Modified nano zero-valent iron coupling microorganisms to degrade BDE-209: Degradation pathways and microbial responses.

Polybrominated diphenyl ethers (PBDEs) in soil and groundwater have garnered considerable attention owing to the significant bioaccumulation potential and toxicity. Currently, the coupling treatment method of nano zero-valent iron (nZVI) with dehalogenation microorganisms is a research hotspot in the field of PBDE degradation. In this study, various systems were established within anaerobic environments, including the nZVI-only system, microorganism-only system, and the nZVI + microorganisms system. The aim was to investigate the degradation pathway of BDE-209 and elucidate the degradation mechanism within the coupled system. The results indicated that the degradation efficiency of the coupled system was better than that of the nZVI-only or microorganism-only system. Two modified nZVI (carboxymethyl cellulose and polyacrylamide) were prepared to improve the coupling degradation efficiency. CMC-nZVI showed the highest stability, and the coupled system consisting of microorganisms and CMC-nZVI showed the best degradation effect among all of the systems in this study, reaching 89.53% within 30 days. Furthermore, 22 intermediate products were detected in the coupling systems. Notably, changing the inoculation time did not significantly improve the degradation effect. The expression changes of the two reductive dehalogenase genes, e.g. TceA and Vcr, reflected the stress response and self-recovery ability of the dehalogenating bacteria, indicating such genes can be used as biomarker for evaluating the degradation performance of the coupling system. These findings provide a better understanding about the mechanism of coupling debromination process and the direction for the optimization and on-site repair of coupled systems.

Interaction between Phthalate Ester and Rice Plants: Novel Transformation Pathways and Metabolic-Network Perturbations.

Our understanding is limited concerning the interaction mechanism between widespread phthalate esters and staple crops, which have strong implications for human exposure. Therefore, this study was aimed at illuminating the transformation pathways of di-n-butyl phthalate (DnBP) in rice using an untargeted screening method. UPLC-QTOF-MS identified 16 intermediate transformation products formed through hydroxylation, hydrolysis, and oxidation in phase I metabolism and further by conjugation with amino acids, glutathione, and carbohydrates in phase II metabolism. Mono-2-hydroxy-n-butyl phthalate-l-aspartic acid (MHBP-asp) and mono-2-hydroxy-n-butyl phthalate-d-alanyl-ß-d-glucoside (MHBP-ala-glu) products were observed for the first time. The proteomic analysis demonstrated that DnBP upregulated the expression of rice proteins associated with transporter activity, antioxidant synthesis, and oxidative stress response and downregulated that of proteins involved in photosynthesis, photorespiration, chlorophyll binding, and mono-oxygenase activity. Molecular docking revealed that DnBP can affect protein molecular activity via pi-sigma, pi-alkyl, and pi-pi interactions or by forming carbon-hydrogen bonds. The metabolomic analysis showed that key metabolic pathways including citrate cycle, biosynthesis of aminoacyl-tRNA, and metabolism of amino acids, sphingolipids, carbohydrates, nucleotides, and glutathione were activated in rice plants exposed to DnBP and its primary metabolite mono-n-butyl phthalate (MnBP). Furthermore, exposure to 80 ng/mL MnBP significantly perturbed the metabolic profile and molecular function in plants, with downregulation of the levels of beta-alanine (0.56-fold), cytosine (0.48-fold), thymine (0.62-fold), uracil (0.48-fold), glucose (0.59-fold), and glucose-1-phosphate (0.33-fold), as well as upregulation of the levels of l-glutamic acid (2.97-fold), l-cystine (2.69-fold), and phytosphingosine (38.38-fold). Therefore, the degradation intermediates of DnBP pose a potentially risk to plant metabolism and raise concerns for crop safety related to plasticizer pollution.

Synergistic activation of persulfate by FeS@SBA-15 for imidacloprid degradation: Efficiencies, activation mechanism and degradation pathways.

