Degradation Of Diethyl Phthalate Research Articles

Efficient destruction of emerging contaminants in water by UV/S(IV) process with natural reoxygenation: Effect of pH on reactive species

UV/sulfite systems with oxygen have recently been considered as advanced oxidation processes in view of the participation of oxysulfur radicals. However, the contribution of •OH and the efficiency of destructing emerging contaminants (ECs) in water remain largely unclear. Here, the UV/S(IV) process was applied with natural reoxygenation to degrade two typical ECs, diethyl phthalate (DEP) and bisphenol A (BPA) showing different properties. Solution pH played the key role in determining the reactive species, and both DEP and BPA were more favorably degraded at more alkaline conditions with higher utilization efficiency of SO32−. Specifically, the H•, O2•−, •OH and SO3•− were identified at acidic condition, but the amount of •OH accumulated significantly with the elevation of pH. Competitive quenching experiments showed that eaq− and •OH dominated the degradation of DEP and BPA at alkaline condition, respectively. Besides, DEP showed higher quantum efficiency for the indirect photolysis and mineralization degree than that of BPA at pH 9.2 mainly due to the direct use of the primary photoproduct. The possible transformation mechanisms of S(IV) and mineralization routes of both pollutants were proposed. This study may provide new insights into the mechanisms involved in UV/S(IV) process and a promising alternative for efficient removal of ECs in water.

Sunlight-driven degradation of diethyl phthalate via magnetically modified biochar catalysts in water: Internal electron transfer mechanism

This study presents a one-step synthetic approach for magnetic biochar (MBC) photo-degradation of diethyl phthalate (DEP). The results showed that MBC exhibited better catalytic property for DEP degradation than BC, and its catalytic performance was influenced by the amount of Fe doping. Electron paramagnetic resonance (EPR), quenching experiments, and chemical probe studies confirmed the presence of persistent free radicals (PFRs), hydroxyl radicals (·OH), and superoxide anion radical (·O2−) in both of BC and MBC. Solar light promoted the formation of PFRs in BC system, which transferred electrons to oxygen to form ·O2−, thus yielding ·OH. On the other hand, electron transfer occurred between PFRs and Fe3+ for MBC, Fe2+ played an important role in activation of O2 and ·O2− production. Subsequently, photo-Fenton reaction was primarily responsible for ·OH formation. This work compared the different generation pathways for ROS between BC and MBC and provides new insight into the possible mediatory roles of BC in O2 activation under solar light by transition metals.

Biodegradation of diethyl-phthalate (DEP) by halotolerant bacteria isolated from an estuarine environment

Phthalates are widely used as plasticizers in many industrial products due to their chemical properties that confer flexibility and durability to building materials, lubricants, solvents, insect repellents, clothing, cosmetics, being widely distributed in the environment. Besides persistent, they are also considered endocrine-disrupting compounds (EDCs), causing a global concern about their release into the environment, once they can alter the reproductive and endocrine health of humans systems. Under natural conditions, photodegradation and hydrolysis rates of phthalates are often very slow; therefore, microbial degradation is a natural way to treat these pollutants. In this context, three bacterial consortia (CMS, GMS and GMSS) were isolated from environmental samples from the Santos Estuarine System (SES) and were able to grow on diethyl-phthalate (DEP) as an only carbon source. From the GMSS consortium, three different strains were isolated and identified as Burkholderia cepacia, Pseudomonas koreensis and Ralstonia pickettii by molecular and mass spectrometry (MALDI-TOF-Biotyper) techniques. Considering there are no reports about Ralstonia genus on phthalates degradation, this strain was chosen to proceed the kinetics experiments. Ralstonia pickettii revealed a great ability to degrade DEP (300mg/L) in less than 24 h. This is the first report implicating R. pickettii in DEP degradation.

