Degradation of organic contaminants through the activation of oxygen using zero valent copper coupled with sodium tripolyphosphate under neutral conditions

In this study,sodium tripolyphosphate(STPP) was used to promote the removal of organic pollutants in a zero-valent copper(ZVC)/O_2 system under neutral conditions for the first time.20 mg/L p-nitrophenol(PNP) can be completely decomposed within 120 min in the ZVC/O_2/STPP system.The PNP degradation process followed pseudo-first-order kinetics and the degradation rate of PNP gradually increased upon the decreasing ZVC particle size.The optimal pH of the reaction system was 5.0.Our mechanism investigation showed that Cu~+generated by ZVC corrosion was the main reducing agent for the activation of 02 to produce ROS.-OH was identified as the only ROS formed during the degradation of PNP and its production pathway was the double-electron activation of O_2(O_2→H_2 O_2→·OH).In this process,STPP did not only promote the release of Cu~+through its complexation,but also promoted the production of OH by reducing the redox potential of Cu~(2+)/Cu~+.In addition,we could initiate and terminate the reaction by controlling the pH.At pH 8.1,ZVC/02/STPP could continuously degrade organic pollutants;at pH 8.1,the reaction was terminated.STPP was recycled to continuously promote the corrosion of ZVC and O_2 activation as long as the pH was 8.1.This study provided a new and efficient way for O_2 activation and organic contaminants removal.     

Degradation kinetics and mechanism of aniline by heat-assisted persulfate oxidation

Oxidation of aniline by persulfate in aqueous solutions was investigated and the reaction kinetic rates under different temperature, persulfate concentration and pH conditions were examined in batch experiments. The results showed that, the aniline degradation followed pseudo first-order reaction model. Aniline degradation rate increased with increasing temperature or persulfate concentration. In the pH range of 3 to 11, a low aniline degradation rate was obtained at strong acid system (pH 3), while a high degradation rate was achieved at strong alkalinity (pH 11). Maximum aniline degradation occurred at pH 7 when the solution was in a weak level of acid and alkalinity (pH 5, 7 and 9). Produced intermediates during the oxidation process were identified using liquid chromatography-mass spectrometry technology. And nitrobenzene, 4-4’-diaminodiphenyl and 1-hydroxy-1,2-diphenylhydrazine have been identified as the major intermediates of aniline oxidation by persulfate and the degradation mechanism of aniline was also tentatively proposed.     

Non-radical activation of persulfate with Bi2O3/BiO1.3I0.4 for efficient degradation of propranolol under visible light

Non-radical activation of persulfate (PS) by photocatalysts is an effective approach for removing organic pollutants from aqueous environments.In this study,a novel Bi₂O₃/BiO_1.3I_0.4heterojunction was synthesized using a facile solvothermal approach and used for the first time for non-radical activation of PS to degrade propranolol (PRO) in the presence of visible light.The findings found that the degradation rate of PRO in the Bi₂O₃     

Photodegradation of Orange Ⅱ using waste paper sludge-derived heterogeneous catalyst in the presence of oxalate under ultraviolet light emitting diode irradiation

A waste paper sludge-derived heterogeneous catalyst(WPS-Fe-350) was synthesized via a facile method and successfully applied for the degradation of Orange Ⅱ in the presence of oxalic acid under the illumination of ultraviolet light emitting diode(UV-LED) Powder X-ray diffraction,Fourier-transform infrared spectroscopy,scanning electronic microscopy and N2 sorption isotherm analysis indicated the formation of α-Fe2O3 in the mesoporous nanocomposite.The degradation test showed that WPS-Fe-350 exhibited rapid Orange Ⅱ(OⅡ) degradation and mineralization in the presence of oxalic acid under the illumination of UV-LED.The effects of p H,oxalic acid concentration and dosage of the catalyst on the degradation of OⅡ were evaluated,respectively.Under the optimal conditions(1 g/L catalyst dosage,2 mmol/L oxalic acid and p H 3.0),the degradation percentage for a solution containing 30 mg/L OⅡ reached 83.4% under illumination by UV-LED for 80 min.Moreover,five cyclic tests for OⅡ degradation suggested that WPS-Fe-350 exhibited excellent stability of catalytic activity.Hence,this study provides an alternative environmentally friendly way to reuse waste paper sludge and an effective and economically viable method for degradation of azo dyes and other refractory organic pollutants in water.     

