Dimethyl Phthalate Solution Research Articles

Study on the mechanism and degradation behavior of Encifer adhaerens DNM-S1 capturing dimethyl phthalate

The global concern surrounding pollution caused by phthalates is escalating, with dimethyl phthalate (DMP) emerging as one of the most prevalent contaminants within the phthalates (PAEs) category. Although the biodegradation of DMP is considered both safe and efficient, its underlying degradation mechanism is not yet fully elucidated, and the degradation performance can be somewhat inconsistent. To address this issue, our study isolated a DMP-degrading bacterium (DNM-S1) from a vegetable greenhouse. The resulting data revealed that DNM-S1 exhibited a remarkable degradation performance, successfully degrading 84.98% of a 2000 mg L−1 DMP solution within 72 h. Remarkably, it achieved complete degradation of a 50 mg L−1 DMP solution within just 3 h. DMP degradation by DNM-S1 was also found to be efficient even under low-temperature conditions (10 °C). Our research further indicates that DNM-S1 is capable of capturing DMP through the ester bond in the bacterium's cell wall fatty acids, forming hydrogen bonds through hydrophobic interactions. The DMP was then transported into the DNM-S1 protoplasm using an active transport mechanism. Interestingly, the secondary metabolites of DNM-S1 contained natural carotenoids, which could potentially counteract the damaging effects of PAEs on cell membrane permeability. In summary, these findings highlight the potential of DNM-S1 in addressing PAEs pollution and provide new insights into the metabolic mechanism of PAEs degradation.

Plasticizer phthalate esters degradation with a laccase from Trametes versicolor: effects of TEMPO used as a mediator and estrogenic activity removal.

Phthalate esters (PAEs) are toxic and persistent chemicals that are ubiquitous in the environment and have attracted worldwide attention due to their threats to the environment and human health. Dimethyl phthalate (DMP) is a relatively simple structure and one of the most observed PAEs in the environment. This study investigated the degradation of the DMP using Trametes versicolor laccase and its laccase-mediator systems. The degradation effect of laccase alone on DMP was poor, while the laccase-mediator systems can effectively enhance the degradation efficiency. Within 24h, 45% of DMP (25mg/L) was degraded in the presence of 0.8 U/mL laccase and 0.053mM 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO). A certain concentration (1mM) of metal ions Al3+, Cu2+ or Ca2+ can positively promote DMP degradation with the laccase-TEMPO system. Moreover, the structure of PAEs also had a great influence on the degradation efficiency. Higher degradation efficiencies were observed when incubating PAEs with short alkyl side chains by the laccase-TEMPO system compared to that with long alkyl side chains. Additionally, the branched-chain PAEs had a better degradation effect than the straight-chain. The estrogenic activity of the DMP solution after reaction was much smaller than that of the original solution. Finally, transformation products ortho-hydroxylated DMP and phthalic acid were identified by GC-MS and the possible degradation pathway was proposed. This study verifies the feasibility of the laccase-TEMPO system to degrade PAEs and provides a reference for exploring more potential value of laccase.

Exploring simultaneous elimination of dimethyl phthalate and nitrogen by a novel constructed wetlands coupled with dielectric barrier discharge plasma

Dimethyl phthalate (DMP) contamination, as an emerging pollutant, has posed acute health risks to humans due to its potential disruption in reproductive function and endocrine system disorders. In this study, the dielectric barrier discharge (DBD) plasma and constructed wetlands (CWs) were coupled to explore the simultaneous enhancement of DMP and nitrogen removal. The results showed that the coupling DBD plasm and CWs obtained an efficient elimination of DMP (87.7–97.3%), and nitrogen removal was also improved simultaneously with higher removal of ammonia nitrogen (97.7–98.6%) and total nitrogen (TN, 22.6–40.6%). TN removal efficiency was promoted gradually by increasing the concentration of influent DMP due to the DMP decomposition into small molecules by DBD plasma, which could provide carbon source to promote denitrification for subsequent CWs. The DMP degradation processes in the coupling system were reflected by three-dimensional excitation emission matrix fluorescence spectrum and gas chromatograph-mass spectrometer, which indicated that DMP solution was activated in the DBD plasma and more organic by-products were produced. Additionally, monomethyl phthalate and phthalic acid were main degradation intermediate products of DMP. It indicated that coupling DBD plasma and CWs broke the carbon–oxygen single bond of DMP and converted it into less toxic compounds with less-refractory substances. This study provides assistant information on the application of the coupling DBD plasma and CWs technology for treating wastewater containing toxic and non-biodegradable contaminants.

