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The objective of this work was to develop a mathematical model of an electrochemical flow reactor for the degradation of 2-chlorophenol. The reactor operates in batch recirculation and undivided mode under mass transport control and under galvanostatic conditions. The mathematical model proposed here was simulated on COMSOL Multiphysic® 5.3 software (involving the continuity and Navier-Stokes equation in a laminar regime, and the diffusion-convection equation with reaction term) interacting with the MATLAB® version R 2017a software (continuous stirred tank). The electrolysis process was carried out at a current density of 0.14 A m−2, a liquid flow rate of 1 L min−1 and pH = 7.3. The main results show that the mathematical model proposed here is in a very good agreement with the experimental study (correlation coefficient of 0.9917 and a reduced root-mean-square error of 0.4041). The final concentration of 2-chlorophenol estimated by the mathematical model was 0.0013 mol m−3, while the experimental concentration reached was 0.0001 mol m−3, confirming the predictive capacity of the mathematical model, as well as the efficiency of the electrochemical process implemented.ᅟ [ABSTRACT FROM AUTHOR]

The novel hierarchical sea-urchin-like Fe3O4/SnO2 heterostructures with SnO2 nanorod arrays grown on Fe3O4 nanoparticles were fabricated via a SnO2-seeded heteroepitaxial growth of SnO2 nanorod arrays on Fe3O4 nanoparticles. Moreover, the Fe3O4/SnO2 heterostructures showed notable photocatalytic degradation compared with the pure SnO2 in aqueous solution. The degradation reached 89% in 5 h. The remarkable improvement in photocatalytic efficiency was ascribed to larger specific surface area introducing more active sites. In addition, the decline in degradation efficiency of p-chlorophenol is not more than 11.4% after recycling for seven times in accordance with practice which indicates the excellent repeated availability. The enhanced photocatalytic performance and features that can be easily recovered and separated make Fe3O4/SnO2 have great potential application in the environmental remediation. [ABSTRACT FROM AUTHOR]

Abstract In order to retain a high concentration of activated sludge in the wastewater treatment plant, the dense activated sludge is entrapped into the polyvinyl alcohol (PVA) cryogel beads. For protecting the entrapped activated sludge biomass from the inhibitory effect exerted by recalcitrant pollutant, i.e., 4-chlorophenol (4-CP), the novel PVA cryogel beads with external surface covered by the powdered activated carbon (PAC) were successfully synthesized in this study. The synthesis was achieved by extruding the biomass-PVA polymeric matrix into the gelatin solution containing PAC. The maximum PAC density on the external surface of cryogel beads was calculated to be in the range of 938–978 mg/m2. The PAC distributed on the external surface of cryogel beads was found to possess a higher 4-CP adsorption capacity than the beads with homogenized PAC. These cryogel beads were also capable of shielding the activated sludge biomass entrapped within beads from being directly exposed to the inhibitory effect of 4-CP via adsorption by PAC distributed on the external surface. Thus, only low concentration of 4-CP was diffused into the beads and biodegraded to achieve a total removal of 4-CP. This beneficial effect was later confirmed could last for more than 20 cycles of uses in removing 4-CP via the simultaneous adsorption and biodegradation processes. Highlights • Immobilized biomass cryogel beads synthesis with PAC attached on external surface. • Biomass shielding from inhibitory effect of 4-chlorophenol via adsorption by PAC. • Removal of 4-cholrophenol via the simultaneous adsorption and biodegradation. • Recyclability of cryogel beads in treating wastewater containing 4-chlorophenol. [ABSTRACT FROM AUTHOR]

Highlights • Sulfate consumption decreased as the concentration of the o -chlorophenol increased. • Fluidized fixed biofilm and a upflow sludge blanket reactor shows same pattern. • Biomass under sulfate-reduction conditions was adapted to chlorophenolic compounds. Abstract The effect of increasing the concentration of o -chlorophenol (2-Chlorophenol, 2-CP) was evaluated on a sulfate-reducing consortium in a fluidized fixed biofilm reactor (FFB) and a upflow sludge blanket reactor (SB), this process was evaluated and compared in both reactors. The FFB continuous reactor was fed with formic acid as an inducer at a COD/SO 4 -2 of 0.76 with 2-CP concentrations of 0.19, 0.27 and 0.39 mmol/L, achieving a maximum degradation of 39% of 2-CP at 0.19 mmol/L. The degradation capacity of 2-CP in the bioreactor decreased as the concentration of the toxic compound increased, and a proportional diminution of sulfate consumption was observed. On the other hand, an SB reactor was fed under similar conditions and using the same 2-CP concentrations for comparison. In this case, a maximum degradation of 51% of the 2-CP was observed at 0.19 mmol/L. Sulfate consumption followed the same pattern as in the FFB reactor. This study suggests that biomass adaptation under sulfate-reduction conditions could be used to obtain microorganism adapted to 2-CP and probably chlorophenolic compounds in reactors. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Co-substrate strategy could favor to resist photo-H 2 O 2 stress on biofilm in ICPB. • Living cells enhanced by 19.6%, and cell morphology showed no disinfection. • Shannon index increased from 3.45 to 4.05, showed promoted microbial diversity. • The improvements caused 4-CP and COD removal to increase by ∼27% and ∼23%, respectively. Abstract Intimately coupled photocatalysis and biodegradation (ICPB) is an emerging technology for treating refractory wastewater. The prerequisite of successful ICPB is that photocatalytic reactive oxygen species (ROSs) attack refractory pollutants and yield biodegradable intermediates, but “instantly” extinct before they transfer to the biofilms. However, photocatalytic induced H 2 O 2 (a typical ROS) is different from others due to its long half-life. Photo-H 2 O 2 in ICPB could potentially damage the biofilm; however, this has not been verified to date. In this study, we show that photo-H 2 O 2 damages biofilms in ICPB, and we successfully addressed this issue using a strategy with the co-substrate (NaAC). Under H 2 O 2 stress, the living cell percentage in ICPB dropped significantly, and the cell morphology presented the disinfection of bacteria cells, with enlarged size and disappeared organelles. By adding NaAC, the living cell percentage increased by 19.6% and the bacterial intracellular structure became integrated. The Shannon index increased from 3.45 to 4.05, indicating enhanced microbial diversity. Thauera and Dechloromonas were dominant genera, which played important roles in the breaking of the aromatic ring and in dechlorinating. As a result, 4-CP removal and mineralization increased by ∼27% and ∼23%, respectively. Here, we identified the negative effects of photo-H 2 O 2 on the microbial survival of ICPB and for the first time propose an efficient co-substrate strategy to remedy this issue. [ABSTRACT FROM AUTHOR]

Non-metallic graphene oxide (GO) and carbon nanodots (CDots) co-doped BiOBr ternary system (GO/CDots/BiOBr) were successfully synthesized via a simple one-step solvothermal process. The compositional characterization, optical and electrical properties of photocatalysts were investigated in detail. The prepared ternary photocatalysts possessed the excellent visible-light driven photocatalytic 4-chlorophenol (4-CP) degradation. Additionally, the 4-CP removal efficiencies decreased in the order of GO/CDots/BiOBr (88.9%) > CDots/BiOBr (62.9%) > GO/BiOBr (60.5%) > pristine BiOBr (46.9%) in 6 h under visible light irradiation. The dissolved organic carbon (DOC) removal and the dechlorination efficiency by the GO/CDots/BiOBr were 58.4% and 78.2%, respectively, much higher than pristine BiOBr. The co-existence of GO and CDots on the BiOBr greatly promoted visible light harvesting and utilizing ability and inhibited the recombination of photogenerated electron/hole pairs. The synergistic effect between GO, CDots and BiOBr was expounded, and the photocatalytic reaction mechanism was proposed in detail via the band structure analysis and free radical trapping experiments. [ABSTRACT FROM AUTHOR]

