Developing polyetherimide/graphitic carbon nitride floating photocatalyst with good photodegradation performance of methyl orange under light irradiation

Floating photocatalysts as promising materials for environmental detoxification and energy production: A review

The oxygenation process of the catalyst surface, the incident-light harvesting capability, and facile recycling of utilized photocatalysts play key role in the outstanding photocatalytic performances. The typical existing photocatalysts in powder form have many drawbacks, such as difficult separation from the treated water, insufficient surface oxygenation, poor active surface area, low incident-light harvesting ability, and secondary pollution of the environment. A great number of scientific works introduced novel and fresh ideas related to designing floating photocatalytic systems by immobilizing highly active photocatalysts onto a floatable substrate. Thanks to direct contact with the illuminated light and oxygen molecules in the interface of water/air, the photocatalytic performance is maximized through production of more reactive species, employed in the photocatalytic reactions. Furthermore, facile recovering of the utilized photocatalysts for next processes avoids secondary pollution as well as diminishes the process's price. This review highlights the performance of developed floating photocatalysts for diverse applications. Furthermore, different floating substrates and possible mechanisms in floating photocatalysts are briefly mentioned. In addition, several emerging self-floating photocatalytic systems are taken attention and discussed. Specially, coupling photo-thermal and photocatalytic effects seems to be a good strategy for introducing a new class of floating photocatalyst to utilize the free, abundant, and green sunlight energy for the aims of water desalination and purification. Despite of a large number of attempts about the floating photocatalysts, there are still plenty of rooms for more in-depth research to be carried out for attaining the required characteristics of the large scale utilizations of these materials.

Precursor dependent - Visible light-driven g-C3N4 coated polyurethane foam for photocatalytic applications

Photocatalysis has emerged as a highly effective method for eliminating organic pollutants from wastewater. The immobilization of photocatalysts on a suitable solid surface is highly desired to achieve enhanced photocatalytic activity. In this work, graphitic carbon nitride (g-C3N4) is synthesized with three different precursors (melamine, thiourea, and urea) via a simple thermal exfoliation method and successfully immobilized on a polyurethane (PU) foam using the facile dip coating method. The photocatalytic activity of g-C3N4 bulk and g-C3N4 nanosheets-coated PU foams are compared using methyl orange dye and tetracycline hydrochloride as a test pollutant under visible light irradiation. Our results show that the type of precursors and surface area of the sample have a significant role in photocatalytic dye degradation. The urea-based g-C3N4 - PU foam shows better photocatalytic activity than the melamine or thiourea based g-C3N4 - PU foam. The scavenger test unveils that superoxide radical (O2●-) and holes (h+) are the main reactive oxidative species responsible for MO dye and TcH degradations. The cycling experiments are also carried out to confirm the reusability of the g-C3N4 floating catalyst for practical applications. Furthermore, a possible reaction mechanism has also been proposed.

Research status and prospects of organic photocatalysts in algal inhibition and sterilization: a review

An increasing amount of sewage has been discharged into water bodies in the progression of industrialization and urbanization, causing serious water pollution. Meanwhile, the increase of nutrients in the water induces water eutrophication and rapid growth of algae. Photocatalysis is a common technique for algal inhibition and sterilization. To improve the utilization of visible light and the conversion efficiency of solar energy, more organic photocatalytic materials have been gradually developed. In addition to ultraviolet light, partial infrared light and visible light could also be used by organic photocatalysts compared with inorganic photocatalysts. Simultaneously, organic photocatalysts also exhibit favorable stability. Most organic photocatalysts can maintain a high degradation rate for algae and bacteria after several cycles. There are various organic semiconductors, mainly including small organic molecules, such as perylene diimide (PDI), porphyrin (TCPP), and new carbon materials (fullerene (C60), graphene (GO), and carbon nanotubes (CNT)), and large organic polymers, such as graphite phase carbon nitride (g-C3N4), polypyrrole (PPy), polythiophene (PTH), polyaniline (PANI), and polyimide (PI). In this review, the classification and synthesis methods of organic photocatalytic materials were elucidated. It was demonstrated that the full visible spectral response (400-750 nm) could be stimulated by modifying organic photocatalysts. Moreover, some problems were summarized based on the research status related to algae and bacteria, and corresponding suggestions were also provided for the development of organic photocatalytic materials.

