Simultaneous determination of ten aminoglycoside antibiotics in aquatic feeds by high-performance liquid chromatography quadrupole-orbitrap mass spectrometry with pass-through cleanup.

A simple and sensitive method has been established based on pass-through cleanup and high-performance liquid chromatography quadrupole-orbitrap mass spectrometry (HPLC-Q/Orbitrap MS) for the simultaneous determination of ten aminoglycosides (AGs) in aquatic feeds. The extraction solution and cleanup procedure had been optimized, and good sensitivity, accuracy, and precision were obtained. The calibration curves of AGs were linearity (R2 > 0.99) in the range of 2.0 to 200 µg/L (or 5.0 to 500 µg/L). The limits of detection of AGs were between 10 and 25 µg/kg. The recoveries of AGs ranged from 74.9% to 94.3%, and the intraday and interday relative standard deviations were less than 15%. Finally, this method was successfully applied to determine ten AGs in 30 aquatic feed samples. It might be the first time to use pass-through cleanup approach combined with HPLC-Q/Orbitrap MS method for AGs determination in aquatic feed samples.

Transcriptome Analysis of Rice Roots in Response to Root-Knot Nematode Infection.

Meloidogyne incognita and Meloidogyne graminicola are root-knot nematodes (RKNs) infecting rice (Oryza sativa L.) roots and severely decreasing yield, whose mechanisms of action remain unclear. We investigated RKN invasion and development in rice roots through RNA-seq transcriptome analysis. The results showed that 952 and 647 genes were differently expressed after 6 (invasion stage) and 18 (development stage) days post inoculation, respectively. Gene annotation showed that the differentially expressed genes were classified into diverse metabolic and stress response categories. Furthermore, phytohormone, transcription factor, redox signaling, and defense response pathways were enriched upon RKN infection. RNA-seq validation using qRT-PCR confirmed that CBL-interacting protein kinase (CIPK) genes (CIPK5, 8, 9, 11, 14, 23, 24, and 31) as well as brassinosteroid (BR)-related genes (OsBAK1, OsBRI1, D2, and D11) were altered by RKN infection. Analysis of the CIPK9 mutant and overexpressor indicated that the RKN populations were smaller in cipk9 and larger in CIPK9 OX, while more galls were produced in CIPK9 OX plant roots than the in wild-type roots. Significantly fewer numbers of second-stage infective juveniles (J2s) were observed in the plants expressing the BR biosynthesis gene D2 mutant and the BR receptor BRI1 activation-tagged mutant (bri1-D), and fewer galls were observed in bri1-D roots than in wild-type roots. The roots of plants expressing the regulator of ethylene signaling ERS1 (ethylene response sensor 1) mutant contained higher numbers of J2s and developed more galls compared with wild-type roots, suggesting that these signals function in RKN invasion or development. Our findings broaden our understanding of rice responses to RKN invasion and provide useful information for further research on RKN defense mechanisms.

Survival, growth performance and immune capacity of the juvenile lined seahorse Hippocampus erectus fed with rifampicin-treated copepods.

Gastrointestinal disease is one of the most serious diseases in cultured seahorse juveniles. Treatment with antimicrobials of live food (i.e. copepods and Artemia) that is used to feed the juveniles may be a promising measure to alleviate the occurrence of gastrointestinal disease. However, relevant investigations are rare. In the present study, we first investigated the antimicrobial efficacies on bacteria within copepods that were treated with 4 antimicrobials, including 3 antibiotics (i.e. enrofloxacin hydrochloride, oxytetracycline and rifampicin [RFP]) that are approved for use in aquaculture and 1 disinfectant (i.e. povidone iodine). We then assessed the effects of copepods treated with the antimicrobial that had the best antimicrobial efficacy on survival, growth performance and immune capacity of juvenile lined seahorses Hippocampus erectus. The results showed that RFP had the best antimicrobial efficacy on both Pseudoalteromonas spp. and Vibrio spp., 2 dominant bacteria with potential pathogenicity within the copepods; the proper concentration of RFP was 6 mg l-1. Moreover, H. erectus juveniles fed with RFP-treated copepods demonstrated an improved survivorship and immune capacity and had a lower abundance of pathogenic bacteria within their gastrointestinal tracts compared to juveniles fed with untreated copepods. These results suggest that treating live food with RFP is a potential measure for reducing the incidence of gastrointestinal disease in seahorse juveniles.