A novel Zn 0 -CNTs-Fe 3 O 4 composite was synthesized by the chemical co-precipitation combined with high sintering process at nitrogen atmosphere. The as-prepared composite was characterized by SEM, EDS, XRD, XPS, VSM and N 2 adsorption/desorption experiments. A novel heterogeneous Fenton-like system, composed of Zn 0 -CNTs-Fe 3 O 4 composite and dissolved oxygen (O 2 ) in solution, which can in situ generate H 2 O 2 and OH, was used for the degradation of 4-chlorophenol (4-CP). The influences of various operational parameters, including the initial pH, dosage of Zn 0 -CNTs-Fe 3 O 4 and initial concentration of 4-CP on the removal of 4-CP were investigated. The removal efficiencies of 4-CP and total organic carbon (TOC) were 99% and 57%, respectively, at the initial pH of 1.5, Zn 0 -CNTs-Fe 3 O 4 dosage of 2 g/L, 4-CP initial concentration of 50 mg/L and oxygen flow rate of 400 mL/min. Based on the results of the radical scavenger effect study, the hydroxyl radical was considered as the main reactive oxidants in Zn 0 -CNTs-Fe 3 O 4 /O 2 system and a possible degradation pathway of 4-CP was proposed. [ABSTRACT FROM AUTHOR]

4-chlorophenol (4-CP) is one of the most important phenolic compounds in various industries. Different technologies have been applied for 4-CP degradation in aquatic environment. Current study is focused on 4-CP degradation by the combination of UV and MnO 2 for peroxymonosulfate (PMS) activation to degrade 4-CP. MnO 2 nanoparticles were synthesized and characterized by X-ray powder diffraction, field emission scanning electron microscope, energy-dispersive X-ray spectroscopy and Brunauer–Emmett–Teller (BET). The effects of operational parameters were evaluated and their results indicated the highest performance in pH = 4.0, 1 mM PMS and 0.25 g/L MnO 2 . Complete degradation of 4-CP during 30 min was a representative of high performance of UV/MnO 2 /PMS. Kinetic study showed that the co-activation of PMS by MnO 2 and UV had a synergistic effect on 4-CP degradation. MnO 2 could keep its performance at least 4th cycle while Mn leaching was negligible. Bicarbonate and hydrogen phosphate ions suppressed the performance of the process in degradation of 4-CP whereas no change was observed in the presence of chloride ions. Quenching experiments showed that hydroxyl radical was dominant radical for 4-CP degradation. The results of toxicity and biodegradability tests indicated that treated sample by UV/MnO 2 /PMS process was relatively non-toxic and easy biodegradable. The function of UV/MnO 2 /PMS system for treatment of real industrial wastewaters (pharmaceutical and petrochemical wastewaters) was tested. Finally, it was concluded that hybrid activation of PMS can be a new perspective for PMS-based processes to treat industrial wastewater. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the mechanisms, stoichiometry, and stability of 4-chlorophenol (4CP) biodegradation kinetics by phenol-acclimated activated sludge using open respirometry. While the removal of 4CP was higher than 98%, the removal of chemical oxygen demand (COD) ranged between 69 and 79% due to the accumulation of an intermediate metabolite. The value obtained from respirometric profiles for the stoichiometric ratio of O2 to 4CP (YO2/4CP) was 1.95 ± 0.04 mol of oxygen consumed per mol of 4CP removed. This YO2/4CP value reflected the action of the oxygenases responsible for the first steps of the aerobic oxidation of 4CP. The 4CP degradation activity decreased noticeably when successive pulses of 4CP were added to the respirometer. A mathematical model was developed to represent the aerobic biodegradation of 4CP. The fitted model adequately predicted the oxygen consumption rate, total phenols, and soluble COD concentrations as a function of time. The results presented could help to predict the dynamic of biodegradation of chlorophenols in a biological wastewater treatment system. [ABSTRACT FROM AUTHOR]

A series of metal silver (Ag) and carbon dots (CDots) co-doped BiOBr ternary systems (Ag/CDots/BiOBr) were successfully prepared by a two-step method. The CDots and Ag nanoparticles were successively introduced into BiOBr with the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide ([C 16 mim]Br) as the precursor. The sphere-like structure of the as-prepared ternary photocatalyst was 1–2 μm in diameter. The compositional characterization and optical and electrical properties of photocatalysts were investigated in detail. The prepared ternary photocatalysts possessed the excellent visible-light driven photocatalytic degradation for 4-chlorophenol (4-CP) with Ag content at 0.9 wt% and CDots content at 2 wt%. Additionally, the 4-CP removal efficiencies decreased in the order of 0.9Ag/2CDots/BiOBr (88.58%) > 0.9Ag/BiOBr (68.12%) > 2CDots/BiOBr (62.12%) > BiOBr (47.15%) under visible light illumination in 6 h. The dissolved organic carbon (DOC) removal and the dechlorination efficiency by the Ag/CDots/BiOBr were 62.3% and 81.5%, much higher than those by the pristine BiOBr. The coexistence of Ag and CDots on the BiOBr promoted visible light harvesting capability and prevent the recombination of photo-generated electron/hole pairs. The Ag/CDots/BiOBr photocatalytic mechanism was discussed by band structure analysis and free radical trapping experiments. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes based on sulfate radical (SO 4 − ) have obtained great attention in water treatment and in-situ ground water/soil remediation. In this study, the degradation of chlorophenols (CPs) in Co 2+ activated peroxymonosulfate (PMS) oxidation process was explored. It was found that 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol could be effectively removed in Co 2+ /PMS oxidation process. Presence of Br − greatly accelerated the transformation of the CPs, which can be explained by the formation of reactive bromine species including both bromine radical species and free bromine from the oxidation of Br − by SO 4 − . Br − could also be oxidized by PMS directly to form free bromine. Thus, degradation of the CPs was also observed in PMS oxidation process without any activators in the presence of Br − . Reactions between CPs and reactive bromine species resulted in the formation of brominated intermediates and disinfection byproducts (DBPs). Brominated phenolic intermediates such as Br 2 Cl-CP, BrCl 2 -CP, and Br 2 Cl 2 -CP were found in both Br − /PMS and Br − /Co 2+ /PMS systems. However, oxidized intermediates such as Br 2 Cl 2 -quinones were only identified in Br − /Co 2+ /PMS system. SO 4 − and radical bromine species are believed to be responsible for the formation of oxidized products. Bromoform and dibromoacetic acid were the main DBPs in both Br − /Co 2+ /PMS and Br − /PMS processes. Dichlorinated DBPs species, such as CHBrCl 2 and dichloroacetic acid, were only found in Br − /Co 2+ /PMS system. Formation of dichlorinated DBPs suggests both dechlorination and chlorination reactions occurred, during which SO 4 − played a key role. The findings of this study indicate that presence of Br − can significantly facilitate the removal of organic contaminants but lead to brominated DBPs in PMS oxidation process, which should be taken into consideration when PMS is applied in environmental matrices containing Br − . [ABSTRACT FROM AUTHOR]