Recent advances in g-C3N4-based photocatalysis for water treatment: Magnetic and floating photocatalysts, and applications of machine-learning techniques

Over the past decade, there has been a substantial increase in research investigating the potential of graphitic carbon nitride (g-C3N4) for various environmental remediations. Renowned for its photocatalytic activity under visible light, g-C3N4 offers a promising solution for treating water pollutants. However, traditional g-C3N4-based photocatalysts have inherent drawbacks, creating a disparity between laboratory efficacy and real-world applications. A primary practical challenge is their fine-powdered form, which hinders separation and recycling processes. A promising approach to address these challenges involves integrating magnetic or floating materials into conventional photocatalysts, a strategy gaining traction within the g-C3N4-based photocatalyst arena. Another emerging solution to enhance practical applications entails merging experimental results with contemporary computational methods. This synergy seeks to optimize the synthesis of more efficient photocatalysts and pinpoint optimal conditions for pollutant removal. While numerous review articles discuss the laboratory-based photocatalytic applications of g-C3N4-based materials, there is a conspicuous absence of comprehensive coverage regarding state-of-the-art research on improved g-C3N4-based photocatalysts for practical applications. This review fills this void, spotlighting three pivotal domains: magnetic g-C3N4 photocatalysts, floating g-C3N4 photocatalysts, and the application of machine learning to g-C3N4 photocatalysis. Accompanied by a thorough analysis, this review also provides perspectives on future directions to enhance the efficacy of g-C3N4-based photocatalysts in water purification.

Developing self-floating N-defective graphitic carbon nitride photocatalyst for efficient photodegradation of Microcystin-LR under visible light

The frequent occurrence of algal blooms in water bodies leads to a significant accumulation of microcystin-LR (MC-LR). In this study, we developed a porous foam-like self-floating N-deficient g-C3N4 (SFGN) photocatalyst for efficient photocatalytic degradation of MC-LR. Both the characterization results and DFT calculations indicate that the surface defects and floating state of SFGN synergistically enhance light harvesting and photogenerated carrier migration rate. The photocatalytic process achieved a nearly 100 % removal rate of MC-LR within 90 min, while the self-floating state of SFGN maintained good mechanical strength. ESR and radical capture experiments revealed that the primary active species responsible for the photocatalytic process was OH. This finding confirmed that the fragmentation of MC-LR occurs as a result of OH attacking the MC-LR ring. LC-MS analysis indicated that majority of the MC-LR molecules were mineralized into small molecules, allowing us to infer possible degradation pathways. Furthermore, after four consecutive cycles, SFGN exhibited remarkable reusability and stability, highlighting the potential of floating photocatalysis as a promising technique for MC-LR degradation.

Developing boron carbon nitride/boron carbon nitride-citric acid quantum dot metal-free photocatalyst and evaluating the degradation performance difference of photo-induced species for tetracycline via theoretical and experimental study

For opening a way to synthesize novel metal-free catalysts and clarifying the photodegradation performance difference of photoactive species (such as ·O₂^-, h⁺), a series of metal-free photocatalysts have been synthesized by using different existing forms of the same materials (boron carbon nitride (BCN) and boron carbon nitride-citric acid quantum dot (BCQD)) as precursors via calcinating their mixture at 350 °C. BCQD has good fluorescence and up-conversion fluorescence performance. BCN/BCQD-350 has the highest removal efficiency (90%, including adsorption 60% and photodegradation 30%) for tetracycline (TC) among all samples under visible light irradiation. TC adsorption by BCN/BCQD-350 conforms to pseudo-second-order kinetic and Langmuir isotherm models. TC photodegradation by BCN/BCQD-350 conforms to type II heterojunction mechanism. Photoactive species capture experiments suggest that·O₂^- makes a higher contribution for TC photodegradation, followed by h⁺, ·OH, ¹O₂ and e^-. From LC-MS results, TC photodegradation is initiated by the dehydration step. TC dehydration activated by ·O₂^- has the lowest barrier (43.4 kcal/mol) than that (50.1 kcal/mol) activated by h⁺, that (64.8 kcal/mol) without the activation by photoactive species. TC removal rate of BCN/BCQD-350 (0.01563 min^-1) is higher than that of g-C₃N₄, P25 (TiO₂), BNPA, BCNPA, etc. Furthermore, BCN/BCQD-350 can also photodegrade TC under infrared light irradiation (λ > 800 nm).

