Multilayered surface for the interactive separation of perchlorate from aqueous medium

Abstract

Environmental contextPerchlorate from rocket fuel plants or firework manufacturing units can seriously contaminate drinking water. We developed a separation skin on a microfiltration membrane and on sand that can remove perchlorate from water in the presence of competing ions. This method is suitable for a domestic water purification unit selective for perchlorate removal. AbstractThis study reports an interactive separation of perchlorate (ClO4−) by polyethyleneimine (PEI) and poly (styrene sulfonate) (PSS) deposited on a microfiltration membrane and on sand surfaces. The variation of the interaction with respect to deposition and feed variables was assessed. The 9 bilayered ((PEI/PSS) 0.15M NaCl, pH 6)) membranes showed a ClO4− rejection of ~80%. An increase in the feed concentration to 25mgL−1 reduced the rejection to 58%. With a feed pH from 4 to 10, the rejection varied between almost 100% and 16%. The presence of ions reduced the rejection percentage of ClO4− with the interference by the ions in the order of SO42−>HCO3−>NO3−>Cl−. The interference is attributed to the characteristics of the competing ions and the nature of the multilayers. A positive impact of post-treatment (98%) and capping layers on rejection percentage (80% to nearly complete) for synthetic and ClO4− contaminated field water samples is clearly established. The presence of competing ions is also accounted for by a capped membrane system. The selectivity of the competing ions increases with capping layers of 1M NaCl in the order of HCO3−>NO3−>SO42−. In the field water samples up to a SO42− concentration of 3.0mgL−1, the capping layers with 0.4M NaCl result in a near complete rejection of ClO4−, whereas further enhancement requires a capping layer of 1M NaCl. A sand filtration system was developed by incorporating the pre-optimised polyelectrolyte multilayer on sand. Deposition of a single bilayered PEI/PSS multilayer on sand effectively (nearly completely) removes ClO4−.

Ultrastable Nanofiltration Membranes Engineered by Polydopamine-Assisted Polyelectrolyte Layer-by-Layer Assembly for Water Reclamation

“…Meanwhile, the LBL-based NF membrane performance could also be compromised in strong alkaline conditions due to the deprotonation of amine groups of the weak cationic polyelectrolytes . This was witnessed by the decline in ClO 4 – rejection of the (PEI/PSS) 9 membrane from above 80% to ∼16% after subjecting to pH 10 solution . In this study, the PEI molecules were covalently bonded with PDA via Michael addition and Schiff base reactions. , The covalent bonds and cross-linking between PDA and PEI restricted the movement of PEI chains to a certain extent and significantly improved the chemical stability of the membrane.…”

“…It has been reported that in the conventional LBL assembly system, the polyelectrolyte multilayers formed with weak cationic polyelectrolytes such as PAH and PEI might suffer from significant swelling in the strong acid conditions due to strong electrostatic repulsion between protonated amine groups, which influenced both the chemical and physical integrity of the multilayers . For example, after exposure to pH 4 solution for 30 min, the flux of the (PEI/PSS) 9 membrane (nine bilayers) increased by 31%, ascribing to the structural rearrangement of the polyelectrolyte multilayers . Meanwhile, the LBL-based NF membrane performance could also be compromised in strong alkaline conditions due to the deprotonation of amine groups of the weak cationic polyelectrolytes .…”

“…22 For example, after exposure to pH 4 solution for 30 min, the flux of the (PEI/PSS) 9 membrane (nine bilayers) increased by 31%, ascribing to the structural rearrangement of the polyelectrolyte multilayers. 56 Meanwhile, the LBL-based NF membrane performance could also be compromised in strong alkaline conditions due to the deprotonation of amine groups of the weak cationic polyelectrolytes. 4 This was witnessed by the decline in ClO 4…”

“…− rejection of the (PEI/PSS) 9 membrane from above 80% to ∼16% after subjecting to pH 10 solution. 56 In this study, the PEI molecules were covalently bonded with PDA via Michael addition and Schiff base reactions. 57,58 The covalent bonds and cross-linking between PDA and PEI restricted the movement of PEI chains to a certain extent and significantly improved the chemical stability of the membrane.…”

Detection of bromate in packaged drinking water and its removal using polyelectrolyte multilayer membranes

“…This is found to be an effective method to enhance the removal efficiency of low pressure–driven membranes. Suitability of polyelectrolyte multilayer membranes in ion removal was well studied in the past, and the efficiency of these membranes to remove ions at lower energy expense is commendable (Cheng et al., 2018; Disha et al., 2012; Liu et al., 2017; Sahin et al., 2020; Sanyal et al., 2015; Shalumon et al., 2019).…”