Efficient activation of peroxymonosulfate by copper sulfide for diethyl phthalate degradation: Performance, radical generation and mechanism

Copper-containing minerals have been extensively used in Fenton-like processes for degradation of pollutants and have exhibited great potential for environmental remediation. This work reports the first use of copper sulfide (CuS), a typical Cu-mineral, for the activation of peroxymonosulfate (PMS) for pollutant degradation; the study also elucidates the underlying mechanism of these processes. Copper sulfide effectively activated PMS to degrade diethyl phthalate (DEP). Electron paramagnetic resonance, free radical quenching, X-ray photoelectron spectroscopy, X-ray diffraction analyses and DFT calculations confirmed that ≡Cu (I)/≡Cu (II) cycling on the surface of CuS provided the main pathway to activate PMS to produce highly oxidative species. Unlike conventional sulfate radical-based PMS activation processes, hydroxyl radical (•OH) were found to be the dominant radical in the tested CuS/PMS system, which performed more efficiently than an alternative •OH-based oxidation system (CuS/H2O2) for DEP degradation. In addition, the presence of anions such Cl− and NO3− has limited inhibition effects on DEP degradation. Overall, this study provides an efficient pathway for PMS-based environmental remediation as well as a new insight into the mechanism of PMS activation by Cu-containing minerals.

Efficient transformation of diethyl phthalate using calcium peroxide activated by pyrite

In this study, pyrite (FeS2) was used as a novel activator of calcium peroxide (CaO2) for the degradation of diethyl phthalate (DEP) in both aqueous solution and soil. DEP (10 mg/L) in aqueous solution was completely degraded within 5.0 min by the FeS2 (0.30 g/L)/CaO2 (1.0 mM) system at pH 3.5. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), free radical quenching, and X-ray photoelectron spectroscopy (XPS) were used to elucidate the mechanism of the catalytic decomposition of CaO2, radical formation and DEP degradation in the presence of by pyrite. The results show that hydroxyl radicals (OH) are the dominant active species responsible for DEP degradation. Surface or lattice Fe(II) of FeS2 readily activates H2O2 generated by CaO2 decomposition to produce OH, while the reducing sulfur species of FeS2 promotes the regeneration of surface of Fe(II) that catalyzes the production of additional OH, leading to the efficiently oxidative degradation of DEP. Although high concentration of common anions, such as Cl−, NO3−, SO42−, and HCO3−, exert inhibitory effects on DEP degradation by pyrite/CaO2, the reaction system can still efficiently degrade DEP in realistic soil. It was observed that 78% of DEP (25 mg kg−1) was degraded by 2.5% CaO2 (w/w) and 0.5% FeS2 (w/w) within 24 h. These results provide new insight into the mechanistic processes of CaO2 activation and OH formation by the novel FeS2 catalyst, demonstrating a promising alternative to the traditional H2O2-base Fenton process for contaminated soil remediation.

Experimental and simulation investigations of UV/persulfate treatment in presence of bromide: Effects on degradation kinetics, formation of brominated disinfection byproducts and bromate

Bromide (Br−), which is omnipresent in water bodies, can not only affect the degradation kinetics of target pollutants but may also form undesired byproducts (such as bromate (BrO3-) and brominated disinfection byproducts (Br-DBPs)) through sulfate radical (SO4∙-)-based advanced oxidation processes (AOPs). This study found that Br− significantly suppressed the degradation of diethyl phthalate (DEP) based on the ultraviolet (UV)/persulfate (PS) treatment and was efficiently converted into reactive species (radicals and free bromine) by the SO4∙- or hydroxyl radical (HO) generated in the UV/PS system. These reactive bromine species could, in turn, brominate the phenolic degradation intermediates of DEP as well as natural organic matter (NOM), yielding Br-DBPs, including tribromomethane (TBM), which was observed when Br−, DEP and/or NOM coexisted in this UV/PS system. However, the Br-DBPs were a short-lived form of bromine during the transformation of Br– and were degraded by the excessive oxidants (e.g., SO4∙- and HO). Instead, Br− was eventually transformed into BrO3-, with free bromine acting as the requisite intermediate. The BrO3- formation initially showed a delay before increasing monotonically. In general, raising the PS dosage and the initial Br− concentrations enhanced both the maximum concentration of TBM and the formation of BrO3-, while increasing the amounts of DEP and NOM facilitated the former and inhibited the latter. The maximum concentration of TBM increased while the formation of BrO3- was suppressed with increasing pH from 5.0 to 8.0. In addition, through simulating the steady-state concentration of radicals, it was found that the contribution of bromine atom radical (Br) towards oxidizing free bromine to BrO3- was far greater than those of SO4∙- and HO. The findings demonstrate the potential negative effects of Br− on SO4∙--based AOPs, which need to be considered when this technology is applied in practice.

