High-efficiency periodate activation by CeO2 under solar light via coordination environment modulation: Synergy between facets and cu species modification.

Biochar-activated periodate (PI) is a promising technology toward antibiotic wastewater purification. However, the mechanism of pyrolysis temperature on PI activation efficiency by biochar has not yet been revealed. Herein, this work selected water hyacinth stems as raw materials to prepare biochar with different pyrolysis temperatures (400, 500, 600, and 700 °C), and applied it to degrade tetracycline (TC) wastewater through PI activation. The results show that biochar with a pyrolysis temperature of 700 °C (BC-700) possesses the best TC degradation performance (∼100% within 30 min). Besides, the degradation of TC by BC-700 is less interfered by coexisting anions and water matrix, and exhibits good reusability. Quenching experiments and open circuit voltage tests verified that IO3•, 1O2, and reactive complex BC-PI* are active species involved in TC degradation. In addition, by constructing the relationship between biochar surface properties and degradation rate kobs, it was revealed that the dominant role of pyridinic N in PI adsorption and formation of reactive complexes as well as the promotion of sp2-hybridized carbon in the electron transfer process. This work provides novel insights into the application of biochar in antibiotic wastewater treatment via PI activation.

Insight into the activation of periodate by Mn(II) for rapid degradation of sulfadiazine: Performance and mechanisms

Metal-organic frameworks (MOFs) are highly versatile materials with tunable chemical and structural properties, making them promising for triboelectric nanogenerators (TENGs) and electrocatalysis. However, achieving precise control over MOF coordination structures to optimize facet-dependent properties remains challenging. Here, a facile and scalable dual-solvent synthesis strategy is presented to fabricate dendrite Co-2-methylimidazole MOF (ZIF-67-D), enabling tailored preferred facet and coordination environments. Using density functional theory (DFT) calculations and synchrotron-based X-ray absorption spectroscopy, it is demonstrated that ZIF-67-D, enriched with (112) facets, features a reduced Co coordination number and enhanced electron-donating ability compared to the conventionally (011) facet-dominated rhombic dodecahedron ZIF-67 (ZIF-67-R). This facet engineering boosts TENG charge density by 2.4-fold, OER current density by 9.9-fold (@1.65V), and HER current density by 1.9-fold (@-0.3V). The (112)/(011) facet ratio can be also tuned to precisely alter TENG output. Moreover, the optimized ZIF-67-D shows excellent stability, maintaining electrolyzer performance for 72h and enabling TENG devices even in high humidity. Consequently, ZIF-67-D-based TENG (D-TENG) devices exhibit robust energy generation and power ZIF-67-D||ZIF-67-D electrolyzers for continuous hydrogen (H2) production. These findings introduce a new paradigm for converting mechanical energy into sustainable chemical energy, offering insights into facet engineering for high-performance energy harvesting systems.