In this work, FeS supported SBA-15 mesoporous silica catalyst (FeS@SBA-15) was synthesized successfully, characterized and first applied to persulfate (PS) activation for the degradation of imidacloprid in wastewater. The as-prepared 3.5-FeS@SBA-15 presented an impressive imidacloprid removal efficiency of 93.1% and reaction stoichiometric efficiency (RSE) of 1.82% after 5 min, ascribed to the synergetic effects of improved FeS dispersion and abundant surface sites by SBA-15. Electron paramagnetic resonance spectra and quenching experiments proved that both SO4·- and ·OH were produced in FeS@SBA-15/PS system, and SO4·- played a dominant role in the degradation process. The S2- can accelerate the cycling of Fe(III)/Fe(II) during activation and increase the steady-state concentration of Fe(II). More importantly, the constructed heterogeneous system exhibited an efficient and stable catalytic activity over a wide range of pH (3.0-9.0), temperature (283K-313K), inorganic ion (NO3-) and humic acid (1-20 mg/L). Moreover, the density functional theory calculations were conducted to predict the potential reaction sites of imidacloprid. Based on eighteen identified intermediates, four main degradation pathways were proposed: hydroxylation, dechlorination, hydrolysis, and the ring cleavage of the imidazolidine. ECOSAR analysis indicated hydroxylation and dechlorination played a key role in the detoxification of the formed compounds. These findings would provide new insights into the application of FeS@SBA-15 catalyst in wastewater treatment and the removal mechanism of imidacloprid from wastewater.

Visible light-driven photocatalytic degradation of Microcystin-LR by Bi2WO6/Reduced graphene oxide heterojunctions: Mechanistic insight, DFT calculation and degradation pathways.

Developing heterostructure photocatalysts for removing Microcystin-LR (MC-LR) under visible light was of positive significance to control the risk of Microcystins and ensure the safety of water quality. Herein, the Bi2WO6/Reduced graphene oxide (RGO) nanocomposites were prepared via a simple one-spot hydrothermal method for the first time to degrade MC-LR. The optimized Bi2WO6/RGO (Bi2WO6/RGO3%) achieved a removal efficiency of 82.3% toward MC-LR, with 1.9-fold higher efficiencies than Bi2WO6, and it showed superior reusability and high stability after 5 cycles. The degradation efficiency of MC-LR demonstrated a negative trend with the initial concentration of MC-LR, fulvic acid, and initial algal density increased, while MC-LR removal rate for the presence of anions was in the order of Cl- > CO3-2 > NO3- > H2PO4-. The degradation efficiency of MC-LR could reach up to 82.3% within 180 min in the neutral condition. The active species detection experiments and EPR measurements demonstrated that the holes (h+), hydroxide radicals (∙OH), and superoxide radicals (∙O2-) participated in the degradation of MC-LR. The DFT calculations showed that 0.56 of electron transferred from Bi2WO6 to RGO, indicating RGO introduction could prevent the recombination of photoelectrons and holes and was beneficial for MC-LR degradation. Finally, the possible intermediate products and degradation pathways were also proposed by the LC-MS/MS analysis.

[Effects of pH value on stachydrine biosynthesis of hydroponic Leonurus japonicus and its physiological mechanism].

The present study explored the physiological mechanism of the effects of different pH treatments on the growth, physiological characteristics, and stachydrine biosynthesis of Leonurus japonicus to provide references for the cultivation and quality control of L. japonicus. Under hydroponic conditions, different pH treatments(pH 5,6,7,8) were set up. The growth, physiology, and the content of stachydrine and total alkaloids of L. japonicus, as well as the content of key intermediate products in stachydrine biosynthesis pathway(i.e., pyruvic acid, α-ketoglutaric acid, glutamic acid, and ornithine) were monitored to explore the physiological mechanism of the effects of pH on the growth and active components of L. japonicus. The results showed that L. japonicus. could grow normally in the pH 5-8 solution. The pH treatment of neutral acidity was more conducive to the accumulation of photosynthetic pigments and the increase in soluble protein in leaves of L. japonicus. to promote its growth and yield. However, since stachydrine is a nitrogen-containing pyrrolidine alkaloid, its synthesis involves the two key rate-limiting steps of nitrogen addition: reductive ammoniation reaction and Schiff base formation reaction. High pH treatments promote the synthesis and accumulation of substrates and products of the above two reactions, indicating that the alkaline environment can promote the nitrogen addition reaction, thereby promoting the biosynthesis and accumulation of stachydrine.

