Urchin-like CO2-responsive magnetic microspheres for highly efficient organic dye removal

CO2-responsive materials have emerged as promising adsorbents for the remediation of refractory organic dyes-contaminated wastewater without the formation of byproducts or causing secondary pollution. However, realizing the simultaneous adsorption-separation or complete removal of both anionic and cationic dyes, as well as achieving deeper insights into their adsorption mechanism, still remains a challenge for most reported CO2-responsive materials. Herein, a novel type of urchin-like CO2-responsive Fe3O4 microspheres (U-Fe3O4 @P) has been successfully fabricated to enable ultrafast, selective, and reversible adsorption of anionic dyes by utilizing CO2 as a triggering gas. Meanwhile, the CO2-responsive U-Fe3O4 @P microspheres exhibit the capability to initiate Fenton degradation of non-adsorbable cationic dyes. Our findings reveal exceptionally rapid adsorption equilibrium, achieved within a mere 5 min, and an outstanding maximum adsorption capacity of 561.2 mg g-1 for anionic dye methyl orange upon CO2 stimulation. Moreover, 99.8% of cationic dye methylene blue can be effectively degraded through the Fenton reaction. Furthermore, the long-term unresolved interaction mechanism of organic dyes with CO2-responsive materials is deciphered through a comprehensive experimental and theoretical study by density functional theory. This work provides a novel paradigm and guidance for designing next-generation eco-friendly CO2-responsive materials for highly efficient purification of complex dye-contaminated wastewater in environmental engineering.

One-Step Synthesis of Ag2O/Fe3O4 Magnetic Photocatalyst for Efficient Organic Pollutant Removal via Wide-Spectral-Response Photocatalysis-Fenton Coupling

Photocatalysis holds great promise for addressing water pollution caused by organic dyes, and the development of Ag₂O/Fe₃O₄ aims to overcome the challenges of slow degradation efficiency and difficult recovery of photocatalysts. In this study, we present a novel, environmentally friendly Ag₂O/Fe₃O₄ magnetic nanocomposite synthesized via a simple coprecipitation method, which not only constructs a type II heterojunction but also successfully couples photocatalysis and Fenton reaction, enhancing the broad-spectrum response and efficiency. The Ag₂O/Fe₃O₄ (10%) nanocomposite demonstrates exceptional degradation performance toward organic dyes, achieving 99.5% degradation of 10 mg/L methyl orange (MO) within 15 min under visible light irradiation and proving its wide applicability by efficiently degrading various dyes while maintaining high stability over multiple testing cycles. Magnetic testing further highlighted the ease of Ag₂O/Fe₃O₄ (10%) recovery using magnetic force. This innovative approach offers a promising strategy for constructing high-performance photocatalytic systems for addressing water pollution caused by organic dyes.

Construction of an S-Scheme Ag2MoO4/ZnFe2O4 Nanofiber Heterojunction for Enhanced Photoelectrocatalytic Activity under Visible Light Irradiation

The removal of organic dyes and pathogenic bacteria from contaminated water remains a significant challenge. In the present study, S-type heterojunction Ag₂MoO₄/ZnFe₂O₄ (AMO/ZFO) composite nanofibers were synthesized by electrospinning and co-precipitation and fabricated into photoanodes. It is found that the constructed S-type heterojunction of AMO/ZFO composites effectively inhibits the recombination of photogenerated carriers, in addition to the benefits of more exposed active sites and a greater specific surface area. When several properties are improved, AMO/ZFO composites exhibit excellent photoelectrocatalytic performance. The results demonstrate that under visible light irradiation, the photoelectrocatalytic degradation rate of AMO/ZFO-3 to methylene blue reached 76.2% within 50 min, and the killing rate of Salmonella was 83.6% within 80 min. The enhanced photoelectrocatalytic activity was due to the synergy of both electrochemical and photocatalytic effects. More importantly, after four testing cycles, AMO/ZFO-3 still has a better ability to kill pathogenic bacteria and degrade organic dyes due to its high stability. This work provides a feasible method for oxidizing organic dyes and pathogenic bacteria.

Fabrication of chitosan-based food packaging film impregnated with turmeric essential oil (TEO)-loaded magnetic-silica nanocomposites for surimi preservation

Successful modification of chitosan (CS) film using magnetic-silica nanocomposite to encapsulate turmeric essential oil (TEO) obtained by super critical CO2 extraction for enhanced preservation of surimi was performed. TEO exhibited antioxidant and antibacterial activities against Bacillus cereus. The core magnetic nanoparticles (MNPs) were capped with porous silica (Si) to form core-shell nanocomposites, into which TEO was loaded with 75.24% encapsulation efficiency. The fabricated nanocomposite was characterized, blended with CS to cast a bionanocomposite active film and characterized for efficient impregnation of bionanocomposite. The physical and mechanical properties of film were significantly improved after adding MNPs/Si/TEO nanocomposite. Uncontrolled release of TEO from CS film resulted in bacterial growth after 6 days of storage whereas bionanocomposites exhibited a sustained release of TEO that controlled the microbial load from 4.0 log CFU/g to 2.78 log CFU/g over 14 days. The overall study demonstrated that the CS/MNPs/Si/TEO bionanocomposite film was efficient as a packaging material for prolonged shelf-life of surimi.