Atmospheric plasma-based approaches for the degradation of dimethyl phthalate (DMP) in water

Cold plasma based treatment of contaminated water is becoming a promising novel green remediation option. This study assessed the performance of two different cold plasma reactors, using, respectively, a self-pulsing discharge (SPD) and a multipin corona discharge (MCD), in the degradation of dimethyl phthalate (DMP), a persistent and ubiquitous pollutant of the aquatic environment. The process kinetics and energy efficiency, as well as the main plasma generated reactive species were determined under various operating conditions concerning the plasma feed gas and flowrate, the voltage polarity, the input power, the DMP initial concentration, the liquid conductivity, and the aqueous matrix used to prepare DMP solutions for these experiments. The MCD reactor, operated with air as plasma feed gas and negative voltage polarity, gave the best results in terms of rate and energy efficiency. Moreover, variations in plasma input power and in the liquid conductivity have limited effect on DMP degradation rate, making this reactor suitable for treating liquids with a range of initial conductivities The effects of DMP initial concentration on its rate of degradation and on the process energy efficiency were also investigated. Differences in the efficiency of production and distribution of plasma generated reactive species, notably •OH and H2O2, observed for the two tested reactors are discussed in terms of different extension of the plasma/liquid interface and diffusion into the bulk solution. It is proposed that among the reactive species, •OH foremost, and O3 to a lesser extent, play a pivotal role in DMP degradation, while the contribution of H2O2 appears to be limited. The rate of DMP degradation was not drastically different in Milli-Q water and in tap water, a positive outcome in view of practical applications of the technology. The lower rate observed in tap than in Milli-Q water is attributed to the presence of bicarbonate and carbonate, which are known scavengers of hydroxyl radicals.

High-efficient removal of phthalate esters from aqueous solution with an easily regenerative magnetic resin: Hydrolytic degradation and simultaneous adsorption

Efficient removal of phthalate esters (PAEs) is of considerable concern since they pose serious ecological and human health risks. In this study, a magnetic strong base anion-exchange resin named MAER-OH was prepared and used as a solid basic catalyst and effective adsorbent. The MAER-OH was systematically characterized by scan electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermos-gravimetric analyses and vibrating sample magnetometer. Various factors influencing the removal of dimethyl phthalate (DMP) such as initial DMP concentration, resin dosage and temperature were investigated. The DMP can be completely converted to far less toxic phthalate at the final treatment stage, and more attractively, the potential hydrolysis intermediates were ion-exchanged by the resin simultaneously without obvious change of solution pH. The co-existing chloride was found to obviously enhance the DMP removal efficiency but result in an obvious increase of solution pH and formation of much more hydrolytic intermediates. The exhausted MAER-OH could be regenerated by 8.0% NaOH solution with negligible efficiency loss, and maintain its virgin removal efficiency for 20 successive cycles. Sequencing batch jar tests indicated that more than 5000 bed volumes of DMP solution (10 mg L−1) were efficiently treated by the MAER-OH and the saturated capacity of MAER-OH for DMP removal was 134.9 mg g−1. Taken together, this highly effective and reusable MAER-OH can be easily modularized and separated, promising its huge potential for industrial-scale PAEs wastewater treatment.

Evaluation of the optimal operation conditions using response surface methodology for the treatment of DMP by electrocoagulation

