A new approach to catalytic degradation of dimethyl phthalate by a macroporous OH-type strongly basic anion exchange resin

Facet effect of hematite on the hydrolysis of phthalate esters under ambient humidity conditions

Phthalate esters (PAEs) have been extensively used as additives in plastics and wallcovering, causing severe environmental contamination and increasing public health concerns. Here, we find that hematite nanoparticles with specific facet-control can efficiently catalyze PAEs hydrolysis under ambient humidity conditions, with the hydrolysis rates 2 orders of magnitude higher than that in water saturated condition. The catalytic performance of hematite shows a significant facet-dependence with the reactivity in the order {012} > {104} ≫ {001}, related to the atomic array of surface undercoordinated Fe. The {012} and {104} facets with the proper neighboring Fe-Fe distance of 0.34-0.39 nm can bidentately coordinate with PAEs, and thus induce much stronger Lewis-acid catalysis. Our study may inspire the development of nanomaterials with appropriate surface atomic arrays, improves our understanding for the natural transformation of PAEs under low humidity environment, and provides a promising approach to remediate/purify the ambient air contaminated by PAEs.

Selective oxidation of aldehydes by oxygen over macroporous alkaline resin

In this reaction, the oxidation of aldehydes is selectively catalyzed by basic resin D201-OH for the first time. Moreover, mild and high-yield oxidation of aldehydes can be achieved without any cocatalyst.

Enhanced Radical Generation in an Ultraviolet/Chlorine System through the Addition of TiO2

Ultraviolet (UV)/chlorine draws increasing attention for the abatement of recalcitrant organic pollutants. Herein, it was found that TiO₂ would significantly promote the degradation of dimethyl phthalate (DMP) in the UV/chlorine system (from 19 to 84%). Hydroxyl radicals (HO^•) and chlorine radicals (Cl^•) were the dominant reactive species for DMP degradation in the UV/chlorine/TiO₂ system. Chlorine decayed much faster in UV/chlorine/TiO₂ compared with UV/chlorine, which is possibly because photogenerated electrons (e_cb^-) and superoxide radicals (O₂^•-) have high reactivity with chlorine. As a result, the recombination of photogenerated holes (h_vb⁺) and e_cb^- was inhibited and the accumulation of HO^• and Cl^• was facilitated. A kinetic model was established to simulate the reaction process, and it was found that the concentrations of HO^• and Cl^• were several times to dozens of times higher in UV/chlorine/TiO₂ than that in UV/chlorine. The contributions of HO^• and Cl^• to DMP degradation were 70.3 and 29.7% by model simulation, respectively, and were close to the probe experiment result. In the UV/chlorine/TiO₂ system, the degradation of DMP did not follow pseudo-first-order kinetics but the degradation of benzoate fitted well with pseudo-first-order kinetics. This phenomenon was elucidated by the structure of the pollutant and TiO₂ and further tested by calculating the adsorption energy (E_ads)/binding energy (E_b) with density functional theory. Due to faster decay of chlorine, lower amounts of disinfection byproducts formed in UV/chlorine/TiO₂ compared with UV/chlorine. Adding TiO₂ into the UV/chlorine system can promote the degradation of recalcitrant organic pollutants in an aqueous environment.

Hydrochemical composition, distribution, and sources of typical organic pollutants and metals in Lake Bangong Co, Tibet

Lake Bangong Co is a special lake in western Tibet, with characteristics of increased salinity from the eastern area to the western area. Due to its remote location and poor environmental conditions, there are few background data on the water environment of this lake. In this study, the water chemical composition of Lake Bangong Co was studied, and the concentration levels, distribution characteristics, and pollution sources of polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), and metals (As, Pb, Cr, Mn, Cu, Cd, Ni, and Zn) were investigated. The hydrochemical characteristics of the lake showed significant spatial differences. Conductivity, salinity, degree of mineralization, total hardness, Cl^-, and SO₄^2- generally increased from the eastern part to the western part. Most water quality parameters met the class III standards of the Chinese surface water standards; however, the Cl^- and SO₄^2- concentrations in the western part exceeded the surface water standard limits. ΣPAH and ΣPAE concentrations in lake water have no significant relationship with hydrochemical parameters. Among the 16 target PAHs, 4 PAH monomers with a (5 + 6)-ring were not detected in the lake water. The main sources of PAHs included emissions from biomass combustion, petroleum volatilization, and automobile exhaust. Six PAE monomers were detected at all sampling sites with relatively low concentrations, and di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) were the main pollutants. The main source of PAEs was domestic waste, which might be related to increasing human activities in this area recently. In general, the concentrations of metals in the water of Lake Bangong Co were lower than those in the regions affected by anthropogenic activities except As. The results of PCA showed that As, Cu, and Cr mainly originated from natural sources; Pb, Mn, and Cr came from both natural and anthropogenic sources; and Cd was highly likely from anthropogenic sources.

