Ammonium perchlorate-binding poly(allylamine hydrochloride) hydrogels for wastewater remediation

Systems that are capable of removing highly toxic anions from wastewater ef fluents, even at extremely low concentrations, are a major need in the defe nse industry. This study reports on the features of two new batch and conti nuous-flow sorption processes with regard to ultimate removal and recovery of the perchlorate (ClO4-) anion from ammonium perchlorate (NH4ClO4) wastew ater. 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 chain s with epichlorohydrin (EPI). The perchlorate-binding capacity of the polym er gels was measured in standard solutions and studied as a function of gel synthesis parameters. Equilibrium perchlorate loadings of 5770 +/- 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 Warfar e Center (NSWC) Indian Head Division showed that perchlorate concentrations decreased by 85% Preliminary lab-scale packed-column experiments in wastew ater achieved up to 40% reduction in total perchlorate content. The regener ation ability of the gels was demonstrated by release of the bound perchlor ate anions, upon washing with a LN NaOH solution, providing opportunities t o 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. (C) 2001 John Wiley & Sons, Inc.