Photo-induced heterogeneous regeneration of Fe(Ⅱ) in Fenton reaction for efficient polycyclic antibiotics removal and in-depth charge transfer mechanism

Innovative zero-valent cobalt decoration on MIL-88 A(Fe)@β-CD for high-efficiency and reusable cr(VI) removal

Herein, the magnetic ZVCo-MIL-88 A(Fe)@β-CD composite was fabricated via post-synthetic decoration of MIL-88 A(Fe)@β-CD with ZVCo to produce a magnetic efficient adsorbent for Cr(VI) removal. The experimental findings denoted that the ZVCo decoration boosted the adsorption capability of MIL-88 A(Fe)@β-CD, where the adsorption % of Cr(VI) improved from 73.07 to 94.02% after its decoration with 10 wt% of ZVCo. Furthermore, the ZVCo decoration ameliorated the recycling feature of MIL-88 A(Fe)@β-CD since the removal % of Cr(VI) by MIL-88 A(Fe)@β-CD and ZVCo-MIL-88 A(Fe)@β-CD reached 27.24 and 84.98%, respectively. The optimization experiments of the Cr(VI) ions clarified that the higher adsorption % fulfilled 94.02% at pH = 3, using ZVCo-MIL-88 A(Fe)@β-CD dosage = 0.5 g/L, Cr(VI) concentration = 50 mg/L, and at room temperature. Notably, the concentration of the adsorbed Cr(VI) brings off the equilibrium stage within an hour, implying the fast adsorption property of ZVCo-MIL-88 A(Fe)@β-CD. The kinetic and isotherms assessments denoted the contribution of the physical and chemical adsorption pathways in adsorbing the Cr(VI) species onto ZVCo-MIL-88 A(Fe)@β-CD. In addition, the XPS spectra and zeta potential results supposed that the process inside the Cr(VI)/ZVCo-MIL-88 A(Fe)@β-CD system proceeded through reduction reaction, coordination bonds, electrostatic interactions, and pore-filling mechanisms.

One-step green synthesis of melamine-modified cellulose nanofiber composite aerogels for efficient removal of Pb(II) and Cu(II): Experiments and DFT calculations

A composite aerogel (CGMA) with high porosity (98.32 %) and multiple active sites was prepared for the adsorption of Pb(II) and Cu(II) by sol-gel combined with freeze-drying process using melamine and (3-Glycidyloxypropyl)trimethoxysilane as cellulose nanofiber modifying materials. Characterized by SEM-EDS, XPS, FTIR, BET, MIP and TG, CGMA has a hierarchical pore structure and abundant adsorption sites. At pH = 6, the adsorption reached equilibrium within 120 min, following the Pseudo second-order kinetic model and the Langmuir model, with maximum capacities of 268.1 mg/g for Pb(II) and 152.6 mg/g for Cu(II). The process was primarily governed by homogeneous chemisorption. The coexisting ion, organic matter, and water quality experiments confirmed the excellent anti-interference properties of CGMA. Competitive adsorption experiments showed that CGMA has excellent selective adsorption performance for Pb(II). After 5 cycles, Pb(II) and Cu(II) adsorption performance decreased to 79.21 % and 83.40 %, respectively. FTIR, XPS, DFT and RDG analysis showed that amino groups and oxygen-containing groups were the main sites of adsorption. CGMA forms coordination bonds and complexes with Pb(II) and Cu(II) via amine and oxygen groups and adsorbs via electron transfer, hydrogen bonding, and van der Waals forces, with Pb(II) being more selective. CGMA has good prospects for application in heavy metal ion treatment.

A photocatalysis-self-Fenton system based on NCDs@ZnIn2S4 composites at neutral pH and low amount of Fe2+ for the effective degradation of antibiotics

Photocatalysis-self-Fenton combining photocatalytic production of H2O2 with Fenton reaction has been a hotspot, but the pH limitation and iron sludge production problems remain unsolved. Herein, we proposed a self-fenton system based on N-doped carbon dots modified ZnIn2S4 (NCDs@ZnIn2S4) composites that exhibits effective degradation of antibiotics under neutral pH using low amounts of Fe2+. The decoration of ZnIn2S4 with NCDs significantly increased the surface area, visible light absorption, charge transfer ability and oxygen adsorption ability. NCDs@ZnIn2S4 composites exhibited a high H2O2 production rate (1528 μM g-1•h-1) under visible light, which was 1.9 and 5.3 times higher than ZnIn2S4 and NCDs, respectively. Meanwhile, the Fe2+/NCDs@ZnIn2S4 system with a low concentration of Fe2+(1 mg/L) could remove over 95% levofloxacin and oxytetracycline within 30 min. Interestingly, the highest degradation efficiency occurred under neutral pH. Quenching experiments and analytical measurements indicated that the high catalytic performance under pH = 7 with low amounts of Fe2+ stemmed from the higher amount of inner-generate H2O2 under neutral pH and easy regeneration of Fe2+ by photoinduced electrons for high •OH yields. Additionally, the Fe2+/NCDs@ZnIn2S4 system exhibited high degradation performance under different water matrix and ultrahigh degradation efficiency towards levofloxacin under real sunlight irradiation. The work shows the prospects of photocatalysis-self-Fenton systems for overcoming the pH limitation and the difficulty of iron sludge separation in the purification of effluents.

