Search Results (12)

Bimetallic catalysts can effectively enhance the catalytic degradation efficiency of peroxymonosulfate (PMS), which is usually attributed to the enhancement of electron transfer, but currently, there is no clear explanation of the mechanism of how the electron transfer is enhanced. A nitrogen-doped Fe/Mn composite biochar (FeMn-NBC) was co-constructed by hydrothermal synthesis and high-temperature calcination. The FeMn-NBC activated PMS more efficiently than the monometallic one due to the enhanced electron transfer between Fe and Mn. The FeMn-NBC/PMS system activated PMS with Mn as the active center, and the high oxidation state of Mn⁴⁺ promoted the acceleration of the PMS adsorption of the generation of Mn²⁺/Mn³⁺. This gaining effect accelerated the electron cycling between Fe²⁺/Fe³⁺ and Mn²⁺/Mn³⁺/Mn⁴⁺, which enhanced the PMS catalysis to generate free radicals (•OH, SO₄^•− and •O₂⁻) and non-radicals (¹O₂) for the efficient degradation of diisobutyl phthalate (DIBP). Benefiting from this gaining effect, the degradation rate of DIBP by the FeMn-NBC/PMS system was increased by 2.43 and 3.38 times compared to Fe-NBC and Mn-NBC. The bimetallic-enhanced electron transfer mechanism proposed in this study facilitated the development of efficient catalysts for more efficient and selective removal of organic pollutants. Full article

Acesulfame potassium (ACE) is an emerging pollutant with the potential to induce a range of health hazards. In this study, waste natural pyrite (with some oxides on its surface) was washed and used as an activator to activate potassium peroxomonosulfate (PMS) to degrade ACE in water. The experimental results demonstrate that waste natural pyrite with an oxidized layer exhibited a significant degradation effect on ACE. Under conditions of 0.7 g/L pyrite and 60 μM PMS, a degradation rate of 99.3% for ACE was achieved within 15 min, and the mineralization rate reached 15.3% within 30 min. In addition, concerning its applicability, waste natural pyrite demonstrates strong activation ability within a pH range of 3 to 7. It is important to note that while HCO₃⁻ and Ca²⁺ can influence the effectiveness, other common anions and cations do not significantly affect the degradation process. Mechanistic studies reveal that the primary active species in the waste natural pyrite/PMS system were sulfate radicals (SO₄^•−) as well as hydroxyl radicals (^•OH), which contributed 50.6% and 36.9%, respectively. In addition, the analysis of ACE degradation products indicates that no highly toxic intermediates were generated during the degradation process. Overall, this study underscores the outstanding performance of waste natural pyrite as an activator, providing a safe, efficient, and cost-effective approach for degrading organic pollutants like ACE. Full article

Advanced oxidation processes (AOPs) based on activated persulfate (PS) are gradually being employed in the treatment of novel pollutants. In this study, an efficient and reliable CoNiFe-layered double hydroxide (LDH) was prepared by a hydrothermal method, which could effectively activate peroxomonosulfate (PMS) and cause free sulfate radical (SO₄^•−) oxidation to decompose atrazine (ATZ). The degradation rate of ATZ was greater than 99% within 60 min at pH 7 when the initial concentration of ATZ was 10 mg·L⁻¹, and the dosages of PMS and activator were 0.6 mM and 80 mg·L⁻¹. The analysis of ATZ degradation confirmed the reusability of the activator and its strong structural stability. The generation of four free radicals was analyzed and confirmed, and the influence on the degradation reaction was SO₄^•− > O₂^•− > ¹O₂ > •OH. The analytical results showed that the metal ions reacted with HSO₅⁻ in PMS to cause an oxidation–reduction cycle change in the valence state of the metal ions and generated the primary factor affecting the degradation reaction—SO₄^•−. Nine degradation intermediates with reduced toxicity were detected and possible ATZ degradation pathways were deduced, thus confirming the activation mechanism of CoNiFe-LDH. Full article

The pyrolysis of metal-organic frameworks (MOFs) is a popular strategy for the synthesis of nanoporous structures. Polymetallic oxides (POMs) are a class of polyhedral structural compounds with unique physicochemical properties. Little effort has been paid to evaluate MOF-POM hybrid-derived materials for peroxomonosulfate (PMS) activation. In this study, a cobalt-based MOF, ZIF-67, together with three types of POMs (phosphomolybdic acid, silicotungstic acid, and phosphotungstic acid), were used as precursors for the synthesis of PMS activation catalyst via pyrolysis. Three T-POMs@ZIF-67 nanohybrids (T-PMo@ZIF-67, T-SiW@ZIF-67, and T-PW@ZIF-67) were obtained by pyrolyzing the prepared precursors at 500 °C. Furthermore, the prepared T-POMs@ZIF-67 nanomaterials were evaluated for the catalytic activation of PMS in the degradation of levofloxacin (LEV). The results showed that the LEV degradation rate could reach 91.46% within 30 min under the optimized conditions when T-PW@ZIF-67 was used as the PMS activation catalyst. The catalytic efficiency of the catalyst decreased by only 9.63% after five cycles, indicating that the material has good stability. This work demonstrates the great potential of POMs@MOF derivatives for application in the field of wastewater treatment. Full article