<div> <p>Phthalic acid esters, commonly called as phthalates, are of a common use in the industrial activities and are known with their hazardous impact on the environment and on humans such as endocrine disrupting agents, carcinogenic and toxic effects. These adverse effects have led to increasing interest and research on the treatment and control of phthalates. Over the past two decades, there has been growing interest in the use of electrochemical techniques such as electrocoagulation (EC) for the treatment of organic pollutants particularly toxic organics. During the course of EC, where iron or stainless steel electrodes are used as electrodes, different mechanisms are operative for the elimination of organic matter, namely (a) adsorption (b) direct anodic oxidation, and (c) indirect oxidation of pollutants in the bulk solution. A statistical-based technique named as response surface methodology (RSM) is a powerful tool for modeling the complex systems (such as EC), evaluating the simultaneous effects of several factors (independent variables), and thus searching optimum conditions for desirable responses (dependent variables). Until now, RSM has not been used as a modeling and optimization tool for the EC treatment of phthalates. In this study, EC treatment, using stainless steel anode, of dimethyl phthalate (DMP), was investigated and optimized via RSM, central composite design (CCD). Initial DMP concentration (DMP<sub>o</sub>; 20-100 mg L<sup>-1</sup>), current density (J<sub>c</sub>; 4.5-22.5 mA cm<sup>-2</sup>), electrolyte concentration (NaCl, 750-1750 mg L<sup>-1</sup>), treatment time (t<sub>r</sub>; 60-180 min) were selected as critical process parameters while DMP, total organic carbon (TOC) removals and electrical energy consumption (EEC, in kWh m<sup>-3</sup>) values were selected as the responses. The EC process was optimized to improve the abatements of DMP and TOC and to reduce the EEC values. Separate validation experiments were conducted for each initial DMP concentrations at optimum EC conditions established by the software module to check the goodness of fit and quality of the regression models. According to the established second-order polynomial regression models, DMP, TOC removal efficiencies and EEC values were affected by the process variables in the following decreasing order; J<sub>c</sub>>t<sub>r</sub>>DMP<sub>o</sub>>NaCl (negative impact), t<sub>r</sub>>DMP<sub>o</sub> (negative impact)>J<sub>c</sub>>NaCl (negative impact) and t<sub>r</sub>>J<sub>c</sub>>NaCl (negative impact)>DMP<sub>o</sub> (negative impact), respectively. Analysis of variance indicated that the experimental design models obtained for the EC treatment of aqueous DMP solutions in terms of the model pollutant and mineralization were statistically significant. The response surfaces of DMP established between initial DMP concentration and current density showed that DMP removal efficiencies can be enhanced by increasing the current density to a certain value indicating that an optimum value of current density exists for maximum DMP removal.</p> </div> <p> </p>

Catalytic activity of Fe/SBA-15 for ozonation of dimethyl phthalate in aqueous solution

The catalytic activity of iron-loaded SBA-15 (Fe/SBA-15) for ozonation of dimethyl phthalate (DMP) in aqueous solution was investigated. SBA-15 was synthesized by a hydrothermal method and Fe/SBA-15 was prepared by an incipient wetness impregnation method. The materials were characterized by a low and wide angle X-ray powder diffraction (XRD), N2 adsorption–desorption, and atomic absorption spectrometer (AAS). Under the chosen conditions (50mgh−1 ozone dosage, 10mgl−1 DMP solution and 0.20gl−1 catalyst dosage), Fe/SBA-15/O3 process obviously improved DMP and total organic carbon (TOC) removal efficiency due to the generation of hydroxyl radical (HO), which was approved by tert-butanol (TBA). The mineralization of DMP followed an apparent first-order kinetics. The rate constant in Fe/SBA-15/O3 was 0.0058min−1, 3.9 times higher than that of O3 alone, 3.4 and 1.9 times higher than those of SBA-15/O3 and Fe2O3/O3 processes respectively. The iron content, reaction temperature and initial pH of DMP solution played important roles in Fe/SBA-15/O3 process, while chloride ion exhibited the slight influence. The synergetic effect between O3 and Fe/SBA-15 adsorption illustrates that Fe/SBA-15 is a promising catalyst for ozonation process.