Assessing main process mechanism and rates of sulfate reduction by granular biomass fed with glycerol under sulfidogenic conditions.

Sulfate-reducing bioreactors for sulfide production are the initial stage of processes targeting elemental sulfur recovery from sulfate-rich effluents. In this work, the principal reactions involved in glycerol fermentation and sulfate reduction using glycerol and its fermentation products as electron donors were assessed together with their specific consumption/production rates. A battery of batch activity tests with and without sulfate were performed with glycerol and with each fermentation product using a non-methanogenic but sulfidogenic granular sludge from an up-flow anaerobic sludge blanket (UASB) reactor operated under long-term while fed with crude glycerol. As a result, a mechanistic approach based on the experimental observations is proposed in this work. Glycerol was mainly fermented to 1,3-propanediol, ethanol, formate, propionate and acetate by fermentative bacteria. All organic intermediates were found to be further used by sulfate reducing bacteria (SRB) for sulfate reduction except for acetate. The most abundant genus detected under sulfidogenic conditions were Propionispora (15.2%), Dysgonomonas (13.2%), Desulfobulbus (11.6%) and Desulfovibrio (10.8%). The last two SRB genera accounted for 22.4% of the total amount of retrieved sequences, which were probably performing an incomplete oxidation of the carbon source in the sulfidogenic UASB reactor. As single substrates, specific sulfate reduction rates (SRRs) using low molecular weight (MW) carbon sources (formate and ethanol) were 39% higher than those using high-MW ones (propionate, 1,3-propanediol and butanol). However, SRRs in glycerol-fed tests showed that 1,3-propanediol played a major role in sulfate reduction in addition to formate and ethanol.

Mechanism of bio-electrokinetic remediation of pyrene contaminated soil: Effects of an electric field on the degradation pathway and microbial metabolic processes.

In this study, the mechanism of bio-electrokinetic (BIO-EK) remediation to improve the degradation of pyrene was evaluated based on an analysis of the intermediate products and the microbial community. The results show that BIO-EK remediation has a higher pyrene degradation efficiency on pyrene and its intermediate products than the bioremediation and electrokinetic (EK) remediation processes. A series of intermediate products were detected. According to the type of the intermediate products, two degradation pathways, biological metabolism and electrochemical oxidation, are proposed in the BIO-EK remediation of pyrene. Furthermore, the primary microbial taxa involved in the pollutant degradation changed, which led to variations in the functional gene components. The abundant and functional genes related to metabolism were specifically analyzed. The results indicate that the electric field promotes the expression of metabolisms associated with 14 carbohydrates, 13 lipids, 13 amino acids, five energies, and in particular, 11 xenobiotics. These results suggest that in addition to the promotion effect on the microbial metabolism caused by the electric field, BIO-EK remediation can promote the degradation of pollutants due to the coexistence of a microbial metabolic pathway and an electrochemical oxidation pathway.

Enhanced removal of oxytetracycline antibiotics from water using manganese dioxide impregnated hydrogel composite: Adsorption behavior and oxidative degradation pathways.

