Search

Employing perylene diimide supermolecule (PDI) as metal-free cocatalyst, a novel PDI/g-C

Tri(2-chloroethyl) phosphate (TCEP) with the initial concentration of 5 mg/L was degraded by UV/H2O2 oxidation process. The removal rate of TCEP in the UV/H2O2 system was 89.1% with the production of Cl− and PO43− of 0.23 and 0.64 mg/L. The removal rate of total organic carbon of the reaction was 48.8% and the pH reached 3.3 after the reaction. The oxidative degradation process of TCEP in the UV/H2O2 system obeyed the first order kinetic reaction with the apparent rate constant of 0.0025 min−1 (R2=0.9788). The intermediate products were isolated and identified by gas chromatography-mass spectrometer. The addition reaction of HO• and H2O and the oxidation reaction with H2O2 were found during the degradation pathway of 5 mg/L TCEP in the UV/H2O2 system. For the first time, environment risk was estimated via the “ecological structure activity relationships” program and acute and chronic toxicity changes of intermediate products were pointed out. The luminescence inhibition rate of photobacterium was used to evaluate the acute toxicity of intermediate products. The results showed that the toxicity of the intermediate products increased with the increase of reaction time, which may be due to the production of chlorine compounds. Some measures should be introduced to the UV/H2O2 system to remove the highly toxic Cl-containing compounds, such as a nanofiltration or reverse osmosis unit.

An efficient method for the determination of eight parabens in human breast tumor ( n = 102) and peripheral adipose tissue samples ( n = 87) was successfully developed. After a precipitation procedure (acetonitrile-water-15% (w/v) zinc sulfate solution) was applied to finely-chopped tissue samples, ultrasound-assisted dispersive liquid-liquid microextraction was conducted on the sample solution. The extracted parabens were determined by gas chromatography–mass spectrometry. Significant factors influencing extraction efficiency were screened and optimized using Plackett-Burman design and central composite design. The optimized conditions were obtained at 93 μL 1‑decanol, 500 μL methanol, and ultrasound irradiation power 156 W for 44 s. Under the optimum condition, the proposed method showed enrichment factors between 44.9 and 60.5. The detection limits for parabens were between 0.5 and 1.0 ng g −1 . Calibration curves showed good linearity with coefficients of determination higher than 0.993. Relative standard deviations were lower than 11.8%. No significant matrix effects were observed as recoveries from spiked tissue samples ranged between 79.6% and 113.6%. The sample pretreatment procedure and analytical characteristics showed comparable or superior to those of the previously reported methods. Finally, the procedure was successfully employed in real samples and results indicated a wide existence of parabens in the tested tissues. At least one paraben was detected in 98.9% tissues and the levels ranged from 0.5 to 5931.1 ng g −1 , depending on the types of analytes and tissues.

Photocatalyst composites were prepared by coprecipitation and characterized by XRD, SEM, and UV–Vis DRS methods. A substantially enhanced photocatalyst activity was observed in degradation of diesel pollutants in seawater, compared to zinc oxide without dopant. Photocatalytic degradation of diesel pollutants in seawater and the effects of factors on the composite’s photocatalytic effectiveness were studied under visible light and various conditions. This degradation in seawater was optimized using an orthogonal experimental plan. According to the results, diesel removal was 26.95% without any catalyst (losses only by evaporation) and the greatest effects occurred when the initial diesel concentration was 0.25 g/L, catalyst dose at 0.4 g/L, catalyst-doping ratio at 10%, pH at 9.0, H 2 O 2 at 6.0 mg/L, and illumination time at 2.5 h, in which case the diesel removal rate reached 93.89%. This study elaborated a means for making zinc oxide utilize visible light more efficiently and thus accelerate the practical application of photocatalytic technology in organic pollutant remediation.

