Photolysis Process Research Articles

Bifenthrin’s Environmental Fate: An Insight Into Its Soil Sorption and Degradation Studies

To fully comprehend each pesticide’s behavior and interactions with soil and the environment, a thorough and nuanced analysis of each one is thought necessary. In this study, 10 randomly selected heterogeneous soil samples, each with distinct characteristics, were subjected to sorption trials as well as disintegration tests using biodegradation, hydrolysis, and photolysis. For sorption tests, the batch equilibrium approach was used, which revealed a dependence on the soils’ physicochemical characteristics. Bifenthrin’s distribution coefficient (Kd) varied from 7.27 to 25.89 μg·ml−1, with R2 values varying from 0.92 to 0.99. Each soil physicochemical characteristic was associated with the various sorptive outcomes, which suggested an exothermic adsorptive reaction based on the negative thermodynamic values. The hydrolysis, soil‐induced biodegradation, and photolysis processes had the shortest half‐lives of bifenthrin, measuring 13.5 days, 12 days, and 121.5 days, respectively. According to these findings, bifenthrin has a moderate amount of binding and stability in soil, which makes partial decomposition of parent and daughter molecules challenging. This research advances our knowledge of bifenthrin’s deteriorating processes and aids in the creation of cutting‐edge strategies for ecological restoration using natural processes.

Photolysis characteristics and influencing factors of adenosine 5′-monophosphate in seawater

Environmental context Organophosphorus (OP) is bioavailable to phytoplankton with photolysis can play an important role in the process. The photolysis behaviour of an OP (adenosine 5′-monophosphate, AMP) in seawater was investigated, and AMP can release inorganic phosphate under environmentally relevant light conditions, indicating OP photodegradation might be important in the phosphorus biogeochemical cycle. The results are helpful to further understand the bioavailability and cycle of OP in marine environment. Rationale Organic phosphorus (OP) is a potential source of bioavailable phosphorus for phytoplankton through photolysis and other degradation processes. Therefore, OP photodegradation plays an important role in phosphorus biogeochemical cycle. Methodology Taking adenosine 5′-monophosphate (AMP) as a model OP, we investigated the photolysis behaviour in seawater and discussed the mechanism. The photolysis dynamics were studied based on the inorganic phosphorus production at appropriate time intervals, which was analysed by spectrophotometric molybdenum blue method. The effects of medium, light and radicals were investigated. Results It was found that AMP can release inorganic phosphate under photosynthetically active radiation and ultraviolet (UV) with UVB being the most reactive band. The degradation of AMP in seawater was lower than that in deionised water under the same conditions, and the fresh seawater was more beneficial than aged seawater. The kinetics could be described by a pseudo-first order equation. Fe3+ can promote the photolysis due to the generation of ·OH radicals, while within the range of this study, changes of Fe3+ content have no substantial effect on the promotion. The influence of ethanol and tetrahydrofuran as radical inhibitor showed evident inhabitation to the degradation, indicating that ·OH and 1O2 played an important role in the process, and ·OH seemed more important than 1O2. Discussion OP photodegradation is of importance in the phosphorus biogeochemical cycle. Varying properties of the medium and light can affect the OP transformation in seawater. The results are helpful to further understand the bioavailability and cycle of OP in the marine environment.

