KINETICS OF THE ALKALINE-HYDROLYSIS OF HIGH EXPLOSIVES RDX AND HMX INAQUEOUS-SOLUTION AND ADSORBED TO ACTIVATED CARBON

Aqueous alkaline hydrolysis of bulk quantities and wastewater contamin ated with high explosives is a promising technology for treatment and disposal of the worldwide surplus of munitions. We investigated the hy drolysis kinetics of the high explosives hexahydro-1,3,5-trinitro-1,3, 5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) for temperatures ranging from 50 to 80 degrees C and in the pH r ange from 10 to 12. The experimental data were described using a pseud o-first-order model with subsequent calculation of second-order rate c onstants from experiments with excess hydroxide concentration. The tem perature dependency of the rate constants was evaluated using the Arrh enius model. The activation energies were determined to be E(RDX) = 99 .9 +/- 1.9 kJ mol(-1) and E(HMX) = 111.9 +/- 0.8 kJ mol(-1). The rate of HMX hydrolysis is much slower than the rate of RDX hydrolysis and m ay become rate limiting in the treatment of RDX/HMX mixtures. The alka line hydrolysis of RDX yields 1.6 M NO2-, 1.5 M HCOO-, 0.1 M CH3COO-, 1.1 M HCHO (11), 0.9 M NH3, 1.1 M N2O, and 0.34 M N-2 per mol of RDX h ydrolyzed. Acetate ion (CH3COO-) is a previously unknown end product o f the alkaline hydrolysis of RDX. A mass balance showed a recovery of 94% carbon and 90% nitrogen. During GC/MS analysis of the end products , no further unknown products could be found. In batch desorption stud ies, it was also shown that RDX-laden activated carbon can be regenera ted using alkaline hydrolysis (T = 80 degrees C, pH 12) and that the d esorption of the hydrolysis products is complete.