The present work provides the first attempt of using manganese dioxide loaded poly(sodium acrylate) hydrogel (MnO2@PSA) to address potential threats posed by oxytetracycline (OTC) antibiotics in aqueous environment. The MnO2@PSA was prepared via a facile approach and demonstrated enhanced removal performance even under extremely high concentrations of OTC. The outstanding performance exhibited by MnO2@PSA was attributed to synergetic effects of adsorption oxidative degradation. The synthesized composite was characterized evaluated under varying conditions. The adsorption pH was optimized at pH 5, at which the removal efficiency OTC was reached 91.46%. According to the kinetics study, the pseudo-second-order kinetic model was the best to explain the adsorption data, implying the interaction mechanisms were dominated by chemisorption. The Langmuir isotherm model was the best to explain the isotherm data, and the corresponding maximum adsorbed amount of OTC was 1150.4 mg g-1. The MnO2@PSA was highly selective for OTC adsorption and degradation under the presence of natural organic matter and common environmental metal ions. The oxidative degradation study indicated that OTC molecules were structurally degraded into 15 intermediate products via six reaction pathways. Both the theoretical models and spectroscopic methods demonstrated the removal mechanism of OTC onto MnO2@PSA was governed by ion exchange, cation-π bonding, hydrogen-bonding, and π-π electron donor-acceptor. Overall, MnO2@PSA is an excellent and environmentally sustainable material to remove OTC from water and wastewater via the combined effects of adsorption and oxidative degradation.

Substrate-Binding Mode and Intermediate-Product Distribution Coguided Protein Design of Alginate Lyase AlyF for Altered End-Product Distribution.

Recently, we reported alginate lyase AlyF that predominantly produced trisaccharides (the trisaccharide content is 87.0%), and the determination of its substrate-binding mode facilitated its protein engineering for new product distribution. To clarify the relationship between the substrate-binding pocket and end-product distribution, the open binding pocket change was initially designed. The resulting F128T_W172R mutant of AlyF exhibited different intermediate-product distributions but still similar end-product distributions. However, these observations suggested that cleavage pattern changes for intermediate products might contribute to an altered end-product distribution. Structural analysis indicated that the sugar-binding affinity at subsite -2 should be redesigned to achieve this goal. Thus, residue Arg266, which is involved in sugar binding at subsite -2, was selected for site-saturation mutagenesis in the F128T_W172R mutant. The dominant end products of the F128T_W172R_R226H mutant were altered to disaccharides and trisaccharides (the disaccharide content increased to 40.5%).

Oxidation of benzophenone-3 in aqueous solution by potassium permanganate: kinetics, degradation products, reaction pathways, and toxicity assessment.

Benzophenone-3 (BP-3) is used in a wide range of personal care products and plastics to resist ultraviolet light, which has aroused considerable public concern due to its endocrine-disrupting effects. In this work, we systematically investigated the chemical oxidation process of BP-3 by KMnO4. The influences of several factors, such as pH, oxidant dose, temperature, coexisting water constituents, and water matrices, on BP-3 degradation efficiency were evaluated. The removal rate of 10 µM BP-3 could reach 91.3% in 2 h under the conditions of pH = 8.0, [BP-3]0:[KMnO4]0 = 1:20, and T = 25 °C, with the observed rate constant (kobs) value of 0.0202 min-1. The presence of typical anions (Cl-, NO3-, SO42-) and HA could slightly increase BP-3 removal, while HCO3- caused a relatively significant promotion of BP-3 degradation. On the basis of mass spectrometry and theoretical calculations, hydroxylation, direct oxidation, and carbon-carbon bridge bond cleavage were mainly involved in the oxidation process. Toxicity assessment revealed that the acute and chronic toxicities were reduced significantly, which suggested KMnO4 is a promising technique for BP-3 removal.

Meta-cresol degradation by persulfate through UV/O3 synergistic activation: Contribution of free radicals and degradation pathway.