Enhanced Fenton Degradation of Tetracycline over Cerium-Doped MIL88-A/g-C3N4: Catalytic Performance and Mechanism

Since enormous amounts of antibiotics are consumed daily by millions of patients all over the world, tons of pharmaceutical residuals reach aquatic bodies. Accordingly, our study adopted the Fenton catalytic degradation approach to conquer such detrimental pollutants. (Ce0.33Fe) MIL-88A was fabricated by the hydrothermal method; then, it was supported on the surface of g-C3N4 sheets using the post-synthetic approach to yield a heterogeneous Fenton-like (Ce0.33Fe) MIL-88A/10%g-C3N4 catalyst for degrading the tetracycline hydrochloride drug. The physicochemical characteristics of the catalyst were analyzed using FT-IR, SEM-EDX, XRD, BET, SEM, and XPS. The pH level, the H2O2 concentration, the reaction temperature, the catalyst dose, and the initial TC concentration were all examined as influencing factors of TC degradation efficiency. Approximately 92.44% of the TC was degraded within 100 min under optimal conditions: pH = 7, catalyst dosage = 0.01 g, H2O2 concentration = 100 mg/L, temperature = 25 °C, and TC concentration = 50 mg/L. It is noteworthy that the practical outcomes revealed how the Fenton-like process and adsorption work together. The degradation data were well-inspected by first-order and second-order models to define the reaction rate. The synergistic interaction between the (Ce0.33Fe) MIL-88A/10%g-C3N4 components produces a continuous redox cycle of two active metal species and the electron-rich source of g-C3N4. The quenching test demonstrates that •OH is the primary active species for degrading TC in the H2O2-(Ce0.33Fe) MIL-88A/10%g-C3N4 system. The GC-MS spectrum elucidates the yielded intermediates from degrading the TC molecules.

Antibacterial Mechanism of d-Cysteine/Polyethylene Glycol-Functionalized Gold Nanoparticles and Their Potential for the Treatment of Bacterial Infections

Bacterial infection has always posed a severe threat to public health. Gold nanoparticles (Au NPs) exhibit exceptional biocompatibility and hold immense potential in biomedical applications. However, their antibacterial effectiveness is currently unsatisfactory. Herein, a chiral antibacterial agent with high stability was prepared by the modification of Au NPs with d-cysteine with the assistance of polyethylene glycol (PEG). The as-synthesized d-cysteine/PEG-Au NPs (D/P-Au NPs) exhibited a stronger (99.5-99.9%) and more stable (at least 14 days) antibacterial performance against Gram-negative (Escherichia coli and Listeria monocytogenes) and Gram-positive (Salmonella enteritidis and Staphylococcus aureus) bacteria, compared with other groups. The analysis of the antibacterial mechanism revealed that the D/P-Au NPs mainly affected the assembly of ribosomes, the biosynthesis of amino acids and proteins, as well as the DNA replication and mismatch repair, ultimately leading to bacterial death, which is significantly different from the mechanism of reactive oxygen species-activated metallic antibacterial NPs. In particular, the D/P-Au NPs were shown to effectively accelerate the healing of S. aureus-infected wounds in mice to a rate comparable to or slightly higher than that of vancomycin. This work provides a novel approach to effectively design chiral antibacterial agents for bacterial infection treatment.

FeCu bimetallic metal organic frameworks photo-Fenton synergy efficiently degrades organic pollutants: Structure, properties, and mechanism insight

The high ion leaching, low photogenerated charge separation efficiency, and slow metal valence cycling of Fe-based metal organic frameworks (MOFs) have limited their application in the deep treatment of organic pollutants. Herein, FeCu bimetallic MOFs (FeCuBDC) were synthesized using a modified solvothermal method, and a coupled photo-Fenton degradation system was successfully constructed. Degradation performance tests showed that FeCuBDC could efficiently degrade 99.3% ± 0.1% of 50 mg/L phenol within 40 min. The reaction rate constants of the photo-Fenton system were 11.0 and 64.7 times higher than those of the single Fenton reaction and photocatalysis, respectively. FeCuBDC also exhibits good cycling stability, degradation generalization, and excellent photoelectric catalytic properties. Such a considerable enhancement in the overall performance pertains to the following. First, the introduction of Cu into Fe-MOFs not only improves the crystallinity and stability, but also reduces the band gap value, increases the absorption capacity of visible light, and promotes the generation of photogenerated carriers. Second, the FeCu in MOFs are all mixed valence. Initially, the high-valence FeCu captures photogenerated electrons and promotes photogenerated charge separation and transfer. Then, the low-valence FeCu adsorbs and decomposes H2O2, accelerating the valence cycling of the bimetallic sites. The core of the reaction mechanism is that FeCuBDC effectively promotes the photo-Fenton synergy.

In-situ production and activation of H2O2 over hydroxyapatite modified CuFeO2 for self-sufficient heterogeneous photo-Fenton degradation of doxycycline hydrochloride

The self-sufficient heterogeneous photo-Fenton (SH-PF) system was constructed for doxycycline hydrochloride (DOH) degradation with hydroxyapatite (Hap) modified CuFeO2 (Hap/CuFeO2) composites through H2O2 in-situ production. The modification of Hap could improve the specific surface area, visible-light response, light conversion efficiency, photoelectron lifetime and oxygen vacancies (OVs) of CuFeO2, which was conducive to H2O2 production and DOH degradation in SH-PF system. Notably, Hap/CuFeO2 fabricated with 0.5 g Hap (Hap/CuFeO2-0.5) displayed more superior performance for DOH degradation compared to other synthesized catalysts. The Hap/CuFeO2-0.5 load and initial solution pH for DOH degradation in SH-PF system were optimized, and the Hap/CuFeO2-0.5 had good reusability and stability. The •OH was the main active species for DOH degradation, and the facilitation effect of •O2- and photoelectrons on DOH degradation was associated with the H2O2 production in the present work. In addition, the capture of photogenerated holes suppressed the recombination of photogenerated carriers, elevating the production of photoelectrons and thereby enhancing H2O2 production and DOH degradation. The degradation pathways for DOH were proposed and the comprehensive toxicities of DOH were relieved after degradation in SH-PF system.