Scalable fabrication of bimetal modified polyacrylonitrile (PAN) nanofibrous membranes for photocatalytic degradation of dyes

Recent Progress in Photocatalytic Applications of Electrospun Nanofibers: A Review

Electrospun fiber-based photocatalysts demonstrate significant potential in addressing global environmental and energy challenges, primarily due to their high specific surface areas and unique properties. This review examines recent advances in the application of these materials in photocatalytic processes, with a particular focus on water splitting and hydrogen production. The principles of the electrospun method are described in detail, along with the operating parameters, material characteristics, and environmental conditions that affect the fiber formation. Additionally, the review discusses the challenges, advantages, and future prospects of photocatalysts incorporating carbon materials, metals, semiconductors, and hybrid structures with improved performance. These materials have the potential to significantly improve the efficiency of hydrogen energy production, water purification, and CO2 recovery, highlighting their importance in engineering sciences.

Development of inorganic and mixed matrix membranes for application in toxic dyes-contaminated industrial effluents with in-situ treatments

Dyes are the most ubiquitous organic pollutants in industrial effluents. They are highly toxic to both plants and animals; thus, their removal is paramount to the sustainability of ecosystem. However, they have shown resistance to photolysis and various biological, physical, and chemical wastewater remediation processes. Membrane removal technology has been vital for the filtration/separation of the dyes. In comparison to polymeric membranes, inorganic and mixed matrix (MM) membranes have shown potentials to the removal of dyes. The inorganic and MM membranes are particularly effective due to their high porosity, enhanced stability, improved permeability, higher enhanced selectivity and good stability and resistance to harsh chemical and thermal conditions. They have shown prospects in filtration/separation, adsorption, and catalytic degradation of the dyes. This review highlighted the advantages of the inorganic and MM membranes for the various removal techniques for the treatments of the dyes. Methods for the membranes production have been reviewed. Their application for the filtration/separation and adsorption have been critically analyzed. Their application as support for advanced oxidation processes such as persulfate, photo-Fenton and photocatalytic degradations have been highlighted. The mechanisms underscoring the efficiency of the processes have been cited. Lastly, comments were given on the prospects and challenges of both inorganic and MM membranes towards removal of the dyes from industrial effluents.

Recent development of substrates for immobilization of bimetallic nanoparticles for wastewater treatment: a review

Bimetallic nanoparticles (BMNPs) have gained considerable attention due to their remarkable catalytic properties, making them invaluable in wastewater treatment applications. One of these challenges lies in the propensity of BMNPs to aggregate due to Van der Waals interactions, which can reduce their overall performance. Additionally, retrieving exhausted NPs from the treated solution for subsequent reuse remains a significant hurdle. Moreover, the leaching of NPs into the discharged wastewater can have harmful effects on humans as well as aquatic life. To overcome these issues, various substrates have been researched to maximize the efficiency and stability of the NPs. This review paper delves into the pivotal role of various substrates in immobilizing BMNPs, providing a comprehensive analysis of their performances, advantages, and drawbacks. The substrates encompass a diverse range of materials, including organic, inorganic, organic-inorganic, beads, fibers, and membranes. Each substrate type offers unique attributes, influencing the stability, efficiency, and recyclability of BMNPs. This review paper aims to provide an up-to-date and detailed analysis and comparison of the substrates used for the immobilization of BMNPs. This work further reviews the underlying mechanisms of the composites involved in treating pollutants from wastewater and how these mechanisms are enhanced by the synergistic effects produced by the substrate and BMNPs. Furthermore, the reusability and sustainability of these composites are discussed. Also, high-performing substrates are highlighted to give direction to future research focusing on the immobilization of BMNPs in the application of wastewater treatment.

A Review on Polyacrylonitrile as an Effective and Economic Constituent of Adsorbents for Wastewater Treatment

Water gets polluted due to the dumping of untreated industrial waste into bodies of water, particularly those containing heavy metals and dyes. Industrial water contains both inorganic and organic wastes. Numerous adsorbents that are inexpensive and easily available can be used to address the issue of water deterioration. This review report is focused on polyacrylonitrile as an efficient constituent of adsorbents to extract toxic ions and dyes. It discusses the various formulations of polyacrylonitrile, such as ion exchange resins, chelating resins, fibers, membranes, and hydrogels, synthesized through different polymerization methods, such as suspension polymerization, electrospinning, grafting, redox, and emulsion polymerization. Moreover, regeneration of adsorbent and heavy metal ions makes the adsorption process more cost-effective and efficient. The literature reporting successful regeneration of the adsorbent is included. The factors affecting the performance and outcomes of the adsorption process are also discussed.

