Chitosan-Functionalized Recycled Polyethylene Terephthalate Nanofibrous Membrane for Sustainable On-Demand Oil-Water Separation

Recycling and high-value utilization of polyethylene terephthalate wastes: A review

Polyethelene terephthalate (PET) is a well-known thermoplastic, and recycling PET waste is important for the natural environment and human health. This study provides a comprehensive overview of the recycling and reuse of PET waste through energy recovery and physical, chemical, and biological recycling. This article summarizes the recycling methods and the high-value products derived from PET waste, specifically detailing the research progress on regenerated PET prepared by the mechanical recycling of fiber/yarn, fabric, and composite materials, and introduces the application of PET nanofibers recycled by physical dissolution and electrospinning in fields such as filtration, adsorption, electronics, and antibacterial materials. This article explains the energy recovery of PET through thermal decomposition and comprehensively discusses various chemical recycling methods, including the reaction mechanisms, catalysts, conversion efficiencies, and reaction products, with a brief introduction to PET biodegradation using hydrolytic enzymes provided. The analysis and comparison of various recycling methods indicated that the mechanical recycling method yielded PET products with a wide range of applications in composite materials. Electrospinning is a highly promising recycling strategy for fabricating recycled PET nanofibers. Compared to other methods, physical recycling has advantages such as low cost, low energy consumption, high value, simple processing, and environmental friendliness, making it the preferred choice for the recycling and high-value utilization of waste PET.

Recent progress and future directions of membranes green polymers for oily wastewater treatment

The preparation, modification and application of green polymers such as poly-lactic acid (PLA), chitosan (CS), and cellulose acetate (CA) for oily wastewater treatment is summed up in this review. Due to the low environmental pollution, good chemical resistivity, high hydrophobicity, and good capacity for water-oil emulsion separation of the presented polymers, it then highlights the various membrane production methods and their role in producing effective membranes, with a focus on recent advances in improving membrane properties through the addition of various Nano materials. As a result, the hydrophilic/hydrophobic properties that are critical in the oil separation mechanism are highlighted. Finally, it looks at the predictions and challenges in oil/water separation and recovery. These ideas are discussed with a focus on modern production methods and oil separation proficiency.

Special Superwetting Materials from Bioinspired to Intelligent Surface for On-Demand Oil/Water Separation: A Comprehensive Review

Since superwetting surfaces have emerged, on-demand oil/water separation materials serve as a new direction for meeting practical needs. This new separation mode uses a single porous material to allow oil-removing and water-removing to be achieved alternately. In this review, the fundamentals of wettability are systematically summarized in oil/water separation. Most importantly, the two states, bioinspired surface and intelligent surface, are summarized for on-demand oil/water separation. Specifically, bioinspired surfaces include micro/nanostructures, bioinspired chemistry, Janus-featured surfaces, and dual-superlyophobic surfaces that these superwetting materials can possess asymmetric wettability in one structure system or opposite underliquid wettability by prewetting. Furthermore, an intelligent surface can be adopted by various triggers such as pH, thermal and photo stimuli, etc., to control wettability for switchable oil/water separation reversibly, expressing a thought beyond nature to realize innovative oil/water separation by external stimuli. Remarkably, this review also discusses the advantages of all the materials mentioned above, expanding the separation scope from the on-demand oil/water mixtures to the multiphase immiscible liquid-liquid mixtures. Finally, the prospects of on-demand oil/water separation materials are also concluded.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Recycling and Reutilizing Polymer Waste via Electrospun Micro/Nanofibers: A Review

The accumulation of plastic waste resulting from the increasing demand for non-degradable plastics has led to a global environmental crisis. The severe environmental and economic drawbacks of inefficient, expensive, and impractical traditional waste disposal methods, such as landfills, incineration, plastic recycling, and energy production, limit the expansion of their applications to solving the plastic waste problem. Finding novel ways to manage the large amount of disposed plastic waste is urgent. Until now, one of the most valuable strategies for the handling of plastic waste has been to reutilize the waste as raw material for the preparation of functional and high-value products. Electrospun micro/nanofibers have drawn much attention in recent years due to their advantages of small diameter, large specific area, and excellent physicochemical features. Thus, electrospinning recycled plastic waste into micro/nanofibers creates diverse opportunities to deal with the environmental issue caused by the growing accumulation of plastic waste. This paper presents a review of recycling and reutilizing polymer waste via electrospinning. Firstly, the advantages of the electrospinning approach to recycling plastic waste are summarized. Then, the studies of electrospun recycled plastic waste are concluded. Finally, the challenges and future perspectives of electrospun recycled plastic waste are provided. In conclusion, this paper aims to provide a comprehensive overview of electrospun recycled plastic waste for researchers to develop further studies.

Polymeric Membranes for Oil-Water Separation: A Review

This review is devoted to the application of bulk synthetic polymers such as polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF) for the separation of oil-water emulsions. Due to the high hydrophobicity of the presented polymers and their tendency to be contaminated with water-oil emulsions, methods for the hydrophilization of membranes based on them were analyzed: the mixing of polymers, the introduction of inorganic additives, and surface modification. In addition, membranes based on natural hydrophilic materials (cellulose and its derivatives) are given as a comparison.

Reuse of Textile Waste to Production of the Fibrous Antibacterial Membrane with Filtration Potential

Wasted synthetic fabrics are a type of textile waste source; the reuse of them brings environmental protection and turns waste into a valuable material. In this work, the used nylon (polyamide) stockings were transmuted into a fine fibrous membrane via an electrospinning process. In addition, the safety antibacterial agent, monoacylglycerol (MAG), was incorporated into a recycled fibrous membrane. The results revealed that the neat, recycled polyamide (rPA) fibers with a hydrophobic surface could be converted into hydrophilic fibers by blending various amounts of MAG with rPA solution prior to electrospinning. The filtration efficiency and air/water vapor permeability of the two types of produced membranes, neat rPA, and rPA/MAG, were tested. Their filtration efficiency (E100) was more than 92% and 96%, respectively. The membranes were classified according to Standard EN1822, and therefore, the membranes rPA and rPA/MAG were assigned to the classes E10 and E11, respectively. The air permeability was not affected by the addition of MAG, and water vapor permeability was slightly enhanced. Based on the obtained data, prepared rPA/MAG fibrous membranes can be evaluated as antifouling against both tested bacterial strains and antimicrobial against S. aureus.

Biomass-based superhydrophobic coating with tunable colors and excellent robustness

Multicolored superhydrophobic coating with high durability has been receiving tremendous attention in decorative applications. Herein, a facile method to fabricate multicolored superhydrophobic coating with excellent robustness has been developed by using cellulose and chitosan. The multicolored coatings can be obtained through single dyeing or mixed dyeing based on three primary dyes. The coating can be applied on hard substrates (e.g. glass, aluminum sheet) and soft substrates (e.g. cotton fabric) by diverse methods including spraying, dip-coating and painting. The colorful coating firmly adheres to the substrates due to the multiple interactions (siloxane covalent bonds and hydrogen bonds). The colorful coating exhibits water-repellant behaviors and can withstand sandpaper abrasion, tape-peeling cycles, water impact, salt spray test and UV environments. Furthermore, the multicolored coating can be used as a new type of pigment for painting on different substrates and is expected to have a huge potential application in technological design or decoration.