Microwave irradiation directly excites semiconductor catalyst to produce electric current or electron-holes pairs

Insights into structural and functional regulation of chalcopyrite and enhanced mechanism of reactive oxygen species (ROS) generation in advanced oxidation process (AOP): A review

Chalcopyrite, renowned for its distinctive mixed redox-couple characteristics, exhibits excellent electron transfer properties both on its surface and within its crystal structure. This unique characteristic has attracted significant attention in various fields, including optics, electronics, and magnetism, as well as demonstrated remarkable catalytic efficacy in the environmental field. The rapid and effective electron transfer capability of a catalyst is crucial for advanced oxidation processes (AOPs). However, the performance of CuFeS2 in AOPs is hindered by its low electron transfer efficacy. This review aims to summarize the key steps and mechanisms of chalcopyrite-induced AOPs and provide strategies for enhancing effective electron transfer efficacies by controlling the structure and function of synthetic/natural chalcopyrite. These strategies include enhancing the catalytic performance of chalcopyrite and constructing composites to enhance catalytic activity (e.g., chelating agents, heterojunctions). Additionally, the factors influencing the generation of reactive oxygen species in chalcopyrite-induced AOPs are investigated, such as the types and properties of oxidants (e.g., H2O2, peroxymonocarbonate), the microstructure of catalysts, and reaction conditions in catalytic systems (e.g., pH values, dosage, temperature). Future perspectives on the applications of chalcopyrite are presented at the end of this paper. Overall, this review assists in narrowing the scope of chalcopyrite studies in AOPs and aids researchers in optimizing synthetic/natural catalysts for contaminant treatment.

Viral inactivation using microwave-enhanced membrane filtration

Pathogenic viruses (e.g., Enteroviruses, Noroviruses, Rotaviruses, and Adenovirus) present in wastewater, even at low concentrations, can cause serious waterborne diseases. Improving water treatment to enhance viral removal is of paramount significance, especially given the COVID-19 pandemic. This study incorporated microwave-enabled catalysis into membrane filtration and evaluated viral removal using a model bacteriophage (MS2) as a surrogate. Microwave irradiation effectively penetrated the PTFE membrane module and enabled surface oxidation reactions on the membrane-coated catalysts (i.e., BiFeO₃), which thus elicited strong germicidal effects via local heating and radical formation as reported previously. A log removal of 2.6 was achieved for MS2 within a contact time as low as 20 s using 125-W microwave irradiation with the initial MS2 concentration of 10⁵ PFU∙mL^-1. By contrast, almost no inactivation could be achieved without microwave irradiation. COMSOL simulation indicates that the catalyst surface could be heated up to 305 ^oC with 125-W microwave irradiation for 20 s and also analyzed microwave penetration into catalyst or water film layers. This research provides new insights to the antiviral mechanisms of this microwave-enabled catalytic membrane filtration.

Oxidative degradation of p-chlorophenol by the persulfate-doped Fe-Mn bimetallic hydroxide, the parametrical significance, and systematical optimization

Aqueous Fe(II)-catalyzed activation commonly deteriorates the oxidation performance of persulfate (PS) to the treatment of organic contaminants. In this study, a PS-doped layered bimetallic hydroxide (Fe-Mn hydroxide) was synthesized to construct a heterogeneously catalytic system to solve the issue brought by homogeneity. The molar ratio of Fe(II) to Mn(II) and the mass ratio of PS to Fe-Mn hydroxide both had a significant impact on the catalytic degradation of p-CP. Reaction temperatures engaged in the most essential role in influencing the degradation and removal of p-chlorophenol (p-CP). The optimal combination of factors for the preparation of PS-hydroxide and the treatment of p-CP was finally determined by significance analysis. The degradation process was appropriately fitted by the pseudo-first-order kinetic model. The benzene ring in p-CP was broken by PS-hydroxide during the adsorption. The surface modification of PS-hydroxide caused by the valence transition of Mn was beneficial to the adsorption and catalytic degradation of p-CP.

Sustainable chemical processing of flowing wastewater through microwave energy

Iron oxide nanostructured catalysts have emerged as potential candidates for efficient energy conversion and electrochemical energy storage devices. However, synthesis and design of nanomaterial plays a key role in its performance and efficiency. Herein, we describe a one-pot solution combustion synthesis (SCS) of α-Fe₂O₃ with glycine as a fuel, and a subsequent reduction step to produce iron-containing catalysts (i.e., Fe₃O₄, Fe-Fe₃O₄, and Fe⁰). The synthesized iron-based nanoparticles were investigated for methyl orange (MO) degradation through Microwave (MW) energy under continuous flow conditions. Fe-Fe₃O₄ showed higher MO degradation efficiency than α-Fe₂O₃, Fe₃O₄ and Fe⁰ at low absorbed MW power (i.e. 5-80 W). The enhanced degradation efficiency is associated to the combination of higher availability of electron density and higher heating effect under MW energy. Investigation of dielectric properties showed relative dielectric loss of Fe₃O₄, Fe-Fe₃O₄, and Fe⁰ as 3847, 2010, and 1952, respectively. The calculated average local temperature by the comparative analysis of MW treatment with conventional thermal (CT) treatment showed a marked thermal effect of MW-initiated MO degradation. This work highlights the potential of microwave-driven water depollution under continuous-flow processing conditions and demonstrates the positive impact that earth-abundant Fe catalyst synthesized by green SCS method can have over the treatment of wastewater.