High-strength and anti-bacterial BSA/carboxymethyl chitosan/silver nanoparticles/calcium alginate composite hydrogel membrane for efficient dye/salt separation

In order to solve the problems of poor mechanical property, non-antibacterial and low flux of calcium alginate (CaAlg) membrane, silver nanoparticles (AgNPs) were synthesized with bovine serum albumin (BSA) and carboxymethyl chitosan (CMCS) for improving CaAlg membrane in this paper. Meanwhile, the dispersion property of silver nanoparticles and the mechanical property, thermal stability, antibacterial property and filtration efficiency of the composite membrane were explored. The results illustrated CMCS observably strengthened the mechanical property and thermal stability of the composite membrane, and AgNPs endowed the composite membrane with excellent antibacterial property. The flux of the BSA/CMCS/AgNPs/CaAlg composite membrane was raised compared to CaAlg membrane. Finally, the viscose fiber/polyethylene terephthalate fiber (VF-PET) nonwoven fabric was introduced as the support layer to further improve the filtration flux and mechanical property of the composite membrane. VF-PET/BSA/CMCS/AgNPs/CaAlg membrane had a rejection rate of over 99.0 % for dye molecules and <9.0 % for salt ions, while the flux maintained 38.5 L·m^-2·h^-1. Furthermore, VF-PET/BSA/CMCS/AgNPs/CaAlg membrane also had excellent separation effect on actual dye wastewater. The separation of dye and salt by the membrane mainly depended on the screening mechanism of membrane pore size, rather than adsorption. The composite membrane had an outstanding performance on the separation of dye molecules and inorganic salt ions.

Fabrication of Rechargeable Photoactive Silk Fibroin/Polyvinyl Alcohol Blend Nanofibrous Membranes for Killing Bacteria

Antibacterial materials that prevent bacterial infections and mitigate bacterial virulence have attracted great scientific interest. In recent decades, bactericidal polymers have been presented as promising candidates to combat bacterial pathogens. However, the preparation of such materials has proven to be extremely challenging. Herein, photoactive silk fibroin/polyvinyl alcohol blended nanofibrous membranes grafted with 3,3',4,4'-benzophenone tetracarboxylic dianhydride (G-SF/PVA BNM) were fabricated by an electrospinning technique. The premise of this work is that the G-SF/PVA BNM can store photoactive activity under light irradiation and release reactive oxygen species for killing bacteria under dark conditions. The results showed that the resultant G-SF/PVA BNM exhibited the integrated properties of an ultrathin fiber diameter (298 nm), good mechanical properties, robust photoactive activity and photo-store capacity, and great photoinduced antibacterial activity against E. coli and S. aureus (99.999% bacterial reduction with 120 min). The successful construction of blended nanofibrous membranes gives a new possibility to the design of highly efficient antibacterial materials for public health protection.

High-performance photocatalytic membranes for water purification in relation to environmental and operational parameters

Growing technologies, increasing population and environmental pollution lead to severe contamination of water and require advanced water treatment technologies. These aspects lead to the need to purify water with advanced smart materials. This paper reviews the recent advances (during the last 5 years) in photocatalytic composite membranes used for water treatment. For this purpose, the authors have reviewed the main materials used in the development of (photocatalytic membranes) PMs, environmental and operational factors affecting the performance of photocatalytic membranes, and the latest developments and applications of PMs in water purifications. The composite photocatalytic membranes show good performance in the removal and degradation of pollutants from water.

Multi-Component Nanofiber Composite Membrane Enabled High PM0.3 Removal Efficiency and Oil/Water Separation Performance in Complex Environment

Currently, industrial waste gas and oily wastewater are usually at high temperature and contain corrosive components (e.g., acid, alkali, oxidant, or high salt, etc.), presenting great challenges on filtration/separation materials. Here, a multi-purpose Poly(m-phenylene isophthalamide)/polyacrylonitrile/silica (PMIA/PAN/SiO₂) nanofiber composite membrane with a high yield was prepared simply via electrospinning to satisfy the demands of air filtration and oil/water separation in complex environments. Under the synergy of PMIA, PAN and SiO₂, the composite membrane possesses high PM_0.3 removal capacity of 99.69%, robust purification ability against real smoke PM_2.5, effective oil/water separation performance of > 99.6%, superior high temperature stability (about 250 °C) and excellent chemical resistance, showing the potential application in filtration/separation process under complex conditions. Moreover, the influence mechanism of SiO₂ NPs on mechanical properties and filtration performance was systematically investigated through experiments and simulations, paving the way for future intensive research. This study provides an option for the facile and effective preparation of high-performance filtration/separation membranes applied in the field of dust filtration and oily wastewater separation, even in harsh environments.

Electrospun Ceramic Nanofibers for Photocatalysis

Ceramic fiber photocatalysts fabricated by electrospinning hold great potential in alleviating global environmental and energy issues. However, many challenges remain in improving their photocatalytic efficiencies, such as the limited carrier lifetime and solar energy utilization. To overcome these predicaments, various smart strategies have been invented and realized in ceramic fiber photocatalysts. This review firstly attempts to summarize the fundamental principles and bottlenecks of photocatalytic processes. Subsequently, the approaches of doping, surface plasmon resonance, and up-conversion fluorescent to enlarge the light absorption range realized by precursor composition design, electrospinning parameter control, and proper post heat-treatment process are systematically introduced. Furthermore, methods and achievements of prolonging the lifetime of photogenerated carriers in electrospun ceramic fiber photocatalysts by means of introducing heterostructure and defective composition are reviewed in this article. This review ends with a summary and some perspectives on the future directions of ceramic fiber photocatalysts.