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In this review, the history of the graphene and their excellent structure and properties were briefly explained. The form of graphene in different allotropes and derivatives were also discussed as each type possessed different structures and properties, that were important in specific applications depending the quality of the produced graphene. On top of that, the main sustainability issues arise in the different synthesis methods for fabrication of graphene and graphene-based materials were discussed and reviewed. This review also focused in finding the cost-efficient, environmental-friendly, energy efficient, and low carbon footprint graphene precursors as an insight for potential development of sustainable graphene materials. Rice husk as an abundant and cheap lignocellulosic biomass wastes with high content of cellulose is a great candidate for sustainable graphene precursor. The excellent morphological structure, physicochemical, thermal, mechanical, and electrical properties of rice husks-derived graphene for utilization in wide-range of applications were discussed. This review also concluded on the future insights and perspectives of the rice husk-derived graphene.

There have been tremendous advances in membrane distillation (MD) since the concept was introduced in 1961: new membrane designs and process configurations have emerged, and its commercial viability has been evaluated in several pilot-scale studies. However, its high energy consumption has hindered its commercialization. One of the most promising ways to overcome this obstacle is to develop more energy-efficient membrane modules. The MD research community has therefore developed diverse new module configurations for hollow fiber and flat sheet membranes that increase the thermal energy efficiency of MD by minimizing thermal polarization, increasing mass transfer across the membrane, and improving heat recovery from the condensed vapor. This review summarizes the progress that has been made in the design of hollow fiber and flat sheet membrane modules for MD applications. It begins with a brief introduction to MD and its configurations before describing developments in module fabrication and highlighting key areas where further research is needed.

The solvent is a vital element in the production of membranes, playing a critical role in determining their structure, properties, and performance. In the process of manufacturing membranes, a substantial quantity of conventional organic solvents is typically employed. Traditional solvents, such as dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and tetrahydrofuran possess potential hazards. They can be highly flammable, irritating, and even pose reproductive toxicity risks. Furthermore, aside from their high toxicity, the energy consumption required to remove or recycle these solvents from water is significant. While conventional petroleum-derived solvents have conventionally been employed in membrane fabrication, there is growing attention toward greener alternatives with lower toxicity. This shift is motivated by the desire to reduce the adverse effects on human health and the environment associated with their use. As the world moves toward a more bio-based manufacturing approach, the global potential for new bio-derived solvents with reduced hazards is expected to increase.

Polymeric membranes are widely recognized for their high efficiency and minimal environmental impact in advanced separation technologies. However, membrane production processes' sustainability and environmental friendliness still pose significant challenges. During the membrane manufacturing process, the use of nonbiodegradable petroleum-based polymers and hazardous solvents is prevalent. These materials not only contribute to the energy crisis but also create disposal challenges at the end of their lifespan, posing risks to both workers and the environment. To address these concerns, it is imperative to replace traditional materials with biobased polymers and green solvents in membrane preparation. Additionally, the wastewater generated during membrane fabrication contains significant amounts of organic solvents, necessitating effective treatment or recycling prior to discharge. Furthermore, instead of end-of-life membrane being discarded in landfills, a large quantity of spent membrane elements should be repurposed and recovered. This chapter provides valuable insight aimed at improving the sustainability of membrane technology, specifically highlighting progress made in the aforementioned areas. By analyzing the requirements for transforming the membrane industry, the chapter underscores the importance of embracing circular economy principles.

Solvent toxicity is a major barrier to sustainable fabrication of polymeric membranes. This study introduces three dibasic esters (DBEs) as alternative membrane fabrication solvents that are biodegradable, non-carcinogenic, non-corrosive, and non-hazardous. The use of DBEs in fabrication processes shifts the monotectic point in the phase diagram of PVDF/solvent systems towards higher polymer concentrations, enabling membrane formation by liquid–liquid phase inversion to produce a bicontinuous structure that confers outstanding performance. The best-performing membrane prepared in this way had an exceptional flux of 42.40 kg m⁻² h⁻¹ and a high rejection rate (>99%) in the decontamination of synthetic nuclear wastewater. Compared to membranes prepared previously using toxic and non-toxic solvents, membranes fabricated in DBEs exhibited superior mechanical performance due to their bicontinuous structure, which effectively distributes external forces throughout the membrane. Moreover, DBEs are cheaper than toxic conventional solvents and are readily available in bulk, making them attractive options for industrial-scale membrane production.

Thermally-induced phase separation (TIPS) is one of the most popular methods considered for membrane preparation. Since its introduction by Castro in 1981, there has been significant progress in understanding, controlling, and implementing TIPS. This review provides a critical and integrative evaluation of the literature in this area that effectively defines the current state-of-the-art. It begins with an overview of the basic principles of TIPS and the used materials (polymers, diluents and additives) paying particular attention to the sustainability of the TIPS process. The subsequent sections examine the parameters affecting the outcome of TIPS technique, the role of mass transfer, and methods for modeling TIPS. This is followed by a discussion of current and potential applications of TIPS membranes. Finally, the review concludes with a discussion of likely future developments and prospects for the TIPS process.

Technologies based on polymeric membranes have diverse applications in purification, desalination, and decontamination processes. However, current membrane production techniques are neither sustainable nor environmentally benign. A Life-Cycle Assessment (LCA) was conducted to determine how the choice of membrane polymer (fossil-based or bio-based), the solvent (toxic or green), and the energy source used in membrane fabrication affect their environmental impacts. The results showed that solvent toxicity is the main obstacle to sustainable membrane production. The harmful environmental effects of current membrane production processes are largely due to the use of toxic solvents, particularly polar aprotic solvents such as N-methyl pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). It was also found that replacing these solvents with the green solvent, ethylene carbonate (EC), would reduce the environmental impact of membrane production by up to 35%. Developing sustainable membrane fabrication techniques using green solvents could thus be highly beneficial.

