A comparative study of chemical and microwave synthesized activated carbon from corn cob

Project Abstract

Activated carbon is a versatile adsorbent material widely used in various applications due to its high surface area and porosity. In this study, activated carbon was synthesized from corn cob using two different methods chemical activation with phosphoric acid and microwave activation. The goal was to compare the properties and performance of the activated carbon produced by these two methods. The chemical activation process involved impregnating the corn cob with phosphoric acid followed by carbonization at high temperatures. The microwave activation process, on the other hand, utilized microwave radiation to heat the corn cob directly, leading to the activation of the carbonaceous material. The activated carbons obtained from both methods were characterized using various techniques including scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and Fourier-transform infrared spectroscopy (FTIR). The results showed that the microwave-synthesized activated carbon had a higher surface area compared to the chemically synthesized activated carbon. The microwave activation process resulted in a more efficient activation of the carbonaceous material, leading to the development of a higher surface area and more porous structure. This enhanced surface area is beneficial for adsorption applications as it provides more active sites for the adsorption of target molecules. Furthermore, the microwave-synthesized activated carbon exhibited a higher degree of carbonization and lower ash content compared to the chemically synthesized activated carbon. The FTIR analysis indicated that both activated carbons contained similar functional groups, suggesting that the basic chemical structure of the carbon material was preserved during the activation process. In terms of adsorption performance, both activated carbons showed good adsorption capacities for methylene blue, a common dye pollutant. However, the microwave-synthesized activated carbon displayed slightly higher adsorption efficiency due to its higher surface area and porosity. Overall, this study demonstrates that microwave activation is a promising alternative method for the synthesis of activated carbon from corn cob. The microwave-synthesized activated carbon showed superior properties in terms of surface area, porosity, carbonization degree, and adsorption performance compared to the chemically synthesized activated carbon. These findings highlight the potential of microwave activation as a more efficient and environmentally friendly approach for the production of activated carbon from agricultural waste materials.

Project Overview

<p> </p><p><strong>INTRODUCTION</strong></p><p><strong>1.1 BACKGROUND OF STUDY</strong></p><p>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.2Preparation 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).</p><p>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 shapes3and 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.</p><p><strong>1.2 STATEMENT OF PROBLEM</strong></p><p>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 most4effective 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.</p><p><strong>1.3 OBJECTIVE OF THE RESEARCH</strong></p><p>The aim of this research project is to determine and compare the performance of chemically and microwave synthesized activated carbon from corn cob.</p><p><strong>1.4 SIGNIFICANCE OF THE RESEARCH</strong></p><p>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.5iv. It will attract foreign exchange for Nigeria as activated carbon has very wide industrial applications.</p><p><strong>1.5 SCOPE OF RESEARCH</strong></p><p>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.</p> <br><p></p>