Title: Walnut shells: food processing waste from western Himalayan state of Himachal Pradesh as an excellent source for production of activated carbon with highly acidic surface

Authors: Ripu Daman Kumar; Krishna Kadirvelu; G.K. Kannan

Addresses: Department of Environmental Sciences, Bharathiar University, Coimbatore, T.N., India ' DRDO-BU Centre for Life Sciences, Bharathiar University Campus, Coimbatore, T.N., 641 046, India ' Scientist 'E' Defence Bio Engineering and Electro Medical Laboratory (DEBEL), Defence R&D Organization (DRDO), Ministry of Defence, Government of India, CV Raman Nagar, Bangalore, 560093 Karnataka, India

Abstract: Activated carbon one of the best adsorbent for various organic and inorganic pollutants can be made from various raw materials and by different methods of processing. The activated carbon was produced at different temperature, i.e., 300°C, 350°C, 400°C and 500°C respectively. The properties of the activated carbon were further modified and enhanced by treating it with H2SO4, H3PO4 and ZnCl2. Development of porous structure as a consequence of chemical activation is clearly visible from the SEM micrographs of these carbons. Out of the three different chemically activated carbon produced, i.e., sulphuric acid activated walnut shell carbon (SAAWSC), zinc chloride activated walnut shell carbon (ZCAWSC) and phosphoric acid activated walnut shell carbon (PAAWSC), the sulphuric acid activated carbon has been found having the highest surface area of 745 m2/g. The surface of these activated carbons is highly acidic with a maximum phenol group (5.72 meq/g) in the case of phosphoric acid activation. The pHzpc ranges between 4-4.5 for these activated carbons from waste walnut shells.

Keywords: activated carbon; walnut shells; surface area; porosity; chemical activation; acidic groups.

DOI: 10.1504/IJEWM.2019.10019833

International Journal of Environment and Waste Management, 2019 Vol.23 No.3, pp.274 - 299

Received: 14 Nov 2017
Accepted: 08 Jun 2018

Published online: 12 Apr 2019 *

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