Efficient photo-assisted Fenton-like reaction of yolk-shell CuSe(Cu2Se)/g-C3N4 heterojunctions for methylene blue degradation

Herein, a CuSe(Cu₂Se) yolk-shell structure (CC) was synthesized when room temperature was 25 degree Celsius using Cu₂O as a soft template, and the g-C₃N₄/CuSe(Cu₂Se) heterojunction (CC-G) was formed by coupling appropriate amounts of g-C₃N₄ in the selenization process to provide a novel, green, economical, and efficient photo-Fenton catalytic material. Photo-Fenton degradation experiments proved that in the presence of hydrogen peroxide (H₂O₂), a small amount of g-C₃N₄ hybridization on Cu-based Fenton catalysts significantly improved methylene blue (MB) degradation. The suitable amount of g-C₃N₄ hybridization was selected according to the degradation efficiency. The mass of g-C₃N₄ constituted 20% of the mass of the Cu₂O soft template. The composite material prepared using this combination (CC-G-20) exhibited the best MB degradation performance. The MB degradation efficiency in the CC-G-20/H₂O₂/visible light system was almost 98.3% after 60 min, which is higher than those of the parent materials (g-C₃N₄, 12.7%; CC, 58.6%) and had cyclic stability. The catalytic system can also stably degrade MB under dark conditions, where the MB degradation was almost 82% after 60 min. The heterojunction prevented excessive electrons and holes (e ^- and h⁺) recombination, stabilizing the reactive active substance of hydroxyl in the photo-Fenton-like catalytic system. Electron paramagnetic resonance and photoluminescence experiments confirmed this inference.

Simultaneous decolorization of anionic and cationic dyes by 3D metal-free easily separable visible light active photocatalyst

To overcome the hard and costly post-treatment separation of ultrathin graphitic carbon nitride nanosheets (UGCN), it was supported on polyurethane foam (PUF). The ratio of PUF/UGCN was optimized for the removal of a mixture of methylene blue (MB) and methyl orange (MO) dyes. The characteristics of the composite photocatalyst and its photocatalytic performance were detailly studied. The X-ray diffraction and Fourier transform infrared results proved the successful preparation of UGCN and PUF and that the PUF/UGCN composite combines the features of both pure materials. The transmission electron microscopy illustrated the ultrathin nanosheet shape of the UGCN, while the scanning electron microscope showed the highly porous 3D-hierarchical structure of PUF. Compared to the pure components, the composite photocatalyst with PUF/UGCN mass ratio of 4 achieved better decolorization of MO and almost same decolorization of MB as UGCN. Neutral pH and 1 g/L of the composite photocatalyst were the optimum conditions for MB/MO mixture decolorization. The composite photocatalyst kept its efficiency for five successive cycles. Hydroxyl radicals were the dominant in the degradation of MB, while superoxide radicals were the most influencer in MO degradation. Conclusively, supporting UGCN onto PUF kept the photocatalytic efficiency of UGCN toward MB decolorization and improved its efficiency toward MO. Moreover, it enabled the reuse of the composite photocatalyst and facilitated the post-treatment separation process.

