Sono-photo hybrid process for the synergistic degradation of levofloxacin by FeVO4/BiVO4: Mechanisms and kinetics

Enhancing treatment performance of Chlorella pyrenoidosa on levofloxacin wastewater through microalgae-bacteria consortia: Mechanistic insights using the transcriptome

Microalgae-bacteria consortia (MBC) system has been shown to enhance the efficiency of microalgae in wastewater treatment, yet its effectiveness in treating levofloxacin (LEV) wastewater remains unexplored. This study compared the treatment of LEV wastewater using pure Chlorella pyrenoidosa (PA) and its MBC constructed with activated sludge bacteria. The results showed that MBC improved the removal efficiency of LEV from 3.50-5.41 % to 33.62-57.20 % by enhancing the growth metabolism of microalgae. The MBC increased microalgae biomass and extracellular polymeric substance (EPS) secretion, yet reduced photosynthetic pigment content compared to the PA. At the phylum level, Proteobacteria and Actinobacteriota are the major bacteria in MBC. Furthermore, the transcriptome reveals that the growth-promoting effects of MBC are associated with the up-regulation of genes encoding the glycolysis, the citrate cycle (TCA cycle), and the pentose phosphate pathway. Enhanced carbon fixation, coupled with down-regulation of photosynthetic electron transfer processes, suggests an energy allocation mechanism within MBC. The up-regulation of porphyrin and arachidonic acid metabolism, along with the expression of genes encoding LEV-degrading enzymes, provides evidence of MBC's superior tolerance to and degradation of LEV. Overall, these findings lead to a better understanding of the underlying mechanisms through which MBC outperforms PA in treating LEV wastewater.

An Efficient Approach for Advancing Performance in Rapid Detection Based on Molybdenum Disulfide Nanoflower Supported Binary Transition Metal Oxides

Binary transition metal oxides (BTMOs) have drawn considerable attention in recent years for their excellent catalytic properties and chemical stability in the sensing field. Regrettably, the loss of active site exposure originating from the agglomerate during preparation largely restricted their sensing applications. In this work, we report an efficient strategy for advancing the performance of BTMOs in rapid detection based on a 3D molybdenum disulfide nanoflower. The larger surface area, multiple active site exposures, and higher electrical conductivity promote the dispersion of BTMOs and the redox reaction of analytes on the surface of nanocomposites, thereby enhancing the sensitivity and widening the quantitative range. As a proof-of-method application, ferric vanadate (FeVO4) and ciprofloxacin (CIP) were chosen as model catalysts and analytes, respectively. This approach exhibits excellent sensitivity, selectivity, repeatability, and stability. The detection limit could be as low as 26.6 nM, and the linear range covered 3 orders of magnitude (from 0.1 to 500 μM). It also demonstrated good practicality in milk, honey, and drinking water with a recovery of 90.6% to 100.8%. To our knowledge, this is the first report on incorporating MoS2 into BTMOs for augmenting sensing performance in rapid detection.

Mechanistic insight into the impact of interaction between goethite and humic acid on the photooxidation and photoreduction of bifenthrin

Numerous application of pyrethroid insecticides has led to their accumulation in the environment, threatening ecological environment and human health. Its fate in the presence of iron-bearing minerals and natural organic matter under light irradiation is still unknown. We found that goethite (Gt) and humic acid (HA) could improve the photodegradation of bifenthrin (BF) in proper concentration under light irradiation. The interaction between Gt and HA may further enhance BF degradation. On one hand, the adsorption of HA on Gt may decrease the photocatalytic activity of HA through decreasing HA content in solution and sequestering the functional groups related with the production of reactive species. On the other hand, HA could improve the photocatalytic activity of Gt through extending light absorption, lowing of bandgap energy, hindering the recombination of photo-generated charges, and promoting the oxidation and reduction reaction on Gt surface. The increased oxygen vacancies on Gt surface along with the reduction of trivalent iron and the nucleophilic attack of hole to surface hydroxyl group contributed to the increasing photocatalytic activity of Gt. Electron paramagnetic resonance and quenching studies demonstrated that both oxidation species, such as hydroxyl radical (•OH) and singlet oxygen (1O2), and reducing species, such as hydrogen atoms (H•) and superoxide anion radical (O2•-), contributed to BF degradation in UV-Gt-HA system. Mass spectrometry, ion chromatography, and toxicity assessment indicated that less toxic C23H22ClF3O3 (OH-BF), C9H10ClF3O (TFP), C14H14O2 (OH-MBP), C14H12O2 (MBP acid), C14H12O3 (OH-MBP acid), and chloride ions were the main degradation products. The production of OH-BF, MPB, and TFP acid through oxidation and the production of MPB and TFP via reduction were the two primary pathways of BF degradation.

