Preparation and Characterization of Activated Carbons Obtained from Maize Cobs by Zinc Chloride Activation

Abstract

Aims: To set up high adsorbent materials at lower cost from agricultural wastes in this case maize cobs and to characterize these materials. Study Design: Determination of the textural and physicochemical properties of the prepared materials. Place and Duration of Study: Technological University of Chalmers, Nuclear Chemistry Laboratory, Goteborg, Sweden, between November 2010 and January 2011. Methodology: Five activated carbon samples of maize cobs were prepared by chemical activation with zinc chloride (ZnCl2). They were characterized and the values of their textural (SEM images and XRD patterns) and physicochemical properties (specific surface area, pore volume, pore size and functional groups) were determined and compared with those of a commercial activated carbon of animal origin. Results: The results showed that the part of the cob used, the residence time, the quantity and the state of the activating agent affected the activated carbon produced. Thus, the carbon material obtained from the woody belt (hard part of the cob) showed the most significant properties with a specific surface area of 701.68 m2/g and a porous volume of about 0.39 cm3/g. On the other hand, samples obtained from the soft part of the cob mixed with small particles of woody belt, gave low specific surface area (0.43-11.62 m2/g) and porous volumes (0.00028-0.11 cm3/g). In addition, all these chars presented acidic functions at their surfaces. Conclusion: The study revealed that maize cobs particularly the hard part of the cobs, an agricultural waste, can be used as raw material for the preparation of activated carbon.