Visible light induced acceleration of Fe(III)/Fe(II) cycles for enhancing phthalate degradation in C60 fullerenol modified Fe(III)/peroxymonosulfate process

Hydroxylated fullerene (fullerenol) has gained increasing attention in the field of water environment remediation based on its intrinsic properties of photosensitivity and high water solubility. In this work, C60 fullerenol was added to the Fe(III)/PMS process to enhance diethyl phthalate (DEP) degradation both with and without visible light. The DEP removal ratio was increased from 2.2% to 58.8% with the addition of fullerenol at 60 min in dark condition, and the removal of DEP was completely achieved within 50 min under visible light irradiation. Mechanism investigation shows that carboxyl and carbonyl were formed via keto-enol isomerization at acid condition, resulting in the formation of open-cage fullerenol. The open-cage fullerenol can act as complex agent and electron donor to enhance oxidizing capability of the Fe(III)/PMS process by promoting Fe(III)/Fe(II) cycles. Competitive radical capture tests by electron spin resonance (ESR) and radical quenching analysis demonstrate that hydroxyl radical and sulfate radical were primarily responsible for DEP removal, but not superoxide radical and singlet oxygen. The DEP removal in the F/Fe(III)/PMS process is more efficiency at initial pH ranging from 2.1 to 4.9. Moreover, the DEP degradation route was proposed involving the generation of various intermediary products. This study provides a novel method for the application of fullerene derivatives on environment remediation by combining with metal catalyzed advanced oxidation processes.

Promoting the photogeneration of hydrochar reactive oxygen species based on FeAl layered double hydroxide for diethyl phthalate degradation

Improving the photocatalytic capacity of hydrochar to apply in wastewater treatment is of great significance. In this study, a novel heterogeneous photocatalytic material was prepared by compounding hydrochar with FeAl layered double hydroxide (FeAl-LDH). Furthermore, hydrochar was separated into hydrochar carbon matrix (HCM) and dissolved organic matter (DOM) to analyse their contribution in the reactive oxygen species (ROS) generation. The characterization and photocatalytic property of three composites (hydrochar-LDH, HCM-LDH and DOM-LDH) were investigated. The results showed that three composites were successfully synthesized with the formation of nano-sized LDH, graphitic carbon and oxygen vacancies. Persistent free radicals (PFRs) existed in hydrochar and the amount of them increased distinctly with the presence of FeAl-LDH. The degradation efficiency of DEP by hydrochar-LDH, HCM-LDH and DOM-LDH was 5.0, 4.2 and 1.5 times than that of hydrochar within 180 min, respectively. The reasons were proposed as: (i) Both HCM-LDH and DOM-LDH could induce the formation of OH, O2− and 1O2, while HCM-LDH was the main contributor to generate O2− and OH; (ii) HCM-LDH possessed many oxygenated functional groups, which were key factors affecting the formation of ROS; (iii) Fe could enhance the electron transfer process during the photoreaction, promoting the formation of ROS.

Treatment of Diethyl Phthalate Leached from Plastic Products in Municipal Solid Waste Using an Ozone-Based Advanced Oxidation Process.

Plastic products in municipal solid waste result in the extraction of phthalates in leachate that also contains large amounts of organic matter, such as humic substances, ammonia, metals, chlorinated organics, phenolic compounds, and pesticide residues. Phthalate esters are endocrine disruptors, categorized as a priority pollutant by the US Environmental Protection Agency (USEPA). Biological processes are inefficient at degrading phthalates due to their stability and toxic characteristics. In this study, the peroxone (ozone/hydrogen peroxide) process (O3/H2O2), an O3-based advanced oxidation process (AOP), was demonstrated for the removal of diethyl phthalate (DEP) in synthetic leachate simulating solid-waste leachate from an open dump. The impact of the O3 dose during DEP degradation; the formation of ozonation intermediate by-products; and the effects of H2O2 dose, pH, and ultraviolet absorbance at 254 nm (UVC) were determined during ozonation. Removal of 99.9% of an initial 20 mg/L DEP was obtained via 120 min of ozonation (transferred O3 dose = 4971 mg/L) with 40 mg/L H2O2 in a semi-batch O3 system. Degradation mechanisms of DEP along with its intermediate products were also determined for the AOP treatment. Indirect OH radical exposure was determined by using a radical probe compound (pCBA) in the O3 treatment.