The kinetic and pathway of meta-cresol (m-cresol) degradation were studied by persulfate oxidation through UV/ozone activation (UV/O3-Na2S2O8) to improve m-cresol removal to eliminate ecological risks. Experimental results showed that the degradation effect of m-cresol with an initial concentration of 50 mg/L was 99.8% in 30 min under the optimization conditions. The reaction kinetic model in the UV/O3-Na2S2O8 system shows that the initial pH value, the respective ozone, and the persulfate dosage were positively correlated with the degradation rate constant value (k). The apparent degradation rate of m-cresol in the UV/O3-Na2S2O8 system was 0.2216 min-1, and the synergy factor (f) was larger than 1, thereby demonstrating a synergistic effect of UV, ozone, and persulfate. The dominant free radicals in the system were sulfate radical (SO- 4·) and hydroxyl radical (·OH), and the contribution ratio of SO- 4· to m-cresol degradation was higher than ·OH. The degradation process of m-cresol by UV/O3 - Na2S2O8 was mainly through the electrophilic addition reaction to substitute the ortho- and para-positions of the hydroxyl group on the benzene ring, followed by the ring-opening reaction and mineralization of the aliphatic compound to achieve the complete degradation of m-cresol.

The products from fermentation of wheat bran fiber by Auricularia polytricha strain and the effects of the products on rheological properties of dough sheet.

Being classified within the Basidiomycota, Auricularia polytricha has been proved to degrade lignocellulose, a major component of wheat bran fiber. During the fermentation of lignocellulose by A. polytricha strain, a large number of intermediate products are produced, which affect the further degradation of lignocellulose. Therefore, it is essential to analyze the fermentation intermediates for study on the degradation mechanism of wheat bran fiber. In this study, the effectiveness of fermentation of wheat bran fiber by A. polytricha strain was confirmed via scanning electron microscopy. Additionally, the results of gas chromatography-mass spectrometry indicated that the A. polytricha strain could degrade wheat bran fiber and produce several aromatic compounds, and that the number of products obtained after 7 days of fermentation was significantly lower than that after 3 days of fermentation. It has also been demonstrated that diisooctyl phthalate and 9-octadecenamide belong to metabolites produced during the fermentation of wheat bran fiber, by culturing A. polytricha with wheat bran fiber and glucose as carbon source, respectively. Moreover, by conducting an ultraviolet wavelength scanning of the culture liquid containing vanillin fermented by A. polytricha, it has been indicated that the strain could degrade vanillin and further demonstrated that the strain has the ability to degrade wheat bran fiber. Furthermore, adding the products of wheat bran fiber fermented for 3 days by A. polytricha could improve the elasticity of the dough sheet.

Novel quantification of formation trend and reaction efficiency of hydroxyl radicals for investigating photocatalytic mechanism of Fe-doped TiO2 during UV and visible light-induced degradation of acid orange 7.

A detailed mechanistic investigation of the hydroxyl radical (•OH) formation and organic pollutant degradation over transition metal-doped and undoped TiO2 photocatalysts was performed by the quantitative measurement of •OH and the identification of intermediate products under various experimental conditions. The Fe-doped TiO2 as a typical subject was prepared, characterized and used to degrade an azo dye Acid Orange 7 (AO7). It is indicated that the enhanced photocatalytic activity of Fe-doped TiO2 for AO7 degradation was attributed to the increase in surface area, the facilitated charge transfer via Fe-dopant, and a red shift of absorbable wavelength, maintaining a great formation of •OH under visible irradiation. The oxidation of H2O by holes was estimated as the major pathway of •OH formation rather than the reduction of dissolved O2 by electrons, and their formation trends reached to approximately 75% and 25%, respectively. Meanwhile the synergistic effect of Fe-dopant produced nearly 10% of extra •OH by visible light photoactivation. The intermediate products and pathways of AO7 degradation varied greatly with different photocatalysts and conditions of the process, involving several reaction mechanisms such as the azo bond cleaving, naphthalene oxidation, desulfonation, and hydroxylated products generation. Through the quantification of •OH-reacted efficiency we proposed, a stoichiometry of •OH affecting overall reaction mechanisms in the TiO2-assisted photodegradation of AO7 was further established. This study can provide new insights on how to better clarify the variation regularity of organic pollutant degradation from different treatments of the •OH-based advanced oxidation processes.

