Characterization of V_2O_5/MoO_3 composite photocatalysts prepared via electrospinning and their photodegradation activity for dimethyl phthalate

Vanadium pentoxide（V2O5）/molybdenum trioxide（MoO 3） composites with different molar ratios of vanadium（V） to molybdenum（Mo） were synthesized via a simple electrospinning technique. The photocatalytic activity of the composites were evaluated by their ability to photodegrade methylene blue and dimethyl phthalate（DMP） under visible-light irradiation. Compared with pure V2O5 and MoO 3,the V2O5/MoO 3 composites showed enhanced visible-light photocatalytic activity because of a V 3d impurity energy level and the formation of heterostructures at the interface between V2O5 and MoO 3. The optimal molar ratio of V to Mo in the V2O5/MoO 3 composites was found to be around 1/2. Furthermore,high-performance liquid chromatographic monitoring revealed that phthalic acid was the main intermediate in the photocatalytic degradation process of DMP.

Mechanistic studies on peroxymonosulfate activation by g-C3N4 under visible light for enhanced oxidation of light-inert dimethyl phthalate

Excitation of metal-free graphitic carbon nitride(g-C3N4) under visible light can successfully achieve efficient activation of peroxymonosulfate(PMS). Synergistic effects and involved mechanism were systematically investigated using a light-inert endocrine disrupting compound, dimethyl phthalate(DMP), as the target pollutant. Under visible light irradiation, DMP could not be degraded by direct g-C3 N4-mediated photocatalysis, while in the presence of PMS, the dominant radicals were converted from ·O2 to SO4·– and ·OH, resulting in effective DMP degradation and mineralization. Results showed that higher dosage of PMS or g-C3 N4 could increase the activation amount of PMS and corresponding DMP degradation efficiency, but the latter approach was more productive in terms of making the most of PMS. High DMP concentration hindered effective contact between PMS and g-C3 N4, but could provide efficient use of PMS. Higher DMP degradation efficiency was achieved at p H lower than the point of zero charge(5.4). Based on intermediates identification, the DMP degradation was found mainly through radical attack(·OH and SO4·–) of the benzene ring and oxidation of the aliphatic chains.

Anoxic biodegradation of dimethyl phthalate (DMP) by activated sludge cultures under nitrate-reducing conditions

Worldwide extensive use of plasticized plastics has resulted in phthalates pollution in different environment. Nitrates from industry and agriculture are also widely disseminated in the soils, natural waters and wastewaters. Dimethyl phthalate （DMP） biodegradation by activated sludge cultures under nitrate-reducing conditions was investigated. Under one optimized condition, DMP was biodegraded from 102.20 mg/L to undetectable level in 56 h under anoxic conditions and its reaction fitted well with the first-order kinetics. Using the high-performance liquid chromatography （HPLC） and liquid chromatography mass spectrometry （LC-MS） analysis, mono-methyl phthalate （MMP） and phthalic acid （PA） were detected as the major intermediates of DMP biodegradation. When combined with the determination of chemical oxygen demand （CODer） removal capacity and pH, DMP was found to be mineralized completely under anoxic conditions. The biodegradation pathway was proposed as DMP → MMP→ PA→…→ CO2 ＋ H2O. The molar ratio of DMP to nitrate consumed was found to be 9.0：1, which agrees well with the theoretical stoichiometric values of DMP biodegradation by nitrate-reducing bacteria. The results of the non-linear simulation showed that the optimum pH and temperature for the degradation were 7.56 and 31.4℃, respectively.

Electrochemical incineration of dimethyl phthalate by anodic oxidation with boron-doped diamond electrode

The anodic oxidation of aqueous solutions containing dimethyl phthalate （DMP） up to 125 mg/L with sodium sulfate （Na2SO4） as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond （BDD） as anode. Electrolyses were carded out at constant current density （1.5-4.5 mA/cm^2）. Complete mineralization was always achieved owing to the great concentration of hydroxyl radical （-OH） generated at the BDD surface. The effects of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency were investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography （HPLC） revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography- Mass Spectrometry （GC-MS） and a general pathway for the electrochemical incineration of DMP on BDD was proposed.