Identifying the spatial effects of cobalt cations in cobalt-based heterogeneous catalysts contributes to develop effective peroxymonosulfate (PMS) activators in water treatment. Herein, we investigated typical tetrahedral and octahedral cobalt ions in CoAl2O4 and ZnCo2O4 via an inactive cation substitution strategy towards spinel Co3O4. ZnCo2O4 (0.095 min−1) performs remarkably better than CoAl2O4 (0.007 min−1) for degrading rhodamine B, while non-radical 1O2 is the dominant reactive oxygen species. Then, interface kinetics characterized by systemic electrochemical techniques indicate the feasibility of Co2+/Co3+ transformation and charge transfer resistance at catalyst-electrolyte interface determine intrinsic activity. Octahedral cobalt species exhibit superior intrinsic activities comparing with tetrahedral ones on the removal of several dye and aromatic pollutants. Additionally, flat band potentials of cobalt-based oxides reflecting Fermi level positions is a thermodynamic factor to activate PMS. Our work attempts to further understand spatial occupation-activity relationship of cobalt sites to design efficient PMS activators.

Persulfate (PS) is extensively employed as an oxidant to develop the sulfate radical-based advanced oxidation processes for removing organic pollutants and various PS activation methods have been explored. Iohexol (IOH), as a typical iodinated X-ray contrast media, poses a threat to human health and ecological environment, which is difficult to be removed by conventional treatment methods. In our work, a photocatalytic coupling persulfate system was constructed for efficient IOH degradation. A novel binary photocatalyst of biochar loaded with perylene diimide (PDI/BC, PB) was successfully prepared via a one-pot water bath heating method, which achieved BC acidification and PDI self-assembly simultaneously. Different mass ratios of BC and PDI lead to variance in average particle size, electronegativity, bandgap width and electron/hole separation efficiency. The optimized efficiency of 10 mg/L IOH on PB-9 (PDI:BC = 1:9, w/w) reached 100% in 2 h with 1.5 mM sodium persulfate under visible light irradiation. Based on the results of trapping experiments and electron paramagnetic resonance, holes and hydroxyl radicals were the dominant active species and the free radical chain reaction and mutual conversion reaction of active species occurred. The amide hydrolysis, amine and C-OH oxidation, hydrogen extraction, deiodination and OH addition were observed during the degradation process. Density functional theory calculation was conducted to confirm the free radical attack sites. The findings of this work demonstrate that metal-free supramolecular loaded photocatalyst has the potential for application in the removal of organic pollutants for water remediation.

Photocatalytic degradation of diesel pollutants in seawater and the effects of factors on the effectiveness of composite photocatalysts are studied in this paper by using ZrO 2 (Er 3+ )/TiO 2 under visible light and changing doping ratio of catalysts, pH value, dose of catalysts, illumination time, and initial concentration of diesel. The degradation of diesel pollution in seawater was optimized by orthogonal experiment. According to the results, the degradation rate of diesel is around 30% without any catalysts (only by evaporation for 2.0 h). The best effect exists when the initial concentration of diesel is 0.20 g/L, the dose of catalysts is 0.8 g/L, the doping ratio of catalysts is 0.4, the pH value is 7, and the illumination time is 2.5 h. The degradation rate of diesel can reach 87.74%. ZrO 2 (Er 3+ )/TiO 2 can effectively degrade the diesel pollutants in seawater under visible light.

A novel Co3O4/g-C3N4/Bi2O2CO3 (BCCN) photocatalyst with p-n/n-n heterojunction was synthesized through a solvent-thermal method. The degradation efficiency of 20 mg/L iohexol reached 94 % in 60 min (kapp =0.0417 min−1) in BCCN/light/PS system, which was 2.8 and 6.5 times higher than systems of BCCN/light (kapp =0.0150 min−1) and BCCN/PS (kapp =0.0064 min−1). The g-C3N4 addition lowered conduction band of the prepared material to produce superoxide radicals, activate persulfate and further prevent the recombination of photoelectrons and holes. Superoxide radicals and singlet oxygens were dominant radicals for iohexol degradation. Besides, persulfate could act as electron acceptor to enhance efficiency of electron transfer. The interaction between sulfate, superoxide and hydroxyl radicals improved singlet oxygens production. Furthermore, theoretical calculation and liquid chromatography mass spectrometry were performed to analyze degradation pathway of iohexol in the system. Ultimately, the BCCN/light/PS system can provide a new method to degrade organic pollutants in aquatic environments.

