Utilization of Crofton weed for preparation of activated carbon by microwave induced CO2 activation
Introduction
Activated carbons (AC) are important kinds of porous carbon material with abundantly developed pore structure, strong adsorption ability, high surface area and thermo stability, they are widely used in many different industries, such as separation and purification processes, including both gas and aqueous media [1], [2], [3], catalyst supports [4] and removal of organic dyes and pollutants from industrial wastewater [5] and from other aqueous media [6]. The selection of an appropriate precursor plays an important role deciding the characteristics of the AC as well as the economics of the manufacturing plant. To identify new precursors that are cheap, accessible and available in large quantity has been a perennial challenge in commercial manufacture for economic benefits [7]. Toward which, different biomass based feedstock such as rice bran, coconut shell and waste materials were used as the raw materials since they are sustainable sources having high fixed carbon content [8], [9], [10].
Croton weed, a kind of global exotic weeds originated from Mexico, and which has spread extensively in many countries around the world such as America, Australia and the countries in Southeast Asia due to its strong ability to adapt to different environmental conditions [11]. Since 1940s, Croton weed has spread extensively in south and western of China. Lots of the farm lands, pasture fields and forests have been destroyed causing huge economic losses. This has drawn the attention of the society and many methods have been developed to control it, such as manual, chemical and biological control, no obvious progress is made. In 2003, the Chinese ministry of environmental protection released a list of “The First Batch of Exotic Invasive Species” and croton weed was rated the first [12], [13]. According to the published literatures, croton weed can be used as bio-pesticide [14], organic fertilizer and feedstuff, feedstock for production of marsh gas [15]. Although, croton weed can be utilized as a biomass resource to prepare the AC, the relevant literature is very limited. The attempts pertaining to preparation of CWAC has been limited to Xia et al. and Wu et al. [16], [17].
Activated carbons have been traditionally produced by the partial gasification of the char either with steam or CO2 or a combination of both. The gasification reaction results in removal of most reactive carbon atoms and in the process simultaneously produce a wide range of pores (predominantly micropores), resulting in porous activated carbon. In general, the methods for AC production are divided into two classes: physical activation and chemical activation. Physical activation is essentially a two-step process, where the carbonization of a carbonaceous material forms the first step, while the second step involves the activation of the resulting char at elevated temperature in the presence of suitable oxidizing gases such as carbon dioxide, steam, air or their mixtures. Chemical activation involves the impregnation of a carbonaceous material with an activation agent and heat treatment of the impregnated material under inert atmosphere. Physical activation is widely adopted industrially for commercial production owing to the simplicity of process and the ability to produce AC with well developed micro porosity and desirable physical characteristics such as the good physical strength.
Referring to the heating methods for the preparing of AC, interests are growing in the application of microwave (MW) heating. The conventional heating methods do not ensure a uniform temperature of the precursor owing to their variation in the size and shape as the mode of heating is through conduction and convection. This conventional heating mode generates a temperature gradient from the hot surface of the sample particle to its interior and impedes the effective removal of gaseous products to its surroundings, demanding higher processing time and energy consumption. Recently, microwave heating is being increasingly utilized for variety of applications, as heating is uniform, where the absorbed microwave readily transforms into heat inside the particles by dipole rotation and ionic conduction [18], [19], [20]. Recently MW heating has been widely used to produces as well as to regenerate AC, the relevant literature is very limited [21], [22], [23]. There is no study regarding AC prepared from the Crofton weed with MW heating in the presence of physical activation.
This urged research toward upgrading and utilization of the harmful biomass Crofton weed. In this regard, the objective of this work is to evaluate the operational conditions for improving the porosity and adsorption capacity of CWAC using MW heating. Effects of the activation temperature, activation duration and CO2 rate on the adsorption capacity and yield of CWAC were investigated systematically. The resultant products were characterized using the nitrogen adsorption isotherm, FTIR and SEM analysis.
Section snippets
Materials
Crofton weed were collected from Kunming, Yunnan Province of China. The raw materials were crushed, sieved into a uniform size of 5–7 mm, then were washed thoroughly with distilled water to remove foreign material and then oven-dried at 105 °C overnight and stored in a moisture free environment for utilization in the experiment. The proximate analyses of the Crofton weed were as follow: volatile 76.41%, ash 1.90% and fixed carbon 21.69%.
Carbonization of Crofton weed
The carbonization of raw precursors was carried out by
Results and discussion
Table 2 shows the experimental conditions for preparation of CWAC generated by the Design Expert software covering the parameters such as activation temperature, activation duration and CO2 flow rate. The CWAC are characterized for iodine number, yield and results are listed as well in Table 2.
Conclusions
Crofton weed, a harmful biomass is utilized for preparing AC with microwave heating exhibits well developed pore structure. The effects of three vital process parameters, activation temperature, activation duration and CO2 flow rate on the adsorption capacity and yield of AC were investigated systematically. The process parameters were optimized utilizing the Design Expert software and were identified to be an activation duration of 90 min, an activation temperature of 980 °C and a CO2 flow rate
Acknowledgements
The authors would like to express their gratitude to the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20115314120014) and the Kunming University of Science and Technology Personnel Training Fund (No. KKSY201252077) for financial support.
References (34)
- et al.
Preparation of activated carbon from Enteromorpha prolifera and its use on cationic red X-GRL removal
Appl. Surf. Sci.
(2011) - et al.
Development of highly microporous activated carbon from the alcoholic beverage industry organic by-products
Biomass Bioenergy
(2011) - et al.
The preparation of active carbons from coal by chemical and physical activation
Carbon
(1996) - et al.
Decolorization of sugar syrups using commercial and sugar beet pulp based activated carbons
Bioresour. Technol.
(2008) - et al.
Adsorption of basic dye (methylene blue) onto activated carbon prepared from rattan sawdust
Dyes Pigm.
(2007) - et al.
Microwave assisted preparation of efficient activated carbon from grapevine rhytidome for the removal of methyl violet from aqueous solution
J. Anal. Appl. Pyrolysis
(2011) - et al.
Preparation and characterization of activated carbon from rice bran
Bioresour. Technol.
(2007) - et al.
Preparation of microporous activated carbon from raw coconut shell by two-step procedure
Chin. J. Chem. Eng.
(2006) - et al.
Waste materials for activated carbon preparation and its use in aqueous-phase treatment: a review
J. Environ. Manage.
(2007) - et al.
Kinetics and equilibrium adsorption study of lead (II) onto the low cost adsorbent—Eupatorium adenophorum Spreng
Process Saf. Environ.
(2009)
Evaluation of feeding value of Eupatorium adenophorum in combination with mulberry leaves
Livest. Sci.
Recent developments in the preparation and regeneration of activated carbons by microwaves
Adv. Colloid Interface
A novel method for production of activated carbon from waste tea by chemical activation with microwave energy
Fuel
An overview of microwave processing and dielectric properties of agri-food materials
Biosyst. Eng.
Production of activated carbon from Luscar char: experimental and modelling studies
Microporous Mesoporous Mater.
Determination of cost optimal operating conditions for decoloration and mineralization of CI Reactive Blue 268 by UV/H2O2 process
Chem. Eng. J.
Response surface methodology (RSM) analysis of photo induced decoloration of toludine blue
Chem. Eng. J.
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