All-solid-state Z-scheme ZnFe-LDH/rGO/g-C3N5 heterojunction for enhanced sonophotocatalytic degradation of ciprofloxacin: Performance and mechanistic insights

The fabrication of all-solid-state Z-scheme sonophotocatalysts is vital for improving the transfer rate of photogenerated electrons to remove antibiotics present in wastewater. Herein, a novel indirect Z-scheme ZnFe-layered double hydroxide (LDH)/reduced graphene oxide (rGO)/graphitic carbon nitride (g-C3N5) heterojunction was synthesized using a simple strategy. The ZnFe-LDH/rGO/g-C3N5 (ZF@rGCN) ternary composites were systematically characterized using different techniques. Results revealed that the 15%ZF@rGCN catalyst achieved a ciprofloxacin (CIP) degradation efficiency of 95% via the synergistic effect of sonocatalysis and photocatalysis. The improved sonophotocatalytic performance of the ZF@rGCN heterojunction was attributed to an increase in the number of active sites, a Z-scheme charge-transfer channel in ZF@rGCN, and an extended visible light response range. The introduction of rGO further enhanced the charge-transfer rate and preserved the reductive and oxidative sites of the ZF@rGCN system, thereby affording additional reactive species to participate in CIP removal. In addition, owing to its unique properties, rGO possibly increased the absorption of incident light and served as an electronic bridge in the as-formed ZF@rGCN catalyst. Finally, the possible CIP degradation pathways and the sonophotocatalytic Z-scheme charge-migration route of ZF@rGCN were proposed. This study presents a new approach for fabricating highly efficient Z-scheme sonophotocatalysts for environmental remediation.

LDH/MXene Synergistic Carrier Separation Effects to Improve the Photoelectric Catalytic Activities of Bi2WO6 Nanosheet Arrays

Photoelectric catalysis is a green and efficient way to degrade pollutants, which has been paid more and more attention by researchers. Among them, Bi2WO3 has been proved to have excellent photocatalytic oxidation activity on its {001} facets. In this study, {001}-oriented facets with high exposure were successfully integrated into Bi2WO6 nanoplate arrays (Bi2WO6 NAs) to create a photoelectrode. This structure was grown in situ on an indium tin oxide (ITO) substrate. To promote photogenerated carrier separation efficiency and reduce agglomeration of Bi2WO6 photocatalysts, the electrochemical deposition of NiFe-layered double hydroxide (NiFe-LDH) and Ti3C2 (MXene) were introduced in this research to synergistically catalyze pollutant degradation. Morphology, spectral characterization, and electrochemical analysis jointly confirmed that the outstanding performance of hole capture behavior with LDH and electron conduction properties with MXene were the main reasons for the improvement in catalytic activity of the photoelectrode. Taking bisphenol A (BPA) as the model pollutant, the rate constant k of the NiFe-LDH/Ti3C2/Bi2WO6 NAs photoelectrode reaches 0.00196 min-1 under photoelectrocatalytic (PEC) conditions, which is 4.5 times that of the pure Bi2WO6 NAs photoelectrode. This work provides a new way to improve the reaction kinetics of the PEC degradation of pollutants.

Research progress on composite material of bismuth vanadate catalyzing the decomposition of Quinolone antibiotics

Since quinolone is a kind of synthetic broad-spectrum antibacterial drugs, with the widespread use of this class of antibiotics, the risk and harm to human health have been attendant to the sewage containing quinolones which are discharged into the environment. Photocatalysis is considered as a promising technology for antibiotic degradation for its strong redox properties and reaction rate. As a metal oxidizing substance, Bismuth vanadate (BiVO4) is such a popular and hot material for the degradation of organic pollutants recently due to its good photocatalytic activity and chemical stability. Numerous studies have confirmed that BiVO4 composites can overcome the shortcomings of pure BiVO4 and cleave the main structure of quinolone under photocatalytic conditions. This paper mainly outlines the research progress on the preparation of BiVO4 composites and the degradation of quinolone antibiotics from the perspective of improving the catalysis and degrading the efficiency mechanism of BiVO4 composites.

