Separation Techniques and Circular Economy

Topic Information

Dear Colleagues,

Efficient separation techniques play an important role in the process of resource recovery, such as physical, chemical, physico-chemical, and/or biological methods, which are selected due to being low-cost, low-energy, and free of secondary pollution. Additionally, the highest possible value added of the separated products is obtained to enhance the economy. For example, to address concerns regarding the contamination of water resources, various separation techniques, such as membrane separation, adsorption, ion exchange, solvent extraction, magnetic separation, filtration, flocculation, sedimentation, and centrifugal separation with physico-chemical processes, have been developed for wastewater treatment to effectively recycle various substances such as phosphates, humic substances, biological plastics, cellulose, polysaccharides, proteins, lipids, extracellular polymer substances, organics, and precious metals. Furthermore, parallel developments in biorefinery technologies further enable the transformation of biomass into renewable chemicals and biofuels, reducing the dependence on petrochemical feedstocks. This Topic, entitled “Separation Techniques and Circular Economy”, aims to address novel separation technologies involving resource recovery in various fields. It seeks to include, but is not limited to, recent progress in separation technologies, both at the industrial and scientific levels, as well as studies relating to value-added products and economic assessments.

We look forward to receiving your contributions.

Yours faithfully,

Dr. Da-Qi Cao
Prof. Dr. Qunhui Wang
Dr. Yuanyuan Ren
Dr. Yangmo Zhu
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Fermentation fermentation	3.3	5.7	2015	19.5 Days	CHF 2100	Submit
Membranes membranes	3.6	7.9	2011	15.3 Days	CHF 2200	Submit
Recycling recycling	4.6	8.9	2016	18.9 Days	CHF 1800	Submit
Sustainability sustainability	3.3	7.7	2009	17.9 Days	CHF 2400	Submit
Separations separations	2.7	4.5	2014	16 Days	CHF 2600	Submit
ChemEngineering ChemEngineering	3.4	4.9	2017	32.8 Days	CHF 1800	Submit

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Published Papers (4 papers)

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All Fermentation Membranes Recycling Sustainability Separations ChemEngineering

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Supplementary material:
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20 pages, 1277 KB  

Open AccessArticle

Ammonia Recovery from Animal Manure via Hollow Fibre Membrane Contactors: Impact of Filtration Pre-Treatment and Organic Foulants on Mass Transfer and Performance

by Niloufar Azizi, Shaun Connolly, Dominika Krol and Eoin Syron

Membranes 2026, 16(1), 15; https://doi.org/10.3390/membranes16010015 - 31 Dec 2025

Viewed by 329

Abstract

Ammonia (NH₃) recovery from animal manure offers both environmental and economic benefits by reducing nitrogen emissions and producing valuable fertilisers. Hollow fibre membrane contactors (HFMCs) are a promising technology for this purpose, yet their performance is strongly influenced by the complex [...] Read more.

Ammonia (NH₃) recovery from animal manure offers both environmental and economic benefits by reducing nitrogen emissions and producing valuable fertilisers. Hollow fibre membrane contactors (HFMCs) are a promising technology for this purpose, yet their performance is strongly influenced by the complex composition of manure. In this study, the effects of solids concentration and organic foulants concentration on the mass transfer coefficients governing NH₃ recovery were systematically investigated. Total suspended solids (TSS) were reduced through graded filtration, and protein concentrations in the ammonium solutions were quantified to assess their role in limiting mass transfer. Results showed that TSS concentration primarily affected the shell-side film resistance. After extensive filtration, residual proteins attached to the membrane surface induced partial wetting, thereby reducing the effective membrane mass transfer coefficient. Using a penalty function approach, it was possible to separately describe TSS- and protein-related resistances, enabling improved prediction of effective model coefficients under real world conditions. These findings highlight the dual importance of solid–liquid separation and protein management in optimising HFMC operation for NH₃ recovery and provide a framework for up-scaling the technology in agricultural nutrient management systems. Full article

(This article belongs to the Topic Separation Techniques and Circular Economy)

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31 pages, 4884 KB  

Open AccessReview

A Paradigm Shift in End-of-Life Membrane Recycling: From Conventional to Emerging Techniques

by Noman Khalid Khanzada, Yazan Ibrahim, Muzamil Khatri, Mohamed Khayet and Nidal Hilal

Membranes 2025, 15(12), 350; https://doi.org/10.3390/membranes15120350 - 23 Nov 2025

Cited by 1 | Viewed by 1232

Abstract

The conventional linear life cycle of membrane materials, spanning fabrication, use, and disposal through landfilling or incineration poses serious sustainability challenges. The environmental burden associated with both the production of new membranes and the disposal of end-of-life (EoL) modules is considerable, further intensified [...] Read more.