Plasma levels of immune factors and sex steroids in the male seahorse Hippocampus erectus during a breeding cycle.

To better understand the endocrine- and immune-response pattern during reproduction in a fish species having parental care behaviors and also to accumulate the endocrine- and immune-related data for future explanations of the low reproductive efficiency in seahorse species, the variations of immune factors and sex steroids in the plasma of the male lined seahorse Hippocampus erectus at different breeding stages, i.e., pre-pregnancy, pregnancy (early, middle, and late periods), and post-pregnancy, were investigated in the present study. The immune factors included monocytes/leucocytes (M/L), leucocyte phagocytic rate (LPR), immunoglobulin M (Ig M), interleukin-2 (IL-2), interferon-α (IFN-α), and lysozyme (LZM). The sex steroids included testosterone (T), 11-ketotestosterone (11-KT), 11ß-hydroxytestosterone (11ß-OHT), 17α-methyltestosterone (17α-MT), 17ß-estradiol (E2), and 17α-hydroxy-20ß-dihydroprogesterone (17α-20ß-P). Moreover, the immune metabolic activity of epithelium cells in the brood pouch at different breeding stages was also analyzed through ultrastructural observations of the abundance of cytoplasmic granules, mitochondria, endoplasmic reticulum, lysosomes, and exocytosis. The results show that a higher immune level was observed during pregnancy, particularly in the early and middle periods, and a lower immune level was noted during pre-pregnancy. Correspondingly, the epithelium cells in the brood pouch also showed a stronger immune metabolic activity during pregnancy and weaker activity during pre-pregnancy. Four sex steroids of T, 11ß-OHT, 17α-MT, and E2 were higher during pre-pregnancy and lower during post-pregnancy, whereas 11-KT and 17α-20ß-P, which were positively correlated with part immune factors, were higher during pregnancy. No negative correlations between sex steroids and immune factors were observed. In conclusion, the higher immune competence during pregnancy may indicate that parental care could improve immunity, which may be the major factor for no immunosuppressive effect of sex steroids during reproduction in the seahorse H. erectus, unlike noncaregiving fishes in which inhibitions of sex steroids on immunity are frequently observed. Moreover, higher 11-KT and 17α-20ß-P during pregnancy than during pre-pregnancy and post-pregnancy may suggest that these two steroids are also involved in parental care regulation.

Parental care improves immunity in the seahorse (Hippocampus erectus).

In the present study, the sexual dimorphism in immune response in the seahorse Hippocampus erectus in which males compete for mates and invest heavily in parental care was assessed. Variability in immunocompetence in virginal seahorses with differing levels of sexual maturity (i.e., immaturity, early maturity and maturity) and with different mating statuses (i.e., virginal, experienced mating failure and experienced mating success) were analyzed by evaluating immune parameters in the plasma. Additionally, ultrastructural characteristics of the inner epithelium of the brood pouch were compared between males that had experienced mating failure and those that had succeeded. Generally, immunity in sexually mature virgin males was greater than in females, and mating competition significantly reduced males' immunity. However, parental care gave males stronger immune and metabolic abilities and resulted in their immunity significantly rebounding after a successful mating. The present study quantitatively clarifies, for the first time, how parental care and mating competition jointly affect immunity. Moreover, previous findings that females display more efficient immune defenses than males in conventional species (i.e., males are as competitor and females as care giver) and that males' immunity is higher than females' in the pipefish (i.e., females are as competitor and males as care giver) in combination with the present results indicate that parental care is a key factor for sexual dimorphism in immunity. The care-giving sex has strong immunity regardless of the sex in charge of mating competition or not.

Variations of immune parameters in the lined seahorse Hippocampus erectus after infection with enteritis pathogen of Vibrio parahaemolyticus.

Enteritis has been increasingly recognized as one of the major obstacles for the lined seahorse Hippocampus erectus mass culture success. In the present study, the intestinal bacteria strains of the lined seahorses H. erectus suffered from enteritis were isolated, then their pathogenicities were confirmed by artificial infection, and one pathogenic bacteria strain named DS3 was obtained. The median lethal dose (LD50) of strain DS3 for 10 days was determined. The seahorses with different infection levels of uninfected (control), early stage of infection (ESI) and late stage of infection (LSI) were respectively sampled at 0, 3, 6 and 9 days post infection, and 12 immune parameters in the plasma were analyzed. The strain DS3 identified with a biochemical test combined with a molecular method was Vibrio parahaemolyticus, and its LD50 for 10 days was 1.3 × 10(3) cfu/fish. Six parameters including monocytes/leucocytes, leucocytes phagocytic rate, interleukin-2, interferon-α, lysozyme and immunoglobulin M exhibited a generally similar variation trend: highest in the control, second in the ESI and lowest in the LSI throughout the entire experiment. In view of the infection level of V. parahaemolyticus to H. erectus is largely decided by the seahorse's own immune capacity, therefore, these immune parameters were high in the non- or slightly infected seahorses, and low in the severely infected individuals may be an indicator for immune level. These immune parameters may be reliable indicators for the juvenile and broodstock quality assessment. Moreover, clarification of the enteritis pathogen also provides guidances for targeted medicine choice for the lined seahorse.