A novel PDI/PS/Vis system was constructed and the photocatalytic activity of PDI with various degrees of self-assembly was explored. Perylene diimide (PDI) as photocatalysts possesses excellent charge separation efficiency and the electron injection from the PDI to persulfate (PS) can produce active species more efficiently. With the PDI/PS/Vis system, 5 mg/L bisphenol A (BPA, 50 mL) could be completely removed in 15 min with 0.5 g/L photocatalyst and 1.5 mM PS under visible light (λ>420 nm). Nearly 71.1 % of BPA was mineralized after 1 h degradation. Radical quenching tests and electron paramagnetic resonance (EPR) spectra revealed that h+, ·O2−, ·OH and SO4·- all contributed to organics elimination with radical process. Based on the results of theoretical calculations and toxicity assessment, BPA will eventually be converted into non-toxic ring-opening products. Therefore, the highly efficient PDI/PS/Vis system has great potential for application in water environment remediation.

In this work, 5 mg/L of tri(dichloropropyl) phosphate (TDCP) was degraded by UV/H2O2 system in aqueous solution. At 900 min, the removal rate of total organic carbon (TOC), pH values, concentrations of Cl− and PO43− reached 31.7 %, 3.5, 0.09 mg/L, and 0.10 mg/L for TDCP, respectively. The degradation process of TDCP obeyed the pseudo-first-order kinetic formula with a reaction rate constant k of 0.0021 min−1. The intermediates of the degradation of TDCP were detected, which contained some dechlorinated and hydroxylated products. The degradation pathway of TDCP in the UV/H2O2 system was proposed based on the intermediates and calculations of density functional theory (DFT). For the first time, the environmental risks of the intermediates of TDCP were estimated via the “ecological structure-activity relationships” (ECOSAR) program, and acute and chronic toxicity changes of intermediate products were pointed out. The measurement of the luminescence inhibition rate suggested that the intermediates of TDCP degraded by UV/H2O2 system were more toxic than TDCP because of the production of Cl-containing compounds. The study of the environmental behavior of TDCP helps to deepen the understanding of organic phosphorus flame retardants, and provides a scientific basis for the comprehensive prevention and control of such substances and the formulation of environmental regulations.

A photodegradation technology based on the combination of ultraviolet radiation with H2O2 (UV/H2O2) for degrading tri(chloroisopropyl) phosphate (TCPP) was developed. In ultrapure water, a pseudo-first order reaction was observed, and the degradation rate constant reached 0.0035 min−1 (R2 = 0.9871) for 5 mg L−1 TCPP using 250 W UV light irradiation with 50 mg L−1 H2O2. In detail, the yield rates of Cl− and PO43− reached 0.19 mg L−1 and 0.58 mg L−1, respectively. The total organic carbon (TOC) removal rate was 43.02%. The pH value of the TCPP solution after the reaction was 3.46. The mass spectrometric detection data showed a partial transformation of TCPP into a series of hydroxylated and dechlorinated products. Based on the luminescent bacteria experimental data, the toxicity of TCPP products increased obviously as the reaction proceeded. In conclusion, degradation of high concentration TCPP in UV/H2O2 systems may result in more toxic substances, but its potential application for real wastewater is promising in the future after appropriate optimization, domestication and evaluation.

Organic matter-induced black bloom frequently occurs in a number of large eutrophic shallow lakes; this can result in the release of malodorous compounds and has a negative impact on water quality. In the study, a microcosm system containing Zizania latifolia (Z. latifolia), a common aquatic plant, was established and the release of seven taste and odour compounds, dimethyl sulphide (DMS), dimethyl disulphide (DMDS), dimethyl trisulphide (DMTS), 2-methylisoborneol (MIB), geosmin (GSM), β-cyclocitral, and β-ionone, was investigated. The results showed that these compounds were all detected during Z. latifolia decay, and that volatile organic sulphur compounds (VOSCs), such as DMS, DMDS, and DMTS, were the main factors responsible for the strong foul odour (the maximum reached 5.0 μg L−1). The release of odorous compounds was stronger during the initial seven days, and then progressively decreased in the middle stage of the experiment. Furthermore, large amounts of nutrients were released into the overlying water; nutrient concentration increased with increasing plant biomass. A positive correlation was observed between the odorant concentration and plant biomass. These results indicate that the density of aquatic plants should be controlled as part of future management of aquatic ecosystems.