INCHEM-Py v1.2: a community box model for indoor air chemistry

Abstract. The Indoor CHEMical model in Python, INCHEM-Py, is an open-source and accessible box model for the simulation of the indoor atmosphere and is a refactor (rewrite of source code) and significant development of the INdoor Detailed Chemical Model (INDCM). INCHEM-Py creates and solves a system of coupled ordinary differential equations that include gas-phase chemistry, surface deposition, indoor–outdoor air change, indoor photolysis processes and gas-to-particle partitioning for three common terpenes. It is optimised for ease of installation and simple modification for inexperienced users, while also providing unfettered access to customise the physical and chemical processes for more advanced users. A detailed user manual is included with the model and updated with each version release. In this paper, INCHEM-Py v1.2 is introduced, and the modelled processes are described in detail, with benchmarking between simulated data and published experimental results presented, alongside discussion of the parameters and assumptions used. It is shown that INCHEM-Py achieves excellent agreement with measurements from an experimental campaign which investigate the effects of different surfaces on the concentrations of different indoor air pollutants. In addition, INCHEM-Py shows closer agreement to experimental data than INDCM. This is due to the increased functionality of INCHEM-Py to model additional processes, such as deposition-induced surface emissions. A comparative analysis with a similar zero-dimensional model, AtChem2, verifies the solution of the gas-phase chemistry. Published community use cases of INCHEM-Py are also presented to show the variety of applications for which this model is valuable to further our understanding of indoor air chemistry.

Elucidating the performance of UV-based photochemical processes for the removal of trace organic contaminants: Degradation and toxicity evaluation

In this study, the performance of standalone ultraviolet (UV) photolysis and UV-based advanced oxidation processes (AOPs), namely, UV/hydrogen peroxide, UV/chlorine, UV/persulphate, and UV/permonosulphate, were investigated for the degradation of 31 trace organic contaminants (TrOCs). Under the tested conditions, standalone UV photolysis did not achieve effective removal of TrOCs. To improve the degradation efficiency of UV photolysis, four different oxidants were added individually to the test solution. The effect of these oxidants in the absence of UV irradiation was also explored and only chlorine showed promising degradation of some contaminants. During the chlorination of 31 investigated TrOCs, only six demonstrated greater than 50% degradation. The combined UV-based AOPs demonstrated much improved degradation (ranging from 65 to 100%) depending on TrOC-structure and oxidant concentration. The UV/hydrogen peroxide process showed similar degradation of TrOCs, irrespective of the functional groups (i.e., electron withdrawing groups, EWGs and electron donating groups, EDGs) present in their structures. Conversely, the UV/sulphate and UV/chlorine based processes achieved better degradation of the TrOCs with EDGs in their structures. TrOCs degradation improved up to 40% when oxidants concentrations were increased from 0.1 to 1 mM, and further increasing the concentration to 2 mM did not improve degradation. Toxicity evaluation using bioluminescence test (BLT assay) demonstrated that except for UV/hydrogen peroxide, all UV-based AOPs increased the toxicity of the treated effluent, indicating generation of toxic by-products. This study elucidates the performance of four different UV-based AOPs for the removal of commonly detected diverse TrOCs for the first time.

Accumulation of Ag(0) Single Atoms at Water/Mineral Interfaces during Sunlight-Induced Reduction of Ionic Ag by Phenolic DOM.

Silver (Ag) undergoes a complex and dynamic Ag+/Ag0 cycle under environmental conditions. The Ag+ → Ag nanoparticles (AgNPs) transformation due to the combined actions of sunlight, O2, and dissolved organic matter has been a well-known environmental phenomenon. In this study, we indicate that this process may be accompanied by a pronounced accumulation of Ag(0) single atoms (Ag-SAs) on the minerals' surfaces. According to spherical aberration-corrected scanning transmission electron microscopy and high-energy-resolution X-ray adsorption fine structure analyses, humic acid (HA) and phenol (PhOH) can induce Ag-SAs accumulation, whereas oxalic acid causes only AgNPs deposition. Ag-SAs account for more than 20 wt % of total Ag(0) on the γ-Al2O3 surfaces during HA- and PhOH-mediated photolysis processes. HA also causes Ag-SAs to accumulate on two other prevalent soil minerals, SiO2 and Fe2O3, and the fractions of Ag-SAs are about 15 wt %. Our mechanism studies suggest that a phenolic molecule acts as a reducing agent of Ag+ and a stabilizer of Ag-SAs, protecting Ag-SAs against autocatalytic nucleation.