Production of laccase by Coriolus versicolor and its application in decolorization of dyestuffs: (Ⅱ) Decolorization of dyes by laccase containing fermentation broth with or without self-immobilized mycelia

The capability of decolorization for commercial dyes by Coriolus versicolur fermentation broth containing laccase with or without immobilized mycelium was evaluated.With cell-free fermentation broth containing laccase,high decolorization ratio was achieved for acid orange 7,but not for the other dyes concerned.The immobilized mycelium was proved to be more efficient than the cell-free system.All the four dyestuffs studied were found being decolourized with certain extent by immobilized mycelium.The repeated-batch decolorization was carried out with satisfactory results.The experimental data showed that the continuous decolorization of wastewater from a printing and dyeing industry was possible by using self-immobilized C.Versicolor.     

Insights into the mechanism of multiple Cu-doped Co Fe2O4 nanocatalyst activated peroxymonosulfate for efficient degradation of Rhodamine B

The multiple metal catalyst as a promising nanomaterial has shown excellent activity in the peroxymonosulfate (PMS) activation for pollutant degradation.However,the role of special sites and in-depth understanding of the PMS activation mechanism are not fully studied.In this study,a Cu-doped CoFe₂O₄nanocatalyst (0.5CCF) was synthesized by a sol-gel and calcination method,and used for PMS activation to remove Rhodamine B (RhB).The results showed that the Cu doping obviously ...     

ORC-GAC-Fe0 system for the remediation of trichloroethylene and monochlorobenzene contaminated aquifer: 1. Adsorption and degradation

Activities at a former Chemistry Triangle in Bitterfeld, Germany, resulted in contamination of groundwater with a mixture of tdchloroethylene(TCE) and monochlorobenzene(MCB). The objective of this study was to develop a barrier system,which includes an ORC(oxygen release compounds) and GAC(granular activated carbon) layer for adsorption of MCB and bioregeneration of GAC, a Fe^0 layer for chemical reductive dechlorination of TCE and other chlorinated hydrocarbon in situ. A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system. This experiment was performed using a series of continuous flow Teflon columns including an ORC column, a GAC column, and a Fe^0 column. Simulated MCB and TCE contaminated groundwater was pumped upflow into this system at a flow rate of 1.1 ml/min. Results showed that 17%-50% of TCE and 28%-50% of MCB were dissipated in ORC column. Chloride ion, however, was not released, which suggest the dechlorination do not happen in ORC column. In GAC column, the adsorption of contaminants on activated carbon and their induced degradation by adapted microorganisms attached to the carbon surface were observed. Due to competitive exchange processes, TCE can be desorbed by MCB in GAC column and further degraded in iron column. The completely dechlorination rate of TCE was 0.16-0.18 cm^-1, 1-4 magnitudes more than the formation rate of three dichloroethene isomers. Cis-DCE is the main chlorinated product, which can be cumulated in the system, not only depending on the formation rate and its decaying rate, but also the initial concentration of TCE.     

Catalytic degradation of methylene blue by Fenton like system: model to the environmental reaction

To develop more efficient chemical methods for the demineralization of organic pollutants from water bodies, which one was also mimic to the nature, a degradation of methylene blue by Fe( Ⅲ ) and H2O2 in the absence of light instead of Fe( Ⅱ ) and H2O2 was studied. Results showed that use of Fe ( Ⅲ ) is more promising than Fe( Ⅱ ). The present study reflects that Fenton reaction is more efficient, in the presence of a small amount of salicylic acid is added which is a one of the priority pollutant.     