Insights on photochemical activities of organic components and minerals in dissolved state biochar in the degradation of atorvastatin in aqueous solution.

This study systematically investigated the photocatalytic activity of dissolved state biochar (DSB) with different pyrolysis temperature to the degradation of atorvastatin (ATV), a medicine widely used to combat hyperlipidemia. It was found that the photocatalytic efficiency of DSB increased with the decrease of pyrolysis temperature, that is, DSB300 (DSB with 300 °C of pyrolysis temperature) had the greatest photocatalytic activity in same condition, which was attributed to the dual role of DSB300 as heterogeneous photocatalyst and photosensitizer. The mineral components were responsible for the heterogeneous photocatalytic activity of DSB300. Organic carbon components could synergistically enhance the heterogeneous photocatalytic activity by enhancement of electron-hole separation, and contribute to the formation of singlet oxygen (1O2) and triplet-excited state (3DSB*) as well. The identification of intermediate products and X-ray photoelectron spectroscopy (XPS) analysis of irradiated DSB300/ATV revealed that cross-coupling reaction between ATV and DSB existed in the photodegradation process of ATV. The detailed photodegradation pathways of ATV were proposed, which was triggered by oxygen insertion of pyrrole ring and hydroxyl addition. Meanwhile, the modification of DSB300 under irradiation was evidently attenuated with ATV as shown by multiple characterizations, which helped to keep the stability of DSB300 in photochemical reaction process.

Research on the Feasibility and Supervision Strategy of Using Intermediate Products to Prepare Children ’s Small- sized Preparations in Medical Institutions in China / 中国药房

OBJECTIVE：To provide reference for improving th e availability of clinical medication for children in China. METHODS：Based on the current laws and regulations of China ，referring to the relevant excellent experience and mode of foreign countries，the definition and regulatory attributes of intermediate products and final small-sized children ’s preparations were analyzed，and the feasible regulatory pathway of children ’s medicine preparedby intermediate products entering medical institutions were discussed. RESULTS & CONCLUSIONS ：According to the clinical dosage and characteristics of medication ，small-sized preparations for children in medical institutions could be divided into preparations for children ’s medical institutions and personalized preparations for children. From the analysis of foreign experience ，legal policies and technical conditions ，it was feasible for medical institutions to use intermediate products to formulate children ’s small-sized preparations ，but they also faced certain difficulties as the difficulty to supervise ，unclear quality standards ，vague subject and scope of use ，etc. In terms of supervision，it wa s suggested that intermediate products should be taken as the main quality management object when children ’s small-sized preparations prepared by intermediate products entered medical institutions. Meanwhile ，quality risk management should be paid attention to it. In the management of small-sized preparations for children in medical institutions ，it is necessary to formulate the preparation specifications of small-sized preparations for children in medical institutions ，prepare guidelines for the use of excipients and improve the quality inspection standards of preparations ；in the aspect of preparation supervision ，the small-sized preparations for children in medical institutions with large clinical demand are strictly controlled ，and those with high personalized degree in medical institutions are under loose supervision ；in terms of registration and approval ，technical evaluation should be carried out at the same time as the implementation of registration/filing management ；in terms of price setting ，appropriate profit margins should be formulated according to the innovation degree ，clinical demand ，children’s family affordability and public opinion feedback of price of children ’s small-sized preparations in medical institutions. Indiviclualized preparations are forma- lated ased on the price of preparations inmedical institutions ， with reference to the differential price comparice rules. Mean- while，pharmaceutical service fees are charged to compensate pharmacists’time and labor ；in terms of medical insurancepayment，the drugs are classified and managed according to whether they are included in the medical insurance list ，so as to ensure the same drug availability for children and adults .