A biodegradation facilitator which catalyzes the initial steps of 4-chlorophenol (4-CP) oxidation was prepared by immobilizing multiple enzymes (monooxygenase, CphC-I and dioxygenase, CphA-I) onto a natural inorganic support. The enzymes were obtained via overexpression and purification after cloning the corresponding genes ( cphC-I and cphA-I ) from Arthrobacter chlorophenolicus A6. Then, the recombinant CphC-I was immobilized onto fulvic acid-activated montmorillonite. The immobilization yield was 60%, and the high enzyme activity (82.6%) was retained after immobilization. Kinetic analysis indicated that the Michaelis-Menten model parameters for the immobilized CphC-I were similar to those for the free enzyme. The enzyme stability was markedly enhanced after immobilization. The immobilized enzyme exhibited a high level of activity even after repetitive use (84.7%) and powdering (65.8%). 4-CP was sequentially oxidized by a multiple enzyme complex, comprising the immobilized CphC-I and CphA-I, via the hydroquinone pathway: oxidative transformation of 4-CP to hydroxyquinol followed by ring fission of hydroxyquinol. [ABSTRACT FROM AUTHOR]

Biodegradability of 2-Chlorophenol (2-CP), 3-Chlorophenol (3-CP), 4-Chlorophenol (4-CP), 2,4-Dichlorophenol (2,4-DCP) and 2,4,6 Trichlorophenol (2,4,6-TCP) has been tested in surface waters in the urban area of Buenos Aires. Samples were taken from the La Plata River and from the Reconquista and Matanza-Riachuelo basins, with a total amount of 18 sampling points. Water quality was established measuring chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and both Escherichia coli and Enterococcus counts. Biodegradability was carried out by a respirometric method, using a concentration of 20 mg L−1 of chlorophenol, and the surface water as inoculum. Chlorophenols concentration in the same water samples were simultaneously measured by a solid phase microextraction (SPME) procedure followed by gas chromatography-mass spectrometry (GC-MS). 2,4-DCP was the most degradable compound followed by 2,4,6-TCP, 4-CP, 3-CP and 2-CP. Biodegradability showed no correlation with compound concentration. At most sampling points the concentration was below the detection limit for all congeners. Biodegradability does not correlate even with COD, BOD5, or fecal contamination. Biodegradability assays highlighted information about bacterial exposure to contaminants that parameters routinely used for watercourse characterization do not reveal. For this reason, they might be a helpful tool to complete the characterization of a site. [ABSTRACT FROM AUTHOR]

The titanate nanotube/single-wall carbon nanotube (TNT/SWCNT) nanocomposites from different titania precursors were prepared by a two-step hydrothermal process. These nanocomposites were characterized by XRD, BET, Raman, FESEM, TEM, EDX, EDS, EIS, UV–vis DRS and FTIR techniques. The FESEM and TEM images showed the high porous nanocomposites with two types of tubular structure relating to TNTs and SWCNTs which were interwoven together uniformly. The XRD and Raman analysis further corroborated the chemical interaction between the SWCNT and the TNT in the nanocomposites. The photocatalytic performance of the as-synthesized composites were examined by the photodegradation of 4-CP under solar and UV illumination. The results revealed an impressive enhancement in photocatalytic activity of the nanocomposites under both irradiation conditions comparison to bare TNPs and TNTs. Amongst the TNT/SWCNT nanocomposites, 10% loading of SWCNT under UV irradiation and 5% loading of SWCNT under solar irradiation exhibited the maximum photocatalytic performance while the photocatalytic degradation efficiency of nanocomposites were not affected considerably by the type of precursor. Moreover, the mechanism and role of SWCNT were investigated and the plausible degradation pathways of 4-CP was suggested. TOC analyses was performed for determination of 4-CP mineralization rate and results showed complete mineralization after 240 and 390 min under UV and solar irradiation, respectively. The trapping experiments corroborated the O 2 − and OH radicals as the main reactive species in 4-CP degradation process. Langmuir-Hinshelwood kinetic model was fittingly matched with the experimental data (R 2 : 0.9218 and 0.9703 for UV and solar irradiation). Additionally, the stability of the nanocomposites were investigated and revealed 8% decrease in degradation efficiency after four cycles. [ABSTRACT FROM AUTHOR]

A magnetically recoverable B,F,P-TiO 2 /Fe 3 O 4 nanophotocatalyst was prepared via a microwave-hydrothermal process and subsequent calcination after grinding B,F,P-TiO 2 and Fe 3 O 4 nanosheets in an agate mortar. The synergetic effects of B,F,P-tridoping and Fe 3 O 4 coupling on promoting the photogenerated charge separation of TiO 2 were confirmed by photoluminescence spectroscopy (PL), surface photovoltage spectra (SPS), and electrochemical impedance spectroscopy (EIS). B,F,P-TiO 2 /Fe 3 O 4 exhibited typical superparamagnetic behavior and sufficient magnetic recycling property, as well as excellent photoactivity for the degradation of 4-chlorophenol (4-CP) under simulated sunlight irradiation ( K app = 1.1 × 10 −2 min −1 ), almost equal to that of P25 TiO 2 ( K app = 1.13 × 10 −2 min −1 ). •OH radical was confirmed to be a main activated species in the photocatalytic processes. No positive correlation between surface hydroxyl content and •OH radical generation amount was observed. Photogenerated charge separation efficiency superior to other factors including photoabsorption ability, phase structure, surface hydroxyl, and textural property, played a dominant role in improving the photoactivity. This work provides a promising approach to develop magnetically recoverable high-performance photocatalysts suitable to wide application for wastewater treatment. [ABSTRACT FROM AUTHOR]

Chlorophenols are widespread and of environmental concern due to their toxic and carcinogenic properties. Development of less costly and less technically challenging remediation methods are needed; therefore, we developed a formulation based on micronized vermiculite that, when air-dried, resulted in a granular product containing the 4-chlorophenol (4-CP)-degrading Gram-positive bacterium Arthrobacter chlorophenolicus A6. This formulation and stabilization method yielded survival rates of about 60% that remained stable in storage for at least 3 months at 4 °C. The 4-CP degradation by the formulated and desiccated A. chlorophenolicus A6 cells was compared to that of freshly grown cells in controlled-environment soil microcosms. The stabilized cells degraded 4-CP equally efficient as freshly grown cells in two different set-ups using both hygienized and non-treated soils. The desiccated microbial product was successfully employed in an outdoor pot trial showing its effectiveness under more realistic environmental conditions. No significant phytoremediation effects on 4-CP degradation were observed in the outdoor pot experiment. The 4-CP degradation kinetics from both the microcosms and the outdoor pot trial were used to generate a predictive model of 4-CP biodegradation potentially useful for larger-scale operations, enabling better bioremediation set-ups and saving of resources. This study also opens up the possibility of formulating and stabilizing also other Arthrobacter strains possessing different desirable pollutant-degrading capabilities. [ABSTRACT FROM AUTHOR]

