A comparative study on rice husk and rice straw as bioresources for production of carbonaceous adsorbent and silica
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ORIGINAL ARTICLE
A comparative study on rice husk and rice straw as bioresources for production of carbonaceous adsorbent and silica Eisa Khoshnood Motlagh 1 & Neda Asasian-Kolur 1
&
Seyedmehdi Sharifian 1
Received: 29 June 2020 / Revised: 11 October 2020 / Accepted: 9 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The conversion of rice crop residues into activated carbon (AC) and nanosilica was performed via an integrated procedure including successive carbonization, K2CO3 activation, and extraction steps. For the first time, rice husk and rice straw were utilized comparatively as the raw materials for parallel AC and silica production, and the main characteristics of the corresponding products were compared. However, AC produced from rice straw at 1000 °C and impregnation ratio of 1.5 showed a larger surface area and total pore volume (2229 m2/g and 1.6 cm3/g) than AC produced from rice husk (1941 m2/g and 1.5 cm3/g); no definite and general conclusion can be made about the superiority of rice straw as the raw material. This is attributed to the close characteristics of the products, the large variety of rice crop residues, and the strong influence of the operating conditions on the properties of products. The rice husk– and rice straw–based activated carbons had no significant difference in their functional groups and chemical characteristics. The amorphous silica nanosize particles (< 50 nm) were obtained from both raw materials; however, the presence of little crystalline phase impurities (potassium chloride) and silica (tridymite and coesite) was also observed. The most important superiority of rice husk to rice straw was its larger silica production yield from the initial biochar (40% compared to 25%). Keywords Rice husk . Rice straw . Chemical activation . Activated carbon . Silica
1 Introduction Rice straw and rice husk are the two main agricultural wastes of the north of Iran and all areas in the world with major rice production. To obtain 1 kg of milled rice, 0.7 to 1.4 kg rice straw and 0.28 kg rice husk as waste is produced consequently [1]. Because of the low value of untreated rice crop residues, the collecting and transportation costs usually cannot be afforded by farmers, and therefore, they tend to burn these wastes in farms particularly in undeveloped countries. The enormous volume of gaseous and solid pollutants resulted from wastes burning in rice fields brings many difficulties for people and cities around. Therefore, finding new ways for the conversion of these agricultural wastes into high value-added products may prevent environmental pollution
* Seyedmehdi Sharifian [email protected] 1
Chemical Engineering Department, Fouman Faculty of Engineering, College of Engineering, University of Tehran, P. O. Box 43515-1155, Fouman 43516-66456, Iran
consequently. In addition to burning rice straw wastes and utilizing the energy produced in rural applications, rice straw is classically used as animal bedding and feed [2]. It is established that due t
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