Novel photo-sulfite system: toward simultaneous transformations of inorganic and organic pollutants.

An efficient and green advanced oxidation process (i.e., photo-sulfite reaction) for the simultaneous oxidation of sulfite and organic pollutants in water is reported. The photo-sulfite system (UV-Fe(III)-sulfite) is based on the Fe-catalyzed sulfite oxidation and photochemistry of Fe(III) species. SO4(•-) and (•)OH radicals were identified in the photo-sulfite system with radical scavenging experiments using specific alcohols. This novel technology was consistently proven to be more favorable than the alternative Fe(III)-sulfite systems for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP) and other organic pollutants at all conditions tested. The reactivity of photo-sulfite system was sustained due to the spontaneous switch of photoactive species from Fe(III)-sulfito to Fe(III)-hydroxo complexes with the depletion of sulfite and the decrease in pH. In contrast, in the absence of light the performance of the Fe(III)-sulfite system was greatly diminished after the consumption of sulfite. The formation of the Fe(III)-sulfito complex is a necessary step for initiating the photo-sulfite reaction. Inhibition of the oxidation of 2,4,6-TCP and methyl orange (MO) was observed in the presence of ligands that can stabilize one or more of the reactants: Fe(III), Fe(II), or sulfite. Our study provides a new facile route for the generation of SO4(•-) and simultaneous removal of organic and inorganic pollutants.

Role of NOM in the Photolysis of Chlorine and the Formation of Reactive Species in the Solar/Chlorine System.

The solar/chlorine system has been proposed as a novel advanced oxidation process (AOP) for efficient pollutant degradation and water disinfection by producing a series of reactive species including hydroxyl radicals (HO•), chlorine radicals (Cl•), and so forth. In this study, the role of natural organic matter (NOM) in the photolysis of free available chlorine (FAC) and the formation of HO• and Cl• in the solar/chlorine system was investigated employing nitrobenzene and benzoic acid as selective chemical probes. The decay rate of FAC was significantly accelerated in the presence of NOM at pH 5.5 under simulated solar irradiation, likely due to the photoreaction between FAC and the photoexcited NOM. The decay rate of FAC increased upon increasing the electron-donating capacity of NOM, which indicated that phenolic components play a significant role in the photodegradation of FAC. This acceleration mechanism was further verified using 4-nitrophenol as a model phenolic compound. NOM promoted Cl• formation and quenched HO• in the solar/chlorine system. The proposed reaction mechanism included the reaction of excited singlet phenolic compounds in NOM with FAC, which yielded Cl•. This study provides a useful insight into future applications for using the solar/chlorine system as a novel AOP for wastewater treatment or disinfection.

Resolving the kinetic and intrinsic constraints of heat-activated peroxydisulfate oxidation of iopromide in aqueous solution.

Iopromide (IOP) has been identified as one of the most persistent pharmaceuticals in wastewater treatment processes, however, kinetic and intrinsic factors constraining its fast removal in advanced oxidation processes (AOPs) are yet to be resolved. Here oxidation of IOP by heat-activated peroxydisulfate (PDS) was investigated both experimentally and theoretically. Rates of IOP degradation were enhanced by elevating solution temperature and acidity. An apparent kinetic rate equation was developed, based on the pseudo-first-order reaction model and assumption of steady state of SO4-. The common water constituents showed inhibitory effects on IOP decomposition to various extent. An insufficient supply of SO4- was considered as the major kinetic constraint. Eight byproducts were identified and most of which had intact triiodinated benzene ring. O-demethylation, oxidation of amino moiety and oxidation/elimination of alcohol groups are proposed as the primary degradation pathways, in accordance with the incomplete mineralization and non-detectable release of inorganic iodine. Quantum chemical calculations predict that oxidation of alkyl chains of IOP preferentially occurs and IOP byproducts with shorter side chains and intact triiodinated ring are more reactive than IOP. By virtue of the identified kinetic and intrinsic constraints, strategies to maximize degradation efficiency of IOP are proposed.

