Solubility study and selective purification of HMX explosive in organic electrolyte solution of zinc acetate/diethylene glycol

Abstract

In this study, an organic electrolyte solution based on zinc acetate/diethylene glycol (ZA/DEG) is introduced for the selective purification of cyclotetramethylene tetranitramine (HMX) high explosive from its identical homologue cyclotrimethylene trinitramine (RDX). The dielectric constant of various organic solutions were investigated through Electrochemical Impedance Spectroscopy (EIS) in the range of 1.0 Hz–30 MHz. and some quantum-chemical descriptors of RDX and HMX dissolutions in the ZA cosolvent were analyzed using Density Functional Theory (DFT). The results show dielectric constant and solubility of RDX is higher than that of HMX, and by increasing of ZA concentration in DEG solvent, the values of dielectric constants were enhanced. Furthermore, the presence of ZA cosolvent on the solubility of two explosives was statistically investigated by Central Composite Design (CCD) of experiment, and some solubility parameters including activity coefficient, dissolving enthalpy, and mixing enthalpies were determined. The experimental results indicate that the weight ratio of RDX to HMX solubility in the proposed organic electrolyte changes up to 30 times, which provides a selective and sequential separation method to separate two materials with similar chemical properties with a separation efficiency >98% and HMX purity> 99.8%. The X-Ray Diffraction (XRD) analysis, High-Performance Liquid Chromatography (HPLC), Laser-Induced Breakdown Spectroscopy (LIBS), and Fourier Transform Infrared Spectroscopy (FT-IR) approves the acceptable quality of the separated materials. The proposed method makes the efficient and safe purification of high-quality HMX for application in oil and gas well perforating gun charges, using a nonvolatile and inflammable organic electrolyte.