G Model JIEC 3540 1–5 Journal of Industrial and Engineering Chemistry xxx (2017) xxx–xxx Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec 1 Extraction-based recovery of RDX from obsolete Composition B 2 Q1 a a a a, b Hyewon Kang , Hyejoo Kim , Chang-Ha Lee , Ik-Sung Ahn *, Keun Deuk Lee 3 a Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 120-749, South Korea 4 b Agency for Defense Development, Daejeon 305-600, South Korea A R T I C L E I N F O A B S T R A C T Article history: Received 3 November 2016 Recovery of explosives from obsolete ammunition has been considered an eco-friendly alternative to Received in revised form 20 July 2017 conventional dumping or detonation disposal methods Composition B, made of 2,4,6-trinitrotoluene Accepted 26 July 2017 (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and paraffin wax, has been used as the main Available online xxx explosive filling in various munitions. It was selected as a model explosive for this study. TNT was extracted from Composition B by exploiting the different solubilities of TNT and RDX in acetonitrile. After Keywords: removing paraffin wax by hexane washing, RDX was recovered from unused Composition B with a purity Composition B higher than 99% and a yield of 84%. Recovery © 2017 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering RDX Chemistry. Extraction Demilitarization 5 29 Introduction destroyed using the following techniques: dumping at sea, outdoor 30 burning, open detonation, and detonation in a mine tunnel [9,10]. 6 31 Ammunition has a limited service life and must be disposed of In the case of dumping at sea, munitions stored in boxes and metal 7 32 at a certain stage [1]. Large quantities of unused ammunition are canisters or containers are transferred to ships. In this process, 8 33 stored throughout the world [2]. For example, Composition B, a leakage of munitions is unavoidable and can cause serious damage 9 34 mixture of two explosives (hexahydro-1,3,5-trinitro-1,3,5-triazine to marine ecosystems. Hence, dumping at sea has been banned by 10 35 (RDX) and 2,4,6-trinitrotoluene (TNT)) and wax, has been used as the London Convention and other related agreements [2]. Outdoor 11 36 the main explosive filling in artillery projectiles, rockets, land burning has been carried out in areas that satisfy the following 12 37 mines, and various other munitions. The term “Composition” in requirements: (1) no danger of the fire spreading; (2) absence of 13 38 Composition B has been used for any explosive material made of flammable objects; (3) dimensions of at least 20 m  20 m; (4) 14 39 RDX. Other RDX-derived explosives that have a long history of presence of an excavated channel of 0.5 m width and 0.25 m depth 15 40 application include Composition A and Composition C. Composi- around the combustion area; and (5) warning signs marking the 16 41 tion A consists of RDX and a small amount (1–9% w/w) of combustion area. Open detonation disposal in a blast chamber has 17 42 plasticizing wax [3,4]. The original Composition C was developed been rarely performed. Open burning and open detonation (OBOD) 18 43 by the British during World War II, but was standardized as methods have been recognized as simple and economical 19 44 Composition C when introduced to the US. It consists of RDX, a processes for the destruction of munitions; however, they cause 20 45 mineral oil-based plasticizer, and a phlegmatizer [3,5,6]. Compo- air pollution due to the release of NOx, acidic gases, and fine dust 21 46 sition C-4 is the most well-known explosive among Composition C [2,11,12] and soil contamination by heavy metals [13]. Detonation 22 47 explosives and has been used not only for military purposes (e.g., in in a mine tunnel has been mostly carried out in an old abandoned 23 48 the Vietnam War) but also in acts of terrorism. Hence, large mine. The tunnel should have a depth of at least 900 m while being 24 49 amounts of Composition explosives have been produced and covered with hard rocks. Moreover, the mine must be equipped 25 50 stored since World War II for its high explosive yield [7,8]. In with emergency bunkers with air conditioning systems indepen- 26 51 addition to posing a potential hazard, storage of surplus ammuni- dent of the main ventilation system. Because of environmental 27 52 tion is undesirable because of the cost and space requirements. pollution and safety issues, the disposal of unused munitions by 28 53 Thus, stockpiles of ammunition have been conventionally these conventional techniques has been strictly forbidden by 54 environmental laws and banned in numerous countries [2,11,12]. 