Straw-Based Activated Carbon: Optimization of the Preparation Procedure and Performance of Volatile Organic Compounds Adsorption.

Zhen Li,Yonghong Li,Jiang Zhu

doi:10.3390/ma14123284

Abstract

Straw is one of the largest agricultural biowastes and a potential alternative precursor of activated carbon. Activated carbon prepared from different types of straw have great differences in structure and adsorption performance. In order to explore the performance of different straw-based activated carbon in volatile organic compounds adsorption, five common straws were selected as potential source materials for the preparation of SAC. The straw-based activated carbons were prepared and characterized via a thermo-gravimetric analysis, scanning electron microscope and the Brunauer–Emmett–Teller method. Among the five straw-based activated carbons, millet straw-derived activated carbon exhibited superior properties in SBET, Smic and adsorption capacities of both toluene and ethyl acetate. Furthermore, the preparation process of millet straw activated carbon was optimized via response surface methodology, using carbonization temperature, carbonization time and impregnation ratio as variables and toluene adsorption capacity, ethyl acetate adsorption capacity and activated carbon yield as responses. The optimal preparation conditions include a carbonization temperature of 572 °C, carbonization time of 1.56 h and impregnation ratio (ZnCl2/PM, w/w) of 1.60, which was verified experimentally, resulting in millet straw activated carbon with a toluene adsorption capacity of 321.9 mg/g and ethyl acetate adsorption capacity of 240.4 mg/g. Meanwhile, the adsorption isothermals and regeneration performance of millet straw activated carbon prepared under the optimized conditions were evaluated. The descriptive ability of the isothermals via the Redlich–Peterson equation suggests a heterogeneous surface on millet straw activated carbon. Recyclability testing has shown that millet straw activated carbon maintained a stable adsorption capacity throughout the second to fifth cycles. The results of this work indicate that millet straw activated carbon may be a potential volatile organic compound adsorbent for industrial application.

Highlights

IntroductionVarious materials, including industrial residues, agricultural and forestry by-products and other low-cost resources, have been proposed for the preparation of Active carbons (ACs) [5]
The corresponding endothermal peaks of these four straws in this stage were all at about 300 ◦ C, which can be attributed to the pyrolysis of cellulose, hemicellulose and lignin [40,41]
Five straw-based activated carbons from common straws were investigated for adsorption of volatile organic compounds

Summary

Introduction

Various materials, including industrial residues, agricultural and forestry by-products and other low-cost resources, have been proposed for the preparation of ACs [5]. Straw from agricultural wastes is a promising resource for the production of ACs due to their low cost and the ability to avoid environmental pollution by incineration. Studies show that the straw-based activated carbons (SACs), prepared from rice straw [6,7,8], wheat straw [2,9,10], sesame straw [11], corn straw [12,13] and maize straw [10] had an adsorption effect on heavy metals and that the SACs, from corn straw [14,15] and wheat straw [14,16] can be used to remove organic dyes from water. SACs are able to remove antibiotics [17,18,19]

Methods

Results

Conclusion