In this thesis, three different pathways were proposed to address sustainability issues in membrane production identified in the LCA study. First, it prompted an investigation into the viability of utilizing three environmentally friendly cyclic carbonate solvents: EC; propylene carbonate (PC); and butylene carbonate (BC) for the production of polyvinylidene fluoride (PVDF) membranes. These solvents are biobased, biodegradable, inexpensive, and readily available on large scales. The study aimed to examine the influence of solvent structure on membrane morphology, polymorphism, and separation performance. It provided valuable insights into the mechanisms governing the formation of pure β-phase PVDF membranes.

Non-ionic deep eutectic solvents (NIDES) are a sub-class of ionic liquids that can be synthesized inexpensively using simple heating processes with no pre- or post-treatment. As such, they could be attractive alternative solvents for membrane fabrication. Three NIDES were synthesized and used to dissolve PVDF: N-methylacetamide-acetamide (DES-1); N-methyl acetamide-N-methyl urea (DES-2); and N-methyl acetamide-N,N’-dimethyl urea (DES-3). The favorable performance of the obtained membranes together with the low cost, low toxicity, and simple large-scale synthesis of NIDES makes this an attractive approach for membrane production. 

Finally, three Dibasic Esters (DBEs) namely dimethyl succinate (DMS), dimethyl glutarate (DMG) and dimethyl adipate (DMA) were introduced as alternative green solvents for PVDF membrane production. DBEs have several desirable properties including biodegradability, non-carcinogenicity, non-corrosiveness, and non-hazardousness. Furthermore, these DBEs are not only more economical compared to hazardous solvents but are also easily accessible in significant quantities, thus increasing their suitability for large-scale industrial membrane manufacturing. Hence, we conducted an assessment of the morphology, properties, and performance of DBEs as a potential solvent alternative for membrane production. 

To conclude, this thesis provides an improved and advanced understanding of sustainable approaches in polymeric membrane production. By investigating different aspects such as solvent choices and introducing alternative solvents, the research contributes valuable insights to the field and promotes the development of more environmentally friendly and sustainable environment membrane manufacturing processes.

Electroactive membranes are attracting attention due to their piezo-, pyro-, and ferro-electric properties. Here we report the fabrication of electroactive membranes from poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), i.e. co-polymers of vinylidene fluoride and trifluoroethylene. A new P(VDF-TrFE)/Polyvinylpyrrolidone (PVP)/Dimethylacetamide (DMAc)/water system was used to tailor the membranes’ structure. Since hot treatment in the air could induce defect on membrane structure (i.e., fracture, shrinkage, and rolling), the annealing was conducted in the glycerin. Thanks to the high boiling point and moderate surface tension of glycerin, the integrity of P(VDF-TrFE) membranes was preserved during the annealing process. X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy experiments revealed that the relative abundance of the β–crystalline phase increased with the annealing temperature when the latter was above the Curie temperature. P(VDF-TrFE) membranes annealed at 130 °C exhibited high crystallinity with grain-like surface, which resulted from multiple stacks of edge-on lamellae, and possessed excellent physicochemical properties of filtration. The anti-fouling performance of pristine and annealed P(VDF-TrFE) membranes was tested by dead-end filtration with a 13.5 mg/L humic acid (HA) solution. Annealed P(VDF-TrFE) membranes achieved greater fluxes and had superior anti-fouling properties, which was attributed to the weaker hydrophobic attraction between HA and the aligned β–phase crystals. This work provides a facile method for designing highly crystalline P(VDF-TrFE) membranes with potential applications in filtration systems, smart wearable devices, and medicine.

Deep eutectic solvents (DES) have recently emerged as a new class of inexpensive biodegradable solvents and additives with diverse applications. In this study, a new family of non-ionic deep eutectic solvents (NIDES) is proposed for the first time for membrane preparation. Three types of NIDES, N-methylacetamide-acetamide (DES-1), N-methyl acetamide-N-methyl urea (DES-2), and N-methyl acetamide-N,N′-dimethyl urea (DES-3) were synthesized and used to dissolve polyvinylidene fluoride (PVDF) polymer. The effects of the additive polyvinylpyrrolidone (PVP) and the type of NIDES on the PVDF membrane characteristics, water permeability and bovine serum albumin (BSA) separation were studied. The membranes prepared with DES-1 and 2 wt% PVP exhibited a good water permeate flux (96.82 L/m2.h) and a high BSA separation factor (96.32%). High performance PVDF membranes can thus be efficiently prepared using biodegradable inexpensive NIDES.

Polyvinylidene fluoride (PVDF) membranes were prepared by phase inversion in the most commonly used solvents for membrane manufacture, with CO2 as a non-solvent additive. The effects of changing the polymer concentration (10, 12.5 and 15% by weight), the type of solvent (NMP, DMAc and DMF) and the coagulation bath with three levels of CO2 concentration on the phase inversion process, as well as the phase diagram, morphology and transport properties of the membranes were studied. The best performing membranes were used to desalinate salt aqueous solutions and decontaminated simulated nuclear wastewater by membrane distillation using two configurations (DCMD and AGMD). All selected membranes showed high rejection with acceptable permeate fluxes reaching an infinite decontamination factor. The proposed approach of this novel idea of using CO2 dissolved in water as a coagulation medium in the field of membranes avoids the increase of the harmful effect on the environment caused by the addition of a harsh non-solvent to the coagulation bath. It constitutes a beneficial use of carbon dioxide that reduces the negative environmental impact of membrane manufacturing and represents a decisive step towards its sustainability. Furthermore, this study highlights the potential benefits of using these membranes in DM for desalination and treatment of simulated nuclear wastewater.