Microfluidic Ratiometric Photoelectrochemical Biosensor Using a Magnetic Field on a Photochromic Composite Platform: A Proof-of-Concept Study for Magnetic-Photoelectrochemical Bioanalysis

Integrating a microfluidic sensor with a ratiometric photoelectrochemical (PEC) strategy to build a bioanalysis device for actual sample testing is often limited to large-volume space-resolution equipment and wavelength-dependent or potential-dependent paired photoactive materials. This work reports a microfluidic ratiometric magnetic-photoelectrochemical (M-PEC) biosensor on the photochromic composite platform to solve the above problems. In particular, as a proof-of-concept study, the platform Bi₂WO_6-x/amorphous BiOCl nanosheets/Bi₂S₃ (p-BWO-s) mediated by photochromic color centers and the magnetic photoactive secondary antibody marker ZnFe₂O₄@Ag₂O are integrated on the microfluidic biosensor. By enhancement of the photochromic color centers, p-BWO-s outputs a considerable photocurrent signal. Meanwhile, the photoactivity of the secondary antibody marker can be changed with a magnetic field; thus, different photocurrent signals can be obtained to realize ratiometric detection. The quenching photocurrent signal without the magnetic field and the difference photocurrent signal under the magnetic field are quantitatively related to the target concentration, which unfolds a novel general strategy for bioanalysis. Different from traditional ratiometric PEC biosensors, this work characterizes the first ratiometric PEC biosensor based on an external magnetic field. Generally speaking, combined with different biorecognition cases, this scheme with good expansibility brings a unique new perspective.

Microwave-initiated recombination of hydrogen bonds of a perylene diimide supramolecule for PPCP photodegradation

Rec-PDI-HCl with “recombinant holes” shows the capability to form an intermolecular polarized electric field to enhance its photocatalytic properties.

Microwave irradiation assisted sodium hexametaphosphate modification on the alkali-activated blast furnace slag for enhancing immobilization of strontium

An inadvertent leakage of ⁹⁰Sr into the environment can induce an easy accumulation in biosphere and cause a continuous radiation to the surrounding ecosystem. In this study, sodium hexametaphosphate (Na₆O₁₈P₆) was employed to modify the blast furnace slags (BFS) to enhance the chemical stabilization of Sr²⁺ ions in the BFS-based cementitious materials. Microwave irradiation (MW) was used to further increase the binder activity of BFS samples and strengthened the mechanical strengths and durability of BFS-based blocks. A combination of experimental factors including the mass ratio of Na₆O₁₈P₆ to BFS-Sr_0.1 of 15%, the ratio of solid to liquid of 1:4 mg/L, the output power of 650 W, and the activation time of 3 min was most conductive to achieving an optimal microwave-irradiation process. Four extraction solutions were sorted by their leaching abilities following as MgSO₄ solution > H₂SO₄ solution > CH₃OOH solution > deionized (DI) water based on their leaching results. Compared with microwave irradiation, an addition of Na₆O₁₈P₆ to BFS samples obtained a better compressive strength for BFS-based blocks. However, a microwave-irradiation treatment was more effective in improving the resistances of blocks to gamma irradiation and thermal-thaw changes. Exposing to gamma irradiation over 6 months and enduring to thermal-thaw tests over 15 cycles, the microwave-treated blocks only lost 3.29% and 2.23% of leaching removal efficiencies in deionized water, respectively. Microwave irradiation increased the mechanical strengths of BFS-based blocks and inhibited leaching of Sr²⁺ ions from matrices mainly by strengthening hydration reactions and Sr²⁺ encapsulation.

Re-Potentiation of β-Lactam Antibiotic by Synergistic Combination with Biogenic Copper Oxide Nanocubes against Biofilm Forming Multidrug-Resistant Bacteria

Biofilm-associated tissue and device infection is a major threat to therapy. The present work aims to potentiate β-lactam antibiotics with biologically synthesized copper oxide nanoparticles. The synergistic combination of amoxyclav with copper oxide nanoparticles was investigated by checkerboard assay and time-kill assay against bacteria isolated from a burn wound and a urinary catheter. The control of biofilm formation and extracellular polymeric substance production by the synergistic combination was quantified in well plate assay. The effect of copper oxide nanoparticles on the viability of human dermal fibroblasts was evaluated. The minimum inhibitory concentration and minimum bactericidal concentration of amoxyclav were 70 μg/mL and 140 μg/mL, respectively, against Proteus mirabilis and 50 μg/mL and 100 μg/mL, respectively, against Staphylococcus aureus. The synergistic combination of amoxyclav with copper oxide nanoparticles reduced the minimum inhibitory concentration of amoxyclav by 16-fold against P. mirabilis and 32-fold against S. aureus. Above 17.5 μg/mL, amoxyclav exhibited additive activity with copper oxide nanoparticles against P. mirabilis. The time-kill assay showed the efficacy of the synergistic combination on the complete inhibition of P. mirabilis and S. aureus within 20 h and 24 h, respectively, whereas amoxyclav and copper oxide nanoparticles did not inhibit P. mirabilis and S. aureus until 48 h. The synergistic combination of amoxyclav with copper oxide nanoparticles significantly reduced the biofilm formed by P. mirabilis and S. aureus by 85% and 93%, respectively. The concentration of proteins, carbohydrates, and DNA in extracellular polymeric substances of the biofilm was significantly reduced by the synergistic combination of amoxyclav and copper oxide nanoparticles. The fibroblast cells cultured in the presence of copper oxide nanoparticles showed normal morphology with 99.47% viability. No cytopathic effect was observed. Thus, the study demonstrated the re-potentiation of amoxyclav by copper oxide nanoparticles.