Organic micropollutants and disinfection byproducts removal from drinking water using concurrent anion exchange and chlorination process

Many traditional drinking water treatment processes have limited removal efficiencies on natural organic matter (NOM) and organic micropollutants (OMPs), and thus may lead to the production of harmful disinfection byproducts (DBPs). We examined four kinds of anion exchange resins (D205, D213, NDMP-3, and M80) in conjunction with chlorination in the treatment of drinking water. Five categories including 40 OMPs at environmentally relevant concentrations were analyzed. M80 showed the best performance to remove OMPs in water. However, it was vulnerable to the presence of humic acid (HA), indicating its limitation on removing OMPs and NOM at the same time. In contrast, D205, D213, NDMP-3 resins were less affected by HA. Besides, D205, D213 and NDMP-3 provided higher efficiencies on the reduction of DBPs than M80. The amount of trihalomethanes (THMs) lowered by 42.7%, 37.6%, 32.1%, and 0%, whereas haloacetic acids (HAAs) were decreased by 34.0%, 31.2%, 23.0%, and 17.9% by D205, D312, NDMP-3, and M80. Notably, D205 showed the highest removal effects on the bromide ion, brominated THMs, and HAAs, supporting that D205 can be a selective resin for the treatment of drinking water in high bromide-containing areas.

Distribution and sources of polycyclic aromatic hydrocarbons and phthalic acid esters in water and surface sediment from the Three Gorges Reservoir

After the impoundment of the Three Gorges Reservoir (TGR), the hydrological situation of the reservoir has changed greatly. The concentration and distribution of typical persistent organic pollutants in water and sediment have also changed accordingly. In this study, the concentration, distribution and potential sources of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 phthalic acid esters (PAEs) during the water drawdown and impoundment periods were investigated in water and sediment from the TGR. According to our results, PAHs and PAEs showed temporal and spatial variations. The mean ΣPAH and ΣPAE concentrations in water and sediment were both higher during the water impoundment period than during the water drawdown period. The water samples from the main stream showed larger ΣPAH concentration fluctuations than those from tributaries. Both the PAH and PAE concentrations meet the Chinese national water environmental quality standard (GB 3838-2002). PAH monomers with 2-3 rings and 4 rings were dominant in water, and 4-ring and 5-6-ring PAHs were dominant in sediment. Di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) were the dominant PAE pollutants in the TGR. DBP and DEHP had the highest concentrations in water and sediment, respectively. The main source of PAHs in water from the TGR was petroleum and emissions from coal and biomass combustion, whereas the main sources of PAHs in sediments included coal and biomass combustion, petroleum, and petroleum combustion. The main source of PAEs in water was domestic waste, and the plastics and heavy chemical industries were the main sources of PAEs in sediment.

Estrogenicity assessment of membrane concentrates from landfill leachate treated by the UV-Fenton process using a human breast carcinoma cell line

Membrane concentrates (MCs) are generated when membranes are used to concentrate landfill leachate. It contains high concentrations of inorganic and organic environmental pollutants, which are highly toxic and carcinogenic. In this paper, the proliferation effect (PE) from MC before and after treatment with the UV-Fenton process was assessed using the human breast carcinoma cell line MCF-7. The highest value of 116% was found at 5% (v/v) concentration after a 10 min reaction. Phthalic acid esters (PAEs) play an important role in the MC estrogenicity. Estrogen simulation solutions (ESS) of PAEs were prepared to simulate the changes in estrogenic active substances during the UV-Fenton process. The ESS degradation conformed to the first-order kinetics model. The estrogenicity decreased after an initial increase until it acted in a non-estrogenic manner. Convincingly, the intermediates were determined by GC/MS, and the estrogenicity was assessed during the degradation process. The estrogenicity was highly related to the generation of intermediates and the PAE concentration. The results provide guidance for UV-Fenton application in MC estrogenicity reduction.

