Production of Activated Carbon From Walnut Shells and Groundnut Shells

Production of Activated Carbon From Walnut Shells and Groundnut Shells

CHAPTER ONE

OBJECTIVES OF THE RESEARCH

The aim of this research work is to produce activated carbon from a mixture of groundnut shells and walnut shells with varying concentrations of activating agents employing Microwave-assisted route and to explore its potentiality for water treatment. The following objectives will guide in achieving the aforementioned aim:

To evaluate the activation power and time for the production of activated carbon from the mixture of the groundnut shells and walnut shells.
To study the structure of the activated carbon produced using Scanning Electron Microscopy.
To characterize the activated carbon produced in terms of elemental composition, adsorption capacity, surface functionality, pore size and phase composition using: (a) XRD, (b) SEM and (c) EDS

CHAPTER TWO

LITERATURE REVIEW

INTRODUCTION

Activated carbon forms a large and important class of porous solids, which have found a wide range of technological applications. As such, the porous structures of these materials and their adsorption of gases, vapors, and liquids have been extensively studied. In this section the micro structural and porous properties of the principal classes of activated carbon are reviewed. It is outside the scope of this contribution to consider the very many industrial applications and processes of activated carbon.

Definition of Activated Carbon

Suguraman (2012) defined Activated carbon (AC) as a tasteless, microcrystalline, graphitic form of black carbonaceous solid material with a porous structure. The main features common to all AC are that they are graphite like planes which show varying degrees of disorientation and the resulting spaces between these planes which constitute porosity. Benaddiet al., (2000) also stated that AC is predominantly an amorphous solid with a large internal surface area and pore volume. Cokes, chars and activated carbon are frequently termed amorphous carbon.

From these definitions, it can be summarized that AC is a black, amorphous solid containing major portions of fixed carbon content and other materials such as ash, water vapor and volatile matters in smaller percentage. Besides that, AC also contains physical characteristics such as internal surface area and pore volume. The large surface area results in a high capacity for adsorbing chemicals from gases or liquids. The adsorptive property stems from the extensive internal pore structure that develops during the activation process.

CHARACTERIZATION OF ACTIVATED CARBON

Characterization for activated carbon (AC) is very important in order to classify AC for specific uses. Basically, LuaandGuo (2004) mentioned that the characteristics of activated carbon depend on the physical and chemical properties of the raw materials as well as activation method used.

Physical properties of AC, such as ash content and moisture content can affect the use of a granular AC and render them either suitable or unsuitable for specific applications. While the specific surface area of activated carbon and surface chemistry is classified as chemical properties, such surface chemistry (surface functional groups) could be characterized using the Fourier Transform InfraRed (FTIR). Furthermore, the porous structure of activated carbon also can be characterized by various techniques such as Scanning Electron Microscopy (SEM), adsorption of gases(N₂, Ar, Kr, CO₂) or vapours (benzene, water), and Transmission Electron Microscopy (TEM).

Moisture Content

Activated carbon is generally priced on a moisture free basis, although occasionally some moisture content is stipulated, e.g., 3, 8, 10%. Unless packaged in airtight containers, some activated carbons when stored under humid conditions will adsorb considerable moisture over a period of 1- 2 months. They may adsorb as much as 25 to 30% moisture and still appear dry. For many purposes, this moisture content does not affect the adsorptive power until the relative humidity exceeds 75%, but obviously it dilutes the carbon (Tierney et al., 2006).

CHAPTER THREE

MATERIALS AND METHOD

MATERIALS

The following are a list of materials/equipment that were used for the research:

Beakers (100ml) ii. Measuring Cylinders iii. Hot plate (C- MAGHS10) iv. Microwave oven (SINGSUNG 19L4)
Walnut Shell vi. Groundnut Shell vii. Sodium Chloride viii. Calcium Chloride ix. Glycine
Ethylene Glycol xi. Oven (CHENSANG JIN-BOMB)
Crucible and pestle xiii. Methylene blue xiv. Volumetric flask (1000ml) xv. Filter papers xvi. SEM coupled with EDS (Phenom Pro X) xvii. XRD(PANalytical BV, Netherlands) xviii. Spectrophotometer (Jenway 6405)

METHODOLOGY

Production of activated carbon was carried out employing Microwave-assisted chemical activation method. In this method, walnut shell and the groundnut shell was dried for 24 hours, ground and crushed to granular sizethrough a mesh of 125µm to remove unwanted particles.Five samples of the mixture of walnut and groundnut shell were prepared containing 5g each of walnut and groundnut shells.The mixture was done in the ratio 1:1.The chemical activation was achieved via a two-stage microwave heating involving partial thermal decomposition of the raw materials in 0.1M solution containing varying concentration of sodium chloride and glycine (amino acetic acid) and subsequent activation of the derivatives in 0.1M solution containing varying concentration of calcium chloride and ethylene glycol. The complete activation process for all the samples was achievedin 20 minutes with maximum power via microwave oven with power level ranging from 700W and maximum frequency of 50Hz.The proportion of Sodium Chloride and Calcium Chloride mixture for the 5 Samples of activated carbon at an activation time of 20 minutes was carried out.

CHAPTER FOUR

RESULTS AND DISCUSSION

INTRODUCTION

This chapter summarizes the analysis of the results obtained from the samples prepared for this study. This include adsorptive studies, characterization of the activated carbon derived from groundnut shell and walnut shell using Scanning Electron Microscopy (SEM), Energy- Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) discussion of the result found in the course of the research.

