Characterization of Chemically Activated Carbons Prepared from Miscanthus and Switchgrass Biomass.

Beata Doczekalska,Bogusława Waliszewska,Joanna Cerazy-Waliszewska,Tomasz Pniewski,Monika Bartkowiak,Grażyna Orszulak

doi:10.3390/ma13071654

Abstract

Lignocellulosic biomass, including that of energy crops, can be an alternative source to produce activated carbons (ACs). Miscanthus and switchgrass straw were used to produce ACs in a two-step process. Crushed plant material was carbonized at 600 °C and then obtained carbon was activated using NaOH or KOH at 750 °C. The content of surface oxygen groups was determined using Boehm’s method. The porosity of ACs was assayed using the nitrogen adsorption/desorption technique, while their thermal resistance using the thermogravimetric method. The ACs derived from miscanthus and switchgrass were characterized by surfaces rich in chemical groups and a highly developed porous structure. The highest specific surface areas, over 1600 m2/g, were obtained after carbon treatment with NaOH. High values of iodine number, 1200–1240 mg/g, indicate an extensive system of micropores and their good adsorption properties. The type of activator affected the contents of oxygen functional groups and some porosity parameters as well as thermal stability ranges of the ACs. Among obtained carbons, the highest quality was found for these derived from M. sacchariflorus followed by switchgrass, after activation with NaOH. Hence, while these crop species are not as effective biomass sources as other energy grasses, they can become valuable feedstocks for ACs.

Highlights

Since the moment activated carbon (AC) was obtained for the first time in 1900 by Raphael VonOstrejko, considered to be the “father of activated carbon”, the demand for this product has been permanently growing [1]
All obtained ACs were characterized by a rich chemical structure of the surface, a well-developed porous structure and sufficient thermal stability
This study has shown that the mechanisms of KOH and NaOH action on carbon precursors were not identical, which directly affected the structure and properties of carbon materials

Summary

Introduction

Since the moment activated carbon (AC) was obtained for the first time in 1900 by Raphael VonOstrejko, considered to be the “father of activated carbon”, the demand for this product has been permanently growing [1]. Major factors driving the market studied include conformance to stringent environmental regulations in water treatment applications and increasing the importance of air pollution control, especially mercury removal [2]. AC has become the preferred option for use in potable water purification, treatment of aquariums, swimming pools and wastewater as well as air and gas filtration. These applications are the most important due to increasing environmental pollution, health concerns and stringent government regulations [4]. Other applications of activated carbon include monitoring gas emissions in automobiles, personal protection in the defense sector, recovery of Materials 2020, 13, 1654; doi:10.3390/ma13071654 www.mdpi.com/journal/materials

Objectives

Methods

Results

Discussion

Conclusion