Enhanced norfloxacin degradation by visible-light-driven Mn3O4/γ-MnOOH photocatalysis under weak magnetic field

MnOOH/carbon-based reactive electrochemical membrane for aqueous organic pollutants decontamination

The electrochemical filtration process (ECFP), which integrates the benefits of membrane separation with electrochemical advanced oxidation, exhibits significant potential for water decontamination. A key aspect in realizing practical applications of ECFP lies in the development of cost-effective, high-performance reactive electrochemical membranes (REM). In this work, a novel carbon-based REM (MCM-30) was prepared by coating the low-cost coal-based carbon membrane (CM) with MnOOH nano-catalyst through a simple and environmentally friendly electrochemical deposition method. Results indicated that the nano-MnOOH catalyst significantly improved the hydrophilicity and electrochemical properties of the CM, thereby enhancing its permeability and removal efficiency towards bisphenol A (BPA). The effects of deposition time, applied voltages, flow rates, electrolyte concentrations, and water matrixes on BPA removal efficiency were systematically investigated. Under optimal conditions, 30 min deposition, 2.0 V applied voltage, 2 mL min-1 flow rate, 0.1 mol L-1 Na2SO4 electrolyte concentration, the BPA removal efficiency of the MCM-30 reached to over 95%, which is much higher than that of the CM. The improved water treatment performance of MCM-30 during the electrochemical filtration could be attributed to the enhancement in both direct and indirect oxidation owing to the nano MnOOH deposition. Furthermore, the MCM-30 is recyclable and can be applied across various water backgrounds and pollutant types.

Nanoclay-Mediated Crystal-Phase Engineering in Biofunctions to Balance Antibacteriality and Cytotoxicity

The crystalline phase of metal oxides is a key determinant of the properties and functions of the nanomaterials. Traditional approaches have focused on replicating bulk-phase structures, with limited exploration of phase diversity due to challenges in controlling the crystal morphology. Here, we introduce a nanoclay-mediated strategy for crystal-phase engineering, using talc to modulate the morphology and phase of manganese oxide (MnOx) nanoparticles. This approach enhances the oxidase activity of the MnOx composite (M/T), optimizing the antimicrobial efficacy while minimizing cytotoxicity. M/T-190 demonstrated 99% bactericidal activity against Escherichia coli and Staphylococcus aureus, coupled with 84% cytocompatibility. Theory calculations suggest that talc modulates the charge distribution and d-band center tuning at the Mn3O4/MnOOH interface, enhancing oxygen activation. When integrated into gauze, M/T exhibits strong antimicrobial activity, low toxicity, and promotes wound healing in both in vitro and in vivo studies. These findings highlight the potential of natural minerals for crystal-phase engineering in biomedical applications.

Revealing multi-level shortrange migration of electrons on full-spectrum response e-LDH/t-BiOCl/Bi2S3 and their essential role in the detoxification of Cr(VI) and refractory organic pollutants

The toxic dyeing wastewater containing both carcinogenic Cr(VI) and refractory dyes poses serious threats to ecological safety and human health. Herein, a novel composite photocatalytic material e-LDH/t-BiOCl/Bi2S3 with an ultrathin sandwich structure constructed achieves removal rate constants of 0.044 and 0.019 min-1 for Cr(VI) and reactive red 2 by adsorption-photocatalysis synergistic mechanism in full-spectrum illumination. This structure employs the interface conditions and built-in electric field to form multilevel short-range charge migration channel, achieving the targeted reduction and oxidation of Cr(VI) and azoxy dyes by electrons (e-) and holes (h+). Besides facilitating the reduction of Cr(VI), e- can also enhance the effective utilization of h+ and mediate the formation of other reactive oxygen species that target RR2 degradation. The degradation mechanism, pathway, and biological toxicity of RR2 single and Cr(VI)/RR2 coexistence reaction system were discussed by DFT calculation, LC-MS characterization, and T.E.S.T. evaluation. Moreover, we further investigated the photocatalytic activity and cost-effectiveness of the e-LDH/t-BiOCl/Bi2S3 system under continuous flow and real water settings, and determined the primary water quality parameters that influence photocatalytic performance. This work establishes a new concept for the rational design of robust ternary heterostructure photocatalysts with desirable morphology and competitive performance for photocatalytic applications.

