Comparative Study Of Chemical And Microwave Synthesized Activated Carbon From Corn Cob

Project Abstract

This research project aimed to conduct a comparative study on the properties of activated carbon derived from corn cob using chemical activation and microwave activation methods. Activated carbon is a widely used material in various applications such as water treatment, air purification, and gas adsorption due to its high surface area and porosity. Corn cob, an agricultural waste product, was chosen as the precursor for activated carbon synthesis due to its abundance and sustainable nature. The chemical activation method involved impregnating the corn cob with a chemical activating agent, typically a strong base like potassium hydroxide (KOH), followed by carbonization and activation processes. On the other hand, the microwave activation method utilized microwave radiation to heat the corn cob precursor in the presence of an activating agent, such as KOH, to produce activated carbon. The activated carbons produced by the two methods were characterized and compared in terms of their surface area, pore size distribution, functional groups, and adsorption properties. The results indicated that the microwave-synthesized activated carbon exhibited higher surface area and micropore volume compared to the chemically synthesized activated carbon. This can be attributed to the rapid and selective heating of the precursor material by microwave radiation, leading to better activation and development of porosity. Furthermore, the adsorption studies revealed that the microwave-synthesized activated carbon showed superior adsorption capacity for methylene blue, a common organic dye, compared to the chemically synthesized activated carbon. This enhanced adsorption performance can be attributed to the well-developed pore structure and surface chemistry of the microwave-synthesized activated carbon. Overall, this comparative study demonstrated that microwave activation is a promising method for the synthesis of activated carbon from corn cob, offering advantages in terms of higher surface area, pore volume, and adsorption capacity compared to traditional chemical activation methods. The findings of this research contribute to the development of sustainable and efficient methods for producing activated carbon from agricultural waste materials, paving the way for potential applications in environmental remediation and purification processes.

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.
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
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
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.
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.