<p indent="0mm">Although ozone has been widely used in water treatment due to its strong oxidation and sterilization abilities, it reveals slow reaction rate with refractory organic pollutant. Heterogeneous catalytic ozonation (HCO) technology has been widely used for removal of refractory organic compounds and improving the biodegradation properties of wastewater. Metal oxides are stable and effective catalysts for HCO. However, not much choice can satisfy the critical requirements of water treatment, such as environmental safety, economic efficiency, availability, catalytic activity and recovery. Crystal facet engineering tunes the atomic arrangement on the surface of metal oxide, resulting in the exposure of specific crystal facets. The type and ratio of exposed crystal facets can significantly affect the efficiency of ozone decomposition, pollutant degradation and disinfection by-product generation during the HCO process. This review comprehensively summarizes and comments on the current crystal facet control methods for the synthesis of HCO catalysts for the first time. The methods are classified into bottom-up methods and top-down methods; the former contains crystalline surface adsorption, solvent conditioning and supercritical oxidation methods, while the later includes thermal decomposition and direct calcination methods. The enhancement mechanism of HCO processes induced by crystal facet engineering is discussed. The modified HCO catalysts are strengthened not only in absorption function, revealing different adsorption behaviors for O₃, water molecule or organic pollutants, but also in free radical producing rate due to the change of surface micro environments. The surface atomic arrangement and coordination mode of modified HCO catalysts may also be changed, leading to the more rapid electron transfer. Finally, the applications of integrated crystal facet modified HCO catalysts in water treatment for the past few decades are synthetically summarized, including the degradation of organic matter, enhanced sterilization, bromate and toxic organic by-products control in HCO processes. The crystal facet engineering modified HCO technologies used in full scale applications or coupled with other advanced oxidation techniques are also presented. Considering that the crystal facet engineering modified HCO material still faces some problems in the depth of scientific exploration and the breadth of practical applications, several significant issues to be solved are listed in the current review, including how to establish the theoretical system for directionally controlling the crystal face exposure, how to mass-produce the facet engineering modified HCO catalysts economically and efficiently, and how to guarantee the stability of the facet engineering modified catalysts during the HCO processes. To address these issues, some future research directions and priorities are proposed. The intrinsic relationship between crystal facet regulation and HCO performance and mechanism should be deeply explored through the intersection of precise synthesis, advanced characterization and theoretical simulation. More types of facet engineering modified HCO catalysts can be applied in practical treatment processes by selecting low-cost green synthesis methods, and so the application will be widened.

The article is devoted to the actual task of studying a dielectric, which is an alternative to silicon dioxide in metal-insulator-semiconductor (MIS) structures. In metal-silicon dioxide-silicon structures, upon going to nanosize, the thickness of the dielectric film decreases so much that it becomes tunnel-transparent and its breakdown voltage decreases. These phenomena can be eliminated by replacing silicon dioxide with a dielectric with a higher dielectric constant. These dielectrics primarily include oxides of transition and rare-earth metals. The parameters and characteristics of the MIS structure are determined by various factors, but the properties of the dielectric and the dielectric-semiconductor interface play a special role. In previous works of the authors, it was theoretically proved that cerium dioxide from a number of candidate dielectrics should have the best quality of the interface with silicon. This work is devoted to a study aimed at determining the flat-band voltage and capacitance of MIS structures and at assessing the quality of the cerium dioxide-silicon interface. The study is carried out by the method of capacitance-voltage characteristics. For this, the high-frequency capacitance-voltage characteristics of the aluminum – cerium dioxide – silicon structures were measured at different temperatures. The capacity of the space charge region (SCR) in the enrichment and weak inversion modes of the near-surface layer of a semiconductoris considered. It is shown that the dependence of this capacitance in the (–2) degree on the voltage at the metal electrode cs-2(VG) is linear. The intersection of this line with the abscissa axis makes it possible to determine the flat-band voltage. The slope tangent of this linear dependence makes it possible to determine the energy density of the charge at the dielectric–semiconductor interface. It is shown that the charge density at the cerium dioxide – silicon interface corresponds to the minimum values of the charge density at the silicon dioxide – silicon interface. The absence of a shift in the capacitance-voltage characteristics of the structures under study with a change in temperature indicates the stability of the charge at the cerium dioxide - silicon interface.

A comparative study of reactive manganese species and electron transfer pathway in oxidation efficiency and environmental impact: Which activation route for potassium permanganate is optimal?