Preparation and Adsorption Performance of Walnut Waste-Based Magnetic Activated Carbon with High Specific Surface Area

Magnetic activated carbon (MAC) derived from agricultural waste shows significant potential for the removal of norfloxacin (NOR) from wastewater. However, understanding the removal mechanisms, efficiency, and recyclability of MAC produced from walnut green husk and ferrocene for NOR remains a challenge. In this study, walnut green husk-based MAC (HQP-MC) was synthesized, and changes in surface functionality, mechanisms for NOR removal, and major influencing factors were investigated. The results indicated that HQP-MC predominantly features a mesoporous structure with a diverse array of surface functional groups, including -OH, NH2, C=O, and C-O. Additionally, HQP-MC demonstrates a remarkable adsorption capacity for NOR, achieving 226.8 mg·g-1 at 298 K and pH 7.0 under various substrates and experimental conditions. This high capacity can be attributed to a significantly enhanced specific surface area and pore volume, which increased by factors of 2.40 and 2.46, respectively, compared with pristine activated carbon. Moreover, HQP-MC exhibited an exceptional saturation magnetic strength of 11.5 emu·g-1, along with a reusability rate of 80.5% after ten cycles. The adsorption kinetics were effectively described by the pseudo-second-order model and the Langmuir isotherm model. This study provides valuable insights into the sustainable development of magnetic adsorbent materials derived from agricultural waste and their applications in wastewater decontamination.

Enhanced nitrogen removal in constructed wetlands with multivalent manganese oxides: Mechanisms underlying ammonium oxidation processes

The ammonium (NH4+) removal efficiency in constructed wetlands (CWs) is often limited by insufficient oxygen. In this study, an extract of Eucalyptus robusta Smith leaves was used to prepare multivalent manganese oxides (MVMOs) as substrates, which were used to drive manganese oxide (MnOx) reduction coupled to anaerobic NH4+ oxidation (Mnammox). To investigate the effects and mechanisms of MVMOs on ammonium nitrogen (NH4+-N) removal, four laboratory-scale CWs (0 %/5 %/15 %/25 % volume ratios of MVMOs) were set up and operated as continuous systems. The results showed that compared to controlled C-CW (0 % MVMOs), Mn25-CW (25 % MVMOs) improved the average NH4+-N removal efficiency from 24.31 % to 80.51 %. Furthermore, N2O emissions were reduced by 81.12 % for Mn25-CW. Isotopic tracer incubations provided direct evidence of Mnammox occurrence in Mn-CWs, contributing to 18.05-43.64 % of NH4+-N removal, primarily through the N2-producing pathway (73.54-90.37 %). Notably, batch experiments indicated that Mn(III) played a predominant role in Mnammox. Finally, microbial analysis revealed the highest abundance of the nitrifying bacteria Nitrospira and Mn-cycling bacteria Pseudomonas, Geobacter, Anaeromyxobacter, Geothrix and Novosphingobium in Mn25-CW, corresponding to its superior NH4+-N removal efficiency. The enhancement of NH4+ oxidation, first to hydroxylamine and then to nitrite, in Mn25-CW was attributed to the upregulation of ammonia monooxygenase genes (amoABC and hao). This study enhanced our understanding of Mnammox and provided further support for the use of manganese oxide substrates in CWs for efficient NH4+-N removal.

In situ bio-mineralized Mn nanoadjuvant enhances anti-influenza immunity of recombinant virus-like particle vaccines

Virus like particles (VLPs) have been well recognized as one of the most important vaccine platforms due to their structural similarity to natural viruses to induce effective humoral and cellular immune responses. Nevertheless, lack of viral nucleic acids in VLPs usually leads the vaccine candidates less efficient in provoking innate immune against viral infection. Here, we constructed a biomimetic dual antigen hybrid influenza nanovaccines THM-HA@Mn with robust immunogenicity via in situ synthesizing a stimulator of interferon genes (STING) agonist Mn3O4 inside the cavity of a recombinant Hepatitis B core antigen VLP (HBc VLP) having fused SpyTag and influenza M2e antigen peptides (Tag-HBc-M2e, THM for short), followed by conjugating a recombinant hemagglutinin (rHA) antigen on the surface of the nanoparticles through SpyTag/SpyCatcher ligating. Such inside Mn3O4 immunostimulator-outside rHA antigen design, together with the chimeric M2e antigen on the HBc skeleton, enabled the synthesized hybrid nanovaccines THM-HA@Mn to well imitate the spatial distribution of M2e/HA antigens and immunostimulant in natural influenza virus. In vitro cellular experiments indicated that compared with the THM-HA antigen without Mn3O4 and a mixture vaccine consisting of THM-HA + MnOx, the THM-HA@Mn hybrid nanovaccines showed the highest efficacies in dendritic cells uptake and in promoting BMDC maturation, as well as inducing expression of TNF-α and type I interferon IFN-β. The THM-HA@Mn also displayed the most sustained antigen release at the injection site, the highest efficacies in promoting the DC maturation in lymph nodes and germinal center B cells activation in the spleen of the immunized mice. The co-delivery of immunostimulant and antigens enabled the THM-HA@Mn nanovaccines to induce the highest systemic antigen-specific antibody responses and cellular immunogenicity in mice. Together with the excellent colloid dispersion stability, low cytotoxicity, as well as good biosafety, the synthetic hybrid nanovaccines presented in this study offers a promising strategy to design VLP-based vaccine with robust natural and adaptive immunogenicity against emerging viral pathogens.