Effective photoelectrocatalysis of levofloxacin antibiotic with Ti/IrO2[sbnd]Nb2O5 in environmental samples

This work reports the development and application of a highly efficient catalyst based on IrO2 and Nb2O5 for the degradation of the antibiotic Levofloxacin (LFX) in simulated and real surface water samples. The IrO2Nb2O5 films, which were obtained by modified Pechini method, were deposited on a titanium substrate, leading to the production of Ti/IrO2Nb2O5 electrode. After being subjected to morphological, structural and electrochemical characterization, the Ti/IrO2Nb2O5 electrode was applied for the degradation of LFX using different processes, including electrolysis (EC) and photoelectrolysis (PhEC), and the results obtained were compared to that of UV–Vis irradiation-based photolysis. The application of the PhEC process led to a relatively higher and faster removal of LFX in the water matrices investigated, where 100% degradation rate and about 70% mineralization rate were obtained at the end of 1.5 h of treatment, compared to the individual photolysis and EC processes. The results obtained from quenching tests showed that LFX degradation under the PhEC process may be associated with the presence of active radicals, such as HO•, SO4•− and O2•−, in addition to the e−/h+ pair formed with the incidence of light during treatment. Apart from excellent photoelectrocatalytic activity and high stability, the Ti/IrO2Nb2O5 electrode exhibited high electrochemically active surface area (ECSA). The excellent results obtained from the application of the PhEC process in terms of TOC removal and the remarkable catalytic properties of Ti/IrO2Nb2O5 point to the high efficiency of the system proposed in this study when applied for the treatment and removal of organic pollutants from real water samples.

Direct photodegradation of internally mixed sodium chloride and malonic acid single aerosols: Impact of the photoproducts on the hygroscopic properties of the particles

Sea-salt aerosols (SSA) are one of the key natural aerosols in our atmosphere, consisting predominantly of sodium chloride (NaCl). Throughout their atmospheric transport, these aerosols undergo complex internal mixing, giving rise to a rich variety of inorganic and organic species, including dicarboxylic acids. This study investigates firstly the composition and deliquescence properties of coarse particles containing pure malonic acid (MA2, CH2(COOH)2) and internally mixed NaCl and MA2, by means of an acoustic levitation system coupled with a Raman microspectrometer. Secondly, we report here the first experimental observation and characterization of the products arising from photochemical reactions under UV–Visible irradiation (338 ≤ λ ≤ 414 nm) in the absence of an oxidant under acoustic levitation conditions in MA2 and NaCl/MA2 aerosols. Furthermore, the impact of photodegradation on the hygroscopic properties of these particles is examined. We confirmed the irreversible formation of monosodium malonate (NaMA, HOOCCH2COONa), which coexists with NaCl or MA2 on non-irradiated particles. We also demonstrated the formation of oxalic acid (OA2, HOOC–COOH) within irradiated MA2 droplets and the appearance of glyoxylic acid (GlyA, HCOCOOH) in NaCl containing droplets. The photolysis process exerts a marked effect on the hygroscopic properties of the particles, resulting in a shift in deliquescence transitions toward higher relative humidity (RH) values. This study contributes to the understanding of the intricate physicochemical processes involved in SSA during their atmospheric transport. Likewise, this work sheds light on the impacts of these types of aerosols on cloud formation and climate change.

Molecular understanding on ultraviolet photolytic degradation of cyano liquid crystal monomers

Cyano liquid crystal monomers (LCMs) are proposed as emerging chemical pollutants with persistent, bioaccumulative, and toxic properties. Herein, five cyano LCMs, including 4-cyano-4′-ethylbiphenyl (2CB), 4-Butyl-4′-cyanobiphenyl (4CB), 4-cyano-4′-ethoxybiphenyl (2OCB), 4-(trans-4-Ethylcyclohexyl)benzonitrile (2CHB) and 4-(trans-4-Vinylcyclohexyl)benzonitrile (2eCHB), were selected to investigate the reaction kinetics and excited state characteristic variations with their molecular structures by ultraviolet (UV) photolysis. Theoretical calculations reveal that the benzene ring, ethoxy and double bond can deeply alter the electron distribution of cyano LCMs. This will affect the exciton separation ability, excitation properties and active sites to electrophilic attack, causing the distinction in photolysis efficiency. Due to the effective charge separation during local excitation (LE) process and the property of being most susceptible to electrophilic attack by 1O2 and O2•−, 2eCHB with double bond exhibits the largest degradation rate. Conversely, the weakest exciton separation of 2OCB with ethoxy during charge transfer (CT) process limits its subsequent sensitized photolysis process. The molecular orbital and fragment contributions to holes and electrons further deepen the understanding of the excited states charge transfer. This study confirmed that the intrinsic molecular structure, chemical nature and existing sites directly defined the excitation and decomposition activity in the UV photolysis of cyano LCMs.