[Determination of seven flavonoids in Qingre Zhike Granules and intermediate product with quantitative analysis of multi-components by single marker].

This study is to determine seven flavonoids( narirutin,naringin,hesperidin,neohesperidin,baicalin,oroxylin A-7-glucoronide and wogonoside) in Qingre Zhike Granules and intermediate products by quantitative analysis of multi-components with a single marker( QAMS). High performance liquid chromatography( HPLC) was performed on Thermo BETASIL C18 chromatographic column( 4.6 mm×250 mm,5 µm) with acetonitrile-0.1% formic acid solution as mobile phase for gradient elution at a flow rate of 0. 8 m L·min-1. The detection wavelength was set at 280 nm and the column temperature was 30 ℃. Six relative correction factors( RCFs)of narirutin,naringin,hesperidin,baicalin,oroxylin A-7-glucoronide and wogonoside were established in the HPLC method with neohesperidin as the internal standard,and then these RCFs were used to calculate the mass fractions of the six components. Such mass fractions were compared with the mass fraction determined by the external standard method( ESM) at the same time to verify the feasibility and accuracy of QAMS method. Within the linear range,the RCFs of narirutin,naringin,hesperidin,baicalin,oroxylin A-7-glucoronide and wogonoside were 1.150,1.109,1.110,0.658,0.723 and 0.572,respectively,with good repeatability in different experimental conditions. There was no significant difference between the QAMS method and ESM method. The QAMS method with neohesperidin as the internal standard is feasible and accurate for the determination of narirutin,naringin,hesperidin,baicalin,oroxylin A-7-glucoronide and wogonoside,and it can be used for quality control of Qingre Zhike Granules and intermediate products.

Degradation of sulfadimethoxine by permanganate in aquatic environment: Influence factors, intermediate products and theoretical study.

The excess sulfadimethoxine (SDM) in the environment could lead to antibiotic resistance by microorganisms and may do harm to many aquatic organisms. In this work, the removal of SDM by potassium permanganate (KMnO4) was comprehensively studied. The influence of various factors, including the pH, oxidant doses, and temperature, on SDM removal were investigated. The optimal reaction conditions were determined to be pH 5.0, T = 25 °C and [KMnO4]0 = 200 µmol L-1. Anions (Cl-, SO42-, HCO32-, and NO3-) and cations (K+, Ca2+, Mg2+, and NH4+) had no significant influence on the removal of SDM. However, H2PO4- improved the efficiency of SDM removal by KMnO4. Humic acid (0-10 mg L-1) promoted the removal of SDM, which was attributed to the generation of in situ MnO2. Meanwhile, the degradation of SDM in various water matrices was studied, and the removal order was ultrapure water > Jiuxiang river water ≈ synthetic water > secondary clarifier effluent. According to ten intermediate products identified and a frontier electron densities (FED) calculation, several pathways were proposed that involve the oxidation of amidogen, the cleavage of CS and SN bonds, and an oligomerization reaction. The predicted toxicity assessment indicated that most of the degradation products were not harmful to aquatic organisms except SDM dimers (connection by HNNH), suggesting that byproducts, such as dimers, formed during the oxidation of SDM and other sulfonamides should be taken into consideration. In sum, KMnO4 has the potential to remove SDM from the aquatic environment.

Roles of reactive oxygen species (ROS) in the photocatalytic degradation of pentachlorophenol and its main toxic intermediates by TiO2/UV.