Chlorophenols are extensively used in the anthroposphere, and their fates in the atmosphere, hydrosphere, biosphere and lithosphere and their degradations under natural light of great interests. The homogeneous photocatalytic degradation of 2-chlorophenol (2-CP) in titanium dioxide suspensions containing copper ions or/and sulfates has been well examined. In this study, TiO 2 is directly doped with copper sulfate by a sol-gel method to promote its visible light activity (VLA) following a post-calcination step. The effects of three parameters of synthesis (calcination temperature, amounts of dopant and nitric acid) on 2-CP degradations were experimentally investigated using a three-factor, two-level factorial design in the first stage. Catalysts of the most significant synthetic parameters were further synthesized at five calcined temperatures and characterized in the second stage. 2-CP was completely removed using catalysts that were doped 0.21 mol.% CuSO 4 with 0.1 vol.% nitric acid and then calcined at 300 °C for 6 h. Morphological variations with doping amount are observed from scanning electron micrographs. XRD patterns demonstrated a transformation from amorphous to the anatase phase, with replacement of Ti 4+ by Cu 2+ in the crystal structure of TiO 2 . UV–visible light diffuse reflectance spectra of the doped catalysts exhibited red-shifts, revealing their VLA. Surface areas, measured by the BET method, decreased as the calcination temperatures increased, and the pore sizes increased. Moreover, effect of three operational parameters, including: (del) initial concentration of 2-CP, initial pH and the photocatalyst dosage, under visible-light irradiation were investigated to simulate the scenarios of degradation in the natural and artificial conditions. Optimal operational parameters were obtained at a catalyst dosage of 3 g·dm −3 , an initial 2-CP concentration of 20 ppm and a solution pH of 5.5. The pH zpc of the undoped and CuSO 4 -doped TiO 2 were determined to be 3.5 and 3.84. [ABSTRACT FROM AUTHOR]

Utilization of hybrid treatment schemes involving advanced oxidation processes and hydrodynamic cavitation in the wastewater treatment forms the prime focus of the present work. The initial phase of the work includes analysis of recent literature relating to the performance of combined approach based on hydrodynamic cavitation (HC) for degradation of different pollutants followed by a detailed investigation into degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The degradation of the priority pollutant, 2,4,6-TCP, using combination of HC based on slit-venturi used as the cavitating device, ozone and H 2 O 2 has been investigated. The effect of operating pressure (2–5 bar) and initial pH (3 −1 1) have been investigated for the degradation using only HC. The degradation using only ozone (100–400 mg/h) and only H 2 O 2 has also been studied. The efficacy of the combined operation of HC + O 3 at different ozone flow rates (100–400 mg/h) and the combined operation of HC + H 2 O 2 at different loadings of H 2 O 2 (2,4,6-TCP:H 2 O 2 as 1:1–1:7) have been subsequently investigated. The degradation efficacy has also been established for the combined treatment strategies of O 3 + H 2 O 2 and HC + O 3 +H 2 O 2 at the optimum conditions of temperature as 30 °C, inlet pressure of 4 bar and initial pH of 7. Extent of 2,4,6-TCP degradation, TOC and COD removal obtained for HC + O 3 process were 97.1%, 94.4% and 78.5% respectively whereas for O 3 + H 2 O 2 process, the values were 95.5%, 94.8% and 76.2% and for HC + O 3 + H 2 O 2 process the extent of reduction were 100%, 95.6% and 80.9% in the same order. The combined treatment approach as HC + O 3 + H 2 O 2 was established as the most efficient approach for complete removal of 2,4,6-TCP with near complete TOC removal. [ABSTRACT FROM AUTHOR]

Single crystals of new polyoxometalate based ionic crystal [Fe(phen) 3 ] 2 [SiW 12 O 40 ]·3DMF ( IC-Fe ), (phen = 1,10-phenanthroline, DMF = N,N -dimethylformamide) and their nanoparticles ( IC-Fe-NPs ) have been synthesized via self-assembly of constituent ions and sonochemical reaction, respectively. All materials have been characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermal gravimetric (TG), powder X-ray diffraction (PXRD), FT-IR spectroscopy and elemental analyses. Effect of sonication conditions on size and morphology of IC-Fe was investigated including time, concentrations of initial reagents and power of irradiation. Further studies have shown that IC-Fe is not only active in photocatalytic degradation of 2,4-dichlorophenol under visible light irradiation, but also is very stable in the various solvents and it can be easily separated and reused for cycles of reaction. [ABSTRACT FROM AUTHOR]

Chlorophenols (CPs) are used in the production of pesticides and preservatives. Although human exposure to CPs has been known for years, current exposure levels to these chemicals in Asian countries are not known. In this study, we analyzed concentrations of eight CPs in 300 human urine samples collected from nine countries. Of these CPs, 2,5-dichlorophenol and 2,4-dichlorophenol were found at the highest median concentrations (median for all nine countries: 1.78 and 0.34 ng/mL, respectively). Pentachlorophenol was found in 59% of the samples analyzed at a median concentration of 0.07 ng/mL. Urine samples from Japan had the highest concentration of total CPs (median: 16.7 ng/mL) with 2,5-dichlorophenol accounting for 93.1% of the total concentration. The estimated daily intake (DI) for precursors of dichlorophenols varied widely, but several samples showed values higher than the acceptable DI recommended by the United States Environmental Protection Agency (EPA). These results suggest that CP exposure, especially to dichlorophenols, is prevalent in several countries, particularly in Asia, suggesting a pressing need for further assessment of the global sources and potential health effects of these chemicals. [ABSTRACT FROM AUTHOR]

This study aimed to clarify the initial 4-chlorophenol (4-CP) biodegradation pathway promoted by a two-component flavin-diffusible monooxygenase (TC-FDM) consisting of CphC-I and CphB contained in Arthrobacter chlorophenolicus A6 and the decomposition function of CphC-I. The TC-FDM genes were cloned from A. chlorophenolicus A6, and the corresponding enzymes were overexpressed. Since CphB was expressed in an insoluble form, Fre, a flavin reductase obtained from Escherichia coli , was used. These enzymes were purified using Ni 2+ -NTA resin. It was confirmed that TC-FDM catalyzes the oxidation of 4-CP and the sequential conversion of 4-CP to benzoquinone (BQN) → hydroquinone (HQN) → HQL. This indicated that CphC-I exhibits substrate specificity for 4-CP, BQN, and HQN. The activity of CphC-I for 4-CP was 63.22 U/mg-protein, and the Michaelis-Menten kinetic parameters were v max = 0.21 mM/min, K M = 0.19 mM, and k cat / K M = 0.04 mM −1 min −1 . These results would be useful for the development of a novel biochemical treatment technology for 4-CP and phenolic hydrocarbons. [ABSTRACT FROM AUTHOR]

Intimate coupling of photocatalysis and biodegradation (ICPB) provides superior treatment for the degradation of bio-recalcitrant compounds, such as chlorophenol. Photocatalytically generated intermediates can be promptly used by the enclosed biofilms. Chlorophenol degradation can theoretically be accelerated by a co-substrate or be compromised by the competition for photocatalytic reactive oxygen species (ROS); however, studies to examine the comparison are limited in number. Non-chlorinated phenols commonly co-exist in real wastewater; thus, we evaluated the influence of phenol (hard to photo-oxidize) and pyrocatechol (easy to photo-oxidize) on the degradation of 4-chlorophenol (4CP). The removal efficiency of 4CP was 51%, which increased to 62% after phenol addition. Meanwhile, the dechlorination efficiency of 4CP increased from 47 to 63%; similarly, the living/dead cell ratio increased from 49/51 to 79/21. However, pyrocatechol addition led to a decrease in 4CP removal efficiency to 32% and a reduction in living/dead cell ratio to 35/65. The differences in the results were attributed to the extra electron donors provided by the photodegraded products of phenol to bacteria, which enhanced 4CP degradation; meanwhile, pyrocatechol competed with 4CP for ROS, thus inhibiting its degradation. Competition for ROS and co-substrate properties should be considered in the treatment of phenolic wastewater by ICPB. [ABSTRACT FROM AUTHOR]