Real-time investigation into thermal and photo decomposition of ruthenium complexes [Ru(acac)2(tmp-mian)] and [Ru(acac)2(tmp-bian)] in acetonitrile by aerodynamic thermal breakup droplet ionization mass spectrometry

Properties and mechanisms of thermal and photo decomposition of ruthenium complexes [Ru(acac)2(tmp-mian)] (1) and [Ru(acac)2(tmp-bian)] (2) [where acac = acetylacetonate, tmp = 2,4,6-{CH3}3C6H2, mian is monoiminoacenaphtheneone, and bian is acenaphthene-1,2-diimine] in acetonitrile were studied in real time by aerodynamic thermal breakup droplet ionization mass spectrometry (ATBDI-MS). A comparison of the ATBDI-MS spectra of complexes 1 and 2 showed a difference between photolysis processes in these structurally similar complexes because the Ru–O– bond in complex 1 is much weaker than the Ru–N bond in complex 2. This difference leads to easier decomposition of complex 1 and facilitates the capture of solvent molecules by products of complex 1′s photolysis. Similarly, the analysis of thermal decomposition of complexes 1 and 2 at increasing temperatures of an ATBDI suction tube (Tsuction) showed that complex 1 is much more susceptible to thermal decomposition and starts to disintegrate already at 100 °C. Complex 2 is much stabler; there was no evidence of its thermal decomposition when Tsuction was raised up to 330 °C.

Photolytic Degradation of the Insecticide Clothianidin in Hydrochar Aquatic Suspensions and Extracts

In this study, the aqueous photolytic degradation of the neonicotinoid pesticide clothianidin was studied in suspensions and aqueous extracts of hydrochar produced from olive kernels. A slight and nonsignificant decrease in the photodegradation rate of clothianidin in aqueous extracts of hydrochar (HCw) with an initial concentration of hydrochar ranged from 50 to 400 mg L−1 (rate constants ranged between k = 0.0034 and 0.0039 min−1) was observed in comparison to the respective rate in the bi-distilled water (k = 0.0040 min−1). On the contrary, in the presence of hydrochar suspensions (HCp), a significant decrease was observed for 50 mg L−1 hydrochar particle concentration (k = 0.020 min−1), while for higher concentrations (100 to 400 mg L−1), rate constants increased but with nonsignificant differences compared with the kinetics followed in the absence of them. Generally, the photodegradation rate of clothianidin, in the presence of HCw and HCp, is reduced compared to the photodegradation rate in bi-distilled aqueous solutions, except in the case of the aqueous suspension with an HCp concentration of 200 mg L−1. The transformation products (TPs) of clothianidin formed in the photolytic degradation processes were identified using ultrahigh-performance liquid chromatography coupled with accurate high-resolution mass spectrometry technique (UHPLC-LTQ-ORBITRAP). The formation profiles of TPs varied according to the matrix showing different degrees of participation of direct and indirect (photosensitized) phototransformation pathways. Photolytic degradation of clothianidin takes place mainly through denitration, hydroxylation and dechlorination pathways. Finally, the toxicity of the identified TPs was studied using the Vibrio fischeri bioassay. Toxicity was slightly reduced after 300 min of irradiation while maximum value was observed after 180–240 min of irradiation showing the formation of more toxic TPs along the photochemical degradation.