Efficient Degradation of Rhodamine B with the BiOCl/Bi2Fe4O9 Heterojunction Photocatalyst

BiOCl/Bi2Fe4O9 photocatalyst was prepared by a coprecipitation-hydrothermal method. The heterojunction structure generated by the composite of BiOCl and Bi2Fe4O9 reduced the electron-hole recombination efficiency and improved the degradation rate of RhB. At 240 min, 20% BiOCl/Bi2Fe4O9 represented the excellent degradation effect on 10 mg/L RhB; the degradation efficiency reached 99.56%; and the reaction rate constant was 0.01534 min-1, which was 5.76 times and 6.06 times that of Bi2Fe4O9 and BiOCl, respectively. The main active substance of the photocatalytic degradation of dyes was superoxide radical O2-·. Five cycles of the experiment proved the relative stability of BiOCl/Bi2Fe4O9.

Iron (II) phthalocyanine loaded tourmaline efficiently activates PMS to degrade pharmaceutical contaminants under solar light

Iron (II) phthalocyanine (FePc) is loaded on the surface of the tourmaline (TM) by the reflow method to obtain FePc/TM. This research effectively prevents the π-π stacking of FePc, increased the effective utilization rate of PMS activation under solar light, and further improved the catalytic performance of the catalytic system. The catalytic oxidation efficiency of FePc/TM on carbamazepine (CBZ) and sulfadiazine (SD) can reach 99% under solar light for 15 and 5 min, the total organic carbon (TOC) removal rate can reach 58% and 69% under solar light for 120 min. After 6 cycles, the CBZ removal rate remained above 95%. In addition, the FePc/TM catalytic system has an excellent removal rate for other pharmaceuticals. The results of spin-trapped electron paramagnetic resonance and classical quenching experiments show that FePc/TM can effectively activate PMS to generate active species under solar light, including superoxide radical (•O2-), singlet oxygen (1O2), hydroxyl radicals(•OH), and sulphate radicals (SO4•-). The intermediates of CBZ were identified by Ultra-high performance liquid chromatography and high resolution mass spectrometry, and the degradation pathway was proposed. As the reaction progresses, all CBZ and intermediates are reduced and converted into small acids, or mineralized to H2O, CO2. This work provides an alternative method for the design of efficient activation of PMS activation catalysts under solar light to eliminate residual pharmaceuticals in actual water bodies.

Mechanistic insight into humic acid-enhanced sonophotocatalytic removal of 17β-estradiol: Formation and contribution of reactive intermediates

In this study, humic acid (HA) enhanced 17β-estradiol (17β-E2) degradation by Er3+-CdS/MoS2 (ECMS) was investigated under ultrasonic and light conditions. The degradation reaction rate of 17β-E2 was increased from (14.414 ± 0.315) × 10-3 min-1 to (122.677 ± 1.729) × 10-3 min-1 within 90 min sonophotocatalytic (SPC) reaction with the addition of HA. The results of quenching coupled with chemical probe experiments indicated that more reactive intermediates (RIs) including reactive oxygen species (ROSs) and triplet-excited states were generated in the HA-enhanced sonophotocatalytic system. The triplet-excited states of humic acid (3HA*), hydroxyl radical (•OH), and superoxide radical (•O2-) were the dominant RIs for 17β-E2 elimination. In addition, the energy- and electron-transfer process via coexisting HA also account for 12.86% and 29.24% contributions, respectively. The quantum yields of RIs in the SPC-ECMS-HA system followed the order of 3HA* > H2O2 > 1O2 > •O2-> •OH. Moreover, the spectral and fluorescence characteristics of HA were further analyzed during the sonophotocatalytic reaction process. The study expanded new insights into the comprehension of the effects of omnipresent coexisting HA and RIs formation for the removal of 17β-E2 during the sonophotocatalytic process.

