Development of nitroguanidine wastewater treatment technologies
Nitroguanidine (NQ) is a nitramine used in many propellant formulations. The purpose of this study was to develop a method for treating nitroguanidine process wastewaters. The major wastewater contaminants were found to be nitroguanidine and guanidine nitrate (GN) (an intermediate product). Pilot tests were conducted for the removal of nitroguanidine using granulated carbon adsorption (GAC) and ion exchange for the removal of GN. The nitroguanidine concentration in demonstration plant wastewater was reduced from 15.5 mg/L to less than 1 mg/L. The carbon capacity was found to be 0.045 g NQ/g carbon. Strong acid resin was found to reduce guanidinium ion Gu⁺ concentration from 14.5 mg/L to 1 mg/L with a resin capacity of 0.13 eq Gu⁺ /L resin. No significant reduction in resin capacity for Gu⁺ was experienced after five regenerant cycles. A unique two-step regeneration was used. This included a 5% calcium nitrate solution to produce a spent regenerant that could be recycled to the production process. This was followed by regeneration with a 15% sodium chloride solution to place the resin in the sodium form. Anion exchange was used for the removal of nitrate ions.