Research on the degradation mechanism of dimethyl phthalate in drinking water by strong ionization discharge

The degradation mechanism of dimethyl phthalate（DMP） in the drinking water was investigated using strong ionization discharge technology in this study. Under the optimized condition, the degradation efficiency of DMP in drinking water was up to 93% in 60 min. A series of analytical techniques including high-performance liquid chromatography, liquid chromatography mass spectrometry, total organic carbon analyzer and ultraviolet–visible spectroscopy were used in the study. It was found that a high concentration of ozone（O_3） produced by dielectric barrier discharge reactor was up to 74.4 mg l^（-1） within 60 min. Tert-butanol, isopropyl alcohol,carbonate ions（CO_3^（2-）） and bicarbonate ions （HCO_3^-） was added to the sample solution to indirectly prove the presence and effect of hydroxyl radicals（·OH）. These analytical findings indicate that mono-methyl phthalate, phthalic acid（PA） and methyl ester PA were detected as the major intermediates in the process of DMP degradation. Finally, DMP and all products were mineralized into carbon dioxide（CO_2） and water（H_2O） ultimately. Based on these analysis results, the degradation pathway of DMP by strong ionization discharge technology were proposed.

Activated sludge-mediated biodegradation of dimethyl phthalate under fermentative conditions

The biodegradation of dimethyl phthalate(DMP)was investigated under fermentative conditions in this study.The nature of the intermediate compounds and the extent of mineralization were probed using high-pressure liquid chromatography(HPLC)and liquid chromatography-mass spectrometry(LC-MS)methods.The fermentative bacteria were able to biodegrade the DMP under anaerobic conditions,with the biodegradation rate of 0.36 mg DMP/(L·h).The results demonstrated that the DMP degradation under fermentative conditions ...

Efficient microwave-assisted photocatalytic degradation of endocrine disruptor dimethyl phthalate over composite catalyst ZrO_x /ZnO

A highly active ZrO x /ZnO catalyst for microwave-assisted photocatalytic （MW/PC） degradation of endocrine disruptor dimethyl phthalate （DMP） has been prepared via cetyltrimethylammonium assisted hydrothermal method. The ZrO x /ZnO was characterized by XPS, XRD, UV-Vis, BET and SEM techniques. The XPS result showed that Zr oxides with different valences （＋2, ＋3, ＋4） co-existed in ZrO x /ZnO. By using the ZrO x /ZnO （0.1 g）, the TOC removal efficiency of DMP （100 mL of 50 mg/L） was 88% after 30 min reaction, which was about 15% higher than P25 TiO 2 . It was found that the removal process of DMP by MW/PC followed pseudo first-order kinetics in all cases, and ZrO x /ZnO significantly accelerated the degradation of DMP. The degradation half-life time of DMP was shortened 45% compared with P25 TiO 2 . A possible catalytic mechanism was proposed based on microwave response and interfacial charge transfer. ZrO x /ZnO could be reused for six times without obvious decrease in catalytic activity. The study offers new insights into designing highly efficient catalysts for MW/PC process and is applicable for MW/PC environmental remediation.

Dimethyl phthalate damages Staphylococcus aureus by changing the cell structure, inducing oxidative stress and inhibiting energy metabolism

Dimethyl phthalate(DMP), used as a plasticizer in industrial products, exists widely in air,water and soil.Staphylococcus aureus is a typical model organism representing Gram-positive bacteria.The molecular mechanisms of DMP toxicology in S.aureus were researched by proteomic and transcriptomic analyses.The results showed that the cell wall, membrane and cell surface characteristics were damaged and the growth was inhibited in S.aureus by DMP.Oxidative stress was induced by DMP in S.aureus.The activities of succinic dehydrogenase(SDH) and ATPase were changed by DMP, which could impact energy metabolism.Based on proteomic and transcriptomic analyses, the oxidative phosphorylation pathway was enhanced and the glycolysis/gluconeogenesis and pentose phosphate pathways were inhibited in S.aureus exposed to DMP.The results of real-time reverse transcription quantitative PCR(RT-qPCR) further confirmed the results of the proteomic and transcriptomic analyses.Lactic acid, pyruvic acid and glucose were reduced by DMP in S.aureus, which suggested that DMP could inhibit energy metabolism.The results indicated that DMP damaged the cell wall and membrane, induced oxidative stress, and inhibited energy metabolism and activation in S.aureus.

Dimethyl phthalate biodegradation by Dunaliella tertiolecta

unaliella tertiolecta has an ability to biodegrade dimethyl phthalate(DMP) was found in this study, and the average of the biodegradation rates were 113 mg/(L·d) and 305 mg/(L·d), and the average of the phthalic acid (PA) production rates were 15 mg/(L·d) and 36 mg/(L·d), for initial 100 mg/L and 300 mg/L DMP, respectively. The larger amount of accumulation by D. tertiolecta under higher DMP concentration may be responsible for the increase of biodegradation rate, and one of products of DMP biodegradation by D. tertiolecta may be PA. By fitting the process of DMP biodegradation by D. tertiolecta with a kinetic equation newly suggested, the standard deviations between calculated and observed values were 25 mg/L and 57 mg/L, respectively.