Graphitic carbon nitride based immobilized and non-immobilized floating photocatalysts for environmental remediation

In solar photocatalysis, light utilization and recycling of powder from reaction solution are the main obstructions that hinder the photocatalytic efficacy of any photocatalyst. In this respect, a floatable system is effective for efficient solar photocatalysis by light utilization. Due to the maximum solar light absorption property, floating nanocomposite photocatalyst is an appealing substitute for effective wastewater treatment. Floating photocatalysts are a non-oxygenated and non-stirred solution that is a good light harvester, stable, non-toxic, biodegradable, naturally abundant in nature. They also have low density, a simple preparation process, no need to stir, and high porosity. Due to these characteristics, floating photocatalysts are widely favored and ideal candidates for practical environmental remediation. Several researchers have come up with new and innovative ways for immobilizing capable photocatalyst on a floatable substrate to produce floating nanocomposite photocatalytic material. In recent decades, g-C₃N₄-based floating photocatalysts have gained a lot of attention as g-C₃N₄ is a visible light active photocatalyst with unique and exceptional properties. It also has good photocatalytic activity in waste water treatment and environmental remediation. Many previous reports have studied the logical design and manufacturing method for heterojunction floating photocatalysts and immobilized floating photocatalysts. Based on those studies, we have focused on the g-C₃N₄ based immobilized and non-immobilized floating photocatalysts for pollutant degradation. We have also categorized immobilized floating photocatalyst based on several lightweight substrates such as expanded perlite and glass microbead. In addition, future challenges have been discussed to maximize solar light absorption and to improve the efficiency of broadband response floating photocatalysts. Floating photocatalysis is an advanced technique in energy conversion and environmental remediation thus requires special consideration.

Photocatalytic hydrogen evolution by degradation of organic pollutants over quantum dots doped nitrogen carbide

Semiconductor photocatalysts are of great importance for addressing current environmental and energy crises. In this study, we developed a simple exfoliation-sonication route to fabricate nitrogen carbide quantum dots (CNQDs) doped nitrogen carbide nanosheet (CNS) composite photocatalysts which were employed to produce hydrogen and degrade organic pollutants (methyl orange, acridine orange, aniline, and phenol) synchronously under visible light irradiation. The presence of acridine orange and aniline enhanced the hydrogen evolution efficiency from 8.8 mmol g^-1 h^-1 to 32.1 and 11.7 mmol g^-1 h^-1, respectively. On the contrary, methyl orange and phenol with the same concentration inhibited hydrogen evolution. Based on the proton chain and energy band analyses, the synchronous mechanism of photocatalytic hydrogen evolution and organic pollutant degradation on CNQDs/CNS was also proposed. On one side, the oxygen-containing functional groups on the surface of CNQDs and the surrounded water molecules constructed proton chains, increasing the combination probability between protons and photo-generated electrons. On the other side, the heterojunction of CNQDs/CNS induced the separation of photo-generated electron-hole pairs. The photo-generated electrons migrate to CNQDs, on which the protons were transformed into hydrogen molecules, while the holes migrated to CNS where the organic pollutants were oxidized synchronously.

TiO2–Based Nanofibrous Membranes for Environmental Protection

Electrospinning is a unique technique that can be used to synthesize polymer and metal oxide nanofibers. In materials science, a very active field is represented by research on electrospun nanofibers. Fibrous membranes present fascinating features, such as a large surface area to volume ratio, excellent mechanical behavior, and a large surface area, which have many applications. Numerous techniques are available for the nanofiber’s synthesis, but electrospinning is presented as a simple process that allows one to obtain porous membranes containing smooth non-woven nanofibers. Titanium dioxide (TiO2) is the most widely used catalyst in photocatalytic degradation processes, it has advantages such as good photocatalytic activity, excellent chemical stability, low cost and non-toxicity. Thus, titanium dioxide (TiO2) is used in the synthesis of nanofibrous membranes that benefit experimental research by easy recyclability, excellent photocatalytic activity, high specific surface areas, and exhibiting stable hierarchical nanostructures. This article presents the synthesis of fiber membranes through the processes of electrospinning, coaxial electrospinning, electrospinning and electrospraying or electrospinning and precipitation. In addition to the synthesis of membranes, the recent progress of researchers emphasizing the efficiency of nanofiber photocatalytic membranes in removing pollutants from wastewater is also presented.

