Project Abstract

Abstract
Activated carbon (AC) is a versatile material with a wide range of applications, including water purification, air filtration, and energy storage. In this study, we compare activated carbon derived from corn cob using two different synthesis methods chemical activation with phosphoric acid and microwave activation. The aim of the study is to evaluate the physicochemical properties and adsorption capacities of the two types of activated carbon and determine which method is more effective in producing high-quality AC from corn cob. The chemical activation method involves impregnating the corn cob with phosphoric acid and then carbonizing it at high temperatures. This process is well-established and widely used in the production of activated carbon. On the other hand, microwave activation is a relatively new technique that offers the advantage of rapid heating and potentially higher activation efficiency. By comparing the two methods, we seek to determine whether microwave activation can produce AC with comparable or superior properties to chemically activated carbon from corn cob. The synthesized activated carbons were characterized using various analytical techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, and Fourier-transform infrared spectroscopy (FTIR). The results show that both chemical and microwave synthesized activated carbons exhibit high surface areas and pore volumes, indicating their suitability for adsorption applications. Adsorption tests were conducted using methylene blue as a model organic pollutant to evaluate the adsorption capacities of the activated carbons. The results indicate that both types of activated carbon show excellent adsorption capacities, with the chemical synthesized AC demonstrating slightly higher adsorption efficiency compared to the microwave synthesized AC. Overall, this comparative study provides valuable insights into the synthesis of activated carbon from corn cob using different methods. The results suggest that both chemical and microwave activation methods are effective in producing high-quality AC with excellent adsorption capacities. However, further research is needed to optimize the synthesis parameters and better understand the mechanisms underlying the activation process to improve the efficiency and sustainability of AC production from agricultural waste materials like corn cob.

Project Overview

INTRODUCTION
1.1 BACKGROUND OF STUDY
Activated 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 (Mattson et al., 1971). The word active is sometimes used in place of activated. It is characterized by high degree of micro porosity. A gram of activated carbon can have a surface area in excess of 500 m2. 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. Activated carbon is most commonly derived from charcoal.
Waste biomass is getting increasing attention all over the world for activated carbon development as it is renewable, widely available, cheap and environmentally friendly resource. The common method of development is thermochemical (Kumar et al., 2005). The main concern is the removal of chemical component by adsorption from the liquid or gas phase (Bansal et al., 1988). Today, activated carbon has been produced from various biomass such as corncob, rice husk, cherry stones, coconut shells, palm shells, to mention but a few.
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Preparation of activated carbon with ultra-high specific surface area from biomass such as lignin, corncob, cornstalk, dates, etc., has attracted much attention. Among these carbon sources, corncob is a good precursor for preparing carbon with ultra-high specific surface area (Li, 2007). The carbons prepared from corncob have been used in wastewater treatment such as removal of organic pollutants (Sun et al., 2006).
However, a comprehensive study of activating corncob with different activation strategies to prepare carbon with ultra-high specific surface area and pore volumes, and their subsequent performance in water purification as the impurity adsorption has not to our knowledge been reported. Therefore, in this study we report the synthesis of ultra-high surface area carbon materials using two preparation strategies namely, chemical activation procedure using a chemical activator such as ammonium sulphate ((NH4)2SO4) and microwave-synthesized activation procedure. We also report the adsorption capacity of those carbons for water purification.
To prepare activated carbon, conventional heating method is usually adopted, in which the heat is produced by electrical furnace. However, in some cases, the thermal process may take several hours, even up to a week to reach the desired level of activation (Yuen et al., 2009). Another problem related to the furnace is that the surface heating does not ensure a uniform temperature for different shapes
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and sizes of samples. This generates a thermal gradient from the hot surface to the kernel of the sample particle, blocks the effective diffusions of gaseous products to its surroundings and finally results in activated carbon quality decrease (Peng et al., 2008). Furthermore, there is a considerable risk of overheating or even thermal runaway (exothermic process) of portion of sample, leading to the complete combustion of the carbon (Williams et al., 2008).
Recently, microwave has been widely used in preparation and regeneration of activated carbon. The main difference between microwave devices and conventional heating systems is heating pattern. In microwave device, the energy is directly supplied to the carbon bed. The conversion of microwave energy is not by conduction or convection as in conventional heating, but by dipole rotation and ionic conduction inside the particles (Jones, 2002). Therefore, the treatment time can be significantly reduced through microwave heating.
1.2 STATEMENT OF PROBLEM
In recent years, increasing awareness of environmental impact of organic and inorganic compounds has prompted the purification of waste water prior to discharge into natural waters. A number of conventional treatment technologies have been considered for treatment of waste water contaminated with organic substance. Among them, the adsorption process has been found to be the most
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effective method while activated carbon is regarded as the most effective material for controlling this organic load. Common active carbons available are usually developed by thermochemical means using activating agents and heating ovens, thus producing activated carbons which take a longer time with limited pore structures. With the advent of microwave technology, a better and efficient activated carbon can be produced within a short period and a cheaper cost.
1.3 OBJECTIVE OF THE RESEARCH The aim of this research project is to determine and compare the performance of chemically and microwave synthesized activated carbon from corn cob. 1.4 SIGNIFICANCE OF THE RESEARCH When this research project is successfully completed, it will provide the following benefits: i. Corn cobs are abundant in Nigeria. ii. Encourage the establishment of industries that will use Agricultural waste materials to produce activated carbon. iii. It will create job opportunities, thereby reducing unemployment in the country.
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iv. It will attract foreign exchange for Nigeria as activated carbon has very wide industrial applications.
1.5 SCOPE OF RESEARCH This research work focuses on the following: i. Preparation of activated carbon from corn cob by thermal and microwave means ii. Comparative study of the adsorption capacities of chemically and microwave synthesized activated carbon.