The result in table 4.1 above gives information about the moisture content and ash content of the various samples of the activated carbon. The ash content is useful in assessing the quality, kind and utility of the mineral content. The moisture content in all the samples fall within the acceptable range of less than 70%, according to Tierney et al., 2006, which indicates that the adsorption of moisture by the samples is also less. Among the carbon, sample E has the least moisture content of 6.50 %. A good activated carbon must have low ash content. A small increase in ash content causes a decrease in adsorptive properties of activated carbon. As activation time and microwave power increases, ash contents of the samples increase. Ash content can lead to increase hydrophilicity and can have catalytic effects, causing restructuring process during regeneration of used activated carbon. The results in the Table 4.1 indicates that moisture content and ash content in all the samples is less, which suggests that the samples used are viable for adsorption.

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

CONCLUSION

In this study, walnut shell and groundnut shell are impregnated with varying concentrations of NaCl and CaCl₂ as activating agents, and activated by microwave radiation at full power (700W) to produce activated carbon. The variation of the impregnation ratio of NaCl and CaCl₂, have significant effects on the adsorption capacity of the activated carbon from the prepared samples. Therefore the optimum conditions were obtained as following: impregnation time of 30 minutes, microwave power of 700 W, and a microwave radiation time of 20 minutes.

Activated carbon prepared from walnut shell and groundnut shell under optimum conditions was employed as an adsorbent for the quantitative removal of methylene blue from aqueous solution. The maximum adsorption capacity for MB on the prepared activated carbon was reached after 30minutes for the sited dye by Sample E and was 333.33 mg/ g. The equilibrium data fitted well in the Langmuir model of adsorption. It was influenced by microwave radiation power and microwave treatments. Development of the porosity of activated carbon was affected by the Microwave power and the presence of activating agents for impregnation.

In SEM, Sample E gives a clearer pore structure, having more volume of pores and better pore structures with little agglomeration, making it more viable for adsorption in comparison with the other prepared samples. In XRD characterization, the presence of irregular patterns of X-Ray diffractograms may be accounted for amorphous state of the samples. A sharp peak, which corresponds to CaCl₂, was observed at 26.5° and also, sharp peaks corresponding to NaCl, were observed at two theta 31.5 and 45.0° in Sample E. The characterizations of the activated carbon produced in this experiment (SEM-EDX, XRD) and ability to remove methylene blue reveals that Sample E produced the best activated carbon as seen from the results, and had an improved adsorption behavior compared to the other samples (samples A-D). Consequently, the activated carbons produced from walnut and groundnut shell can be used as adsorbents for various environmental applications including treatment of drinking water, removing colour from industrial effluents and removal of heavy metals. It can also be seen that CaCl₂ is a very good activating agent judging from the fact that Sample E, having the highest adsorption capacity, was impregnated with more of CaCl₂ than NaCl.

The present study concludes the combination walnut shell and groundnut shell is a very good adsorbent due to its microporous structure comparing its adsorptive capacities with others obtained from others from literature and that microwave heating could shorten processing time significantly and could create porous materials presumably due to its homogeneous structure heating. The prepared samples could be employed as low-cost adsorbents for the removal of dyes and/or impurities within the size range of 1.5nm from wastewater, in general and for the removal of MB, in particular.

RECOMMENDATION

Based on the result, the following are recommended.

Investigation on effect of varying impregnation time and activation temperature on adsorption performance should be carried out
Other chemical activating agents should be tested in order to diversify the activating agent that can be use for chemical activation
The prepared samples should be employed for removal of impurities in water
Surface area and pore volumes should be determined for the prepared samples

REFERENCES

Alireza Dehdashti, Ali Khavanin, Abbas Rezaee, Hassan Asilian (2010). Regeneration of granular activated carbon saturated with gaseous toluene by microwave irradiation. Turkish Journal of Engineering and Environmental Science,4(2): PP.49 – 58.
Ami Cobb, Mikell Warms, Edwin P. Maurer (2012).Low-Technut Shell Activated Charcoal Production. International Journal for Service Learning in Engineering, 1(7): PP. 93104.
Appleton T.J., R.I. Colder, S.W. Kingman, I.S. Lowndes, A.G. Read (2005). Microwave technology for energy efficient processing of waste. International Journal forApplied Energy,81(3): PP. 85-113.
ArrietaS. Mera1, R. Diamant, M. Fern´andez-Guasti, R. Sosa1, L. Escobar-Alarcon, A.F. Muñoz, E. Haro-Poniatowski (1999). Synthesis and characterization of sodium chloride thin films obtained by pulsed laser deposition, International Journal for Service Learning in Engineering, 9(2): PP.34- 41.
Bandosz ,T.J., (2006). Activated Carbon Surfaces in Environmental Remediation. Interface Science and Technology Series, Elsevier,New York. PP 41.
Bradshaw S., Delport S. and Van Wyk E. (1997) ―Qualitative measurement of heating uniformity in a multimode microwave cavity‖. Journal of Microwave Power and Electromagnetic Energy, 32(2): PP.87-95.
Bansal R, Donnet J, Stoeckli F. (1988).Active Carbon Marcel Dekker Inc. New York,PP. 159-163.
Bathen, D. (2003). Physical Waves in Adsorption Technology: an overview of Separation and Purification Technology,2(33): PP.163–177.

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