Surface-bound radical control rapid organic contaminant degradation through peroxymonosulfate activation by reduced Fe-bearing smectite clays

Heterogeneously activated peroxymonosulfate (PMS)-based advanced oxidation technologies (AOTs) have received increasing attention in contaminated water remediation. However, PMS activation by reduced clay minerals (e.g., reduced Fe-bearing smectite clays) has rarely been explored. Herein, PMS decomposition by reduced Fe-bearing smectite clays was investigated, and the hydroxyl radical (OH) and sulfate radical (SO4−) formation mechanisms were elucidated. Reduced nontronite NAu-2 (R-NAu-2) activated PMS efficiently to induce rapid degradation of diethyl phthalate (DEP) within 30 s. Mössbauer spectroscopy, FTIR and XPS analyses substantiated that distorted trans-coordinated Fe(II)Fe(II)Fe(II)OH entities were mainly responsible for rapid electron transfer to regenerate clay surface Fe(II) for PMS activation. Chemical probe, radical quenching, and electron paramagnetic resonance (EPR) results confirmed that OH and SO4− were mainly bound to the clay surface rather than in bulk solution, which resulted in the rapid degradation of organic compounds such as DEP, sulfamethoxazole, phenol, chlortetracycline and benzoic acid. Anions such as Cl− and NO3− had a limited effect on DEP degradation, while HCO3− inhibited the DEP degradation due to the increase of reaction pH. This study provides a new PMS activation strategy using reduced Fe-bearing smectite clays that will contribute to rapid degradation of organic contaminants using PMS-based AOTs.

Comprehensive study on the formation of brominated byproducts during heat-activated persulfate degradation

Applying the highly oxidative sulfate radical (SO4-·) to pollutant degradation may cause it to react with the coexisting bromide (Br−) to form undesired byproducts. This study investigated the transformation of Br− during the degradation process of a contaminant (diethyl phthalate (DEP)) via heat-activated persulfate (PS). Dibromoacetonitrile and bromoform formed with Br− and natural organic matter (NOM) in the solution, while only bromoform was detected without NOM. The formation of these brominated disinfection byproducts (Br-DBPs) can be ascribed to the reactions between the phenolic groups of DEP degradation intermediates or NOM and reactive bromine species (free bromine and radical bromine) generated through the oxidation of Br− by SO4-·. Br-DBPs were degraded by excessive SO4-·, which indicates that organic bromine is a temporary phase during the turnover of Br−. The time-dependent formation of organic and inorganic bromines suggests that Br− may have cycled several times between organic and inorganic forms before eventually turning into bromate. The bromate formation showed a lag phase before continuously increasing. Generally, increasing the temperature, PS dosage, and Br− and organic matter (DEP and NOM) concentrations increased the maximum concentration of Br-DBPs. Additionally, these reaction parameters facilitated bromate formation except for organic matter, whose inhibitory effect is probably due to the consumption of reactive species by organic matter and the generated superoxide anion. The total organic carbon concentration of the solution exhibited a relatively quick reduction followed by a slow decrease. These results highlight the potential risks of PS activation technologies and can help prevent such risks in actual practice.

