Removal of the UV Filter Benzophenone-2 in Aqueous Solution by Ozonation: Kinetics, Intermediates, Pathways and Toxicity

<p>Benzophenone-2 (BP-2) is an important type of UV filter that has been widely used and detected in the aquatic environment with greater estrogenic toxicity. In our work, the removal of BP-2 with the initial concentration of 25 mg L⁻¹ was first carried out by ozone at different pH (ranging from pH 3.0 to 11.0), and we found a positive correlation between the pH values and the degradation efficiency of BP-2, among which the more rapid removal of BP-2 in alkaline condition was observed than acidic and neutral conditions. For the influence of aqueous humic acid (HA, the concentration ranged from 0 ppm to 100 ppm), the degradation rate of BP-2 by ozonation was first increased with the growth of humic acid concentration (from 0 ppm to 5 ppm), reaching to maximum at 5 ppm of HA and subsequently decreased with the growth of HA concentration (from 5 ppm to 100 ppm). Fourteen intermediate products in the ozonation process were distinguished by an electrospray time-of-flight mass spectrometer and then two degradation pathways were proposed. Through the theoretical calculation, we found the carbanyl group of BP-2 has the most reactivity to be easily attacked by ozone, providing us guides and theoretical basis on the supposed intermediate products. Furthermore, the <i>P. phosphoreum</i> acute toxicity test was conducted to evaluate the potential toxicity during the ozonation process.</p

pH-Responsive Pesticide-Loaded Hollow Mesoporous Silica Nanoparticles with ZnO Quantum Dots as a Gatekeeper for Control of Rice Blast Disease

Nanotechnology-enabled pesticide delivery systems have been widely studied and show great prospects in modern agriculture. Nanodelivery systems not only achieve the controlled release of agrochemicals but also possess many unique characteristics. This study presents the development of a pH-responsive pesticide nanoformulation utilizing hollow mesoporous silica nanoparticles (HMSNs) as a nanocarrier. The nanocarrier was loaded with the photosensitive pesticide prochloraz (Pro) and then combined with ZnO quantum dots (ZnO QDs) through electrostatic interactions. ZnO QDs serve as both the pH-responsive gatekeeper and the enhancer of the pesticide. The results demonstrate that the prepared nanopesticide exhibits high loading efficiency (24.96%) for Pro. Compared with Pro technical, the degradation rate of Pro loaded in HMSNs@Pro@ZnO QDs was reduced by 26.4% after 24 h ultraviolet (UV) exposure, indicating clearly improved photostability. In a weak acidic environment (pH 5.0), the accumulated release of the nanopesticide after 48 h was 2.67-fold higher than that in a neutral environment. This indicates the excellent pH-responsive characteristic of the nanopesticide. The tracking experiments revealed that HMSNs can be absorbed by rice leaves and subsequently transported to other tissues, indicating their potential for effective systemic distribution and targeted delivery. Furthermore, the bioactivity assays confirmed the fungicidal efficacy of the nanopesticide against rice blast disease. Therefore, the constructed nanopesticide holds great prospect in nanoenabled agriculture, offering a novel strategy to enhance pesticide utilization

Enhanced permanganate oxidation of phenolic pollutants by alumina and potential industrial application

In this study, we found that alumina (Al2O3) may improve the degradation of phenolic pollutants by KMnO4 oxidation. In KMnO4/Al2O3 system, the removal efficiency of 2,4-Dibromophenol (2,4-DBP) was increased by 26.5%, and the apparent activation energy was decreased from 44.5 kJ/mol to 30.9 kJ/mol. The mechanism of Al2O3-catalytic was elucidated by electrochemical processes, X-ray photoelectron spectroscopy (XPS) characterization and theoretical analysis that the oxidation potential of MnO4− was improved from 0.46 V to 0.49 V. The improvement was attributed to the formation of coordination bonds between the O atoms in MnO4− and the empty P orbitals of the Al atoms in Al2O3 crystal leading to the even-more electron deficient state of MnO4−. The excellent reusability of Al2O3, the good performance on degradation of 2,4-DBP in real water, the satisfactory degradation of fixed-bed reactor, and the enhanced removal of 6 other phenolic pollutants demonstrated that the KMnO4/Al2O3 system has satisfactory potential industrial application value. This study offers evidence for the improvement of highly-efficient MnO4− oxidation systems

A cost-effective approach to measurements of fluorophore temperature sensitivity and temperature change with reasonable accuracy