Controllable One-Step Synthesis of Mixed-Phase TiO2 Nanocrystals with Equivalent Anatase/Rutile Ratio for Enhanced Photocatalytic Performance

In this study, the novel mixed-phase TiO2 nanocrystals (s-TiO2) with nearly equivalent anatase/rutile ratio were fabricated in the reagent of sec-butanol at the relatively low temperature of 80 °C by using a facile one-step condensing reflux method. The photocatalytic water splitting hydrogen production performance of s-TiO2 nanocrystals is close to that of commercial TiO2 (P25), and its photocatalytic degradation performance is about four times that of P25. The energy-level staggered interfaces and surface bridged hydroxyl groups significantly increased due to the anatase/rutile mixed-phase crystal structure and high specific surface area, which might generate the synergistic effect for the improvement of photocatalytic degradation.

UV-light promoted formation of boron nitride-fullerene composite and its photodegradation performance for antibiotics under visible light irradiation

A series of C₆₀/BN composites have been synthesized, which can efficiently photodegrade TC under visible-light irradiation. Compared with C₆₀/BN-D6 and C₆₀/BN-V6 synthesized under dark and visible-light irradiation, C₆₀/BN-U6 synthesized under UV-light irradiation has the largest adsorption and photodegradation performance for TC under visible-light irradiation. FTIR and XPS characterizations suggest that C₆₀/BN composite is most likely the charge transfer composite, in which C₆₀ acts as electron acceptor and BN acts as electron donor. UV-light has the best promotion effect for the formation of C₆₀/BN. The adsorption quantity of TC by C₆₀/BN-U6 is 2.77 times higher than that of BN (131.05 mg g^-1 vs. 47.27 mg g^-1), being due to that C₆₀/BN-U6 has higher surface area than BN (135.7 m² g^-1 vs. 18.8 m² g^-1). The photodegradation of C₆₀/BN-U6 for TC follows Z-scheme heterojunction mechanism, as well as the photo-induced ·O^2- and h⁺ are the dominant photoactive species. Quantitative structure-activity relationship (QSAR) method is applied to evaluate the toxicity of TC and its photodegradation intermediates. The photodegradation rate of C₆₀/BN-U6 for TC is 19.19 times, 10.06 times, 5.83 times, 2.73 times and 1.84 times higher than that of TiO₂ (P25), g-C₃N₄, BNPA, BCNPA, and BN/TiO₂, respectively, implying that C₆₀/BN-U is a good metal-free photocatalyst.

Photocatalytic degradation of microcystin-LR by modified TiO2 photocatalysis: A review

Microcystin-LR (MC-LR), the most toxic and commonly encountered cyanotoxin, is produced by harmful cyanobacterial blooms and potentially threatens human and ecosystems health. Titanium dioxide (TiO₂) photocatalysis is attracting growing attention and has been considered as an efficient, environmentally friendly and promising solution to eliminate MC-LR in the aquatic ecosystems. Over recent decades, scientific efforts have been directed towards the understanding of fundamentals, modification strategies, and application potentials of TiO₂ photocatalysis in degrading MC-LR. In this article, recent reports have been reviewed and progress has been summarized in the development of heterogeneous TiO₂-based photocatalysts for MC-LR photodegradation under visible, UV, or solar light. The proposed photocatalytic principles of TiO₂ and destruction of MC-LR have been thoroughly discussed. Specifically, some main modification methods for improving the drawbacks and performance of TiO₂ nanoparticle were highlighted, including element doping, semiconductor coupling, immobilization, floatability amelioration and magnetic separation. Moreover, the performance evaluation metrics quantum yield (QY) and figure of merit (FOM) were used to compare different photocatalysts in MC-LR degradation. The best performance was seen in N-TiO₂ with QY and FOM values of 2.20E-07 molecules/photon and 1.00E-11 mol·L/(g·J·h). N-TiO₂ or N-TiO₂-based materials may be excellent options for photocatalyst design in terms of MC-LR degradation. Finally, a summary of the remaining challenges and perspectives on new tendencies in this exciting frontier and still an emerging area of research were addressed accordingly. Overall, the present review will offer a deep insight for understanding the photodegradation of MC-LR with modified TiO₂ to further inspire researchers that work in associated fields.