Radical chemistry of diethyl phthalate oxidation via UV/peroxymonosulfate process: Roles of primary and secondary radicals

The UV/peroxymonosulfate (PMS) process forms hydroxyl radicals (OH) and sulfate radicals (SO4−) to degrade micro-pollutants. Both these two radicals can be converted to secondary radicals (e.g. Cl2−, CO3− and Cl) by effects of water matrix components. By using laser flash photolysis, the second-order rate constants for reactions of three PAEs with OH, SO4−, Cl2−, Cl and CO3− were determined as (3.5–4.4) × 109, (4.9–5.6) × 108, (1.1–1.3) × 107, (1.8–2.0) × 1010 and <1 × 106 M−1s−1, respectively. Then diethyl phthalate (DEP) was selected as the target compound to investigate the radical chemistry of its degradation during the 254 nm UV/PMS process. Multiple effects of water matrix components in DEP degradation were investigated. Alkaline condition, chloride, bicarbonate and natural organic matter (NOM) inhibited DEP degradation while their effects were radical specific. SO4− could better withstand the negative effect of alkaline condition, bicarbonate and NOM than OH, while OH was less affected by chloride than SO4−. Cl accounted for 12% of DEP degradation in the presence of 1 mM chloride. Cl2−, CO3− and 1O2 hardly contributed to DEP oxidation but they might be involved in the further oxidation of transformation intermediates. Transient-state intermediates and steady-state products were identified by time-resolved spectroscopy and GC-MS, respectively, from which the degradation pathways of DEP in different water matrices were proposed.

Biodegradation of diethyl phthalate from synthetic wastewater in a batch operated internal loop airlift bioreactor

In the present study, biodegradation of diethyl phthalate (DEP) was carried out with a mixed culture of aerobic bacterial strains isolated from soil contaminated with municipal wastewater. They were identified as Bacillus sp. and Micrococcus sp. based on morphological, biochemical and molecular characteristics. For the treatment of synthetic wastewater containing DEP, an internal loop airlift bioreactor was designed and fabricated. Experiments were carried out for various initial concentrations (100-1500 mg/l) in a batch mode using a mixed culture of isolates. Mass balance and stoichiometric investigation suggested efficient degradation of DEP with a yield of 0.81 g/g if two-thirds of carbon from substrate converted to biomass. Gas chromatography-Mass spectroscopy analysis detected monoethyl phthalate (MEP) and phthalic acid (PA) sequentially to confirm hydrolysis of DEP. Enzymatic assay of the esterase production (929.5 U/l for 1000 mg/l of DEP) was responsible for hydrolysis of DEP to MEP. Growth kinetic study delivered the best fit of experimental data with the Haldane model with the correlation coefficient (r2) 0.95. Biokinetic constants indicated that the high concentrations of DEP inhibited the growth rate of bacteria while dissolved oxygen estimation suggested that the DEP biodegradation was oxygen limited.

Cotransformation of Carbon Dots and Contaminant under Light in Aqueous Solutions: A Mechanistic Study.

In this study, the photochemistry of carbon dots (CDs) and their effects on pollutant transformation were systematically examined. Diethyl phthalate (DEP) degradation was strongly enhanced by CDs under UV light, with the observed reaction rate constant ( kobs) increased by 2.4-15.1-fold by CDs at a concentration of 0.5-10 mg/L. Electron paramagnetic resonance (EPR) spectrometry combined with free radical quenching experiments with various chemical probes indicated the production of reactive oxygen species (ROS), including hydroxyl radicals (•OH), singlet oxygen (1O2), and superoxide radical anions (O2•-), and these contributed to the enhanced DEP degradation. Meanwhile, CDs were also degraded to low-molecular-weight species and partially mineralized to CO2 by ROS, as evidenced by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and total organic carbon (TOC) analysis, and transformation of CDs was accelerated by DEP. Furthermore, CDs were degraded rapidly under natural sunlight, accompanied by the formation of •OH and 1O2. Anions such as CO32-, NO3-, and Cl- had limited effects on transformation of CDs, while humic substances greatly inhibited this process. Our results indicate that photoreactions of CDs play an important role in influencing the transformation of pollutants and CDs themselves in the natural aquatic environment. The findings provide invaluable information for evaluating risks associated with the release of CDs into the natural environment.