A stability indicating method development and validation of a rapid and sensitive RP-HPLC method for Nintedanib and its application in quantification of nanostructured lipid carriers

Background: Nintedanib (NTB) is a multiple tyrosine kinase inhibitor, been investigated for many disease conditions like idiopathic pulmonary fibrosis (IPF), systemic sclerosis interstitial lung disease (SSc-ILD) and non-small cell lung cancer (NSCLC). NTB is available as oral capsule formulation, but its ability to detect degradants formed through oxidative, photolytic and hydrolytic processes makes it difficult to quantify. In the current work, a novel reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated. Methods: The developed method is simple, precise, reproducible, stable and accurate. The inherent stability of NTB was evaluated using the proposed analytical method approach and force degradation studies were carried out. NTB was separated chromatographically on the Shimadzu C18 column as stationary phase (250 ×4.6 mm, 5 µm) using an isocratic elution method with 0.1% v/v triethyl amine (TEA) in HPLC grade water and acetonitrile (ACN) in the ratio 35:65% v/v. The mobile phase was pumped at a constant flow rate of 1.0 ml/min, and the eluent was detected at 390 nm wavelength. Results: NTB was eluted at 6.77±0.00 min of retention time (tR) with a correlation coefficient of 0.999, the developed method was linear in the concentration range of 0.5 µg/ml to 4.5 µg/ml. The recovery rate was found to be in the range of 99.391±0.468% for 1.5 µg/ml concentration. Six replicate standards were determined to have an % RSD of 0.04. Conclusion: The formulation excipients didn't interfere with the determination of NTB, demonstrating the specificity of the developed method. The proposed approach of the analytical method developed can be used to quantify the amount of NTB present in bulk drugs and pharmaceutical formulations.

Simulated-sunlight enhances membrane aerated biofilm reactor performance in sulfamethoxazole removal and antibiotic resistance genes reduction

Membrane aerated biofilm reactors (MABRs) can be used to treat domestic wastewater containing sulfamethoxazole (SMX) because of their favorable performance in the treatment of refractory pollutants. However, biologics are generally subjected to antibiotics stress, which induces the production of antibiotic resistance genes (ARGs). In this study, a simulated-sunlight assisted MABR (L-MABR) was used to promote SMX removal and reduce ARGs production. The SMX removal efficiency of the l-MABR system was 9.62 % superior to that of the MABR system (83.13 %). In contrast from MABR, in the l-MABR, only 28.75 % of SMX was removed through microbial activity because functional bacteria were inactivated through radiation by simulated sunlight. In addition, photolysis (64.61 %) dominated SMX removal, and the best performing indirect photolysis process was the excited state of effluent organic matters (3EfOMs*). Through photolysis, ultraviolet (UV) and reactive oxygen species (ROS) enriched the SMX removal route, resulting in the SMX removal pathway in the l-MABR no longer being limited by enzyme catalysis. More importantly, because of the inactivation of functional bacteria, whether in the effluent or biofilm, the copy number of ARGs in the l-MABR was 1–3 orders of magnitude lower than that in the MABR. Our study demonstrates the feasibility of utilizing simulated-sunlight to enhance the antibiotic removal efficiency while reducing ARG production, thus providing a novel idea for the removal of antibiotics from wastewater.

On the photoinduced degradation of tamsulosin: The simpler the better

In this work, we present a comprehensive investigation of the decomposition of tamsulosin. Experiments were performed in an aqueous solution through photolysis with a 254 nm light source. In general, tamsulosin degradation was observed (presenting a rate of 35.4%, in 180 min), demonstrating that direct photoinduced decomposition is efficient. The simpler uncatalyzed process worked while previous experiments using solid catalysts showed negligible degradation. The kinetic constant of the photolysis process (17.6 ×10−3 min−1) was determined, considering first order kinetics, by fitting plots of ln([Tam]t −[Tam]∞)/ln([Tam]0 −[Tam]∞) versus irradiation time, where [Tam]t is the concentration of tamsulosin at time t, and [Tam]∞ is the limiting concentration of the reacting system. In addition, physical insights regarding tamsulosin photoexcitation and photolysis were obtained through quantum chemistry computations. Density functional theory (DFT) was used to investigate the ground state while its time-dependent formalism (TD-DFT) was used for determining vertical excitation energies and generalized oscillator strengths (GOSs). All the computations were undertaken at the CAM-B3LYP/6-311++G(d,p) level of theory, in water. Regarding the excited states, all five lowest-lying states were determined to have non-zero GOSs, with S3 (found at 5.73 eV (∼216 nm) at the TD-DFT/CAM-B3LYP/6–311++G(d,p) level of theory) presenting the highest GOS (0.1157) among all. Hence, these accessible states may be assigned as those responsible for the photoinduced degradation observed experimentally. Moreover, the computational results suggest tamsulosin undergoes photodecomposition through excited state chemical reaction rather than via a direct photolysis path.