Photo-thermal coupling to enhance CO2 hydrogenation toward CH4 over Ru/MnO/Mn3O4

Upcycling of CO2 into fuels by virtually unlimited solar energy provides an ultimate solution for addressing the substantial challenges of energy crisis and climate change. In this work, we report an efficient nanostructured Ru/MnOx catalyst composed of well-defined Ru/MnO/Mn3O4 for photo-thermal catalytic CO2 hydrogenation to CH4, which is the result of a combination of external heating and irradiation. Remarkably, under relatively mild conditions of 200 °C, a considerable CH4 production rate of 166.7 mmol g-1 h-1 was achieved with a superior selectivity of 99.5% at CO2 conversion of 66.8%. The correlative spectroscopic and theoretical investigations suggest that the yield of CH4 is enhanced by coordinating photon energy with thermal energy to reduce the activation energy of reaction and promote formation of key intermediate COOH* species over the catalyst. This work opens up a new strategy for CO2 hydrogenation toward CH4.

Insight into the reactions of antimonite with manganese oxides: Synergistic effects of Mn(III) and oxygen vacancies

Manganese oxides (Mn_xO_y) are critical for determining the environmental behaviors and fate of antimonite (Sb(III)). However, little is known about the qualitative/quantitative connection between Mn_xO_y structures and Sb(III) fate. Herein, the reactions of Sb(III) and six Mn_xO_y with different structures were systematically investigated. The initial oxidation rates of Sb(III) (r_init) on six Mn_xO_y decreased in the order of γ-MnO₂>δ-MnO₂>α-MnO₂>γ-MnOOH>Mn₃O₄>β-MnO₂ (pH_initial=7.0), from 0.32 ± 0.04 to 11.17 ± 1.61 mmol/min/mol-Mn. The amounts of antimony retained (i.e., the sum of Sb(III) and antimonate (Sb(V))) on these Mn_xO_y followed the same trend as that of oxidation. Oxidation of Sb(III) released Mn(II) and created more sites for adsorption. Outwardly, Mn_xO_y with higher reduction potential (E₀) and specific surface area (SSA) favored faster Sb(III) oxidation. Inwardly, Mn(III) and oxygen vacancies (O_v) exhibited a synergistic effect on Sb(III) oxidation. Mn(III) can easier accept electron than Mn(IV) based on the change in Gibbs free energy calculation. O_v can adsorb free oxygen to form surface oxygen (O_sur) which is much more reactive than lattice oxygen (O_latt). Moreover, O_v is in close proximity to Mn(III) in high-valent Mn_xO_y which facilitated the reactions between Sb(III) and Mn(III) through the enhancement of Sb(III) adsorption and electron transfer. O_v in low-valent Mn_xO_y is adjacent to Mn(II), thus it showed weaker enhancement than that in high-valent Mn_xO_y. Part of δ-MnO₂ and almost all Mn₃O₄ were converted to γ-MnOOH during their reaction with Sb(III), while the other four Mn_xO_y were barely changed. The results obtained provide mechanistic insight into the reactions occurring within Sb(III) and Mn_xO_y, which are helpful for better understanding and prediction of the fate of Sb(III) in Mn-rich environments.

