Ammonium Perchlorate–Binding Poly(allylamine hydrochloride) Hydrogels for Wastewater Remediation

Systems that are capable of removing highly toxic anions from wastewater effluents, even at extremely low concentrations, are a major need in the defense industry. This study reports on the features of two new batch and continuous-flow sorption processes with regard to ultimate removal and recovery of the perchlorate (ClO4 ) anion from ammonium perchlorate (NH4ClO4) wastewater. The sorbent developed is a crosslinked poly(allylamine hydrochloride) (PAAzHCl) polymeric hydrogel. The pH-sensitive PAAzHCl hydrogels were synthesized by chemically crosslinking a solution of linear PAAzHCl chains with epichlorohydrin (EPI). The perchlorate-binding capacity of the polymer gels was measured in standard solutions and studied as a function of gel synthesis parameters. Equilibrium perchlorate loadings of 5770 6 870 mg ClO4 /g gel were calculated from measurement of the decrease in perchlorate concentration in aqueous standard solutions using UV-Vis spectrophotometry. Batch experiments in wastewater originating from the Naval Surface Warfare Center (NSWC) Indian Head Division showed that perchlorate concentrations decreased by 85%. Preliminary lab-scale packed-column experiments in wastewater achieved up to 40% reduction in total perchlorate content. The regeneration ability of the gels was demonstrated by release of the bound perchlorate anions, upon washing with a 1N NaOH solution, providing opportunities to recover and reuse the hydrogel over multiple regeneration cycles. The PAAzHCl hydrogels are demonstrated to be appropriate materials for treating wastewaters that contain ammonium perchlorate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2073–2083, 2001