Sanger's reagent as a new general phototrigger for organelle imaging

Photoactivatable subcellular organelles imaging offers the desirable spatiotemporal resolution in studying the complex biological processes. Developing proper and simple photoremovable protecting groups (PPGs) is the key for constructing such imaging probes. In this study, we designed and synthesized three Sanger's reagent caged fluorescent probes for specific photoactivated organelle imaging. We showed the photoactivated fluorescence recovery of the probes. The photolysis mechanism was verified by mass spectra (MS) analysis, and the highly efficient photolysis process was monitored by high performance liquid chromatography (HPLC). The probes successfully imaged their respective targeted organelle, including mitochondria, lysosomes, and endoplasmic reticulum (ER), in a photoactivated manner, and exhibited high co-localization coefficients when compared to commercially available probes. Given the high reactivity and efficient photodissociation capability of Sanger's reagent with amino groups, our examples demonstrate the potential of Sanger's reagent as a novel general PPG for constructing photoactivatable fluorescent probes.

Application of UVC-LED/H2O2 in wastewater treatments: treatment efficacy on disinfection byproduct precursors and micropollutants

The applications of advanced oxidation processes (AOPs) for controlling microcontaminants are essential to meet the water quality criteria for potable or nonpotable water reuses. The objective of this study is to demonstrate the application of light emitting diode (LED) as a possible light source to substitute traditional low-pressure mercury lamp (LPUV) in UV/H2O2 processes in treating precursors of disinfection byproducts (DBPs) and pharmaceutical and personals care products (PPCPs) in wastewater. The results of this study revealed that UV fluence plays the most crucial role in the efficiency of UV/H2O2. At the same time, the initial concentration of H2O2, dissolved organic carbon (DOC), and turbidity had minimal effects, except that poor efficiency result of UV/H2O2 was observed at a solution with low DOC concentration (2.4 mg L−1). Although the concentrations of organic matter decreased after UV/H2O2 treatment, the concentration of precursors of DBPs increased in the early stage of the photolysis process and decreased after that; moreover, the profiles of precursors for trihalomethanes and haloacetic acids were different. A comparison between LPUV and UVC-LED as light sources revealed that, at a fixed UV fluence input into the UV/H2O2 process, the trends and efficiencies in the degradation of organic matter and DBP precursors were similar. Meanwhile, the photoelectric conversion efficiency of UVC-LED should be improved for future applications in water treatment. Based on the UV/H2O2 treatment results on synthetic PPCPs wastewater solution, this study showed the effectiveness of UV/H2O2 to degrade micro organic contaminants.

Sunlight-induced degradation of COVID-19 antivirals arbidol in natural aquatic environments: Mechanisms, pathways and toxicity

