Effective and highly recyclable nanosilica produced from the rice husk for effective removal of organic dyes Gehan M.K. Tolba a,b , Nasser A.M. Barakat a,c, *, A.M. Bastaweesy b , E.A. Ashour b , Wael Abdelmoez b , Mohamed H. El-Newehy d , Salem S. Al-Deyab d , Hak Yong Kim a a Organic Materials and Fiber Engineering Department, Chonbuk National University, Jeonju 561-756, South Korea b Chemical Engineering Department, Faculty of Engineering, Minia University, El-Minia, Egypt c BioNanosystem Department, Chonbuk National University, Jeonju 561-756, South Korea d Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia Introduction Adsorption is a well-known equilibrium separation process, and an effective and economic process to remove dyes, pigments and other colorants and as well as to control the bio-chemical oxygen demand [1]. Activated carbon has been the most popular and widely used adsorbent in waste water treatment applications all over the world [2–5]. Despite its of productive use, activated carbon remains an expensive material and requires complexing agents to improve its removal performance for inorganic matters [6,7]. Moreover, its regeneration is complicated and non-economic process. In other words, up to now, activated carbon is considered one-time used material. Thus, research is interested in producing alternative inexpensive adsorbents to replace the costly activated carbon [8–10]. Recently, using nanostructured materials as adsorbents affords significant advantages in the environmental applications for water treatment [11–14] due to their high surface areas, large available surface adsorption site density, special functionality, and well- defined morphology. Compared to the traditional materials and their bulk counterparts, the nanosized materials usually exhibit much higher adsorption capacities and faster rates for pollutant removal. Complicated and expensive synthesis methodologies are the main constraints against wide applications for the nano adsorbents. Alternatively, extraction of functional nano materials from costless wastes can be considered industrial desirable strategy. Rice husk is costless and a widely available agricultural waste which is produced from the processing and refining of rice [15]. The Food and Agriculture Organization of the United Nations (FAO) has been estimated that about 719.7 million tones of paddy (rice) were produced in 2012. On the average, 20% of the rice processed is husk meaning that around 144 million tones of rice husk were produced in 2012. In many countries such as Egypt, most of the rice husk produced is either burnt producing rice husk ash or dumped as waste [16]. It was estimated that about 89,000 tons of rice husk were burnt in 2012 (FAO). Moreover, about 75–90% of RH is organic matters such as cellulose, lignin, etc. and the rest (10–25%) are mineral components such as silica, alkalis and trace elements depending on rice variety, soil chemistry, climatic conditions, and even geographic location of growth [17]. Rice husk has been found suitable for using as a fuel [18], in building materials, as a raw materials for the production of high performance silicon and its Journal of Industrial and Engineering Chemistry xxx (2015) xxx–xxx A R T I C L E I N F O Article history: Received 27 October 2014 Received in revised form 14 February 2015 Accepted 7 March 2015 Available online xxx Keywords: Hydrothermal process Adsorption Rice husk Nanosilica Sub-critical water A B S T R A C T Amorphous nanosilica separated from rice-husk at yield of 81% by hydrothermal technique is introduced as effective and reusable adsorbent for the organic pollutants. The prepared nanosilica is spheroid with a particle size of 10–50 nm. As adsorbent, the results indicated that the nanosilica could remove 65% from the methylene blue dye (10 ppm) within the first minute. The calculated thermodynamic parameters indicated that the adsorption of MB is spontaneous and endothermic. Interestingly, regeneration of the introduced material by caclination at 450 8C enhanced the adsorption process as the removing percentage was linearly depending on the number of the successive cycles. ß 2015 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author at: Organic Materials and Fiber Engineering Department, Chonbuk National University, Jeonju 561-756, South Korea. Tel.: +82 632702363; fax: +82 632702348. E-mail address: nasser@jbnu.ac.kr (Nasser A.M. Barakat). G Model JIEC-2461; No. of Pages 12 Please cite this article in press as: G.M.K. Tolba, et al., J. Ind. Eng. Chem. (2015), http://dx.doi.org/10.1016/j.jiec.2015.03.025 Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec http://dx.doi.org/10.1016/j.jiec.2015.03.025 1226-086X/ß 2015 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.