Integrated Electrochemical Treatment Process for Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), Hexavalent Chromium, and Ammonia Using Electroactive Membranes

Ammonium nitrate solution (ANSOL) is generated as a byproduct during the explosive manufacturing process. Historically, ANSOL has been recycled for use in the mining industry; however, the unreliability of the recycling process over recent years has necessitated exploration of its treatment. In this preliminary study, we investigate the feasibility of developing a process that valorizes waste during ANSOL treatment. The novel process employs three electroactive membranes to (i) facilitate oxidation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), (ii) remove hexavalent chromium from solution, and (iii) recover pure ammonium from the contaminated ammonium nitrate stream. The impact of different operational parameters (applied current density and recirculating rate of feed through the anode) was evaluated. Oxidation of RDX was achieved using a porous substoichiometric TiO2, reaching removal rates as high as 120 g/m(2)/h. Ammonia recovery of about 23.26 g-NH3/m(2)/day was observed even at 0 V applied potentials and increased to 119.48 g-NH3/m(2)/day upon the introduction of a cathode chamber by placing a cation exchange membrane adjacent to the hydrophobic membrane. Finally, a preliminary technoeconomic analysis was also conducted to reveal the costs and profit centers of this technology.