In the present study, the immobilizing fermentation characteristics and o-chlorophenol biodegradation of Rhodopseudomonas palustris using mycelial pellets as a biomass carrier were investigated. To improve the o-chlorophenol degradation efficiency of the combined mycelial pellets, eight cultivation variables including glucose concentration, yeast extract concentration, spore inoculum size, pH, and agitation speed were optimized with an integrated strategy involving a combination of statistical designs. First, Plackett-Burman experiments identified glucose, yeast extract, and spore inoculum size as three statistically significant factors important for o-chlorophenol removal. Then, the steepest ascent method was used to access the optimal region of these significant factors. Finally, response surface methodology by Box-Behnken optimization was used to examine the mutual interactions among these three variables to determine their optimal levels. The ideal culture conditions for maximum o-chlorophenol removal according to a second-order polynomial model were as follows: 15.60 g/L glucose, 3.09 g/L yeast extract, and 9% ( v/ v) spore inoculum size, resulting in an expected o-chlorophenol removal rate of 92.60% with an o-chlorophenol initial concentration of 50 mg/L and 96-h culture time. The correlation coefficient ( R = 0.9933) indicated excellent agreement between the experimental and predicted values, whereas a fair association was observed between the predicted model values and those obtained from subsequent experimentation at the optimized conditions. [ABSTRACT FROM AUTHOR]

A non-steady-state mathematical model system for the kinetics of adsorption and biodegradation of 2-chlorophenol (2-CP) by attached and suspended biomass on activated carbon process was derived. The mechanisms in the model system included 2-CP adsorption by activated carbon, 2-CP mass transport diffusion in biofilm, and biodegradation by attached and suspended biomass. Batch kinetic tests were performed to determine surface diffusivity of 2-CP, adsorption parameters for 2-CP, and biokinetic parameters of biomass. Experiments were conducted using a biological activated carbon (BAC) reactor system with high recycled rate to approximate a completely mixed flow reactor for model verification. Concentration profiles of 2-CP by model predictions indicated that biofilm bioregenerated the activated carbon by lowering the 2-CP concentration at the biofilm-activated carbon interface as the biofilm grew thicker. The removal efficiency of 2-CP by biomass was approximately 98.5% when 2-CP concentration in the influent was around 190.5 mg L at a steady-state condition. The concentration of suspended biomass reached up to about 25.3 mg L while the thickness of attached biomass was estimated to be 636 μm at a steady-state condition by model prediction. The experimental results agree closely with the results of the model predictions. [ABSTRACT FROM AUTHOR]

The presence of chlorophenols (CP) in industrial wastewater is a major concern due to their microbial toxicity. The present study was performed to investigate the efficacy of advanced oxidation process (i.e., conventional and modified Fenton's process) for the degradation of 4-chlorophenol (4-CP) in an aqueous solution (concentration = 200 mg L−1) under varying reaction conditions. The decomposition of 4-CP was confirmed by chemical oxygen demand (COD) reduction, total organic carbon (TOC) reduction, detection of low molecular weight carboxylic acids (such as oxalic, acetic, formic and malonic) and Cl- concentration in the treated 4-CP aqueous solution. The maximum COD and TOC reductions were 74% and 42% after 30 min of Fenton reaction at an initial pH, Fe2+ concentration, and H2O2 to Fe2+ molar ratio of 3.0, 1.26 mM and 20, respectively which were found to increase to 79 and 55%, respectively when Cu2+ was also added with Fe2+ during modified Fenton process. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1734-1742, 2017 [ABSTRACT FROM AUTHOR]

In this study, cphC-I and cphB, encoding a putative two-component flavin-diffusible monooxygenase (TC-FDM) complex, were cloned from Arthrobacter chlorophenolicus A6. The corresponding enzymes were overexpressed to assess the feasibility of their utilization for the oxidative decomposition of 4-chlorophenol (4-CP). Soluble CphC-I was produced at a high level (∼50%), and subsequently purified. Since CphB was expressed in an insoluble form, a flavin reductase, Fre, cloned from Escherichia coli was used as an alternative reductase. CphC-I utilized cofactor FADH 2 , which was reduced by Fre for the hydroxylation of 4-CP. This recombinant enzyme complex exhibited a higher specific activity for the oxidation of 4-CP (45.34 U/mg-protein) than that exhibited by CphC-I contained in cells (0.18 U/mg-protein). The Michaelis-Menten kinetic parameters were determined as: v max = 223.3 μM·min −1 , K M = 249.4 μM, and k cat /K M = 0.052 min −1 ·μM −1 . These results could be useful for the development of a new biochemical remediation technique based on enzymatic agents catalyzing the degradation of phenolic contaminants. [ABSTRACT FROM AUTHOR]

This work focused on the anaerobic digestion performance of pulp and paper mill sludge (PPMS) pretreated with the microbial consortium OEM1, and exposing the mechanism of performance variations as well. It was found that the methane yield was increased 1.4-fold by pretreating feedstocks with the active OEM1, and the maximum methane yield of 429.19 mL/gVS was noted. Moreover, an appropriate pH range of 6.1–7.5 was found in this digester, and no VFA inhibition was observed. A higher level of stability was also detected in this system based on the analysis of ORP, alkalinity and VFA/TA ratio. Also, a higher lignin decomposition rate was determined in the coupled pretreatment - AD process with the active OEM1 addition, and a 5-fold increase of AOX degradation efficiency was found in the pretreatment stage. Hence, a brighter future of developing OEM1 pretreatment for PPMS before AD could be predicted based on the capabilities of selective delignification and effective AOX degradation. [ABSTRACT FROM AUTHOR]

Stopped-flow technology and HPLC analysis were used to study the degradation mechanism and reaction kinetics of 4-chlorophenol (4-CP) in Fenton oxidation process. The results indicated that benzoquinone and hydroquinone were simultaneously produced in process of Fenton oxidizing 4-CP by stopped-flow technology analysis. The data obtained by HPLC showed that hydroquinone was generated in great quantities following the decrease of benzoquinone. It could be inferred by batch experiments that benzoquinone would be transformed into hydroquinone in Fenton process and hydroperoxyl radical (HO·) would take the main part in this process. In our study, there would exist two catalytic systems in Fenton process, and one was Feand Fe, the other was hydroquinone and benzoquinone. Moreover, the rate constants of hydroquinone, benzoquinone, and 4-chlorocatechol were 2.78 × 10 L s mol, 9.38 × 10 L s mol, and 6.47 × 10 L s mol, respectively. [ABSTRACT FROM AUTHOR]

W-doped TiO 2 and Mo-doped TiO 2 photocatalysts were synthesized by EISA method and were characterized by different techniques. The photoactivity of these materials was evaluated by the degradation of 4-chlorophenol without oxygen supply. The catalysts exhibited only anatase crystalline phase and high specific surface areas of about 179 m 2 g −1 . The amount of dopant cations in TiO 2 was a key parameter to increase the photoactivity. The results obtained show that with low dopant concentrations the degradation is improved, and this can be attributed to an increase in the lifetime of the photogenerated charges due to that dopant cations may easily trap electrons decreasing the recombination rate. Doped photocatalysts degraded 95% of 4CP, three times faster than Degussa P25. 69% reduction of total organic carbon (TOC) content was achieved by 1 wt.% W-doping. [ABSTRACT FROM AUTHOR]