Pentachlorophenol (PCP) caused water quality problems owe to its past widespread application and stability, harmful to human health. Photocatalysis, which was mainly involved in the reactive oxygen species (ROS) reaction, has large potential as water treatment process. However, the roles of ROS on the degradation process of PCP are not yet clearly defined. The main objectives of this work were to investigate the roles of ROS involved in the whole degradation of PCP and main toxic intermediates and elucidate the degradation mechanisms. Tetrachloro-1,4-benzo/hydroquinone (TCBQ/TCHQ), trichlorohydroxy-1,4-benzoquinone (OH-TrCBQ) and 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (OH-DCBQ) were identified as main intermediates. The roles of generated ROS including OH, O2- and H2O2 were systematically explored for the degradation of PCP and its main intermediates using radical quenchers. The results showed that, OH played the dominant role for the degradation of PCP, O2- played more contributing roles for the degradation of TCBQ, H2O2 exhibited major contribution for the degradation of OH-TrCBQ and OH-DCBQ. These results offered us an insight into the degradation mechanism of PCP involved with ROS. It can also serve as the basis for controlling and blocking the generation of highly toxic substances through regulating the ROS generation during the PCP degradation.

Construction of coated Z-scheme Pd-BaZrO3@WO3 composite with enhanced sonocatalytic activity for diazinon degradation in aqueous solution.

The coated Z-scheme Pd-BaZrO3@WO3 composite as a new-type sonocatalyst with highly sonocatalytic performance is first constructed through sol-gel and hydro-thermal synthesis methods. The chemical configuration, structure and component are characterized by a series of characterization methods. The sonocatalytic degradation of diazinon as a model pollutant is studied to estimate the sonocatalytic performance of coated Z-scheme Pd-BaZrO3@WO3 composite. Some affecting factors such as Pd-BaZrO3 and WO3 mass proportions, ultrasonic (US) irradiation time, reusability and catalyst dosage are researched in detail through UV-vis spectra and gas chromatography (GC). The produced intermediates are detected in the degradation process of diazinon by using gas chromatography-mass spectrometer (GC-MS). The possible reaction mechanism of coated Z-scheme Pd-BaZrO3@WO3 sonocatalyst in sonocatalytic degradation process is also explored. Subsequently, the hydroxyl radicals (OH) and holes (h+) are discriminated to further elaborate the possible sonocatalytic mechanism. The experimental results manifest that the coated Z-scheme Pd-BaZrO3@WO3 sonocatalyst displays a preeminent sonocatalytic performance under ultrasonic irradiation because it can efficaciously suppress recombination of electrons (e-) and holes (h+), extend light response scope and provide almost 100% oxidization surface. In addition, the introduced palladium (Pd) nanorods connecting BaZrO3 and WO3 can expedite e- transfer. Under optimal conditions, the most of diazinon molecules can be disintegrated in the existence of the coated Z-scheme Pd-BaZrO3@WO3 under ultrasonic irradiation for 150 min. This study provides a feasible method for the treatment of environmental pollutions.

Degradation behavior of palm oil mill effluent in Fenton oxidation.

An in-depth study on degradation behavior of palm oil mill effluent (POME) in Fenton oxidation was accomplished with complete carbon and nitrogen balances. Experiments were conducted for real POME with a pH range of 2-5. POME contained high COD (50,000 mg/L), nitrogen (520 mg/L) and phosphorous (510 mg/L). Carboxylic acids and phenol covered 88% of organic carbons while ammonia, NO2- and NO3- contributed for 73% of nitrogen. Most of carboxylic acids and phenol were decomposed forming easily-biodegradable formic, phthalic and acetic acids, and further decomposed to carbonate and gaseous carbon dioxide. Part of carbon in liquid phase in POME transferred to solid phase by oligomerization of aromatic compounds. Ammonia was oxidized to NO2-, NO3- and gaseous N2 while, acetamide degradation led to ammonia formation. 99.9% of phosphorus was removed. Increasing H2O2 concentration elevated organic reduction and the highest TOC reduction of 91% was obtained at TOC:H2O2:Fe2+ molar ratio of 1:3.7:0.6 within 90-180 min which is extremely faster over the available biological treatments. Under the reaction conditions used in this study, Fenton oxidation at pH 3 showed the best result in terms of TOC reduction. Outcomes of this study will provide a platform for advanced oxidation processes and POME treatment.