Achieving remarkable piezo-photocatalytic activity in Sr2Bi4Ti5O18/BiOCl sandwich ferroelectric heterojunction with continuous semi-coherent interfaces via selective etching of Aurivillius perovskite solid

Constructing ferroelectric hetrojuction and utilizing its piezo-photocatalytic performances is a promising approach for environmental remediation and sustainable energy conversion. However, challenges such as electron-hole recombination and interfacial instability limit the performance of piezoelectric heterojunction photocatalysts. In this study, a novel sandwich-structured heterojunction with a lattice-matched interface constructed by Sr2Bi4Ti5O18 (SBTO) bismuth Aurivillius phase ferroelectric material and BiOCl (BOC) was developed via a selective etching strategy. This approach minimizes interfacial defects and stress, while ferroelectric polarization modulates charge distribution, enhancing redox activity. Finite element simulations and experimental results demonstrate that the SBTO/BOC heterojunction leverages intrinsic and interfacial electric fields to form dual electron transport pathways, significantly improving charge separation in both bulk and interface regions. The optimized SBTO/BOC heterojunction achieves a piezo-photocatalytic degradation rate of 0.285 min-1 for Rhodamine B, approximately twice that of Sr2Bi4Ti5O18 under piezo-photocatalysis (0.147 min-1) and 13 times higher than photocatalysis alone (0.022 min-1). The heterostructure also efficiently degrades dyes, antibiotics, and Cr(VI), offering a robust design for high-performance piezo-photocatalytic systems.

Removal of organic matter and ammonia nitrogen from contaminated water by combining hydrotalcites pretreatment and ultrafiltration

In this study, the combined process of hydrotalcite and ultrafiltration was investigated for the treatment of micro-polluted water samples. The study examined the impact of the combined process on the elimination of Total Organic Carbon (TOC) and ammonia nitrogen, varying the dosage of hydrotalcite, the duration of adsorption, and the volume of ultrafiltration backwash water. The experimental outcomes were subjected to analysis. Utilizing response surface methodology, the conditions for the removal of ammonia nitrogen were optimized through single-factor experiments. The results indicated that the interaction of the three factors had a significant impact on the removal of ammonia nitrogen, with the order of significance being: hydrotalcite dosage & adsorption time > adsorption time & backwash water volume > hydrotalcite dosage & backwash water volume. Upon administering an hydrotalcite dosage of 298.25 mg/L, maintaining an adsorption time of 50.49 minutes, and utilizing a backwash water volume of 153.42 L/h, the maximum removal rate of ammonia nitrogen achieved was 73.52%. Through the regeneration performance experiment, it is found that hydrotalcite has a good retention rate and can be reused. And under the prevailing conditions, the combined treatment process achieved the following pollutant removal rates: turbidity reduction of 97.60%, ammonia nitrogen removal of 71.25%, Cr (VI) elimination of 93.41%, and Mn (II) removal amounting to 33.33%. This study offers theoretical support for the future application of ultrafiltration membranes.

Performance of xMg3Al1-LDH@ZIF-8 in High Efficiency Electrocatalytic Reduction of CO2 to CO

This study involves the preparation of the precursor of magnesium aluminum layered double hydroxide (Mg3Al1-LDH) through a hydrothermal synthesis method. Subsequently, altering the loading amount of the precursor to synthesize a series of nanomaterials (xMg3Al1-LDH@ZIF-8, x = 0.2, 0.5, and 0.8) composite with zeolitic imidazolate framework-8 (ZIF-8). The investigation delves into the electrocatalytic performance of the material in the electrochemical reduction of CO2 (CO2RR) for the production of CO. The electrocatalyst is subjected to analysis through various techniques such as XRD, XPS, Raman, FTIR, SEM, EDS, TEM, BET, etc., to examine the elemental composition, microscopic morphology, and surface area with pore size. The electrochemical performance of the materials is tested and analyzed using an electrochemical workstation and gas chromatograph. The research findings reveal that the electrocatalyst with a loading amount of 0.5 g, denoted as 0.5Mg3Al1-LDH@ZIF-8, exhibits a well-defined rhombic dodecahedral morphology with a surface-attached layered structure. This structure, characterized by relatively strong interactions, provides abundant active sites for the reaction, consequently demonstrating superior electrochemical performance. The Faradaic efficiency (CO FE) for CO2RR to produce CO reaches a maximum of 88.08% at -1.5 V vs. RHE. Maintaining a constant applied voltage at -1.4 V vs. RHE ensures stability for up to 4 h.