Methods for the Determination of Endocrine-Disrupting Phthalate Esters

Phthalates are endocrine disruptors frequently occurring in the general and industrial environment and in many industrial products. Moreover, they are also suspected of being carcinogenic, teratogenic, and mutagenic, and they show diverse toxicity profiles depending on their structures. The European Union and the United States Environmental Protection Agency (US EPA) have included many phthalates in the list of priority substances with potential endocrine-disrupting action. They are: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), diethylhexyl phthalate (DEHP), di-iso-nonyl phthalate (DINP), di-iso-decyl phthalate (DIDP), di-n-decyl phthalate (DnDP), and dioctyl phthalate (DOP). There is an ever-increasing demand for new analytical methods suitable for monitoring different phthalates in various environmental, biological, and other matrices. Separation and spectrometric methods are most frequently used. However, modern electroanalytical methods can also play a useful role in this field because of their high sensitivity, reasonable selectivity, easy automation, and miniaturization, and especially low investment and running costs, which makes them suitable for large-scale monitoring. Therefore, this review outlines possibilities and limitations of various analytical methods for determination of endocrine-disruptor phthalate esters in various matrices, including somewhat neglected electroanalytical methods.

Controlled synthesis of Zn(1−1.5x)FexS nanoparticles via a microwave route and their photocatalytic properties

The crystallite size, band gap and structure for the Zn_(1−1.5x)FexS samples have a strong influence on the degradation of DMP from wastewater.

Kinetic study of the removal of dimethyl phthalate from an aqueous solution using an anion exchange resin

Phthalate acid esters are becoming an important class of pollutants in wastewaters. This study addresses the kinetics of removal of dimethyl phthalate (DMP) using the anion exchange resin D201-OH from an aqueous solution. The effects of various factors on the removal rate and efficiency were investigated. An overall initial removal rate (OIRR) law and a pseudo first-order kinetic (PFOK) model were also developed. The internal diffusion of DMP within the resin phase of D201-OH is the rate-controlling step. Optimization of the particle size and pore structure of the resin D201-OH, the DMP concentration, and the reaction temperature can improve the DMP removal rate. The hydrolysis reaction of DMP catalyzed by D201-OH indicates an overall reaction order of 1.76, a value that is between the first order and the second order. The apparent activation energy of the reaction is 34.6 kJ/mol, which is below the homogeneous alkaline hydrolysis activation energy of 44.3 kJ/mol. The OIRR law can quantify the initial removal rate under different conditions. The results also show that the theoretical DMP removal efficiency predicted by the PFOK model agrees well with the experimentally determined values. Our research provides valuable insights into the primary parameters influencing the kinetic process, which enables a focused improvement in the removal or hydrolysis rate for similar processes.

Adsorption of Monobutyl Phthalate from Aqueous Phase onto Two Macroporous Anion-Exchange Resins

As new emerging pollutants, phthalic acid monoesters (PAMs) pose potential ecological and human health risks. In the present study, adsorption performance of monobutyl phthalate (MBP) onto two macroporous base anion-exchange resins (D-201 and D-301) was discussed. It was found that the adsorption isotherms were best fitted by the Langmuir equation while the adsorption kinetics were well described by pseudo-first-order model. Analyses of sorption isotherms and thermodynamics proved that the adsorption mechanisms for DBP onto D-201 were ion exchange. However, the obtained enthalpy values indicate that the sorption process of MBP onto D-301 is physical adsorption. The equilibrium adsorption capacities and adsorption rates of DBP on two different resins increased with the increasing temperature of the solution. D-301 exhibited a higher adsorption capacity of MBP than D-201. These results proved that D-301, as an effective sorbent, can be used to remove phthalic acid monoesters from aqueous solution.