Mechanistic and kinetic studies of the degradation of diethyl phthalate (DEP) by homogeneous and heterogeneous Fenton oxidation

In this work, the degradation of diethyl Phthalate (DEP) by homogeneous and heterogeneous Fenton oxidation was investigated. The influence of several parameters was determined such as the initial pH, the catalyst concentration, the hydrogen peroxide concentration and the initial concentration of DEP on the oxidative degradation kinetics and mineralization efficiency. Different iron sources were tested (Ferrous sulfate, Ferric oxide, Pyrite and FeF2) leading to homogeneous and heterogeneous Fenton system. Ferrous sulfate is used for deeper investigation given its fast catalytic decomposition of hydrogen peroxide directly to generate hydroxyl radicals OH known as the Fenton reaction. The experimental results showed that DEP was completely removed by the hydroxyl radicals (•OH) action generated from Fenton’s reaction under the optimal conditions 100 ppm DEP, [H2O2] = 1000 ppm, [Fe2+] = 50 ppm, and pH = 3.2. Furthermore, under these conditions, more than 95% of the initial TOC was removed, meaning almost complete mineralization of the organic compounds after 300 min of treatment. The absolute rate constant for the DEP oxidation reaction by the hydroxyl radical was determined using the competition kinetics method and found to be 4.4x109 M−1 s−1. HPLC analysis of treated solutions revealed that phtalic acid, 1,2-dihydroxybenzene, 1,2,4-trihydroxybenzene, maleic acid, formic acid and oxalic acid were the intermediates found. Oxalic acid was the major and most persistent oxidized product found at the end of the treatment. Based on the identified reaction intermediates by HPLC and TOC results, a mechanism was proposed for the mineralization of DEP during Fenton process. Finally, it can be said that the Fenton process is a suitable and efficient method for DEP removing and its intermediates from water.

Metabolism of diethyl phthalate (DEP) and identification of degradation intermediates by Pseudomonas sp. DNE-S1

A Pseudomonas sp. DNE-S1 (GenBank accession number MF803832), able to degrade DEP in a wide range of acid-base conditions, was isolated from landfill soil. The growth kinetics of DNE-S1 on DEP followed the inhibition model. Fe3+ could promote the degradation ability of DNE-S1 to DEP probably by over-expression of the gene phthalate dihydrodiol dehydrogenase (ophB) and phthalate dioxygenase ferredoxin reductase (ophA4). The degradation rate of DEP (500 mg L−1 at 12 h) increased by 14.5% in the presence of Fe3+. Cu2+, Zn2+, and Mn2+ showed an inhibiting effect on the degradation performance of the strain and could alter the cellular morphology, surface area and volume of DNE-S1. Three degradation intermediates, namely ethyl methyl phthalate (EMP), dimethyl phthalate (DMP), and phthalic acid (PA), were detected in the biodegradation of DEP, and the biochemical pathway of DEP degradation was proposed. This study provides new information on the biochemical pathways and the responsible genes involved in DEP degradation.

Fast degradation of phthalate acid esters by polyoxometalate nanocatalysts through adsorption, esterolysis and oxidation.

A novel route was created to facilitate the degradation of diethyl phthalate (DEP) upon micellar polyoxometalate (POM) catalysts and H2O2. The best catalytic activity was obtained using [C16H33N(CH3)3]H4PMo10V2O40 (N-hexadecyl-N,N,N-trimethylammonium tetrahydrogen decamolybdo-divanadophosphate, abbreviated as (CTA)H4PMoV) with 90.2% degradation efficiency within 30 min, while the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency were about 77.7% and 74.3% within 40 min. The highest efficiency was attributed to the concentration of DEP by amphiphilic POM catalyst, coupling with its strong Brønsted acidity and higher redox potential to catalyze esterolysis and oxidation of DEP. This allowed the phthalate acid esters (PAEs) with long carbon chains in super low concentration of 0.03 μM to be efficiently decomposed. The above synergistic effects explored DEP being degraded into ethanol, lactic acid and CO2, which were non-toxic to the water surroundings. And the reaction activation energy (Ea) of 12.49 kJ/mol was obtained upon the degradation of DEP with (CTA)H4PMoV followed first-order kinetics. Meanwhile, (CTA)H4PMoV acted as a heterogeneous catalyst, which showed long duration and higher stability with only 3.7% loss amount during ten recycles.

Degradation of diethyl phthalate (DEP) by vacuum ultraviolet process: influencing factors, oxidation products, and toxicity assessment.