Insights into COVID-19 antivirals’ environmental fate and ecological risk are urgently required due to their increasing concentrations in aquatic environments, which have rarely been studied. Herein, we first investigated the photochemical transformation and the resulting alterations in toxicity of arbidol, an antiviral drug with relatively higher toxicity. The photolysis of arbidol was rapid with a rate constant of 0.106 min−1 due to its superior ultraviolet light absorption, in which the direct photolysis was predominated with a contribution of 91.5%. Despite its substantial photolysis, only 14.45% of arbidol was mineralized after 100 min, implying that arbidol and its products might have a long-term impact on aquatic environment. It was inferred that arbidol was photolyzed mainly via the loss of thiophenol, bromine, and alkylamine, based on twelve photolytic products identified. Notably, the experimental results demonstrated that the photolysis process increased the acute toxicity of arbidol, and the toxicity prediction indicated that the ecotoxicity of two photolytic products was very high with LC50 values below 0.1 mg/L. Due to the co-effect of multiple constituents, the photolytic rate observed in wastewater treatment plant effluent and in river water was comparable to that in ultra-pure water, while it was slightly enhanced in lake water. The presence of dissolved organic matter suppressed arbidol photolysis, while NO3− exhibited a promotion effect. These results would be of great significance to assess the fate and risk of COVID-19 antivirals in natural aquatic environments.

Enhanced sonophotocatalytic degradation of amoxicillin antibiotics using Fe3O4@SiO2/PAEDTC surrounded by MIL-101(Fe) in aquatic environment under the COVID-19 pandemic

In the conditions of corona disease, the need for antibiotics in the world has quadrupled, so it is required to remove their residues from the environment. A core–shell metal–organic framework (MOF) composed of Fe3O4, SiO2, and MIL-101 was synthesized by hydrothermal method and used as a sonophotocatalyst for the amoxicillin (AMX) degradation from aqueous solution. The features of the new MOF were determined by SEM, TEM, XRD, FTIR, and BET techniques. The specific area of core–shell magnetic particles was 992 m2/g, which was indicative of its usability to adsorb pollutants and photons. Complete degradation of AMX was achieved by sonophotocatalysis process based on prepared nanocomposite at pH of 5, UV intensity of 36 W, AMX concentration of 50 mg/L, US frequency of 36 kHz, and time of 25 min. Kinetic study with pseudo-first order reaction for the decomposition of AMX showed the order of kinetic constant rate as Ksonophotocatalytic > Kphotocatalytic > Ksonocatalytic > Kadsorption. Hydroxyl radicals (•OH) and holes (h+) were respectively determined as the main species in the decomposition of AMX by performing quenching experiments. Less than an 8% reduction in AMX degradation rate was observed by the sonophotocatalytic process in the presence of prepared nanocomposite during six consecutive reaction cycles. Removal rates of TOC > 77% and BOD5/COD ratio > 0.4 showed that AMX was converted to CO2, H2O, and simple degradable compounds during the sonophotocatalysis process. A toxicity study with the microbial culture of Escherichia coli (E. coli) demonstrated a lower inhibition rate in the sonophotocatalytic process compared to photolysis and photocatalytic processes. All the laboratory results proved that the Fe3O4@SiO2@MIL-101(Fe) is an encouraging candidate for AMX degradation to preserve the ecosystem.

Application of a novel composite of Fe3O4@SiO2/PAEDTC surrounded by MIL-101(Fe) for photocatalytic degradation of penicillin G under visible light.

The novel photocatalyst of Fe3O4@SiO2/PAEDTC@MIL-101(Fe) was prepared based on the sol-gel method, and its structure and morphology were determined by SEM mapping, TEM, XRD, FTIR, and N2 adsorption-desorption analyses. The photocatalytic activity of nanocomposite was evaluated in comparison with other particles as well as adsorption and photolysis processes. The effect of operating parameters showed that the complete degradation of penicillin G (PNG) can be provided at a photocatalyst dosage of 0.6g/L, radiation intensity of 36 W, pH of 5, and time of 60min. In the optimum condition, 84% TOC removal was attained and the BOD5/COD rate for the treated effluent was above 0.4, which was representative of the high biodegradability of the treated effluent compared to the raw sample. The findings of energy consumption showed that PNG can be easily and effectively treated by the photocatalytic process based on magnetic MIL-101(Fe) with electrical energy per order between 10 and 20.87 kWh/m3. Due to the excellent interaction between the MIL-101(Fe) and Fe3O4@SiO2/PAEDTC, the photocatalyst stability test showed a recyclability of the particles for 5 consecutive reaction cycles with a minimum reduction of 7%. Solution treated with photocatalyst under UV and visible light sources explained that the toxicity of the effluent after treatment is significantly reduced with the growth of Escherichia coli. Scavenging experiments showed that •OH radical and hole (h+) are the main agents in degrading PNG to CO2, H2O, and biodegradable and low-toxicity products. Finally, the findings of the diagnostic analysis and comparative experiments proved that with the interaction of Fe3O4@SiO2, NH2, and MIL-101(Fe), a lower band gap can be prepared for more absorption of photons and pollutant and also more and faster production of active radicals.