Identification of thyroid receptor ant/agonists in water sources using mass balance analysis and monte carlo simulation

Some synthetic chemicals, which have been shown to disrupt thyroid hormone (TH) function, have been detected in surface waters and people have the potential to be exposed through water-drinking. Here, the presence of thyroid-active chemicals and their toxic potential in drinking water sources in Yangtze River Delta were investigated by use of instrumental analysis combined with cell-based reporter gene assay. A novel approach was developed to use Monte Carlo simulation, for evaluation of the potential risks of measured concentrations of TH agonists and antagonists and to determine the major contributors to observed thyroid receptor (TR) antagonist potency. None of the extracts exhibited TR agonist potency, while 12 of 14 water samples exhibited TR antagonistic potency. The most probable observed antagonist equivalents ranged from 1.4 to 5.6 µg di-n-butyl phthalate (DNBP)/L, which posed potential risk in water sources. Based on Monte Carlo simulation related mass balance analysis, DNBP accounted for 64.4% for the entire observed antagonist toxic unit in water sources, while diisobutyl phthalate (DIBP), di-n-octyl phthalate (DNOP) and di-2-ethylhexyl phthalate (DEHP) also contributed. The most probable observed equivalent and most probable relative potency (REP) derived from Monte Carlo simulation is useful for potency comparison and responsible chemicals screening.

Sonophotolytic degradation of dimethyl phthalate without catalyst: analysis of the synergistic effect and modeling

The merits of the combined process of high-frequency ultrasound (US) and catalyst-free ultraviolet irradiation (UV) have been evaluated in this study by investigating the sonophotolytic degradation of dimethyl phthalate (DMP). A 400 kHz ultrasonic system and a photolytic system at 253.7 nm were employed individually, sequentially and simultaneously to examine the details of the processes. High UV intensities and low pH conditions enhanced the sonophotolytic degradation of DMP and a clear synergy was evident from the combination of the US and UV irradiation with a synergetic index of 2.6. The role of ultrasonically generated hydrogen peroxide was examined qualitatively and quantitatively, and its generation and photo-decomposition were found to be the principal reason for the process synergy. A novel inverted S-curve model was developed and found to successfully describe the process of sonophotolysis and DMP degradation.

Mechanism of OH-initiated atmospheric oxidation of diethyl phthalate

Diethyl phthalate (1,2-benzenedicarboxylic acid diethyl ester, DEP) is one of a group of widely used plasticizers, which can lead to serious environmental problems. Because of manufacturing and application, DEP can be released into the atmosphere where it can undergo transport and chemical transformation. To assess the atmospheric behavior of pollutants, it is critical to know their atmospheric reactions. In this paper, the reaction mechanism and possible oxidation products for the OH-initiated atmospheric reaction of DEP were theoretically investigated by using the density functional theory (DFT) method. The geometries and frequencies of the reactants, intermediates, transition states, and products were calculated at the MPWB1K/6–31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6–311+G(3df,2p) method. The present study shows that H abstractions from the CH3 and CH2 groups, as well as OH addition to the benzene ring, are energetically favorable reaction pathways for the reaction of DEP with OH radicals. Detailed degradation products are provided.

Study on the interaction of phthalate esters to human serum albumin by steady-state and time-resolved fluorescence and circular dichroism spectroscopy

Phthalate esters (PAEs) are globally pervasive contaminants that are considered to be endocrine disruptor chemicals and toxic environmental priority pollutants. In this paper, the interactions between PAEs and human serum albumin (HSA) were examined by molecular modelling, steady state and time-resolved fluorescence, ultraviolet-visible spectroscopy (UV-vis) and circular dichroism spectroscopy (CD). The association constants between PAEs and HSA were determined using the Stern-Volmer and Scatchard equations. The binding of dimethyl phthalate (DMP) to HSA has a single class of binding site and its binding constants (K) are 4.08 × 10(3), 3.97 × 10(3), 3.45 × 10(3), and 3.20 × 10(3)L mol(-1) at 289, 296, 303, and 310K, respectively. The Stern-Volmer and Scatchard plots both had two regression curves for HSA-butylbenzyl phthalate (BBP) and HSA-di-2-ethylhexyl phthalate (DEHP), which indicated that these bindings were via two types of binding sites: the numbers of binding site for the first type were lower than for the second type. The binding constants of the first type binding site were higher than those of the second type binding site at corresponding temperatures, the results suggesting that the first type of binding site had high affinity and the second binding site involved other sites with lower binding affinity and selectivity. The thermodynamic parameters of the binding reactions (ΔG°, ΔH° and ΔS°) were measured, and they indicated the presences of hydrophobic forces and hydrogen interactions in the PAEs-HSA interactions, which agreed well with the results from molecular modelling. The alterations of protein secondary structure in the presence of PAEs were confirmed by UV-vis and CD spectroscopy. The time-resolved fluorescence study showed that the lifetime of Trp residue of HSA decreased after the addition of PAEs, which implied that the Trp residue of HSA was the main binding site.