Modification of catalysts by multi-heteroatom doping (S, P, B) is an effective way to improve the peroxomonosulfate activation performance of catalysts. In recent years, highly toxic and persistent trace organic contaminants have been frequently detected in water. Consequently, we proposed the advanced oxidation processes of peroxomonosulfate activated by multi-heteroatom doped Fe@CN (X-Fe@CN) to eliminate trace organic contaminants. The physical phases of X-Fe@CN and its precursors were characterized by X-ray diffraction and scanning electron microscopy. In evaluating the catalytic properties and iron ion leaching of X-Fe@CN-activated PMS for the removal of dicamba and atenolol, B-Fe@CN and PB-Fe@CN were selected and optimized. The active sites of the catalysts were characterized by X-ray photoelectron spectroscopy and Raman. The pathways of PMS activation by B-Fe@CN and PB-Fe@CN were identified in combination with electron paramagnetic resonance and electrochemical experiments. Defects, O-B-O and pyrrolic nitrogen on the surface of B-Fe@CN could adsorb and activate PMS to produce SO₄^•−, ·OH and ¹O₂. Further doping with P enhanced the electron transfer on the catalyst surface, thus accelerating the activation of peroxomonosulfate. This study compared the effects of multi-heteroatom modifications and further demonstrated the synergistic effect between P and B, which can provide a theoretical basis for the selection of multi-heteroatom doped catalysts in water treatment. Full article

Metal–organic framework (MOF) materials possess a large specific surface area, high porosity, and atomically dispersed metal active sites, which confer excellent catalytic performance as peroxide (peroxodisulfate (PDS), peroxomonosulfate (PMS), and hydrogen peroxide (H₂O₂)) activation catalysts. However, the limited electron transfer characteristics and chemical stability of traditional monometallic MOFs restrict their catalytic performance and large-scale application in advanced oxidation reactions. Furthermore, the single-metal active site and uniform charge density distribution of monometallic MOFs result in a fixed activation reaction path of peroxide in the Fenton-like reaction process. To address these limitations, bimetallic MOFs have been developed to improve catalytic activity, stability, and reaction controllability in peroxide activation reactions. Compared with monometallic MOFs, bimetallic MOFs enhance the active site of the material, promote internal electron transfer, and even alter the activation path through the synergistic effect of bimetals. In this review, we systematically summarize the preparation methods of bimetallic MOFs and the mechanism of activating different peroxide systems. Moreover, we discuss the reaction factors that affect the process of peroxide activation. This report aims to expand the understanding of bimetallic MOF synthesis and their catalytic mechanisms in advanced oxidation processes. Full article

Perovskite is of burgeoning interest in catalysis, principally due to such material having high thermal stability, modifiable variability, ferromagnetism, and excellent catalytic performance in peroxomonosulfate (PMS) activation. In this study, the SrCo_xMn_1−xO₃ perovskites with different Mn doping were synthesized by a facile sol-gel method for peroxymonosulfate (PMS) activation to degrade Rhodamine B. The obtained SrCo_0.5Mn_0.5O₃ perovskite exhibited the best catalytic efficiency, as Rhodamine B (40 mg/L) was removed completely within 30 min. In the system of SrCo_0.5Mn_0.5O₃–PMS, several reactive species were produced, among which sulfate radicals and the singlet oxygen mainly contributed to Rhodamine B degradation. The relatively high catalytic performance could be attributed to the coupled redox cycle between Mn and Co, and the abundant oxygen vacancies. Moreover, the SrCo_0.5Mn_0.5O₃ catalyst showed excellent stability and reusability, maintaining a high catalytic activity after several cycling tests. This study demonstrated that the Mn doping of SrCoO₃ could not only enhance the B-site activation in SrCo_0.5Mn_0.5O₃ but also enrich the oxygen vacancies, thus improving the efficiency of PMS activation. Full article