To further enhance the photocatalytic properties of doped-TiO 2 , a series of (N, Cu) co-doped TiO 2 /rectorite composites with different amount of N doping were prepared for adsorption and catalytic oxidation of p -chlorophenol ( p -CP) under visible light. The physicochemical properties of the obtained composites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), etc. The results showed that the (N, Cu) co-doped TiO 2 catalyst was immobilized well onto rectorite, and the doping of N and Cu could affect the crystal structure of TiO 2 . The optimal N doping amount was determined by the photocatalytic degradation of p -CP in a stirred quartz reactor under visible light (> 420 nm) irradiation. It was found that the doping of N can improve significantly the degradation of p -CP and the optimum N doping amount is 1.0%. The adsorption of p -CP by the composites could accelerate the degradation rate of p -CP in situ. The photocatalytic activity of the (N, Cu) co-doped TiO 2 /rectorite composites remained stable after five cycles of photoreaction. A possible mechanism for the photocatalytic degradation of p -CP is proposed. Our work implied that rectorite has great potential to be applied in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

Yeast cells exhibit a negative surface potential due to negative charges at the cell membrane surface. Consequently, local concentrations of cations at the periplasmic membrane surface may be significantly increased compared to their bulk environment. However, in cell suspensions only bulk concentrations of cations can be measured directly. Here we present a novel method enabling the assessment of local pH at the periplasmic membrane surface which can be directly related to the underlying cell surface potential. In this proof of concept study using Saccharomyces cerevisiae cells with episomally expressed pH reporter, pHluorin, intracellular acidification induced by the addition of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) was measured using synchronously scanned fluorescence spectroscopy (SSF). The analysis of titration curves revealed that the pH at the periplasmic surface of S. cerevisiae cells was about two units lower than the pH of bulk medium. This pH difference was significantly decreased by increasing the ionic strength of the bulk medium. The cell surface potential was estimated to amount to −130 mV. Comparable results were obtained also with another protonophore, pentachlorophenol (PCP). [ABSTRACT FROM AUTHOR]

This study investigated a novel approach for the synthesis of an integrated ternary nanocomposite which could act as a good photo-catalyst under visible light irradiation for the removal of organic pollutants from aqueous environments. The photo-catalyst included nickel oxide (NiO) as a dopant, and reduced graphene oxide (RGO) as a good carbon basal support for enhancement of the photo-catalytic activity of TiO 2 . Under irradiation with visible light, the ternary nanocomposite (TiO 2 /NiO-RGO) system generates e − /h + pairs, and then reacts with H 2 O and O 2 − molecules to produce oxy-radicals which can be used for the mineralization of o -chlorophenol from aqueous solution. The characteristic of all photo-catalysts were investigated by UV-Vis analysis, with surface area and pore size measurements by Brunauer-Emmett-Teller (BET), crystallinity by X-ray diffraction (XRD), elemental composition by X-ray photoelectron spectroscopy (XPS), and morphology by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The functional groups were measured by Fourier transform infrared (FT-IR) spectroscopy before and after o -chlorophenol degradation. TiO 2 /NiO-RGO was capable of achieving 88.4% photo-degradation of 100 mg/L o -chlorophenol (100 mL) within 8 h with addition of 0.01% H 2 O 2 under visible light irradiation at pH 6.5. The photo-degradation followed a pseudo-first-order reaction. The TiO 2 /NiO-RGO nanocomposite retained its high removal efficiency, even after four photo-catalytic cycles. [ABSTRACT FROM AUTHOR]

In UV-254 nm/HO advanced oxidation process (AOP), the potential degradation pathways for organic pollutants include (1) hydrolysis, (2) direct HO oxidation, (3) UV direct photolysis, and (4) hydroxyl radical (HO) reaction. In this study, the contribution of these pathways was quantitatively assessed in the photochemical destruction of 4-chlorophenol (4-CP), demonstrating pathways (3) and (4) to be predominantly responsible for the removal of 4-CP by UV/HO in 50 mM phosphate buffer solution. Increasing reaction pH could significantly enhance the contribution of direct photolysis in UV/HO process. The contribution of HO oxidation was improved with increasing initial HO concentration probably due to the increased formation of HO. Presence of sodium carbonate (NaCO) as in UV/HO/NaCO system promoted the degradation of 4-CP, with carbonate radical (CO) reaction and direct photolysis identified to be the main contributing pathways. The trends in the contribution of each factor were further evaluated and validated on the degradation of the antibiotic compound oxytetracycline (OTC). This study provides valuable information on the relative importance of different reaction pathways on the photochemical degradation of organic contaminants such as 4-CP and OTC in the presence and absence of a CO precursor. [ABSTRACT FROM AUTHOR]

The kinetics of the oxidation of chlorophenols (CPs) by potassium permanganate was studied in the present study, along with the changes in oxidant dosage, pH, temperature, and real water matrices. The reactions between permanganate and three kinds of CPs, i.e. 4-chlorophenol (4-MCP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP), are second order overall and first-order with respect to each reactant. The degradation rates of the CPs increase with increasing permanganate dosage or temperature. pH plays an important role during permanganate oxidation. With the increase in pH from 4.0 to 10.0, the reaction rates of 4-MCP and 2,4-DCP decrease first and then increase, and finally decrease rapidly when pH > pKa, while the rates of 2,4,6-TCP decrease continuously. The degradation rates of the CPs are obviously higher in real water than in pure water. The reaction rate follows the order of 2,4,6-TCP > 2,4-DCP > 4-MCP under acidic conditions, and follows the reverse order under alkaline conditions in both pure water and real water. [ABSTRACT FROM AUTHOR]

BACKGROUND An innovative approach for ex situ soil bioremediation, based on absorptive polymers extraction combined with biological regeneration of the polymer in a two-phase partitioning bioreactor ( TPPB), was tested to remediate soil contaminated by chlorophenols. The objective of the study was to evaluate the performance of the proposed technology in comparison with conventional technologies, such as slurry bioreactors and solid-phase bioreactors. RESULTS A soil highly contaminated (∼4 g kg−1 for each compound) by a mixture of 4-chlorophenol ( 4CP) and pentachlorophenol ( PCP), was treated with different bioremediation systems. Removal efficiencies achieved with polymer extraction were >70% for a contact time of 24 h; the contaminated polymer was then regenerated in a TPPB (∼100 and 85% biodegradation efficiencies for 4CP and PCP, respectively). No degradation of PCP occurred in conventional bioreactors, while, for 4CP, 40 days were required for its biodegradation in the slurry bioreactor, and 80 days to reach 67% removal in the solid-phase bioreactor. CONCLUSION Advantages of the two-step polymer-based soil treatment in comparison with conventional technologies have been demonstrated for chlorophenols contaminated soils: efficiencies in the range 70-80% for soil decontamination and almost complete mineralization of the two compounds were achieved with reaction times suitable for application (<20 days). © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The effectiveness of ozone and ozone-UV processes on effluents containing chlorophenol was evaluated. Experiments were performed using 3.06 mM of 2,5-dichlorophenol in distilled water and wastewater at pH 7 with ozone dose of 37 mg/L. An ozone dose of 1.2 g/h was effective in completely degrading 2,5-dichlorophenol and reducing the toxicity of its by-products. Overall, ozone-UV process was more effective in the oxidation of 2,5-DCP. Ozone-UV treatment of wastewater showed the highest mineralization (53%), dechlorination (100%), COD removal (75%), and biodegradability (BOD5/COD = 0.85). The organic/inorganic matters in wastewater seem to have a positive effect on the oxidation of 2,5-DCP and supports the use of ozone and ozone-UV processes for industrial effluent treatment. [ABSTRACT FROM AUTHOR]