Bi-doped graphitic carbon nitride nanotubes boost the photocatalytic degradation of Rhodamine B

Polymeric carbon nitride (PCN) is an emerging metal-free photocatalyst with high stability but is plagued by low photocatalytic efficiency due to the rapid charge carrier recombination behavior.

ZnFe2O4-chitosan magnetic beads for the removal of chlordimeform by photo-Fenton process under UVC irradiation

A simple protocol was proposed for the preparation of magnetic chitosan beads ZnFe₂O₄-CS via a co-precipitation method. The use of synthesized magnetic ZnFe₂O₄-CS beads as catalyst for the heterogeneous photo-Fenton treatment of chlordimeform insecticide (CDM) was evaluated. The photo-Fenton experiments were carried out with different synthesized catalysts by varying the molar ratio Zn/Fe in chitosan beads, the catalyst concentration and pH. Under optimal conditions using 1 g of ZnFe₂O₄-CS beads with a molar ratio Zn/Fe = 0.35 and at pH_initial = 3, a real wastewater doped with 20 mg L^-1 of CDM was treated and complete removal of the insecticide was achieved after 7 min with a total TOC removal after 2 h of treatment. The generated carboxylic acids and ions during the photo-Fenton process were identified and quantified. The stability of the photocatalytic activity of the best catalyst in terms of pollutant removal, ZnFe₂O₄-CS(0.35) beads with a molar ratio Zn/Fe equal to 0.35, was satisfactory validated by four consecutive cycles. This optimal catalyst was characterized, before and after use, by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, X-Ray Powder Diffraction and Vibrating Sample Magnetometry analysis.

Surface oxygen vacancies enriched FeOOH/Bi2MoO6 photocatalysis- fenton synergy degradation of organic pollutants

To achieve rapid separation of photogenerated charges, increase photocatalytic degradation activity, a visible light-driven FeOOH/Bi₂MoO₆-OVs photocatalyst was designed and successfully fabricated via solvothermal synthesis and calcination. H₂O₂ was added under visible light irradiation to form a heterogeneous photocatalysis-Fenton synergy system. Using visible light irradiation, 10% FeOOH/Bi₂MoO₆-OVs had the best degradation activity. The removal efficiency of phenol was 100% within 3 h, which was 1.54 times and 1.33 times of the degradation efficiency of photocatalysis and Fenton alone, respectively. The catalyst has high removal activity for various pollutants and good cycle stability. Hydroxyl radicals and superoxide radicals have proven to be the main active substances and a reasonable catalytic mechanism was proposed. Surface oxygen vacancy can not only reduce the width of band gap, promote the separation and migration of photogenerated electron-hole pairs, but also make the OO bond of H₂O₂ elongate and weaken, making it easier to react with FeOOH and realize the synergistic effect of photocatalysis-Fenton. Simultaneously, the oxygen vacancies located near the valence band can capture holes, and the holes are rapidly transferred to the surface of the catalyst and participated in the degradation of pollutants.

Photocatalytic performance of visible active boron nitride supported ZnFe2O4 (ZnFe2O4/BN) nanocomposites for the removal of aqueous organic pollutants

ZnFe₂O₄/BN nanocomposites were synthesized using  solvothermal method. The microscopic images revealed uniform dispersion of ZnFe₂O₄ nanospheres on the surface of BN nanosheets. PL studies showed lower e⁻/h⁺ pair recombination.  ZnFe₂O₄/9.3% BN showed outstanding photocatalytic activity.

Graphene–Magnetic Spinel Ferrite Nanocomposite: Facile Synthesis and Excellent Photocatalytic Performance

Spinel ferrite structured ZnFe2O4 nanoparticles anchored on reduced graphene oxide (rGO) sheets have been prepared via a facile hydrothermal method combined with a solvothermal approach. For the synthesis of the ZnFe2O4/rGO nanocomposites, the rGO nanosheet contains epoxy functional groups serving as the active sites, which allowed the formation of uniform ZnFe2O4 nanoparticles. Due to the structure of the ZnFe2O4/RGO nanocomposites, the aggregation of the ZnFe2O4 nanoparticles can be readily disrupted and electronic transfer through the rGO nanosheets is accelerated. This could in turn enhance the photocatalytic efficiency. It was also demonstrated that ZnFe2O4/rGO (40 wt-%) hybrid nanocomposites almost reached adsorption equilibrium in the RhB dye within 60min. The Langmuir equation model showed that the photodegradation of RhB was well fitted to first order reaction kinetics with k=0.6254min−1. This illustrated that the addition of GO could reduce the bandgap of pure ZnFe2O4, which avoided the combination of electrons and holes. The ZnFe2O4/rGO nanocomposites could also enhance the utilisation of sunlight. In addition, the ZnFe2O4/rGO nanocomposite photocatalyst also demonstrated a supramagnetic property, holding potential to be utilised for water treatment.