Sustainable functionalized smectitic clay-based nano hydrated zirconium oxides for enhanced levofloxacin sorption from aqueous medium

In this study, the functionalized smectitic clay (SC)-based nanoscale hydrated zirconium oxide (ZrO-SC) was successfully synthesized and utilized for the adsorptive removal of levofloxacin (LVN) from an aqueous medium. The synthesized ZrO-SC and its precursors (SC and hydrated zirconium oxide (ZrO(OH)₂)) were extensively characterized using various analytical methods to get insight into their physicochemical properties. The results of stability investigation confirmed that ZrO-SC composite is chemically stable in strongly acidic medium. The surface measurements revealed that ZrO impregnation to SC resulted in an increased surface area (six-fold higher than SC). The maximum sorption capacity of ZrO-SC for LVN was 356.98 and 68.87 mg g^-1 during batch and continuous flow mode studies, respectively. The mechanistic studies of LVN sorption onto ZrO-SC revealed that various sorption mechanisms, such as interlayer complexation, π-π interaction, electrostatic interaction, and surface complexation were involved. The kinetic studies of ZrO-SC in the continuous-flow mode indicated the better applicability of Thomas model. However, the good fitting of Clark model suggested the multi-layer sorption of LVN. The cost estimation of the studied sorbents was also assessed. The obtained results indicate that ZrO-SC is capable of removing LVN and other emergent pollutants from water at a reasonable cost.

Insight into the effects of H2SO4 and HNO3 acidification processes on the properties of coal as an enhanced adsorbent for ciprofloxacin residuals: Steric and energetic studies

A sub-bituminous natural coal sample (R.C) was treated with sulfuric acid (S.C) and nitric acid (N.C) as modified products and enhanced adsorbents for obtaining ciprofloxacin (CFX) antibiotic residuals from water. The characterization studied demonstrates enhancement in the surface area and the incorporation of new active oxygenated, sulfur-bearing, and nitrogen-bearing chemical groups into the structure of coal samples. This was reflected in the adsorption capacities that were enhanced from 164.08 mg/g (R.C) to 489.2 mg/g and 518.5 mg/g for N.C and S.C, respectively. The impact of the acid modification processes was evaluated based on the energetic and steric properties of their adsorption systems considering the parameters of the advanced monolayer equilibrium model with one energy site. The determined occupied active sites’ density of R.C (46.32–61.44 mg/g), N.C (168.7–364.9 mg/g), and S.C (159.2–249.9 mg/g) reflects an increase in the quantities of active centers after the acid treatment processes, especially with HNO3. The higher efficiencies of the active sites of S.C to adsorb more CFX molecules (n = 2.08–2.31) than N.C (n = 1.41–2.16) illustrate its higher adsorption capacity. The energetic investigation [adsorption (˂40 kJ/mol) and Gaussian (˂8 kJ/mol) energies] suggested adsorption of CFX by N.C and S.C mainly by physical processes such as van der Waals forces, hydrogen bonding, dipole bonding, and π–π interactions. Moreover, the determined thermodynamic functions including entropy, internal energy, and free enthalpy reflect the spontaneous and endothermic uptake of CFX on the surfaces of N.C and S.C.

Fabrication of Z-scheme Bi7O9I3/g-C3N4 heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants

Chromium(VI) (Cr(VI)), a highly toxic metal ion, generally co-exists with organic pollutants in industrial effluents. The clean and effective technology for water purification is an imperative issue but still a challenging task. A series of Bi₇O₉I₃/g-C₃N₄ (BOI/CN) composites modified by lignin-derived carbon quantum dots (CQDs) were fabricated by hydrothermal method and applied for synchronous photocatalytic removal of Cr (Ⅵ) and levofloxacin (LEV). With the modification of CQDs in BOI/CN heterojunction, the 0.5-CQD/BOI/CN photocatalyst (0.5% content of CQDs) exhibited stronger light-harvesting capacity, more efficient charge separation, and faster electron transfer. Compared to those of BOI (51.2%), CN (36.8%), and BOI/CN (74.4%), the photoreduction efficiency of Cr(VI) reached up to 100% by 0.5-CQD/BOI/CN under 60 min of light irradiation, together with 94.8% degradation efficiency of LEV. The degradation of LEV was dominantly controlled by active species (•OH and •O₂^-) identified by electron paramagnetic resonance analysis and free radical trapping experiments. The intermediates of LEV were determined by LC-MS and the possible degradation pathway was speculated in combination with density functional theory calculation, involving defluorination, decarboxylation, quinolone rings opening, and piperazine moieties oxidation reactions. This work provides an advanced strategy for the fabrication of high-efficiency CQDs-based Z-scheme photocatalysts for environmental remediation.