Deciphering the degradation/chlorination mechanisms of maleic acid in the Fe(II)/peroxymonosulfate process: An often overlooked effect of chloride.

In recent years, a significant effort has been devoted into investigating the effects of chloride on the degradation kinetics of aromatic pollutants. The impact of chloride on the decomposition of short-chain carboxylic acid intermediates from aromatics degradation has often been overlooked. In this study the roles of chloride in the oxidation of maleic acid (MA) in the Fe(II)/peroxymonosulfate (PMS) process was investigated. Degradation efficiency, reaction intermediates, adsorbable organic halogen (AOX) accumulation and mineralization were examined. The chloride ion (Cl-) was found to have an overall negative impact on MA degradation and mineralization in the Fe(II)/PMS system. The presence of Cl- led to the formation of chlorinated by-products and a high production of AOX. The mineralization of MA was decreased with increasing Cl- concentrations. Kinetic modeling demonstrated the impact of various radicals largely depended on the concentration of Cl-. The significance of Cl2•- or Cl2 for MA destruction was enhanced with increasing Cl- content, and overwhelmed that of SO4•- when the Cl- concentration was over 5 mM. In the absence of Cl-, SO4•- was the primary radical responsible for MA oxidation. A possible degradation pathway is proposed (cis-trans isomerization, decarboxylation and halogenations processes). These results may help to understand the full oxidation pathways of refractory aromatic compounds and the mechanism of chlorinated by-products formation in industrial saline wastewater treatment.

Cactodera chenopodiae (Nematoda: Heteroderidae), a new species of cyst nematode parasitizing common lambsquarter (Chenopodium album) in Liaoning, China.

A new species of cyst nematode, Cactodera chenopodiae n. sp., parasitizing common lambsquarter, Chenopodium album L., is described from native vegetation in Liaoning, China. Cactodera chenopodiae n. sp. has a circumfenestrate pattern typical of the genus and is morphologically similar to C. cacti Krall Krall, 1978. However, in the new species, females and cysts show a larger L/W ratio whereas second-stage juveniles (J2s) have a longer hyaline region. The new species is also morphologically similar to C. milleri Graney Bird, 1990, but the J2s differ by a larger b ratio and longer tail. Based on DNA sequences of the 28S and ITS rRNA, C. chenopodiae n. sp. comes close to C. estonica Krall Krall, 1978, although it is distinct from the latter with respect to the presence of a punctate eggshell and larger b ratio in the J2s. Although morphometric comparisons with additional Cactodera species show the overlapping of diagnostic morphological characters, our phylogenetic analyses based on both rRNA genes support C. chenopodiae n. sp. as a unique lineage.

Significantly enhanced base activation of peroxymonosulfate by polyphosphates: Kinetics and mechanism.

Base activation of peroxydisulfate (PDS) is a common process aiming for water treatment, but requires high doses of PDS and strongly basic solutions. Peroxymonosulfate (PMS), another peroxygen of sulfurate derived from PDS, may also be activated by a less basic solution. However, enhancing the base-PMS reactivity is still challenging. Here it is reported that pyrophosphate (PA) and tripolyphosphate (PB) can efficiently enhance PMS activation under weakly alkaline conditions (pH 9.5) via the formation of superoxide anion radical (O2•-) and singlet oxygen (1O2). The rate constant of Acid Orange 7 (AO7) degradation in PA/PMS system (kPA/PMS) was nearly 4.4-15.9 fold higher than that in PMS/base system (kPMS/base) without any polyphosphates. Increases in PA (or PB) concentration, PMS dose and pH favored the rapid dye degradation. Gas chromatograph-mass spectrometer (GC-MS) data confirmed AO7 and 2,4,6-trichlorophenol (2,4,6-TCP) were decomposed to a series of organic intermediates. The radical quenching and probe oxidation experiments indicate the degradation of organic compounds in the PA/PMS and PB/PMS processes was not reliant on sulfate radical (SO4•-) and hydroxyl radical (OH) species but on O2- and 1O2 reactive species. Comparison experiments show that the polyphosphate/PMS process was much more favorable than PDS/base process. The present work provides a novel way to activate PMS for contaminant removal using industrial polyphosphate wastewaters.