BACKGROUND Electrolysis with an iron anode is a novel way to provide ferrous activators for chemical oxidation. The objective of this study is to evaluate the performance of peroxymonosulfate ( PMS) for chlorophenol destruction when compared with H2O2 and persulfate ( PS), and to see whether the electrolysis mode facilitates the buildup of conditions that favor the activation of PMS and removal of chlorophenols. RESULTS Ferrous species can effectively activate the PMS over a wide pH range. In comparison with H2O2 and PS, PMS is less sensitive to the solution's pH and possesses stronger oxidation capability at alkaline pHs. The optimal molar ratio of PMS to Fe( II) activator is 1:1 for the destruction of 2,4-dichlorophenol (2,4- DCP). The column experiments show that an acidic zone developed downstream from the anode is favorable to maintain ferrous ions and subsequent activation of PMS. The reactivity of the PMS can be manipulated by varying the electrical currents, and the process demonstrates effectiveness for treating organic contaminants. 2,4- DCP contaminated groundwater shows decreased biotoxicity after the chemical oxidation process without considering the residual PMS. CONCLUSIONS Iron electrolysis-assisted peroxymonosulfate chemical oxidation can effectively treat the 2,4-dichlorophenol and mixtures of organic contaminants. This process can be engineered as an in situ chemical oxidation method for groundwater remediation. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, co-metabolic degradation of monochlorophenols (2-CP, 3-CP, and 4-CP) by the Pseudomonas sp. CF600 strain in the presence of phenol, sodium benzoate, and 4-hydroxybenzoic acid as an additional carbon source as well as the survival of bacteria were investigated. Moreover, the changes in cellular fatty acid profiles of bacteria depending on co-metabolic conditions were analyzed. It was found that bacteria were capable of degrading 4-CP completely in the presence of phenol, and in the presence of all substrates, they degraded 2-CP and 3-CP partially. The highest 2-CP and 3-CP removal was observed in the presence of sodium benzoate. Bacteria exhibited three various dioxygenases depending on the type of growth substrate. It was also demonstrated that bacteria exposed to aromatic growth substrates earlier degraded monochlorophenols more effectively than unexposed cells. The analysis of fatty acid profiles of bacteria indicated the essential changes in their composition, involving alterations in fatty acid saturation, hydroxylation, and cyclopropane ring formation. The most significant change in bacteria exposed to sodium benzoate and degrading monochlophenols was the appearance of branched fatty acids. The knowledge from this study indicates that Pseudomonas sp. CF600 could be a suitable candidate for the bioaugmentation of environments contaminated with phenolic compounds. [ABSTRACT FROM AUTHOR]

The solar photocatalytic degradation of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) was investigated individually and combined in the presence of Fe2+ and Fe3+ ions. The results revealed that both Fe2+ and Fe3+ ions enhanced the heterogeneous photocatalytic degradation. Fe3+ ions rapidly converted to Fe2+ ions as soon as the irradiation started. The intermediates formed during the degradation of 4-CP/2,4-DCP were also monitored and identified. Three main intermediates were observed, hydroquinone, phenol, and 4-chlorocatecholwith traces of benzoquinone. The results support a new trend of research by utilising other cheap iron ion sources in the photocatalytic degradation. [ABSTRACT FROM AUTHOR]

Recombinant strain Xz6-1 was constructed by the protoplast fusion technique with the goal of endowing it with the ability to efficiently degrade pentachlorophenol (PCP). This compound was considered as a representative of possible compounds that can be obtained during the bleaching of pulp for papermaking. The potential of Xz6-1 and Pseudomonas putida to treat PCP synthetic wastewater was explored. The majority of PCP was removed within the first 20 h; two degradation curves were obtained that followed first-order reaction kinetics. The kinetics data revealed that the rate constant for degradation of PCP for Xz6-1 was 0.063 h-1, a value that was over 50% greater than that of Pseudomonas putida (0.040 h-1). Aerobic granular sludge was highly fortified with Xz6-1 and Pseudomonas putida to provide PCP degradability improvements of 180.9% and 98.3%, respectively, relative to the original sludge. All results demonstrate that the protoplast fusion technique is an effective approach to construct a high-activity chlorophenol-degrading strain. [ABSTRACT FROM AUTHOR]

Microreactors receive a lot of interest in photochemical application, however, the fundamental effects of micro flow on the photochemical reactions have not been fully understood so far. We report on the investigation of the combined effect of temperature and concentration of dissolved oxygen on degradation of 4-chlorophenol in photo microreactor. Sulfonated zinc phthalocyanine was used as a photosensitizer to generate singlet oxygen. Temperature and dissolved oxygen affect the overall reaction, however, the effect is not straightforward. To investigate their combined effect, the experiments were carried out in the advanced opto-chemical apparatus with a thin-gap photo microreactor. To obtain accurate information on actual process conditions, temperature of the reaction zone was measured by an integrated temperature sensor and the concentration of dissolved oxygen was measured by the in-line oxygen probe. As results, the reaction rate constant of the model reaction was evaluated and the apparent activation energy was calculated. [ABSTRACT FROM AUTHOR]

Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is a widely used antimicrobial agent that undergoes fairly slow biodegradation. It is often found in surface waters in both the acidic (HTric) and basic (Tric − ) forms (pK a ∼8), and it can undergo direct photodegradation to produce several intermediates including a dioxin congener (2,8-dichlorodibenzodioxin, hereafter 28DCDD). The latter is formed from Tric − and causes non-negligible environmental concern. Differently from current literature reports, in this paper we show that the direct photolysis would not be the only important transformation pathway of triclosan in surface waters. This is particularly true for HTric, which could undergo very significant reactions with • OH and, if the laser-derived quenching rate constants of this work are comparable to the actual reaction rate constants, with the triplet states of chromophoric dissolved organic matter ( 3 CDOM*). Model calculations suggest that reaction with 3 CDOM* could be the main HTric phototransformation pathway in deep waters with high dissolved organic carbon (DOC), while reaction with • OH could prevail in low-DOC waters. In the case of Tric − the direct photolysis is much more important than for HTric, but triplet-sensitised transformation could produce 28DCDD + 27DCDD with higher yield compared to the direct photolysis, and it could play some role as dioxin source in deep waters with elevated DOC. [ABSTRACT FROM AUTHOR]

Two examples of heterometallic-organic frameworks (HMOFs) composed of dicarboxyl-functionalized FeIII-salen complexes and d10 metals (Zn, Cd), [Zn2(Fe-L)2(µ2-O)- (H2O)2]∙4DMF∙4H2O (1) and [Cd2(Fe-L)2(m2-O)(H2O)2]∙2DMF∙H2O (2) (H4L=1,2-cyclohexanediamino-N,N'-bis(3-methyl-5- carboxysalicylidene), have been synthesized and structurally characterized. In 1 and 2, each square-pyramidal FeIII atom is embedded in the [N2O2] pocket of an L4- anion, and these units are further bridged by a µ2-O anion to give an (Fe-L)2(µ2-O) dimer. The two carboxylate groups of each L4- anion bridge ZnII or CdII atoms to afford a 3D porous HMOF. The gas sorption and magnetic properties of 1 and 2 have been studied. Remarkably, 1 and 2 show activity for the photocatalytic degradation of 2-chlorophenol (2-CP) under visible-light irradiation, which, to the best of our knowledge, is the first time that this has been observed for FeIII-salenbased HMOFs. [ABSTRACT FROM AUTHOR]