Abiotic mineralization of dissolved organic phosphorus for improved nutrient retention in a large-scale treatment wetland system

The Everglades Stormwater Treatment Areas (STAs) in South Florida are large treatment wetlands that were constructed and managed to reduce phosphorus (P) loads to the Everglades Protection Area. Most P in inflow waters originates from urban, agricultural, and equestrian runoff, as well as discharges from Lake Okeechobee. To effectively reduce dissolved organic P (DOP) in the outflow of the STAs, DOP must be mineralized to soluble reactive phosphorus (SRP) (Ged and Boyer, 2013), and then removed through uptake by aquatic vegetation or co-precipitation with calcite during photosynthesis. In order to explore the effects of sunlight and photolytic processing on dissolved P mineralization within the STAs, a series of photochemical experiments were conducted. First, DOM entering the STAs was measured and found to be highly aromatic (mean SUVA = 0.38) and dominated by large molecular weight molecules (75% of bulk DOM > 10KDa) that are reactive to photolytic degradation. Model molecules, such as phytic acid, and site water from the STAs were exposed to light and produced SRP from DOP after exposure to high energy UV radiation. Additionally, analysis of excitation emission matrices (EEM) found that aromatic and humic structures were photolytically degraded during UV exposure. These findings suggest that photolysis is a significant process in DOM and P cycling in the STAs, and if leveraged in SAV dominated areas, could benefit P removal by co-precipitation with calcite. These findings suggest that vegetation management strategies could be employed to maximize UV photolytic reactions to optimize P retention.

The effect of sodium citrate on the photolytic reaction of catechin following the addition of aluminum chloride under alkaline conditions

Tea has an abundance of aluminum and catechins. As a food additive, citrate is often added to tea. An aluminum ionic species, including its amphoteric Al3+, can be either neutral or negatively charged and exist as intermediates simultaneously in weak alkaline solutions. This study is undertaken to investigate the photolytic processes of 290 mg/L catechin hydrate (CH) upon the addition of 133 mg/L AlCl3 (CHA) and CHA in the presence of 294 mg/L sodium citrate dihydrate (CHAS) to determine the structural changes in catechin and analyze its photoproducts after blue light irradiation at 20 W/m2 in H2O at pH 8 (BLIH) via high-performance liquid chromatography equipped with a diode array detector and mass spectrometry (HPLC-DAD-MS) system. The photolytic effect of blue light on sodium citrate was also determined. When CH is treated with BLIH, A-type and B-type proanthocyanidin dimers, AtPA and BtPA, respectively, are formed by a photochemically driven redox reaction. Relative percentages of the resultant catechin are 46.3, 98.1, and 46.9 for CH, CHA, and CHAS, respectively, after BLIH treatment, suggesting that the photolysis of catechin after BLIH is suppressed by AlCl3 and that sodium citrate restores the process of the catechin-aluminum system under BLIH in alkaline conditions. The addition of AlCl3 reduces the generation of proanthocyanidins during the photolysis of catechin after the dimeric molecule is disconnected by AlCl3, which acts as a catalyst after BLIH. However, under the same conditions, the addition of sodium citrate inhibits the catalytic capacity of AlCl3, and more proanthocyanidins are generated by the catechin-aluminum system under BLIH. Sodium citrate features an inherent reducing potential to maintain the photostability of the catechin-aluminum system and inhibits the catalysis of aluminum ions in alkaline conditions under BLIH.