Perchlorate removal from groundwater by surfactant mediated precipitation and polyelectrolyte enhanced ultrafiltration

Abstract

The large scale contamination of many ground and surface water with perchlorate mostly occurred from the rocket fuel; presents a technical challenge. Existing methods for the perchlorate removal from groundwater involve complicated process and are expensive. The objective of this research is to identify and investigate perchlorate removal methods which are cost effective and easy to implement in groundwater. Surfactant mediated precipitation (SMP) and polyelectrolyte enhanced ultrafiltration (PEUF) processes for the removal of perchlorate were studied in this research. The feasibility in terms of the removal efficiency of perchlorate using these two methods was investigated based on their different parameters in presence of other common groundwater contaminants (nitrate, sulfate and carbonate). Cationic surfactant, cetylpyridinum chloride (CPC) was used in SMP process as precipitating agent to obtain precipitant containing perchlorate ion. The result shows that, up to 1 mM of CPC concentration which is around the CMC (critical micelle concentration, 0.9 mM), the perchlorate is removed in 1:1 or higher molar ratio of CPC to perchlorate due to the precipitant formation by ion exchange. While at 5 mM of CPC which is high above the CMC, perchlorate removal is inhibited due to micelle formation property of surfactant, in which some perchlorate absorbs in the micelle due to electrostatic force and remains in the supernatant. Furthermore, the removal efficiency decreases in presence of other ions (nitrate, sulfate and carbonate) because of the increase of the ionic strength of the solution; that results in the decremented activity of CPC in absorbing perchlorate ion. In PEUF process, poly(diallyldimethylammonium chloride), PDADMAC which is a cationic polyelectrolyte, was used to remove the anionic contaminant, perchlorate. In absence of other ions, perchlorate and PDADMAC system shows that lower amount of PDADMAC (up to 1 mM) can remove almost 90% of perchlorate from ...