Quantum chemical investigation on photodegradation mechanisms of sulfamethoxypyridazine with dissolved inorganic matter and hydroxyl radical

Sulfamethoxypyridazine(SMP) is one of the commonly used sulfonamide antibiotics(SAs).SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic environmental organic pollutants.In this work,SMP was selected as a representative of SAs.We studied the mechanisms of triplet-sensitized photodegradation of SMP and the influence of selected dissolved inorganic matter,i.e.,anions(Br~-,Cl~-,and NO~-_3) and cations ions(Ca~(2+),Mg~(2+),and Zn~(2+)) on SMP photodegradation mechanism by quantum chemical methods.In addition,the degradation mechanisms of SMP by hydroxyl radical(OH·) were also investigated.The creation of SO_2 extrusion product was accessed with two different energy pathways(pathway-1 and pathway-2) by following two steps(step-I and step-II) in the tripletsensitized photodegradation of SMP.Due to low activation energy,the pathway-1 was considered as the main pathway to obtain SO_2 extrusion product.Step-II of pathway-1 was measured to be the rate-limiting step(RLS) of SMP photodegradation mechanism and the effect of the selected anions and cations was estimated for this step.All selected anions and cations promoted photodegradation of SMP by dropping the activation energy of pathway-1.The estimated low activation energies of different degradation pathways of SMP with OH·radical indicate that OH·radical is a very powerful oxidizing agent for SMP degradation via attack through benzene derivative and pyridazine derivative ring.     

Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO2 nano-sheets in aqueous phase

Titanium dioxide(TiO2), which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabutyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetrachloroethene(PCE), trichloroethene(TCE) and 1,1,1-trichloroethane(TCA). The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commercial P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene(NB) as a probe of hydroxyl radical(.OH), the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of.OH generated in UV/synthesized TiO2system. In addition,.OH concentration was confirmed by the strong peak displayed in EPR analysis over UV/synthesized TiO2system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 nm, side length of 50 nm and width of 33 nm and a surface 90.3 m2/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater.     

Photoassisted Fenton degradation of phthalocyanine dyes from wastewater of printing industry using Fe(Ⅱ)/γ-Al2O3 catalyst in up-flow fluidized-bed

Fe(II)/γ-Al2O3 powders synthesized using the dipping method were produced from a mixed aqueous solution containing aluminium oxide(γ-Al2O3) and iron(II)-precursor(FeSO4), and used for photoFenton degradation of phthalocyanine dyes(PCS) under ultraviolet(UV) irradiation in an up-flow fluidized bed. The catalysts were characterized by XRD, ESCA, BET, EDS and SEM. The results showed that Fe2+ion was compounded on the γ-Al2O3 carrier. The effects of different reaction parameters such as catalyst activity, dosage and solution pH on the decolorization of PCS were assessed. Results indicated that maximum decolorization(more than 95%) of PCS occurred with20 wt% Fe(II)/γ-Al2O3 catalyst(dosage of 60 g/L) using a combination of UV irradiation and heterogeneous Fenton system. The degradation efficiency of PCSincreases as pH decreases, exhibiting a maximum efficiency at pH 3.5. The recycled catalyst was capable of repeating three runs without a significant decrease in treatment efficiency, and this demonstrated the stability and reusability of catalyst.     

Degradation of Reactive Yellow 86 with photo-Fenton process driven by solar light

The decolorization of Reactive Yellow 86(RY 86),one of reactive azo dyes,was investigated in the presence of Fenton reagent under solar light irradiation.The decolorization rate was strongly influenced by pH,initial concentrations of H 2 O 2 and Fe(II),and so on.An initial concentration of 40 mg/L was decolored more than 90% after 20 min under optimum conditions.The activation energy of the solar photo-Fenton reaction was 1.50 kJ/mol for RY 86 in the temperature range of 10-60°C.In the kinetic study,the rate constant of RY 86 with OH· radicals could be estimated to be 1.7 × 10 10 L/(mol·sec).The decolorization efficiency of RY 86 under solar light irradiation was comparable to the artificial light irradiation.The decrease of TOC as a result of mineralization of RY 86 was observed during photo-Fenton process.The rate of RY 86 mineralization was about 83% under UV irradiation after 24 hr.The formation of chloride,sulfate,nitrate and ammonium ions as end-products was observed during the photocatalytic process.The decomposition of RY 86 gave two kinds of intermediate products.The degradation mechanism of RY 86 was proposed on the base of the identified intermediates.     