The vacuum ultraviolet (VUV) process, which can directly produce hydroxyl radical from water, is considered to be a promising oxidation process in degrading contaminants of emerging concern, because of no need for extra reagents. In this study, the influencing factors and mechanism for degradation of diethyl phthalate (DEP) by the VUV process were investigated. The effects of irradiation intensity, inorganic anions, natural organic matter (NOM), and H2O2 dosage on the performance of VUV process were evaluated. The results showed that DEP could be more efficiently degraded by the VUV process compared with ultraviolet (UV)-254-nm irradiation. The presence of HCO3-, NO3- and NOM in the aqueous solutions inhibited the degradation of DEP to a different degree, mainly by competing hydroxyl radicals (HO•) with DEP. Degradation rate and removal efficiency of DEP by VUV process significantly enhanced with the addition of H2O2, while excess H2O2 dosage could inhibit the DEP degradation. Moreover, based on the identified seven oxidation byproducts and their time-dependent evolution profiles, a possible pathway for DEP degradation during the VUV process was proposed. Finally, the ecotoxicity of DEP and its oxidation byproducts reduced overall according to the calculated results from Ecological Structure Activity Relationships (ECOSAR) program. The electrical energy per order (EE/O) was also assessed to analysis the energy cost of the DEP degradation in the VUV process. Our work showed the VUV process could be an alternative and environmental friendly technology for removing contaminants in water.

A comparative study on ozone, hydrogen peroxide and UV based advanced oxidation processes for efficient removal of diethyl phthalate in water.

Several Advanced Oxidation Processes (AOPs) including O3/H2O2, O3/TiO2, O3/activated carbon (AC), O3/Al2O3, O3/Fe2+/H2O2 and UV/TiO2 have been investigated and compared for the removal of diethyl phthalate (DEP), an endocrine disrupting compound, in aqueous solutions. Hydroxyl radicals were the main species responsible for DEP degradation and this was supported by computational chemistry calculation, scavenger experiments, and LC/MS/MS analysis. The change of the abundance of reaction products over time was determined. Organic acids as well as anhydride and hydroxylated products were found to accumulate in solution even after long reaction time (2 h). Careful choice of the operating parameters (pH, ozone concentration and catalyst dosage) was crucial to achieve enhanced performance of the combined processes above what each oxidant and catalyst can achieve alone. O3/AC process was found to reduce the oxidation efficiency of O3 at high ozone concentrations. Heterogeneous catalytic ozonation with Al2O3 was the most effective process for DEP removal (∼100% removal in about 15 min) and based on pseudo-first-order kinetics at pH7, the studied oxidation processes followed the order: O3/Al2O3(0.093 min-1)>O3/H2O2/Fe2+(0.076 min-1)>O3/AC(0.069 min-1)>O3/H2O2(0.053 min-1)>O3/TiO2(0.050 min-1)> O3 alone (0.039 min-1)>UV/TiO2(0.009 min-1).

Facile preparation of tungsten oxide doped TiO2 photocatalysts using liquid phase plasma process for enhanced degradation of diethyl phthalate

In a present study, tungsten oxide was employed to improve the removal efficiency of the parent compound diethyl phthalate as well as to reduce the band gap energy of the original photocatalyst titanium dioxide. The modified photocatalyst was prepared by depositing tungsten oxide onto titanium dioxide through the liquid phase plasma. The decomposition of the parent compound was examined by varying the loading of tungsten oxide in the photocatalyst surface under different light sources, UV and blue light sources. Results showed that the band gap energy in the modified photocatalyst was lower than that of the original photocatalyst, which was attributed to increased loading of tungsten oxide in the modified photocatalyst surface resulted from an increase in the initial precursor concentrations. Tungsten doped in the photocatalyst surface existed in the form of the WO3, which led to a decrease in the specific surface area for the modified photocatalyst. The degradation performance of the parent compound increased in response to an increase in the amount of tungsten oxide under blue light, but decreased with increasing the loading of tungsten oxide under UV light. Two intermediates observed during the photocatalytic degradation appeared to be involved in the proposed degradation pathway.