Melts based on mixtures of alkali and/or alkaline earth halides are considered as prospective media for electrowinning rare earth metals as well as for pyrochemical reprocessing spent nuclear fuels. Fluoride or mixed fluoride-chloride baths can be operated at high temperatures yielding molten rare earth metals (REMs) thus simplifying separation of the metal and salt. One of the problems in using fluoride melts is possible formation of fluorine at the anode. This can be avoided by adding a rare earth oxide to the melt both as the source of REM and oxide ions. The latter will be oxidized to oxygen producing carbon mono- or dioxide at the anode. The limiting factor for feeding the electrolysis bath with REM oxides is their solubility in the halide melt.The aim of the present study was determining the effect of temperature and melt composition on solubility of REM oxides in fused halides. The experiments were performed in CaCl2–CaF2 mixtures containing 20 or 75 mol. % CaF2; BaCl2–BaF2 mixtures containing 15 or 73 mol. % BaF2; equimolar CaF2–BaF2 mixture and NaCl–NaF eutectic mixture (34 mol. % NaF). Solubility of REM oxides was determined by the method of isothermal saturation. Time required for reaching the equilibrium between solid REM oxides and fused salts was determined in a preliminary set of experiments. To compare the behavior of 4f- and 5f-elements, solubility of uranium dioxide was also measured.The measurements were performed at the temperatures up to 1400 oC under argon atmosphere. The lower limit of the temperature range varied from 700 to 1100 oC depending on the melting temperatures of the salt mixtures used. Oxides of yttrium, lanthanum, cerium, praseodymium, neodymium and samarium were selected for the study. To assess a possible mutual influence of rare earth elements on solubility of their oxides in fused salts the solubility of a mixture of REM oxides was determined in a separate series of experiments and concentrations of individual REMs in the melt was determined.Solubility of REM oxides increased with increasing temperature and an example of effect of temperature on solubility of neodymium oxide in various melts is shown in Fig.Fig. Concentration of neodymium in alkali and alkaline halide based melts saturated with Nd2O3. Melt: CaCl2–CaF2 20 mol. % (1); CaCl2–CaF2 75 mol. % (2); BaCl2–BaF2 73 mol. % (3); BaCl2–BaF2 15 mol. % (4); CaF2–BaF2 50 mol. % (5; and NaCl–NaF 34 mol. % (6). Figure 1

The results of research and refinement of the technology for producing complex modifiers (CM) by the carbon thermal method from agglomerated raw materials and their use in rolling mill production are presented. These studies were preceded by a study of the modifying effect of individual rare-earth metals (REM) of the cerium group (cerium, lanthanum and samarium) on the crystallization parameters and structure formation of roll cast irons at various cooling rates that take place in real roll form. It was found that the minimum required amount of modifier, which allowed to achieve the maximum level of decrease in the temperature of the onset of eutectic crystallization, depended on the cooling rate. An increase in the cooling rate led to a shift in this amount of modifier towards lower concentrations. Studies on the development of modes for obtaining complex modifiers using the technology of formed ore-carbon materials containing in one piece a reducing agent and oxides of various rare-earth metals of the cerium group were carried out in laboratory and industrial conditions. In laboratory conditions, the studies were carried out on the installation, which consisted of a high-speed heating unit, a forming unit, a sintering and annealing unit. The results of the study showed that the sheer influence of oxides on coal in ore-coal mixtures grew in a number of oxides: cerium dioxide, samarium oxide, lanthanum oxide, and the introduction of lanthanum oxide weakened significantly, and the introduction of cerium dioxide – to a lesser extent. Samarium oxide exerted a thinning effect, more significant than cerium dioxide, but less than lanthanum oxide. According to the developed technological regimes, molded carbon-ore materials containing individual oxides of various rare-earth metals were obtained and used for smelting CM. Modification by these modifiers within the studied concentrations stimulated the crystallization of austenite.

Efficiency of cerium oxide (CeO2) nano-catalyst in degrading the toxic and persistent 4-nitrophenol in aqueous solution

Metoprolol removal and mineralization by TiO2 and iron pillared clay nanocomposite: Impact of operating parameters, water matrices, and solar light.