Abstract The demand for measuring fluorophore temperature sensitivity and temperature change in chemical or biological samples has spurred the search for effective methods. While infrared (IR) light-based thermal devices are popular, they are limited to surface temperature measurement. Fluorescence-based thermometry, which utilizes intensity, lifetime, polarization, and spectrum change, provides the temperature information directly from the samples and can have high temporal and spatial resolution. However, measuring fluorescence can be tricky and expensive. A cost-effective approach to achieving reasonable accuracy is highly desired. This study introduces such an approach, employing a light-emitting diode (LED) for fluorophore excitation and a laser diode (LD) for sample heating, with a phone camera recording fluorescence changes. A data processing method converts the video into digital data, processed through digital filters. Utilizing a small-volume cuvette enhances heating efficiency. This study serves as a practical guide for inexperienced individuals, including students, instructors, and researchers, facilitating entry into the field and navigating the complexities of fluorescence-based thermometry

Rapid Removal of Tetrabromobisphenol A by Ozonation in Water: Oxidation Products, Reaction Pathways and Toxicity Assessment

<div><p>Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants and has attracted more and more attention. In this work, the parent TBBPA with an initial concentration of 100 mg/L was completely removed after 6 min of ozonation at pH 8.0, and alkaline conditions favored a more rapid removal than acidic and neutral conditions. The presence of typical anions and humic acid did not significantly affect the degradation of TBBPA. The quenching test using isopropanol indicated that direct ozone oxidation played a dominant role during this process. Seventeen reaction intermediates and products were identified using an electrospray time-of-flight mass spectrometer. Notably, the generation of 2,4,6-tribromophenol was first observed in the degradation process of TBBPA. The evolution of reaction products showed that ozonation is an efficient treatment for removal of both TBBPA and intermediates. Sequential transformation of organic bromine to bromide and bromate was confirmed by ion chromatography analysis. Two primary reaction pathways that involve cleavage of central carbon atom and benzene ring cleavage concomitant with debromination were thus proposed and further justified by calculations of frontier electron densities. Furthermore, the total organic carbon data suggested a low mineralization rate, even after the complete removal of TBBPA. Meanwhile, the acute aqueous toxicity of reaction solutions to <i>Photobacterium Phosphoreum</i> and <i>Daphnia magna</i> was rapidly decreased during ozonation. In addition, no obvious difference in the attenuation of TBBPA was found by ozone oxidation using different water matrices, and the effectiveness in natural waters further demonstrates that ozonation can be adopted as a promising technique to treat TBBPA-contaminated waters.</p></div

Proposed reaction pathways of TBBPA ozonation.

<p>Molecular ion clusters observed in MS spectra for the identified products are given below their respective structures. Possible transformation of inorganic bromine species was shown in green dash line box.</p

Photodegradation of Polyfluorinated Dibenzo‑<i>p</i>‑Dioxins in Organic Solvents: Experimental and Theoretical Studies

Eighteen polyfluorinated dibenzo-<i>p</i>-dioxins (PFDDs) were synthesized by pyrolysis of fluorophenols. Using a 500 W Xe lamp as the light source, the PFDDs photodegradation kinetics in <i>n</i>-hexane were investigated. The photolysis reactions obeyed the pseudo-first-order rate equation, and higher fluorinated PFDDs tended to photolyze more slowly. Theoretically calculated parameters reflecting the molecular structural properties were used to develop a new model of PFDDs photolysis rates. The results indicated that the substitution pattern for fluorine atoms and the C–O bond length were major factors in the photolysis of PFDDs. We selected octafluorinated dibenzo-<i>p</i>-dioxin (OFDD) as a representative PFDDs to explore the influence of solvent on the photolysis rate of PFDDs, and the results indicated that neither the polarity nor donor hydrogen of organic solvents are independent influencing factors. Mechanistic pathways for the photolysis of OFDD in <i>n</i>-hexane were first studied. The results indicated that photodegradation of OFDD produces octafluorinated dihydroxybiphenyls, octafluorinated phenoxyphenols, and fluorinated phenols. The major pathway for photodegradation of OFDD was C–O bond cleavage. Defluorination reactions did not occur during the photolysis process

Formation of Halogenated Polyaromatic Compounds by Laccase Catalyzed Transformation of Halophenols

Laccases are a type of extracellular enzyme produced by fungi, bacteria, and plants. Laccase can catalyze one-electron oxidation of a variety of phenolic compounds using molecular oxygen as the electron acceptor. In this study, transformation of halophenols (XPs) in laccase-catalyzed oxidation processes was explored. We first examined the intrinsic reaction kinetics and found that the transformation of XPs appeared first order to the concentrations of both XPs and laccase. A numerical model was developed to describe the role of humic acid (HA) in this process. It was demonstrated that HA could reverse the oxidation of XPs by acting as the inner filtrator of XP radical intermediates formed upon reactions between the substrates and laccase. The extent of such reversion was proportional to HA concentration. MS analysis in combination with quantum chemistry computation suggested that coupling products were generated. XPs coupled to each via CC or COC pathways, generating hydroxyl polyhalogenated biphenyl ethers (OH-PCDEs) and hydroxyl polyhalogenated biphenyls, respectively. Many of these polyhalogenated products are known to be hazardous to the ecosystem and human health, but they are not synthetic chemicals. This study shed light on their genesis in the environmental media