Effective Removal of Methylene Blue by Mn3O4/NiO Nanocomposite under Visible Light

Wastewater treatment is indispensable as wastewater can lead to adverse health effects and deteriorate the quality of life on earth. Photocatalysis is a facile methodology to address this issue. In this study, nanocomposites (NCs) of manganese oxide (Mn3O4) and nickel oxide (NiO) were synthesized in different weight ratios via the solid-state reaction route. Structural properties, optical properties, surface morphology, and functional group analysis of the synthesized nanomaterials were conducted using X-ray diffraction (XRD), UV– Vis spectroscopy, scanning electron microscopy (SEM) along with energy-dispersive X-ray (EDX) analysis, and Fourier-transform infrared (FTIR) spectroscopy, respectively. The bandgap of the nanocomposite decreases significantly from 2.35 eV for the Mn3O4 NPs to 1.65 eV for the Mn3O4/NiO nanocomposite (NC). Moreover, adsorption studies followed by the photocatalytic performance of the Mn3O4/NiO NCs were evaluated to determine the removal of methylene blue (MB) dye from wastewater. The photocatalytic performance of the nanocomposite enhances as the ratio of Mn3O4 in the composite increases from one weight percentage to three weight percentage. The photocatalytic degradation efficiency was calculated to be 95%. The results show that the synthesized NCs could play an important role in photocatalytic wastewater purification and environmental remediation.

Complementary and Synergistic Design of Bi-Layered Double Hydroxides Modified Magnesium Alloy toward Multifunctional Orthopedic Implants

Magnesium (Mg)-based alloys have been regarded as promising implants for future clinic orthopedics, however, how to endow them with good anti-corrosion and biofunctions still remains a great challenge, especially for complicated bone diseases. Herein, three transition metals (M = Mn, Fe, and Co)-containing layered double hydroxides (LDH) (LDH-Mn, LDH-Fe, and LDH-Co) with similar M content are prepared on Mg alloy via a novel two-step method, then systematic characterizations and comparisons are conducted in detail. Results showed that LDH-Mn exhibited the best corrosion resistance, LDH-Mn and LDH-Co possessed excellent photothermal and enzymatic activities, LDH-Fe revealed better cytocompatibility and antibacterial properties, while LDH-Co demonstrated high cytotoxicity. Based on these results, an optimized bilayer LDH coating enriched with Fe and Mn (LDH-MnFe) from top to bottom have been designed for further in vitro and in vivo analysis. The top Fe-riched layer provided biocompatibility and antibacterial properties, while the bottom Mn-riced layer provided excellent anti-corrosion, photothermal and enzymatic effects. In addition, the released Mg, Fe, and Mn ions have a positive influence on angiogenesis and osteogenesis. Thus, the LDH-MnFe showed complementary and synergistic effects on anti-corrosion and multibiofunctions (antibacteria, antitumor, and osteogenesis). The present work offers a novel multifunctional Mg-based implant for treating bone diseases.

Degradation of 4-chlorophenol using MnOOH and γ-MnOOH nanomaterials as porous catalyst: Performance, synergistic mechanism, and effect of co-existing anions

Transition metal catalysts have been proven to be a highly-potent catalyst for peroxymonosulfate (PMS) activation. The present work aimed to synthesizes the γ-MnOOH and MnOOH based on the one-pot hydrothermal method as PMS activators for efficient degradation of 4-chlorophenol (4-CP). The effect of operational parameters including solution pH, γ-MnOOH and MnOOH dose, PMS dose, 4-CP concentration, and also mixture media composition was elaborated. The results showed that the combination of MnOOH and γ-MnOOH with PMS noticeably creates a synergistic effect (SF) in 4-CP degradation by both PMS/MnOOH and PMS/γ-MnOOH process, with a SF value of 48.14 and 97.42, respectively. In both systems, the removal of 4-CP decreased in severely alkaline and acidic conditions, while no significant changes were observed in pH 5 to 9. Also, coexisting PO43- significantly reduced the removal efficiency of both systems. In addition, the effect of humic acid (HA) as a classical scavenger was investigated and showed that presence of 4 mg/L HA reduced the removal efficiency of 4-CP in the PMS/MnOOH process from 97.44% to 79.3%. The three consecutive use of both catalysts turned out that MnOOH has better stability than γ-MnOOH with lower Mn ions leaching. More importantly, quenching experiment showed that both non-radical (1O2 and O2-) and radical (SO4- and OH) pathways are involved in 4-CP degradation and non-radical pathway was the dominant one in both systems.