In this study, TiO2 particles were used as photocatalysts for the degradation of aqueous p-chlorophenol (p-CP) under UV irradiation. The effect of TiO2 dose (0–3 g/L), initial p-CP concentration, H2O2 concentration (2–45 mM), solution pH (4.6–9.5), and UV light intensity on the degradation of p-CP were examined. Four oxidative degradation processes, which utilized UV alone (direct photolysis), H2O2/UV, TiO2/UV, and H2O2/TiO2/UV, were compared in a batch photoreactor with a 100-W high-pressure mercury lamp. The photodegradation of p-CP could be described by the pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Moreover, the apparent degradation rate constants increased considerably from 3.5 × 10− 3 min−1 (direct photolysis) to 19.9 × 10− 3 min−1(H2O2/TiO2/UV system). [ABSTRACT FROM AUTHOR]

Toxicand bioresistant compounds have attracted researchers todevelop more efficient and cost-effective technologies for degradationof organic compounds in wastewater. This work demonstrates the degradationof 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, andphenol as model compounds using bicarbonate-activated H2O2oxidation system in the presence of supported catalysts.The catalytic activity of the catalyst was investigated in term ofdegradation of target compounds, chemical oxygen demand (COD), andtotal organic carbon (TOC) removals both for batch mode and in fixedbed reactor using CoMgAl-HTs and CoMgAl-SHTs, respectively. The leachingof cobalt ion was efficiently prohibited because of the presence ofa weakly basic medium provided by bicarbonate, and the CoMgAl-SHTscatalyst was found to retain its stability and good catalytic activityin fixed bed reactor for over 300 h. Extensive chemical probing, fluorescence,and electron paired resonance (EPR) studies were conducted to identifythe actual reactive species in the degradation pathway, which revealedthat the reaction proceeds through generation of superoxide, hydroxylradical along with carbonate radical. [ABSTRACT FROM AUTHOR]

To investigate the enhancement of phenol on the biodegradation of 4-chlorophenol (4-cp), metabolic profiling approach was performed for the first time to analyze metabolite changes of Pseudomonas sp. cbp1-3 using single substrate (succinate, phenol, and 4-cp) and dual substrate (mixtures of phenol and 4-cp). Phosphoric acid, γ-aminobutyric acid, 4-cp, 4-chlorocatechol, and catechol were shown to change significantly. Results indicated that phenols, especially 4-cp, depressed cell growth by inhibiting its primary metabolic pathway. In addition, the addition of phenol into the 4-cp-containing medium had a global influence on cells including the accumulation of amino acids, amines, saturated fatty acids, and monoacylglycerols as well as the concentration changes of metabolite participating in phenols biodegradation, thus enhancing the degradation of 4-cp. This study provided novel insights into the biodegradation of mixed phenolic compounds and the method could be used to investigate the biodegradation of complicated multi-pollutants. [ABSTRACT FROM AUTHOR]

The present investigation focused on a clean and green destruction of 2,4-dichlorophenol (2,4-DCP) under natural sunlight using pristine, carbon doped and carbon–iron co-doped electrospun TiO 2 fibers. The synthesized fibers were characterized by XRD, HR-SEM, EDX, UV–vis spectroscopy and BET specific surface area analysis. From XRD, the co-doped samples were found to contain beneficial fraction of 73% anatase and 27% rutile phases. From HR-SEM, the fibrous structure was found to be retained after the doping and co-doping processes. The effect of operating variables like pH, catalyst dosage, oxidant concentration, solar intensity and initial pollutant concentration was also investigated. Solar photo-Fenton’s degradation of 2,4-DCP was favorable at pH 3 than at basic pH and an oxidant concentration of 9.9 mM/L was sufficient to effectively mineralize 2,4-DCP. The rate of degradation was remarkably high when the intensity of sunlight was >85 kiloLUX and decreased with decrease in solar intensity, however, complete degradation of 2,4-DCP was possible till very low solar intensity of 20 klx. [ABSTRACT FROM AUTHOR]

Bromophenol is listed as priority pollutant by U.S. EPA, however, there is no report so far on its removal in mixed pollutants system by any biological reactor operated in continuous mode. Furthermore, bromophenol along with chlorophenol and nitrophenol are usually the major constituents of paper pulp and pesticide industrial effluent. The present study investigated simultaneous biodegradation of these three pollutants with specially emphasis on substrate competition and crossed inhibition by Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor (UPBR). A 2 full factorial design was employed with these pollutants at two different levels by varying their influent concentration in the range of 250-450 mg l. Almost complete removal of all these pollutants and 97 % effluent toxicity removal were achieved in the UPBR at a pollutant loading rate of 1707 mg l day or lesser. However, at higher loading rates, the reactor performance deteriorated due to transient accumulation of toxic intermediates. Statistical analysis of the results revealed a strong negative interaction of 4-CP on 4-NP biodegradation. On the other hand, interaction effect between 4-CP and 4-BP was found to be insignificant. Among these three pollutants 4-NP preferentially degraded, however, 4-CP exerted more inhibitory effect on 4-NP biodegradation. This study demonstrated the potential of A. chlorophenolicus A6 for biodegradation of 4-BP in mixed pollutants system by a flow through UPBR system. [ABSTRACT FROM AUTHOR]

The present work was designed to developed a granular anoxic baffled reactor (AnBR) and to investigate its performance in the treatment of 2-chlorophenol (2-CP). The acclimation and enrichment of microorganisms in activated sludge to degrade 2-CP was effectively accomplished. Then the influence of inlet 2-CP, hydraulic retention time (HRT), salinity, and type of electron acceptor (nitrate or organic compound) on the performance of AnBR in biodegradation of 2-CP was investigated. The increase of inlet 2-CP from 50 to 500 mg/L at a fixed HRT of 24 h did not adversely affected the AnBR where over 99% of inlet 2-CP was biodegraded. Decreasing the HRT stepwise from 24 to 4 h at an inlet 2-CP of 200 mg/L did not inhibit the rate of biodegradation (>99%). The increase of over 20 g/L salinity in the feed stream strongly inhibited the rate of 2-CP biodegradation in the AnBR, whereas the bioreactor could efficiently tolerate concentrations below 20 g/L NaCl. Moreover, the rate of 2-CP biodegradation under anoxic denitrifying metabolic conditions (presence of nitrate) was much greater than that under anaerobic metabolic conditions (absence of nitrate). Accordingly, the AnBR process is a feasible, simple, low-cost, and thus appropriate process for efficiently biodegrading toxic chlorinated organic compounds. [ABSTRACT FROM AUTHOR]

The variation of the microbial activity during starvation of microorganisms degrading 4-chlorophenol was evaluated in a sequencing batch reactor. During the acclimation, a reduction in the degradation time and an increase in the specific degradation rate were observed. After the acclimation, the biomass was exposed to different starvation periods (8 to 36 h). The results showed that the starvation could decrease the microbial activity and composition. A reduction from 44 to 21% was observed on the specific removal rate, and from 35 to 26% on the specific oxygen uptake rate. The extension of the deacclimation of starved microorganisms was affected by the history of the culture. The effect of starvation on the degradation rate was less significant when microorganisms were starved, recovered and then starved again, than in the case where starvation is cyclically presented without a recovery period. [ABSTRACT FROM AUTHOR]