55 Development of Resource Recovery and Recycling (R3) techni- 56 ques has gained interest in demilitarization activities. For instance, * Corresponding author. Fax: +82 2 312 6401. 57 E-mail address: [email protected] (I.-S. Ahn). waste energy could be recovered from thermal destruction http://dx.doi.org/10.1016/j.jiec.2017.07.036 1226-086X/© 2017 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. Please cite this article in press as: H. Kang, et al., Extraction-based recovery of RDX from obsolete Composition B, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.07.036 G Model JIEC 3540 1–5 2 H. Kang et al. / Journal of Industrial and Engineering Chemistry xxx (2017) xxx–xxx 58 Table 1 operations conducted under the R3 concept while scrap metals 59 Physical properties of TNT and RDX [18–20]. could be collected and sold. Conversion of explosives to fertilizers 60 and commercial chemicals is another example of using TNT RDX 61 R3 technologies [1]. Recycling of unused and obsolete explo- Molecular weight 227.1 222.1 62 sives/munitions is quite valuable since energetic materials are Melting temperature ( C) 80 202–204 63 Decomposition temperature ( C) 240 213 uncompromised and can be reused as commercial explosives, 3 64 Crystal density at 20 C (g/cm ) 1.6 1.8 propellants, military explosives, or fuel supplements [12,14,15]. 65 Detonation velocity (m/s) 6640 8,950 For the recovery of unused explosives, the following separation Detonation pressure (kbar) 210 350 66 methods have gained interest: melting separation, solvent Temperature of detonation (K) 2740 2600–4000 67 extraction separation, and supercritical carbon dioxide extraction 68 separation [16]. The melting separation method is based on the 69 difference between the melting points of waste explosive Experimental 110 70 components. For example, the melting point of TNT is 80 C while 71 that of RDX is 204 C. Appropriate heating to make TNT reach the Materials 111 72 molten state but ensure RDX remains solid allows their separation 73 by simple filtration. The advantages of this method are its simple 112 Composition B, RDX, and TNT were supplied by the Agency for 74 operation and that it does not require any solvent. The disadvan- 113 Defense Development (ADD) of Korea. The acetonitrile, water, and 75 tage is the safety issue caused by heating to relatively high 114 hexane used were all HPLC grade and purchased from Duksan Pure 76 temperatures. The principle of solvent extraction separation is 115 Chemicals Co., Ltd. (Ansan, Korea). The extracted solutions were 77 that, at the same temperature and in the same solvent, there is a 116 filtered through 0.2-mm PTFE membrane filters (Toyo Roshi Kaisha, 78 difference in the solubilities of waste explosive components. By 117 Ltd., Tokyo, Japan). 79 choosing a suitable organic solvent where a molecular explosive of 80 interest is completely soluble, but other components are not, the 118 Extraction of RDX and TNT 81 target explosive can be obtained after recrystallization. The 82 advantages of solvent extraction separation are that high temper- 119 To completely extract TNT from Composition B, 1.5 mL of 83 atures are not required and safety is not breached. However, the 120 acetonitrile was mixed with 2.0 g of Composition B at room 84 use of organic solvents may increase the cost of separation and 121 temperature. Considering that the mass fraction of TNT in 85 recovery, causing secondary pollution. Supercritical carbon dioxide 122 Composition B is about 40% and 100 g of TNT is soluble in 100 g 86 has been used for chemical extraction. It is inert, non-flammable, 123 of acetonitrile at 20 C, 1.5 mL of acetonitrile is about twice the 87 and non-explosive. The relatively low critical temperature and 124 amount needed to dissolve 0.8 g of TNT present in 2.0 g of 88 pressure of CO (e.g., 31.1 C and 72.9 atm) relieves us from the 125 2 Composition B. Mixtures of acetonitrile and water were also tested 89 concern of damaging the explosives. Such low toxicity, environ- 126 as extracting solvents to see if there was a change in the fraction of 90 mental impact, and concern for safety issues have led to an 127 TNT in the extractant due to the addition of water. 91 increase in the number of studies on the use of supercritical CO for 128 2 In order to investigate the effect of the extraction time (i.e., the 92 extracting molecular explosives.