dilute sulphuric acid (H2SO4) has been commercially used to treat a variety of lignocellulosic types such as rice husk, switch grass, corn stover, spruce and poplar. Due to its ability to remove hemicellulose, acid treatments have been used as parts of overall processes in fractionating the components of lignocellulosic materials. Studies by del Campo et al. (2006) and Karimi et al. (2006) have established that 0.5% of H2SO4 is optimal for treatment of wastes from vegetables and rice straw, respectively. Moreover, at low acid concentration (lower than 4 wt %), it will completely solubilizes the hemicelluloses component and a little part of cellulose.
While for the alkaline treatment, the use of an alkali causes the degradation of ester and glycosidic side chains resulting in structural alteration of lignin, cellulose swelling, partial decrystallization of cellulose, and partial solvation of hemicellulose. Sodium hydroxide has been broadly studied for many years, and it has been shown to disrupt the lignin structure of the biomass, increasing the accessibility of enzymes to cellulose and hemicelluloses. Therefore, in order to obtain relatively pure cellulose, acid treatments which are the removal of hemicelluloses and followed by alkali treatment which removes of lignin are necessary.
Biological treatment is considered as environmentally friendly treatment method because it is involve the use of brown or white rot fungi to degrade lignin and hemicelluloses. Cellulose, hemicellulose and lignin each have different reactivity towards these treatment technologies, making the process very complex to simplify.
The RH is obtained from the local rice mills. The collected materials were then washed with tap water for several times to remove all the dirt particles. The washing process was continued till the wash water contains no colour. The washed materials were then dried in an oven at 80ÂÂ°C for 24 h.
Treatment of Rice Husk
The first treatment was grinding the dried RH by using grinder. The grinding materials were then sieved to different particle sizes which is mixed size, 500 ÂÂµm and superfine. Then the samples save in containers according to its particle size. The RH then treated with sulphuric acid a range of 0.2 M at the room temperatures.
The treated RH and untreated RH are analyze by using FTIR. The untreated rice husk is prepared as the control. Next, the results from FTIR for treated and untreated RH are analyzed. The result is analyzed based on the functional group of the treated RH. Finally, the quantities of the functional group for both different treatments are study by comparing the graph.
Design of Experiment (DOE)
DOE is used to build set of experiments to achieve the optimum condition with minimum number of experiments.
Introduction & Literature Review
Submission of Proposal
Correction of the Proposal
Prepare Thesis Chapter 1
Prepare Thesis Chapter 2
Prepare Thesis Chapter 3
Prepare Thesis Chapter 4
Prepare Thesis Chapter 5
Submit Report to Supervisor
Submit Final Report
Gathering details information about pretreatment of lignocellulosic material.
Rice husk collected.
Prepared all material and apparatus regarding treatment process.
Treatment of rice husk.
Optimization the parameter by using DOE
Analysis by using FTIR
RH is often used as a low value material for money purposes this is because; it is either disposed as waste or burnt as fuel. This lignocellulosic material also can be easily found because it usually dumped along the roadside. Hence, the cost for raw material can be minimized. For this current research, the cost can be reduced by operating in reactors of moderate size and by minimizing heat and power requirements. This is due to the temperature used in this study is a room temperature. This is because, the increment of heat and power generated are affected the cost. Moreover, the cost for the chemicals in this current research also can be minimized because acid used is in diluted form. Diluted acid is less hazardous and quit gentle for reactors. Thus, the cost for recovering the materials after treatment can be reduced. At low acid concentration, hemicelluloses of the lignocellulosic material were completely solubilize (Anna, 2011).