This study presents the synthesis of floatable sodium alginate/water lettuce-derived biochar/hollow glass microsphere (SA/WLBC/HGM) beads and their application as activators of periodate (PI) for the degradation of carbofuran (CBF) in a continuous-flow packed-bed photoreactor. The degradation mechanisms and the optimization of continuous-flow photoreactor systems remain insufficiently explored in the existing literature. Under the optimized conditions (catalyst dosage of 4 g, PI concentration of 0.8 g L−1, flow rate of 2 mL min−1, reaction time of 200 min, neutral pH, and ambient temperature), the SA/WLBC/HGMs–PI/light system achieved a CBF degradation efficiency of 94.11%. Under the same conditions, degradation efficiencies of 89.77, 84.50, and 78.12% were obtained for diazinon, malathion, and chlorpyrifos, respectively. Singlet oxygen species were the main contributors to the degradation process, and the degradation mechanism was explored. Toxic iodinated byproducts were not detected in the SA/WLBC/HGMs–PI/light degradation system, and most of the generated intermediates were less toxic compared to CBF. The SA/WLBC/HGMs beads demonstrated high stability under five successive cycles with a total loss of 1.86% in degradation efficiency. The degradation performance was evaluated in the presence of inorganic ions, natural organic matter, and different water matrices. Techno-economic analysis demonstrated the economic feasibility of the treatment system for mixed-pesticide wastewater, as evidenced by a relatively short payback period of 5.5 years, a positive net present value, and a profitability index exceeding unity. This study presents a stable, efficient, and inexpensive continuous-flow packed-bed photoreactor that can be employed for the remediation of real-world industrial effluents.

The electron transfer process (ETP) is able to avoid the redox cycling of catalysts by capturing electrons from contaminants directly. However, the ETP usually leads to the formation of oligomers and the reduction of oxidants to anions. Herein, the charge-confined Fe single-atom catalyst (Fe/SCN) with Fe-N3S1 configuration was designed to achieve ETP-mediated contaminant activation of the oxidant by limiting the number of electrons gained by the oxidant to generate 1O2. The Fe/SCN-activate periodate (PI) system shows excellent contaminant degradation performance due to the combination of ETP and 1O2. Experiments and DFT calculations show that the Fe/SCN-PI* complex with strong oxidizing ability triggers the ETP, while the charge-confined effect allows the single-electronic activation of PI to generate 1O2. In the Fe/SCN + PI system, the 100% selectivity dechlorination of ETP and the ring-opening of 1O2 avoid the generation of oligomers and realize the transformation of large-molecule contaminants into small-molecule biodegradable products. Furthermore, the Fe/SCN + PI system shows excellent anti-interference ability and application potential. This work pioneers the generation of active species using ETP’s electron to activate oxidants, which provides a perspective on the design of single-atom catalysts via the charge-confined effect.

Photocatalytic degradation of aqueous Congo red dye pollutants by rare-earth metal oxide (CeO2) nanorods

Photocatalytic technologies are essential for addressing energy and environmental challenges. Metal halide perovskites (MHPs) have emerged as promising photocatalysts owing to their adjustable bandgaps, high efficiency, and broad visible-light absorption capabilities. However, despite their potential, MHPs encounter obstacles that impede their effective use. These challenges include the necessity to maintain stability in aqueous and oxygen-rich environments as well as at elevated temperatures. Moreover, issues such as electron-hole recombination and limited oxidation activity during photocatalytic processes present significant hurdles that must be overcome for the successful application of MHPs. This review addresses the latest advancements in the application of MHPs for photocatalytic tasks, such as hydrogen production, carbon dioxide reduction, degradation of organic contaminants, and removal of nitrogen oxides. The first part of the review addresses the basic principles of photocatalysis, the crystalline structures, coordination environments, and distinguishing features of MHP photocatalysts. A range of strategies has been investigated to improve the performance of MHP photocatalysts and address challenges such as low stability, excessive charge recombination, and limited active sites. These strategies involve controlling morphology, forming heterojunctions, modifying surfaces or interfaces, and encapsulating the materials. The paper further examines the ongoing challenges and future prospects of MHP photocatalysts, highlighting their promising potential and significant role in a wide range of photocatalytic applications. Highlights Structures, properties, coordination environments, and basic principles of metal halide perovskite photocatalysts. Comprehensive summary of efficient photocatalytic strategies activity and stability of metalhalideperovskites. Current progresses in the photocatalytic H2generation, CO2reduction, organics degradation, and NOx remediation. Current challenges and future prospective of metal halide perovskite as efficient photocatalysts.

A novel FeS2@g-C3N4 composite with enhanced photo-Fenton catalytic activity for pollutant degradation