Comparison of UV/hydrogen peroxide and UV/peroxydisulfate processes for the degradation of humic acid in the presence of halide ions.

This study compared the behaviors of two classic advanced oxidation processes (AOPs), hydroxyl radical-based AOPs ((•)OH-based AOPs) and sulfate radical-based AOPs (SO4 (•-)-based AOPs), represented by UV/ hydrogen peroxide (H2O2) and UV/peroxydisulfate (PDS) systems, respectively, to degrade humic acid (HA) in the presence of halide ions (Cl(-) and Br(-)). The effects of different operational parameters, such as oxidant dosages, halide ions concentration, and pH on HA degradation were investigated in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes. It was found that the oxidation capacity of H2O2 and PDS to HA degradation in the presence of halides was nearly in the same order. High dosage of peroxides would lead to an increase in HA removal while excess dosage would slightly inhibit the efficiency. Both Cl(-) and Br(-) would have depressing impact on the two AOPs, but the inhibiting effect of Br(-) was more obvious than that of Cl(-), even the concentration of Cl(-) was far above that of Br(-). The increasing pH would have an adverse effect on HA decomposition in UV/H2O2 system, whereas there was no significant impact of pH in UV/PDS process. Furthermore, infrared spectrometer was used to provide the information of degraded HA in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes, and halogenated byproducts were identified in using GC-MS analysis in the four processes. The present research might have significant technical implications on water treatment using advanced oxidation technologies.

Enhanced AOX accumulation and aquatic toxicity during 2,4,6-trichlorophenol degradation in a Co(II)/peroxymonosulfate/Cl⁻ system.

Chloride ion is known to affect on degradation kinetics in different ways during HO· and SO4(·-)-based advanced oxidation processes (AOPs). However, its effect on absorbable organic halogen (AOX) evolution and acute toxicity of treated water remains unknown, despite the importance of the two parameters in evaluating the applicability of AOPs. In the present study, Co/peroxymonosulfate (Co/PMS) and UV/hydrogen peroxide (UV/H2O2) treatment of 2,4,6-trichlorophenol was compared in terms of AOX formation, chlorinated byproducts and acute toxicity. Both Co/PMS and UV/H2O2 systems were more reactive under acidic conditions, resulting in elevated AOX levels when compared with those at neutral pH. The presence of high levels of chloride led to an accumulation and increase of AOX in the Co/PMS system. The toxicity of chlorinated byproducts was evaluated using Photobacterium phosphoreum, and the results revealed a sharp increase in acute toxicity of Co/PMS reaction solutions on addition of chloride ion. However, addition of Cl(-) had no apparent impact on AOX and toxicity of UV/H2O2 reaction solutions. These findings may have significant technical implications for selecting feasible technologies to treat high salinity wastewater.

Coprecipitated arsenate inhibits thermal transformation of 2-line ferrihydrite: implications for long-term stability of ferrihydrite.

2-line ferrihydrite, a ubiquitous iron oxy-hydroxide found in natural and engineered systems, is an efficient sink for the toxic metalloids such as arsenic. While much is known of the excellent capacity of ferrihydrite to coprecipitate arsenate, there is little information concerning the long-term stability of arsenate-accumulated ferrihydrite. By thermal treatment methodology, the expedited transformation of ferrihydrite in the presence of coprecipitated arsenate was studied at varying As/Fe ratios (0-0.5) and different heating temperature (40, 300, 450, 600°C). Pure and transformed minerals were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Electron Spin Resonance (ESR), Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Fourier Transform Infrared Spectroscopy (FTIR). Arsenate was found to retard the thermal transformation of ferrihydrite. The extents of ferrihydrite transformation to hematite decreased with increasing As/Fe ratios, but increased at a higher heating temperature. It is predicted that the coprecipitated arsenate can stabilize the amorphous iron oxides against the transformation to more crystalline solids. Arsenate concentration appears to play an important role in this predicted long-term stability.

Transformations of chloro and nitro groups during the peroxymonosulfate-based oxidation of 4-chloro-2-nitrophenol.