Black Mn-containing layered double hydroxide coated magnesium alloy for osteosarcoma therapy, bacteria killing, and bone regeneration

Osteosarcoma (OS) tissue resection with distinctive bactericidal activity, followed by regeneration of bone defects, is a highly demanded clinical treatment. Biodegradable Mg-based implants with desirable osteopromotive and superior mechanical properties to polymers and ceramics are promising new platforms for treating bone-related diseases. Integration of biodegradation control, osteosarcoma destruction, anti-bacteria, and bone defect regeneration abilities on Mg-based implants by applying biosafe and facile strategy is a promising and challenging topic. Here, a black Mn-containing layered double hydroxide (LDH) nanosheet-modified Mg-based implants was developed. Benefiting from the distinctive capabilities of the constructed black LDH film, including near-infrared optical absorption and reactive oxygen species (ROS) generation in a tumor-specific microenvironment, the tumor cells and tissue could be effectively eliminated. Concomitant bacteria could be killed by localized hyperthermia. Furthermore, the enhanced corrosion resistance and synergistic biofunctions of Mn and Mg ions of the constructed black LDH-modified Mg implants significantly facilitated cell adhesion, spreading and proliferation and osteogenic differentiation in vitro, and accelerated bone regeneration in vivo. This work offers a new platform and feasible strategy for OS therapeutics and bone defect regeneration, which broadens the biomedical application of Mg-based alloys.

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Black Mg–Mn(Ⅱ)-Mn(Ⅲ) LDH-engineered Mg-based bone implants were developed.

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The LDH film improved the corrosion resistance and biocompatibility of Mg implant.

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The LDH endowed the Mg alloy implants with superior photothermal/chemodynamic effects.

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The Mg-based implants had antitumor and bone defect regenerating properties.

Recent Advancements in Photocatalysis Coupling by External Physical Fields

Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the requirement of 5% solar energy conversion efficiency. Combining photocatalysis with the other physical fields has been proven to be an efficient way around this barrier which can improve the performance of photocatalysis remarkably. This review will focus on the recent advances in photocatalysis coupling by external physical fields, including Thermal-coupled photocatalysis (TCP), Mechanical-coupled photocatalysis (MCP), and Electromagnetism-coupled photocatalysis (ECP). In this paper, coupling mechanisms, materials, and applications of external physical fields are reviewed. Specifically, the promotive effect on photocatalytic activity by the external fields is highlighted. This review will provide a detailed and specific reference for photocatalysis coupling by external physical fields in a deep-going way.

Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment

In this review, the most recent advances in the field of magnetic composite photocatalysts with integrated plasmonic silver (Ag) is presented, with an overview of their synthesis techniques, properties and photocatalytic pollutant removal applications. Magnetic attributes combined with plasmonic properties in these composites result in enhancements for light absorption, charge-pair generation-separation-transfer and photocatalytic efficiency with the additional advantage of their facile magnetic separation from water solutions after treatment, neutralizing the issue of silver’s inherent toxicity. A detailed overview of the currently utilized synthesis methods and techniques for the preparation of magnetic silver-integrated composites is presented. Furthermore, an extended critical review of the most recent pollutant removal applications of these composites via green photocatalysis technology is presented. From this survey, the potential of magnetic composites integrated with plasmonic metals is highlighted for light-induced water treatment and purification. Highlights: (1) Perspective of magnetic properties combined with plasmon metal attributes; (2) Overview of recent methods for magnetic silver-integrated composite synthesis; (3) Critical view of recent applications for photocatalytic pollutant removal.

Efficient remediation of antibiotic pollutants from the environment by innovative biochar: current updates and prospects

The increased antibiotic consumption and their improper management led to serious antibiotic pollution and its exposure to the environment develops multidrug resistance in microbes against antibiotics. The entry rate of antibiotics to the environment is much higher than its exclusion; therefore, efficient removal is a high priority to reduce the harmful impact of antibiotics on human health and the environment. Recent developments in cost-effective and efficient biochar preparation are noticeable for their effective removal. Moreover, biochar engineering advancements enhanced biochar remediation performance several folds more than in its pristine forms. Biochar engineering provides several new interactions and bonding abilities with antibiotic pollutants to increase remediation efficiency. Especially heteroatoms-doping significantly increased catalysis of biochar. The main focus of this review is to underline the crucial role of biochar in the abatement of emerging antibiotic pollutants. A detailed analysis of both native and engineered biochar is provided in this article for antibiotic remediation. There has also been discussion of how biochar properties relate to feedstock, production conditions and manufacturing technologies, and engineering techniques. It is possible to produce biochar with different surface functionalities by varying the feedstock or by modifying the pristine biochar with different chemicals and preparing composites. Subsequently, the interaction of biochar with antibiotic pollutants was compared and reviewed. Depending on the surface functionalities of biochar, they offer different types of interactions e.g., π-π stacking, electrostatic, and H-bonding to adsorb on the biochar surface. This review demonstrates how biochar and related composites have optimized for maximum removal performance by regulating key parameters. Furthermore, future research directions and opportunities for biochar research are discussed.