We examined the relationship between the intrinsic structure of a carbocatalyst and catalytic activity of peroxomonosulfate (PMS) activation for acetaminophen degradation. A series of nitrogen-doped carbon nanotubes with different degrees of oxidation was synthesized by the unzipping method. The linear regression analysis proposes that pyridinic N and graphitic N played a key role in the catalytic oxidation, rather than pyrrolic N and oxidized N. Pyridinic N reinforce the electron population in the graphitic framework and initiate the non-radical pathway via the formation of surface-bound radicals. Furthermore, graphitic N forms activated complexes (carbocatalyst-PMS*), facilitating the electron-transfer oxidative pathway. The correlation also affirms that -C=O was dominantly involved as a main active site, rather than -C-OH and -COOH. This study can be viewed as the first attempt to demonstrate the relationship between the fraction of N-groups and activity, and the quantity of O-groups and activity by active species (quenching studies) was established to reveal the role of N-groups and O-groups in the radical and non-radical pathways. Full article

The tetramethylammonium hydroxide (TMAH)-controlled alkaline etching of nickel hexacyanoferrate (NiHCF) mesocrystals is explored. The alkaline etching enables the formation of hollow framework structures with an increased surface area, the exposure of active Ni and Fe sites and the retention of morphology. The ambient reaction conditions enable the establishment of a sustainable production. Our work reveals novel perspectives on the eco-friendly synthesis of hollow and colloidal superstructures for the efficient degradation of the organic contaminants rhodamine-B and bisphenol-A. In the case of peroxomonosulfate (PMS)-mediated bisphenol-A degradation, the rate constant of the etched mesoframes was 10,000 times higher indicating their significant catalytic activity. Full article

N-oxides of N-heteroaromatic compounds find widespread applications in various fields of chemistry. Although the strictly planar aromatic structure of 1,10-phenanthroline (phen) is expected to induce unique features of the corresponding N-oxides, so far the potential of these compounds has not been explored. In fact, appropriate procedure has not been reported for synthesizing these derivatives of phen. Now, we provide a straightforward method for the synthesis of a series of mono-N-oxides of 1,10-phenanthrolines. The parent compounds were oxidized by a green oxidant, peroxomonosulfate ion in acidic aqueous solution. The products were obtained in high quality and at good to excellent yields. A systematic study reveals a clear-cut correlation between the basicity of the compounds and the electronic effects of the substituents on the aromatic ring. The UV spectra of these compounds were predicted by DFT calculations at the TD-DFT/TPSSh/def2-TZVP level of theory. Full article

In this investigation, the terminal double bonds of the side chain epoxidized cardanol glycidyl ether (SCECGE) molecule were further epoxidized in the presence of Oxone^® (potassium peroxomonosulfate) and fluorinated acetone. Regular methods for the double bond epoxidation are not effective on the terminal double bonds because of their reduced electronegativity with respect to internal double bonds. The terminal double bond functionality of the SCECGE was epoxidized to nearly 70%, increasing the epoxy functionality of SCECGE from 2.45 to 2.65 epoxies/molecule as measured using proton magnetic nuclear resonance (¹H-NMR). This modified material—side chain epoxidized cardanol glycidyl ether with terminal epoxies (TE-SCECGE)—was thermally cured with cycloaliphatic curing agent 4-4′-methylenebis(cyclohexanamine) (PACM) at stoichiometry, and the cured polymer properties, such as glass transition temperature (T_g) and tensile modulus, were compared with SCECGE resin cured with PACM. The T_g of the material was increased from 52 to 69 °C as obtained via a dynamic mechanical analysis (DMA) while the tensile modulus of the material increased from 0.88 to 1.24 GPa as a result of terminal double bond epoxidation. In addition to highlighting the effects of dangling side groups in an epoxy network, this modest increase in T_g and modulus could be sufficient to significantly expand the potential uses of amine-cured cardanol-based epoxies for fiber reinforced composite applications. Full article

New, more efficient methods of wastewater treatment, which will limit the harmful effects of textile dyes on the natural environment, are still being sought. Significant research work suggests that catalysts based on transition metal complexes can be used in efficient and environmentally friendly processes. In this context, a number of compounds containing manganese have been investigated. A suitable catalyst should have the capacity to activate a selected oxidant or group of oxidants, in order to be used in industrial oxidation reactions. In the present study we investigated the ability of Mn^III(TPPS), where TPPS = 5,10,15,20-tetrakis(4-sulphonatophenyl)-21H,23H-porphyrine, to activate five different oxidants, namely hydrogen peroxide, peracetic acid, sodium hypochlorite, potassium peroxomonosulfate and sodium perborate, via the formation of high valent Mn(TPPS)-oxo complexes. Kinetic and spectroscopic data showed that the oxidation process is highly pH dependent and is strongly accelerated by the presence of carbonate in the reaction mixture for three of the five oxidizing agents. The highest efficiency for the oxidation of Mn^III(TPPS) to high-valent Mn(TPPS)-oxo complexes, was found for peracetic acid at pH ≈ 11 in 0.5 M carbonate solution, which is at least an order of magnitude higher than the rate constants found for the other tested oxidants under similar conditions. Full article