Removal of benzotriazole by heterogeneous photoelectro-Fenton like process using ZnFe2O4 nanoparticles as catalyst

ZnFe2O4 nanoparticles(ZFNPs) were developed as catalyst for the degradation of benzotriazole(BTA) by heterogeneous photoelectroFenton(PE-Fenton) like process.ZFNPs were prepared by a co-precipitation process and then characterized with transmission electron microscopy(TEM),X-ray fluorescence(XRF),X-ray diffraction(XRD) and BET surface area.Using such ZFNPs as catalyst,the degradation of BTA was investigated.Due to the high catalytic activity of ZFNPs,PE-Fenton like process showed efficient degradation of BTA.The influencing factors such as pH,dosage of ZFNPs,applied potential and initial concentration of BTA were systematically investigated.Under the optimum conditions,91.2% of BTA was removed after 180 min treatment.     

A reactor system combining reductive dechlorination with cometabolic oxidation for complete degradation of tetrachloroentylene

A laboratory sequential anaerobic-aerobic bioreactor system, which consisted of an anaerobic fixed film reactor and two aerobic chemostats, was set up to degrade tetrachloroethylene (PCE) without accumulating highly toxic degradation intermediates. A soil enrichment culture, which could reductively dechlorinate 900/zM ( ca. 150 mg/L) of PCE stoichiometrically into cis-l, 2-dichloroethylene ( cis-DCE), was attached to ceramic media in the anaerobic fixed film reactor. A phenol degrading strain, Alcaligenes sp. 115, which can efficiently degrade cis-DCE by co-metabolic oxidation, was used as inocuhim for the aerobic chemostats consisted of a transformation reactor and a growth reactor.The anaerobic fixed film bioreactor showed more than 99 % of PCE transformation into cis-DCE in the range of influent PCE concentration from 5μM to 35μM at hydraulic retention time of 48h. On the other hand, efficient degradation of the resultant cis-DCE by strain R5 in the following aerobic system could not be achieved due to oxygen limitation. However, 54% of the maximum cis-DCE degradation was obtained when 10μmol of hydrogen peroxide (H2O2 ) was supplemented to the transformation reactor as an additional oxygen source. Further studies are needed to achieve more efficient co-metabolic degradation of cis-DCE in the aerobic reactor.     

Ultrasound enhanced heterogeneous activation of peroxydisulfate by bimetallic Fe-Co/GAC catalyst for the degradation of Acid Orange 7 in water

Bimetallic Fe-Co/GAC （granular activated carbon） was prepared and used as heterogeneous catalyst in the ultrasound enhanced heterogeneous activation of peroxydisulfate （PS, S2O8 2-） process. The effect of initial pH, PS concentration, catalyst addition and stirring rate on the decolorization of Acid Orange 7 （AO7） was investigated. The results showed that the decolorization efficiency increased with an increase in PS concentration from 0.3 to 0.5 g/L and an increase in catalyst amount from 0.5 to 0.8 g/L. But further increase in PS concentration and catalyst addition would result in an unpronounced increase in decolorization efficiency. In the range of 300 to 900 r/min, stirring rate had little effect on AO7 decolorization. The catalyst stability was evaluated by measuring decolorization efficiency for four successive cycles.     