Anchoring ZnO on spinel cobalt ferrite for highly synergic sono-photo-catalytic, surfactant-assisted PAH degradation from soil washing solutions

In this study, the photocatalytic activity of ZnO was effectively improved via its combination with spinel cobalt ferrite (SCF) nanoparticles. The catalytic performance of ZnO@SCF (ZSCF) was investigated in coupling with UV irradiation and ultrasound (US), as a heterogeneous sono-photocatalytic process, for the decontamination of phenanthrene (PHE) from contaminated soil. Soil washing tests were conducted in a batch environment, after extraction assisted by using Tween 80. Several characterization techniques such as XRD, FESEM-EDS, BET, TEM, UV-vis DRS, PL and VSM were utilized to determine the features of the as-prepared catalysts. ZSCF showed an excellent catalytic activity toward degradation of PHE in the presence of US and UV with a significant synergic effect. It was found that more than 93% of PHE (35 mg/L) and 87.5% of TOC could be eliminated by the integrated ZSCF/US/UV system under optimum operational conditions (pH: 8.0, ZSCF: 1.5 g/L, UV power: 6.0 W and US power: 70 W) within 90 min of reaction. After five times of use, ZSCF illustrated good reusability in the decontamination of PHE (87%) and TOC (79%). Quenching tests revealed the contribution of h⁺, HO^• and e^- species during PHE degradation over ZSCF/UV/US and an S-scheme photocatalytic mechanisms was proposed for the possible charge transfer routes under the ZSCF system. This study provides the important role of SCF in enhancing the ZnO photocatalytic activity due to its high performance, easy recovery and excellent durability, which it make an efficient and promising catalyst in environmental clean-up applications.

Novel insights into the mechanism of periodate activation by heterogeneous ultrasonic-enhanced sludge biochar: Relevance for efficient degradation of levofloxacin

In this study, a novel heterogeneous ultrasonic (US)-enhanced sludge biochar (SBC) activated periodate (PI) system was established and explored for the rapid removal of levofloxacin in the aqueous environment. This study focused on the mechanisms of US-enhanced SBC co-activation of PI for levofloxacin degradation. The results indicated that US and SBC exhibited a remarkable synergistic reinforcing activation effect on PI compared to single PI activation systems. The SBC/US/PI system achieved approximately 95% of levofloxacin removal, 51.5% of TOC removal, and 22% of dechlorination rate within 60 min with virtually no heavy metals released into the water matrix. In addition, the acute ecotoxicity of the solutions treated with the SBC/US/PI system was substantially reduced. The presence of IO₃^•, ^•OH, ¹O₂ and O₂^•- were identified in the SBC/US/PI system using quenching experiments and EPR technology while ^•OH and ¹O₂ were the predominant reactive species. Mechanistic studies have suggested that the cavitation effect of ultrasonic improved the dispersion and mass transfer efficiency of SBC and accelerated the desorption process of SBC. Possible pathways of levofloxacin degradation were proposed. This study provides a novel and promising strategy for the efficient removal of emerging contaminants such as antibiotics from the water matrix.

Europium-Doped Y2O3-Coated Diatomite Nanomaterials: Hydrothermal Synthesis, Characterization, Optical Study with Enhanced Photocatalytic Performance

Eu-doped Y2O3 coated diatomite nanostructures with variable Eu3+ contents were synthesized by a facile hydrothermal technique. The products were characterized by means of energy dispersive X-ray photoelectron spectroscopy (EDX), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller (BET), UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy techniques. As claimed by PXRD, the particles were crystallized excellently and attributed to the cubic phase of Y2O3. The influence of substitution of Eu3+ ions into Y2O3 lattice caused a redshift in the absorbance and a decrease in the bandgap of as-prepared coated compounds. The pore volume and BET specific surface area of Eu-doped Y2O3-coated diatomite is greater than uncoated biosilica. The sonophotocata-lytic activities of as-synthesized specimens were evaluated for the degradation of Reactive Blue 19. The effect of various specifications such as ultrasonic power, catalyst amount, and primary dye concentration was explored.