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 (ClO −4) anion from ammonium perchlorate (NH4ClO4) wastewater. The sorbent developed is a crosslinked poly(allylamine hydrochloride) (PAA·HCl) polymeric hydrogel. The pH‐sensitive PAA·HCl hydrogels were synthesized by chemically crosslinking a solution of linear PAA·HCl 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 ± 870 mg ClO −4/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 PAA·HCl 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