Biodegradation of Crystal Violet by Agrobacterium radiobacter

Agrobacterium radiobacter MTCC 8161 completely decolorized the Crystal Violet with 8 hr (10 mg/L) at static anoxic conditions. The decreased decolorization capability by A. radiobacter was observed, when the Crystal Violet concentration was increased from 10 to 100 mg/L. Semi-synthetic medium containing 1% yeast extract and 0.1% NH4Cl has shown 100% decolorization of Crystal Violet within 5 hr. A complete degradation of Crystal Violet by A. radiobacter was observed up to 7 cycles of repeated addition (10 mg/L). When the effect of increasing inoculum concentration on decolorization of Crystal Violet (100 mg/L) was studied, maximum decolorization was observed with 15% inoculum concentration. A significant increase in the activities of laccase (184%) and aminopyrine N-demethylase (300%) in cells obtained after decolorization indicated the involvement of these enzymes in decolorization process. The intermediates formed during the degradation of Crystal Violet were analyzed by gas chromatography and mass spectroscopy (GC/MS). It was detected the presence of N,N,N′,N′′-tetramethylpararosaniline, [N; N-dimethylaminophenyl] [N-methylaminophenyl] benzophenone, N; N-dimethylaminobenzaldehyde, 4-methyl amino phenol and phenol. We proposed the hypothetical metabolic pathway of Crystal Violet biodegradation by A. radiobacter. Phytotoxicity and microbial toxicity study showed that Crystal Violet biodegradation metabolites were less toxic to bacteria (A. radiobacter, P. aurugenosa and A. vinelandii) contributing to soil fertility and for four kinds of plants (Sorghum bicolor, Vigna radiata, Lens culinaris and Triticum aestivum) which are most sensitive, fast growing and commonly used in Indian agriculture.     

Enhanced debromination of 4-bromophenol by the UV/sulfite process: Efficiency and mechanism

Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol(4-BP) by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH(6.1–10) and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N_2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.     

Removal of Cd2+ from water by Friedel’s salt (FS: 3CaO.Al2O3·CaCl2·10H2O): Sorption characteristics and mechanisms

The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel’s salt (FS:3CaO·A12O3 ·CaCl2 ·10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(Ⅱ) adsorption. The maximum adsorption capacity of the FS for Cd(Ⅱ) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(Ⅱ) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(Ⅱ) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(Ⅱ) from water.     

Solar active fire clay based hetero-Fenton catalyst over a wide pH range for degradation of Acid Violet 7

Fe(Ⅲ) immobilized fire clay (Fe-FC) was prepared using ferric nitrate by solid state dispersion method and this hetero-Fenton catalyst was applied for the degradation of Acid Violet 7 (AV 7) under natural sunlight. The 26% ferric nitrate loaded fire clay was found to be most efficient. The experimental conditions such as solution pH, H₂O₂ concentration for efficient degradation of AV 7 have been determined. Unlike Fenton catalyst, Fe-FC is photoactive over a wide pH range of 3-7. This catalyst was found to be stable and reusable. The GC-MS analysis of experimental solutions during irradiation revealed the formation of 2,8-diaminonaphthalene-1,3,6-triol, 8-aminonaphthalene-1,2,3,6-tetrol, 2-aminonaphthalene-1,3,6,8-tetrol and 2-aminobenzene-1,3-diol/5-aminonbenzene-1,3-diol/ 2-aminobenzene-1,4-diol as intermediates. The 26% ferric nitrate loaded fire clay was characterized by XRD, ICP-AES, BET surface area, FT-IR, SEM-EDS and UV-DRS studies.     

Degradation of benzene derivatives in the CuMgFe-LDO/persulfate system: The role of the interaction between the catalyst and target pollutants

A novel insight on the role of interactions between target pollutants and the catalyst in the copper-containing layered double oxide(LDO)-catalyzed persulfate(PS) system was elucidated in the present study.4-Chlorophenol(4-CP),as a representative benzene derivative with a hydroxyl group,was completely removed within 5 min,which was much faster than the reaction of monochlorobenzene(MCB) without a hydroxyl group,with the degradation efficiency of 31.7% in 240 min.Through the use of radical quenching and surface inhibition experiments,it could be concluded that the interaction between 4-CP and CuMgFe-LDO,rather than free radicals,played a key role in the decomposition of 4-CP,while only the free radicals participated in the MCB degradation process.According to electron paramagnetic resonance and Xray photoelectron spectroscopy data,the formation of a Cu(II)-complex between phenolic hydroxyl groups and surface Cu(II) was primarily responsible for the degradation of phenolic compounds,in which PS accepted one electron from the complex and generated sulfate radicals and chelated radical cations.The chelated radical cations transferred one electron to Cu(Ⅱ) followed by Cu(I) generation and pollutant degradation successively.