Recent Progress of Layered Double Hydroxide-Based Materials in Wastewater Treatment

Layered double hydroxides (LDHs) can be used as catalysts and adsorbents due to their high stability, safety, and reusability. The preparation of modified LDHs mainly includes coprecipitation, hydrothermal, ion exchange, calcination recovery, and sol-gel methods. LDH-based materials have high anion exchange capacity, good thermal stability, and a large specific surface area, which can effectively adsorb and remove heavy metal ions, inorganic anions, organic pollutants, and oil pollutants from wastewater. Additionally, they are heterogeneous catalysts and have excellent catalytic effect in the Fenton system, persulfate-based advanced oxidation processes, and electrocatalytic system. This review ends with a discussion of the challenges and future trends of the application of LDHs in wastewater treatment.

Strategical development of chrome-free tanning agent by integrating layered double hydroxide with starch derivatives

The development of sustainable and eco-friendly leather industry requires green tanning agents because of unbounded chromium (easily converted into hazardous Cr-VI) in chrome tanned leather. In this study, a chrome-free tanning agent (OS-LDHs) was established by integrating layered double hydroxide (magnesium aluminum zirconium hydrotalcite, LDHs) with starch derivatives. A series of oxidized starch (OS) were prepared as masking agents for LDHs tanning process. Among them, the weight-average molecular weight (Mw) of 1685 g/mol could be reached, which will promise the well-distribution of OS. The SEM and EDS analysis confirmed the uniform penetration of OS-LDHs, avoiding accumulation on the surface of crust leather. Notably, leather tanned by OS-LDHs achieved shrinkage temperature of 66.7 °C, porosity of 75.51 % and tear strength of 66.7 N/mm. Not only the hydrogen bond but also the coordination between NH₂, COOH in collagen and OS-2-LDHs improved the thermal stability of leather without destroying the collagen triple helix.

Facile fabrication of highly dispersed Pd catalyst on nanoporous chitosan and its application in environmental catalysis

With the development of society, the problem of environmental pollution is becoming increasingly serious, such as the typical pollution of nitro compounds or dyes in wastewater. An effective strategy to remove these organic pollutants is catalytic conversion, including converting them into more chemically valuable compounds. Herein, a nanoporous chitosan microsphere derived from seafood waste resources of chitin was constructed via sol-gel method, which was used as supports to successfully fabricate a highly dispersed Pd nano-catalyst (mean diameter ~ 1.8 nm) via a facile way based on its interconnected nanoporous structure and rich functional -OH/-NH₂ groups. The synthetic catalyst was applied to the hydrogenation of toxic nitro compounds, which could efficiently and selectively catalyze the conversion of nitro compounds. The catalyst was also used for the degradation of some representative dyes, which also showed good activity and stability, suggesting potential of applications in green environmental governance.

The Properties and Preparation Methods of Different Boron Nitride Nanostructures and Applications of Related Nanocomposites

Due to special non-metallic polar bond between the III group (with certain metallic properties) element boron (B) and the V group element nitrogen (N), boron nitride (BN) has unique physical and chemical properties such as strong high-temperature resistance, oxidation resistance, heat conduction, electrical insulation and neutron absorption. Its unique lamellar, reticular and tubular morphologies and physicochemical properties make it attractive in the fields of adsorption, catalysis, hydrogen storage, thermal conduction, insulation, dielectric substrate of electronic devices, radiation protection, polymer composites, medicine, etc. Therefore, the synthesis and properties of BN derived materials become the main research hotspots of low-dimensional nanomaterials. This paper reviews the synthetic methods, overall properties, and applications of BN nanostructures and nanocomposites. In addition, challenges and prospect of this kind of materials are discussed.