Dechlorination and denitration are known to occur during the oxidative degradation of chloronitroaromatic compounds, but the possibility of re-chlorination and re-nitration of chloro and nitro groups is not assessed despite of its importance in evaluating the applicability of advanced oxidation processes (AOPs). In this study, transformation of chloro and nitro groups in degradation of 4-chloro-2-nitrophenol (4C2NP) by sulfate radical generated via Co-mediated peroxymonosulfate activation was investigated. Both chloride and nitrate ions were found as the main inorganic products of chloro and nitro groups in 4C2NP, but their levels were much lower than that of degraded parent 4C2NP. A typical dual effect of chloride on the 4C2NP degradation kinetics was observed, whereas no measurable influence was found for addition of low level nitrate. Re-chlorination took place, but re-nitration was not verified because several polychlorophenols but none of polynitrophenols were detected. The specific degradation mechanism involved in the transformation of nitro group and chloro group was proposed.

Distinct effects of oxalate versus malonate on the iron redox chemistry: Implications for the photo-Fenton reaction.

The dicarboxylic acids oxalate (Oxal) and malonate (Mal) are frequently detected as the final low-molecular-weight organic acids during oxidative degradation of aromatic compounds. Here a distinct effect of Oxal versus Mal on iron-based photocatalytic technologies was reported by testing the degradation efficiency of the dye rhodamine B. The rates of dye degradation in irradiated Fe(III) solutions depended on Fe(III/II) speciation, photoreactivities of Fe complexes and reactivities of Fe(II) complexes with H2O2. Photolysis of the Fe(III)-oxalato complex was favorable due to the formation of O2-, HO2 and OH for oxidizing the dye; however, an excess of H2O2 could quench the excited state of ferrioxalate, decreasing the degradation efficiency. In contrast, activities of UV/Fe(III) in the presence of Mal were significantly diminished because Fe(III)-Mal complexes, with much lower quantum yield of Fe(II) from photoreduction, dominated Fe(III) speciation. The results provide data for an understanding of the mechanism of iron redox (photo)chemistry mediated by diacids, which will aid in selecting appropriate Fe ligands, screening photo-Fenton conditions and designing UV/Fe(III) treatability.

Peroxymonosulfate activation by phosphate anion for organics degradation in water.

Activation of peroxygens is a critical method to generate oxidative species, but often consumes additional chemical reagents and/or energy. Here we report a novel and efficient activation reaction for peroxymonosulfate (PMS) by phosphate anions (PBS). The PBS/PMS coupled system, at neutral pH, is able to decompose efficiently even mineralize a variety of organic pollutants, such as Acid Orange 7, Rhodamine B and 2,4,6-trichlorophenol. In contrast, no measurable degradation was observed when the PMS was replaced by other peroxygens (i.e. hydrogen peroxide and peroxydisulfate). Both PMS and PBS are indispensable for the oxidative degradation of pollutants. Increasing pH and concentrations of PMS and PBS significantly accelerate the degradation of organics. It is proposed that OH would be the major radical for contamination degradation at pH 7.0 through the radical quenching experiments. This work provides a new way of PMS activation for decontamination at neutral pH, in particular for phosphate-rich wastewater treatment.

Rapid dye degradation with reactive oxidants generated by chloride-induced peroxymonosulfate activation.

Transition-metal is known to catalyze peroxymonosulfate (PMS) decomposition to produce sulfate radicals. Here we report reactions between PMS and chloride, without a need of transition metals, also can be used to degrade organic dye pollutant (Rhodamine B, (RhB)). Some important operating parameters, such as dosages of PMS and Cl(-), pH of solution, temperature, ionic strength, and several common cations, were systematically investigated. Almost complete decoloration of RhB was achieved within 5 min ([PMS] = 0.5 mM, [Cl(-)] = 120 mM, and pH 3.0), and RhB bleaching rate increased with the increased dosages of both PMS and chloride ion, following the pseudo-first-order kinetic model. However, the total organic carbon (TOC) removal results demonstrated that the decoloration of RhB was due to the destruction of chromophore rather than complete degradation. RhB decoloration could be significantly accelerated due to the high ionic strength. Increasing of the reaction temperature from 273 K to 333 K was beneficial to the RhB degradation, and the activation energy was determined to be 32.996 kJ/mol. Bleaching rate of RhB with the examined cations increased with the order of NH4 (+) < Na(+) < K(+) < Al(3+) < Ca(2+) < Mg(2+). Some major degradation products of RhB were identified by GC-MS. The present study may have active technical implications for the treatment of dyestuff wastewater in practice.

Sequential reduction-oxidation for photocatalytic degradation of tetrabromobisphenol A: kinetics and intermediates.

C-Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC-MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N(2)-saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a two-stage reductive debromination/subsequent oxidative decomposition process in the UV-TiO(2) system by changing the reaction atmospheres.