Transparent floatable magnetic alginate sphere used as photocatalysts carrier for improving photocatalytic efficiency and recycling convenience

Practical application of powder photocatalysts is far from satisfying due to their low photon utilization, inconvenient recovery and potential environmental risk. In this study, an easily recoverable, environmentally friendly and highly transparent floatable magnetic photocatalyst carrier was prepared based on biopolymer alginate and Fe₃O₄ particles. Further, three different types of photocatalysts were chosen as model semiconductor photocatalysts and loaded on the shell of the carriers. The freeze process facilitated the formation of internal cavities that enhanced floating ability and transparency of the spheres. Meanwhile, the excellent floating performance offered massive reaction sites for pollutants reacting with photocatalysts, O₂ and photons on the air/water interface. Photodegradation results showed all three floatable hybrid photocatalysts exhibited enhanced photocatalytic efficiencies compared to the virgin photocatalysts. In short, the carrier can integrate excellent floating ability, environmental friendliness and full recycling with good stability, and it can greatly improve the photocatalytic efficiency of various powder semiconductor photocatalysts.

Fabrication and In Vitro Evaluation of 3D Printed Porous Polyetherimide Scaffolds for Bone Tissue Engineering

For bone tissue engineering, the porous scaffold should provide a biocompatible environment for cell adhesion, proliferation, and differentiation and match the mechanical properties of native bone tissue. In this work, we fabricated porous polyetherimide (PEI) scaffolds using a three-dimensional (3D) printing system, and the pore size was set as 800 μm. The morphology of 3D PEI scaffolds was characterized by the scanning electron microscope. To investigate the mechanical properties of the 3D PEI scaffold, the compressive mechanical test was performed via an electronic universal testing system. For the in vitro cell experiment, bone marrow stromal cells (BMSCs) were cultured on the surface of the 3D PEI scaffold and PEI slice, and cytotoxicity, cell adhesion, and cell proliferation were detected to verify their biocompatibility. Besides, the alkaline phosphatase staining and Alizarin Red staining were performed on the BMSCs of different samples to evaluate the osteogenic differentiation. Through these studies, we found that the 3D PEI scaffold showed an interconnected porous structure, which was consistent with the design. The elastic modulus of the 3D PEI scaffold (941.33 ± 65.26 MPa) falls in the range of modulus for the native cancellous bone. Moreover, the cell proliferation and morphology on the 3D PEI scaffold were better than those on the PEI slice, which revealed that the porous scaffold has good biocompatibility and that no toxic substances were produced during the progress of high-temperature 3D printing. The osteogenic differentiation level of the 3D PEI scaffold and PEI slice was equal and ordinary. All of these results suggest the 3D printed PEI scaffold would be a potential strategy for bone tissue engineering.

Porous oxygen-doped carbon nitride: supramolecular preassembly technology and photocatalytic degradation of organic pollutants under low-intensity light irradiation

In order to overcome photocatalytic technology application limitations in water due to weak light intensity, it is crucial to synthesize photocatalysts that respond to weak light. In this study, porous and oxygen-doped carbon nitride (CN-MC) was synthesized via supramolecular preassembly technology using melamine and cyanuric chloride. The carbon nitride catalyst produced via this technology has a relatively high surface area (63.2 m² g^-1), irregular pores, and oxygen doping characteristics, which enhance the light capture capacity, increase the number of reactive sites, and accelerate electron-hole separation efficiency. Thus, the CN-MC exhibited excellent photocatalytic activity during the degradation of organic pollutants Rhodamine B (RhB, 95% removal within 6 h) and tetracycline hydrochloride (TC-HCl, 70% removal within 6 h) under low-intensity light (the light intensity = 0.8~1.8 mW cm^-2 with a wavelength range of 300-700 nm). Mechanistic analysis showed that ·O₂^- and ·OH were the dominant active free radicals during RhB and TC-HCl photocatalytic degradation over CN-MC. The proposed synthesis strategy effectively improves the photocatalytic activity of graphite carbon nitride under weak light by producing a porous morphology and oxygen atom doping.