The conventional linear life cycle of membrane materials, spanning fabrication, use, and disposal through landfilling or incineration poses serious sustainability challenges. The environmental burden associated with both the production of new membranes and the disposal of end-of-life (EoL) modules is considerable, further intensified by the reliance on fossil fuel-derived polymers, toxic solvents, and resource-intensive manufacturing processes. These challenges underscore the urgent need to integrate sustainability principles across the entire membrane life cycle, from raw material selection to reuse and regeneration. Emerging approaches such as membrane regeneration using recyclable polymers based on covalent adaptable networks (CANs) have introduced a new paradigm of closed-loop design, enabling complete depolymerization and reformation. In parallel, more conventional strategies, including the valorization of recycled plastic waste and the upcycling or downcycling of EoL membranes, offer practical routes toward a circular membrane economy. In this review, we consolidate current advances in membrane recycling, critically evaluate their practical constraints, and delineate the technical and environmental challenges that must be addressed for broader implementation. The insights presented here aim to guide the development of next-generation circular membrane technologies that harmonize sustainability with performance. Full article

(This article belongs to the Topic Separation Techniques and Circular Economy)

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21 pages, 8458 KB  

Open AccessArticle

Chemo-Ultrasonication Rehabilitation of Thin-Film Composite Ultrapure Water Membrane for Spent Dialysate Recovery

by Nuhu Dalhat Mu’azu, Mukarram Zubair, Mohammad Saood Manzar, Aesha H. Alamri, Ishraq H. Alhamed, Asaad Al Alawi and Muhammad Nawaz

Membranes 2025, 15(11), 340; https://doi.org/10.3390/membranes15110340 - 14 Nov 2025

Viewed by 725

Abstract

The ever-increasing number of discarded end-of-life dialysate polyamide thin-film composite membranes (DEoLMs) from presents both environmental and economic challenges for health centers. Traditional thermo-chemical cleaning techniques have been deployed for the rehabilitation of DEoLMs. This study further investigated the application of chemo-ultrasonication rehabilitation [...] Read more.

The ever-increasing number of discarded end-of-life dialysate polyamide thin-film composite membranes (DEoLMs) from presents both environmental and economic challenges for health centers. Traditional thermo-chemical cleaning techniques have been deployed for the rehabilitation of DEoLMs. This study further investigated the application of chemo-ultrasonication rehabilitation of dialysate-production-related DEoLM for potential reuse in spent dialysate recovery considering salt and creatinine—a typical uremic toxin-removal from water. The DEoLM was rehabilitated using low-concentration citric acid (CA) and sodium lauryl sulfate (SLS) under ultrasonic waves (45 kHz, 30 min agitation). Considering different rehabilitation protocols, the synergistic effects of heating (HT) and the chemical agents, with and without and ultrasonic waves (SC) were evaluated through FTIR, SEM, and EDX analyses, and the performance of the rehabilitated DEoLM was assessed via water flux and permeance, and efficiencies for conductivity and creatinine rejection. The fully integrated protocol chemo-ultrasonication (HT + SC + chemical agents) yielded the highest performance, achieving 93.56% conductivity and 96.83% creatinine removal, with water flux of 113.48 L m⁻² h⁻¹ and permeances of 6.31 L m⁻² h⁻¹ bar⁻¹, at markedly reduced pressures. The chemo-sonic-rehabilitated-DEoLM removed the organic–inorganic foulants beyond thermo-chemical cleaning. This suggests that the sonication waves had a great impact regarding rejuvenating the fouled DEoL dialysate membrane, offering a sustainable, cost-effective pathway for extending membrane life, and supporting sustainable water management to achieve circular economy goals within healthcare centers. Full article

(This article belongs to the Topic Separation Techniques and Circular Economy)

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33 pages, 1525 KB  

Open AccessArticle

Mineral Extraction from Mixed Brine Solutions

by M. A. Salman, M. Ahmed, H. Al-Sairfi and Y. Al-Foudari

Separations 2025, 12(10), 266; https://doi.org/10.3390/separations12100266 - 1 Oct 2025

Cited by 2 | Viewed by 958

Abstract

Sulfate minerals (SMs), such as BaSO₄, SrSO₄, and CaSO₄, precipitate when incompatible solutions from the oil industry, such as seawater (SW) and high-salinity brine solutions (HSBSs), are mixed during the oil production process. To investigate the potentiality [...] Read more.

Sulfate minerals (SMs), such as BaSO₄, SrSO₄, and CaSO₄, precipitate when incompatible solutions from the oil industry, such as seawater (SW) and high-salinity brine solutions (HSBSs), are mixed during the oil production process. To investigate the potentiality to extract SM by mixing three different brine solutions, such as HSBS-1, -2, and -3, with SW, at different temperatures and pressures, a practical simple model was used to predict the saturation index (SI), the quantity of precipitated minerals (Y), and the induction time (t_ind) required for precipitation. From the results, it was found that CaSO₄ hemihydrate and SrSO₄ yield lower amounts of precipitate. BaSO₄ precipitation ranges from 20 to 60 mg/L and 1500 mg/L of CaSO₄ anhydrous under ambient conditions. These findings suggest that recovering low-solubility minerals is technically feasible and environmentally preferable to direct disposal. Full article

(This article belongs to the Topic Separation Techniques and Circular Economy)

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