Optimizing nanocarbon shell in zero-valent iron nanoparticles for improved electron utilization in Cr(VI) reduction

A core-shell structured zero-valent iron@carbon (ZVI@C) nanocompoiste was designed to improve the electron utilization of ZVI in the Cr(VI) reduction. The porosity of carbon layer in ZVI@C was optimized for improving the efficiency of electron utilization of ZVI in the Cr(VI) reduction process. The porous structure of carbon layer was controllably synthesized by adjusting the carbon source and the ratio of C/Fe in the precursor. The glucose was suggested as the optimal carbon source, and a high specific surface area (37.067 m²/g) was reached for the prepared ZVI@C when the ratio of C/Fe was controlled at 20. These ZVI@C performed well on Cr(VI) reduction, e.g. a complete reduction of Cr(VI) (2 mg/L) to Cr(III) within 10 min. The removal capacity (800 mg/g) exceeded previously recorded ZVI based adsorbents. The pH and initial Cr(VI) concentration were demonstrated as the key factors for the efficient electron utilization of ZVI. Furthermore, the efficiency of electron utilization of the ZVI increased up to 80% when the concentration of Cr(VI) was 2000 mg/L and the pH was controlled at 3, which was much higher than 8% of the naked ZVI.

Magnetic nanocellulose-magnetite aerogel for easy oil adsorption

HYPOTHESIS

Cellulose aerogels are a new category of high-efficiency adsorbents for treating oil spills and water pollution. However, the hydrophilic properties and recyclability of aerogels after adsorption hamper developments and applications. Combining both hydrophobic and magnetic properties are expected to improve their adsorption capacity and functionality.

EXPERIMENTS

In this study, the effect of oleic acid (OA) and nanomagnetite on the preparation of magnetic nanocellulose aerogels (called as NCA/OA/Fe₃O₄) by a mechanical mixing combined with freeze-drying method have been investigated.

FINDINGS

It has been found that the optimal condition for fabricating this NCA/OA/Fe₃O₄ aerogel is 0.4 wt% nanocellulose, 3 mg mL^-1 OA and 0.5 wt% Fe₃O₄ in the aqueous solution. This aerogel has a very low density of 9.2 mg cm^-3 and demonstrates a high adsorption capacity of 68.06 g g^-1 for cyclohexane. In addition, this aerogel adsorbent demonstrates an excellent magnetic responsivity and can be easily recycled by a permanent magnet after adsorption. As a consequence, this hydrophobic magnetic NCA/OA/Fe₃O₄ aerogel is promising not only for easy oil and organic solvent adsorption but also potentially for other magnetic related applications.

Carbon nitride nanoplatelet photocatalysts heterostructured with B-doped carbon nanodots for enhanced photodegradation of organic pollutants

Decorating electron-accepting materials on carbon nitride (C₃N₄) is a promising strategy to construct heterostructure catalysts for improved photocatalytic abilities. In this study, B-doped carbon-dots (B-C-dots) decorated C₃N₄ (C₃N₄/B-C-dots) catalysts were fabricated through the surface deposition. The benefits from integration of B-C-dots and C₃N₄ are four folds: (i) increasing surface area; (ii) improving visible light absorption; (iii) promoting the transfer of photoinduced carriers; and (iv) reducing the recombination of photoinduced carriers. The optimum photocatalytic activity of B-C-dots/C₃N₄ for Rhodamine B (Rh B) (or tetracycline hydrochloride (TC)) degradation was about 7.21 (6.56) and 4.80 (4.35) times higher than that of C₃N₄ and C-dots/C₃N₄, respectively, exhibiting both remarkable stability and repeatability. Moreover, enhanced photocatalytic activity of C₃N₄/B-C-dots could also be attributed to the type-II heterojunction formed between C₃N₄ and B-C-dots caused by B doping.