Photodegradation of fluazaindolizine in aqueous solution with graphitic carbon nitride nanosheets under simulated sunlight illumination

The photodegradation of fluazaindolizine (FZDL) under simulated sunlight irradiation was accelerated by the catalysis of graphitic carbon nitride (g-C₃N₄). Under optimum conditions, such as 5 mg of amount and dispersion, the photodegradation half-life was dramatically enhanced to 2.7 h. More importantly, the pathway of degradation by g-C₃N₄ was different from both direct photolysis and the catalysis by titanium oxide, with particular negative ions of m/z 221 and 195, corresponding to the cleavage of sulfamide bond and the ring opening of imidazole, respectively. In addition, hydroxyl and superoxide radicals played important roles in photodegradation. The results enriched not only the study of FZDL photodegradation but also the application of g-C₃N₄. It also suggested the possibility of the water purification by photodegradation for pesticide removal in real life.

Simultaneous decolorization and desalination of dye wastewater through electrochemical process

Salt-containing dye wastewater discharged from textile industries causes serious environmental problems. Simultaneous decolorization and desalination of dye wastewater in a laboratory scale electrochemical cell are realized for the first time with boron-doped diamond anode. With initial methyl orange (MO) and NaCl of 50 and 3000 mg L^-1, decolorization and desalination efficiencies of 70.2 and 88.7% were achieved after 6-h treatment with applied voltage of 6 V. Increasing applied voltages resulted in the improvements of both color and salt removal, while higher MO concentrations suppressed decolorization and higher NaCl concentration accelerated desalination rate. MO dissociated into anions transferred through the anion exchange membrane into the anode compartment and reacted with the active species as ·OH, H₂O₂, and ClO^- generated in anode compartment, leading to color removal. Component analysis confirmed the destruction of MO, with generation of low molecular weight compounds such as phenol and indole. Ions balance analysis indicated that Cl^- and Na⁺ moved to the anode and the cathode compartments respectively through the employed membranes driven by external voltage, realizing salt removal. This study has collectively demonstrated an efficient alternative for satisfactory treatment of salt-containing dye wastewater based on electrochemical technology.

Dredged-Sediment-Promoted Synthesis of Boron-Nitride-Based Floating Photocatalyst with Photodegradation of Neutral Red under Ultraviolet-Light Irradiation

A novel floating photocatalyst (BN-DS-7) has been successfully synthesized by calcining the mixture of boron nitride (BN) and dredged sediment (DS) with a specific mass ratio (3:7) at 1100 °C for a half hour. BN is synthesized for the first time using an oxygen-limited method, which consists of a nanoplate ∼30 nm in size and has a bandgap at 3.94 eV. The as-synthesized BN can degrade NR under ultraviolet (UV) light irradiation. For BN-DS-7, X-ray photoelectron spectroscopy analysis suggests that BN mainly interacts with DS through the strong coordination between these N atoms in BN and these Si and Al atoms in DS. This leads to BN-DS-7 having good compression strength (∼9 MPa). Thermogravimetric analysis for BN shows that a few BN (∼13%) synthesized via an oxygen-limited method will pyrolyze at 1100 °C and the released gas can be sealed in the inside of DS at 1100 °C, resulting in that BN-DS-7 can float on the water surface. Photodegradation results show that BN-DS-7 can degrade 84% of NR (20 mg/L) under UV-light irradiation for 5 h, and the active species are •OH and photoinduced hole. Total organic carbon analysis for NR solution before and after photodegradation show that ∼70% of NR has been mineralized into inorganic carbons. This work is helpful to develop a new type of BN-based floating material and enlarge the application field of DS.