Km Prottoy Shariar Piash , Paola Perez-Vega , Poulami Datta , Grace Neller , Ta Nhat Min Luong , Lian-Shin Lin , Oishi Sanyal
{"title":"Tuning polyelectrolyte topology and crosslinking parameters to facilitate same-sized monovalent nutrient ions separation","authors":"Km Prottoy Shariar Piash , Paola Perez-Vega , Poulami Datta , Grace Neller , Ta Nhat Min Luong , Lian-Shin Lin , Oishi Sanyal","doi":"10.1016/j.memsci.2025.124366","DOIUrl":null,"url":null,"abstract":"<div><div>This work focuses on developing a novel nanofiltration membrane platform for separating two same sized monovalent nutrient ions – NH<sub>4</sub><sup>+</sup> and K<sup>+</sup> under neutral pH condition. NH<sub>4</sub><sup>+</sup> and K<sup>+</sup> are two critical fertilizer raw materials and achieving selective separation between them would offer the flexibility to tune the nutrient (N:K) ratio, enabling a final product suitable for diverse fertilizer applications. Separation of NH<sub>4</sub><sup>+</sup> and K<sup>+</sup> is intrinsically challenging, since the hydrated radii of both NH<sub>4</sub><sup>+</sup> and K<sup>+</sup> are identical (0.33 nm) with slight difference in hydration energy (∼10 kJ/mol) between them. In this work, a series of polyelectrolyte modified membranes based on linear and branched polyelectrolytes and crosslinked using different crosslinking parameters (e.g. crosslinker type and concentration, duration of crosslinking etc.) were developed and tested. These membranes showed a broad range of NH<sub>4</sub><sup>+</sup>/K<sup>+</sup> separation performance in terms of NH<sub>4</sub><sup>+</sup> permeance and NH<sub>4</sub><sup>+</sup>/K<sup>+</sup> selectivity, depending on an ion desolvation based separation mechanism. A novel hybrid polyelectrolyte combination consisting of a 1:1 weight ratio of linear (poly allylamine hydrochloride, (PAH) and a branched polyethyleneimine (,PEI)) polycation was further investigated. This configuration, when combined with a polyanion (polyacrylic acid or, PAA) into a 5.5 bilayered uncrosslinked system showed the highest NH<sub>4</sub><sup>+</sup> passage (i.e. lowest NH<sub>4</sub><sup>+</sup> rejection ∼10 %) among all polyelectrolyte systems. The hybrid PAH:PEI configuration when simply deposited as a single layer (without PAA) on the NF 270 membrane and crosslinked with Glutaraldehyde (GA), showed the highest NH<sub>4</sub><sup>+</sup>/K<sup>+</sup> selectivity (>2.5) among all systems. A careful analysis of these various systems indicate that the topologies of the polyelectrolytes (e.g. linear <em>vs.</em> branched polycation and molecular weights) play a pivotal role in the overall NH<sub>4</sub><sup>+</sup>/K<sup>+</sup> separation performance, in conjunction with other important factors such as crosslinking density, polyelectrolyte molecular weight, etc. The best performing 1-layered crosslinked hybrid polyelectrolyte system was also tested with a quaternary ion mixture consisting of 4 similar-sized monovalent ions (Li<sup>+</sup>, Na<sup>+</sup>, NH<sub>4</sub><sup>+</sup> and K<sup>+</sup>). A desolvation based phenomenon, which is aided by the creation of confinement domains by branched polyelectrolytes and polyelectrolyte crosslinking, has been hypothesized to be the primary separation mechanism for the same-sized NH<sub>4</sub><sup>+</sup> and K<sup>+</sup> ions. This study therefore presents a fundamental framework for designing nanofiltration membranes through surface-modifications to achieve selective separation between same-sized and similar sized ions.</div></div>","PeriodicalId":368,"journal":{"name":"Journal of Membrane Science","volume":"733 ","pages":"Article 124366"},"PeriodicalIF":9.0000,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Membrane Science","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0376738825006799","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}
引用次数: 0
Abstract
This work focuses on developing a novel nanofiltration membrane platform for separating two same sized monovalent nutrient ions – NH4+ and K+ under neutral pH condition. NH4+ and K+ are two critical fertilizer raw materials and achieving selective separation between them would offer the flexibility to tune the nutrient (N:K) ratio, enabling a final product suitable for diverse fertilizer applications. Separation of NH4+ and K+ is intrinsically challenging, since the hydrated radii of both NH4+ and K+ are identical (0.33 nm) with slight difference in hydration energy (∼10 kJ/mol) between them. In this work, a series of polyelectrolyte modified membranes based on linear and branched polyelectrolytes and crosslinked using different crosslinking parameters (e.g. crosslinker type and concentration, duration of crosslinking etc.) were developed and tested. These membranes showed a broad range of NH4+/K+ separation performance in terms of NH4+ permeance and NH4+/K+ selectivity, depending on an ion desolvation based separation mechanism. A novel hybrid polyelectrolyte combination consisting of a 1:1 weight ratio of linear (poly allylamine hydrochloride, (PAH) and a branched polyethyleneimine (,PEI)) polycation was further investigated. This configuration, when combined with a polyanion (polyacrylic acid or, PAA) into a 5.5 bilayered uncrosslinked system showed the highest NH4+ passage (i.e. lowest NH4+ rejection ∼10 %) among all polyelectrolyte systems. The hybrid PAH:PEI configuration when simply deposited as a single layer (without PAA) on the NF 270 membrane and crosslinked with Glutaraldehyde (GA), showed the highest NH4+/K+ selectivity (>2.5) among all systems. A careful analysis of these various systems indicate that the topologies of the polyelectrolytes (e.g. linear vs. branched polycation and molecular weights) play a pivotal role in the overall NH4+/K+ separation performance, in conjunction with other important factors such as crosslinking density, polyelectrolyte molecular weight, etc. The best performing 1-layered crosslinked hybrid polyelectrolyte system was also tested with a quaternary ion mixture consisting of 4 similar-sized monovalent ions (Li+, Na+, NH4+ and K+). A desolvation based phenomenon, which is aided by the creation of confinement domains by branched polyelectrolytes and polyelectrolyte crosslinking, has been hypothesized to be the primary separation mechanism for the same-sized NH4+ and K+ ions. This study therefore presents a fundamental framework for designing nanofiltration membranes through surface-modifications to achieve selective separation between same-sized and similar sized ions.
期刊介绍:
The Journal of Membrane Science is a publication that focuses on membrane systems and is aimed at academic and industrial chemists, chemical engineers, materials scientists, and membranologists. It publishes original research and reviews on various aspects of membrane transport, membrane formation/structure, fouling, module/process design, and processes/applications. The journal primarily focuses on the structure, function, and performance of non-biological membranes but also includes papers that relate to biological membranes. The Journal of Membrane Science publishes Full Text Papers, State-of-the-Art Reviews, Letters to the Editor, and Perspectives.