Photolysis of organic pollutants in wastewater with 206 nm UV irradiation

A new-type UV light source （206 nm） was explored for the degradation of organic pollutants in wastewater for the first time. The degradation performances of triphenyltin chloride （TPTCl）, dimethyl phthalate （DMP）, as well as rhodamine B （RhB） were investigated. The results indicated that removal efficiency of 50 mg/L RhB, 60 mg/L DMP and 120 mg/L TPTCI can reach 88.6%, 92.5% and 89.4% for 60 min, 50 min and 75 min, respectively. By comparison of removal efficiency, we found 206 nm is superior to 253.7 nm UV in wastewater treatment, implying it is an effective, promising, and worthwhile exploring technology to decompose organic pollutants in wastewater.

Isolation and characteristics of Arthrobacter sp.strain CW-1 for biodegradation of PAEs

Isolation of new bacterial strains and recognition of their metabolic activities are highly desirable for sustainability of natural ecosystems. Biodegradation of dimethyl phthalate （DMP） under anoxic conditions has been shown to occur as a series of sequential steps using strain CW-1 isolated from digested sludge of Sibao Wastewater Treatment Plant in Hangzhou, China. The microbial colony on LB medium was yellowish, 3-5 mm in diameter, convex in the center, and embedded in mucous externally. The individual cells of strain CW-1 are irregular rods, measuring （0.6-0.7）×（0.9-1.0） pm, V-shaped, with clubbed ends, Gram positive and without any filaments. 16S rDNA （ 1438 bp） sequence analysis showed that the strain was related to Arthrobacter sp. CW-1 and can degrade PAEs utilizing nitrate as electron acceptor, but cannot mineralize DMP completely. The degradation pathway was recommended as： dimethyl phthalate （DMP）→monomethyl phthalate （MMP）--,phthalic acid （PA）. DMP biodegradation was a first order reaction with degradation rate constant of 0.3033 d 1 and half-life 2.25 d. The DMP conversion to PA by CW-1 could be described by using sequential kinetic model.

Kinetics of photoelectrocatalytic degradation of endocrine disrupting chemicals using sulfur-doped TiO_2 /Ti photoelectrodes

In this study,sulfur-doped TiO2 /Ti photoelectrodes were prepared by anodization. The morphology, crystalline structure,composition of sulfur-doped TiO2 /Ti film and light absorption property were examined by SEM,XRD,XRF,XPS and UV/VIS respectively. Dimethyl phthalate( DMP) ,one kind of environmental disrupting chemicals( EDCs) ,was degraded by the optimized photoelectrodes. Power of xenon light,initial concentration of DMP,photoelectrocatalytic( PEC) area of photoelectrode and bias were investigated in the study on kinetics of PEC degradation of DMP. Hence,this study concluded that the optimum conditions were power of xenon light 150 W,initial concentration of DMP 1 mg/L,PEC area of sulfur-doped TiO2 /Ti photoelectrode 10 cm2,bias 1. 3 V in the PEC reaction system.

Catalytic ozonation of organic compounds in water over the catalyst of RuO2/ZrO2-CeO2

This research investigates the performances of RuO2/ZrO2-CeO2 in catalytic ozonation for water treatment. The results show that RuO2/ZrO2-CeO2 was active for the catalytic ozonation of oxalic acid and possessed higher stability than RuO2/Al2O3 and Ru/AC. In the catalytic ozonation of dimethyl phthalate （DMP）, RuO2/ZrO2-CeO2 did not enhance the DMP degradation rate but significantly improved the total organic carbon （TOC） removal rate. The TOC removal in catalytic ozonation was 56% more than that in noncatalytic ozonation. However this does not mean the catalyst was very active because the contribution of catalysis to the overall TOC removal was only 30%. The adsorption of the intermediates on RuO2/ZrO2-CeO2 played an important role on the overall TOC removal while the adsorption of DMP on it was negligible. This adsorption difference was due to their different ozonation rates. In the catalytic ozonation of disinfection byproduct precursors with RuO2/ZrO2-CeO2, the reductions of the haloacetic acid and trihalomethane formation potentials （HAAFPs and THMFPs） for the natural water samples were 38%–57% and 50%–64%, respectively. The catalyst significantly promoted the reduction of HAAFPs but insignificantly improved the reduction of THMFPs as ozone reacts fast with the THMs precursors. These results illustrate the good promise of RuO2/ZrO2-CeO2 in catalytic ozonation for water treatment.