ZrO2-Ag2O nanocomposites encrusted porous polymer monoliths as high-performance visible light photocatalysts for the fast degradation of pharmaceutical pollutants

This work reports a unique ZrO₂-Ag₂O heterojunction nanocomposite uniformly dispersed on a macro-/meso-porous polymer monolithic template to serve as simple and effective visible light-driven heterogeneous plasmonic photocatalysts for water decontamination. The monolithic photocatalysts' structural properties and surface morphology are characterized using various surface and structural characterization techniques. The photocatalytic performance of the proposed photocatalysts is evaluated by optimizing multiple operational parameters. The photocatalytic properties of the fabricated monolithic nanocomposite are monitored through time-dependent photocatalytic disintegration of norfloxacin drug, a widely employed antimicrobial, with considerable aquatic persistence. The analytical results conclude that a (60:40) ZrO₂-Ag₂O nanocomposite embedded polymer monolith exhibits superior photocatalytic activity for the complete mineralization of norfloxacin molecules under optimized conditions of solution pH (3.0), photocatalyst quantity (100 mg), pollutant concentration (15 mg/L), photosensitizers (2.0 mM KBrO₃), visible light intensity (300 W/cm² tungsten lamp) and irradiation time (≤ 1 h). The proposed new-age inorganic-organic hybrid visible light photo-catalysts with superior structural and surface properties exhibit brilliant performance and fast responsiveness for water decontamination applications, in addition to their excellent chemical stability, high durability, multi-reusability, and cost-effectiveness.

Removal of Antimony(V) from Drinking Water Using nZVI/AC: Optimization of Batch and Fix Bed Conditions

Antimony (Sb) traces in water pose a serious threat to human health due to their negative effects. In this work, nanoscale zero-valent iron (Fe0) supported on activated carbon (nZVI) was employed for eliminating Sb(V) from the drinking water. To better understand the overall process, the effects of several experimental variables, including pH, dissolved oxygen (DO), coexisting ions, and adsorption kinetics on the removal of Sb(V) from the SW were investigated by employing fixed-bed column runs or batch-adsorption methods. A pH of 4.5 and 72 h of equilibrium time were found to be the ideal conditions for drinking water. The presence of phosphate (PO43-), silicate (SiO42-), chromate (CrO42-) and arsenate (AsO43-) significantly decreased the rate of Sb(V) removal, while humic acid and other anions exhibited a negligible effect. The capacity for Sb(V) uptake decreased from 6.665 to 2.433 mg when the flow rate was increased from 5 to 10 mL·min-1. The dynamic adsorption penetration curves of Sb(V) were 116.4% and 144.1% with the weak magnetic field (WMF) in fixed-bed column runs. Considering the removal rate of Sb(V), reusability, operability, no release of Sb(V) after being incorporated into the iron (hydr)oxides structure, it can be concluded that WMF coupled with ZVI would be an effective Sb(V) immobilization technology for drinking water.

Comparative Study of the Photocatalytic Hydrogen Evolution over Cd1-xMnxS and CdS-β-Mn3O4-MnOOH Photocatalysts under Visible Light

A series of solid solutions of cadmium and manganese sulfides, Cd_1−xMn_xS (x = 0–0.35), and composite photocatalysts, CdS-β-Mn₃O₄-MnOOH, were synthesized by precipitation with sodium sulfide from soluble cadmium and manganese salts with further hydrothermal treatment at 120 °C. The obtained photocatalysts were studied by the X-ray diffraction method (XRD), UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N₂ low temperature adsorption. The photocatalysts were tested in hydrogen production using a Na₂S/Na₂SO₃ aqueous solution under visible light (λ = 450 nm). It was shown for the first time that both kinds of photocatalysts possess high activity in hydrogen evolution under visible light. The solid solution Cd_0.65Mn_0.35S has an enhanced photocatalytic activity due to its valence and conduction band position tuning, whereas the CdS-β-Mn₃O₄-MnOOH (40–60 at% Mn) samples were active due to ternary heterojunction formation. Further, the composite CdS-β-Mn₃O₄-MnOOH photocatalyst had much higher stability in comparison to the Cd_0.65Mn_0.35S solid solution. The highest activity was 600 mmol g⁻¹ h⁻¹, and apparent quantum efficiency of 2.9% (λ = 450 nm) was possessed by the sample of CdS-β-Mn₃O₄-MnOOH (40 at% Mn).