Application of the UV-C photo-assisted peroxymonosulfate oxidation for the mineralization of dimethyl phthalate in aqueous solutions

In this study, the degradation of dimethyl phthalate (DMP), taken as model compound for phthalate esters, by the photo-assisted peroxymonosulfate (PMS) process was investigated. The high oxidation potential of hydroxyl and sulfate radicals generated by the activation of PMS under UV-C light irradiation was used to completely oxidize aqueous DMP solutions. Experiments were conducted at varying initial pH values (3.0, 6.0, and 9.0) and PMS concentrations (0-60 mM) to evaluate the effect of different reaction conditions on DMP treatment performance with the PMS/UV-C process. It was observed that lowering the initial reaction pH slightly improved the degradation rate of DMP. On the contrary, TOC abatements were slightly enhanced with increasing initial reaction pH. An adequate (optimum) PMS concentration of 40 mM resulted in the fastest and highest DMP degradation rates and efficiencies, respectively. At an initial concentration of 100 mg L(-1), more than 95% DMP removal was obtained after only 20 min under PMS/UV-C treatment conditions. For the proposed adequate PMS concentration (40 mM) the lowest electrical energy per order (EE/O) value was calculated as 2.9 kW h m(-3) order(-1).

A Novel Electro-Fenton Process for Water Treatment: Reaction-controlled pH Adjustment and Performance Assessment

A novel electro-Fenton (E-Fenton) process was developed, in which the desired pH for an effective E-Fenton reaction and for a neutral treated media could be obtained by utilizing the reaction-released H+ and OH- in stead of chemical addition. In the laboratory-scale process using three chambers, the substrate solution pH > 4.0 was designed to be adjusted in situ through three sequencing steps: (I) pH reduction, (II) pH keeping for the effective E-Fenton reaction, and (III) pH recovery to neutral while the E-Fenton reaction continued. Experimental results demonstrated that such three-step pH adjustment was successfully achieved in this novel E-Fenton process, and that the pH adjustment was controlled by the E-Fenton reaction process. The performance of the novel process was assessed in terms of dimethyl phthalate (DMP) degradation in aqueous solution. The results revealed that the novel process was effective to reduce the DMP concentration and the total organic carbon (TOC) at steps II and III. Also, through experiments, the initial DMP solution pH > 4.0 was selected to be reduced to 3.5 in Step I of the process. This pH adjustment not only allowed the E-Fenton reaction to occur in its favorable pH range, but also benefited any potential subsequent biological treatment process or a final discharge. Moreover, the iron species could be recycled in the process.

Diffusion Aspects in the Crystallization of Isotactic Polystyrene from Solutions

Isothermal crystallization rates of isotactic polystyrene from tripropionin (TP), dimethyl sulfoxide (DMSO), and dimethyl phthalate (DMP) solutions were investigated by differential calorimetric measurements. The overall crystallization rate in the DMP solution exhibited a maximum at ca. 70 °C, which indicates that the diffusion factor plays an important role in the solution crystallization. The observed temperature dependence of the isothermal crystallization rate was analyzed on the basis of the Fokker-Planck type formula for the diffusion factor. The frictional interaction between the polymer and solvent was estimated, and the result showed that the diffusion processes (molecular motions) in the solution crystallization do not belong to the diffusion limit of Kramers. This fact has been expected for the solution crystallization, in which the frictional interaction between the polymer and solvent is weak. It has also been shown that the above tendency is remarkably dependent on the solvent. The frictional interaction was qualitatively evaluated to be DMP > DMSO > TP.

Irradiation of CI Disperse Yellow 23 and Disperse Orange 29 in an Ester Environment 1

The title compounds, both disazo dyes, were found to undergo photoisomerism in dimethylphthalate solution and in films cast from a mixture of dye and cellulose acetate. Light-induced isomerism did not occur, however, in PET film that had been extruded, oriented, and dyed with the same two colorants. The prolonged irradiation of disperse yellow 23 in either solution or a polymer matrix produced azobenzene and some mono-substituted azobenzenes. Disperse orange 29 underwent photodegradation to produce a mixture of disubstituted monoazobenzenes, a partially reduced disazo- benzene, and para-nitroaniline.

Growth rate and morphology of isotactic polystyrene crystals in solution at high supercoolings

The morphology and temperature dependence of the lateral growth rate G are reported for isotactic polystyrene crystallized from 0.1% dimethyl phthalate solution at high supercoolings. The outline of a lamella is a rounded hexagon for the highest temperature and a ragged circle for lower temperatures. The edges of the lamellae become ragged and overgrowth is pronounced with decreasing temperature. A linear relationship is found between log( G η ) and 1 TΔT over a wide range of supercooling ( ΔT = T o d − T) from 70 to 170 K, where η is a retardation factor of Arrhenius form with an activation energy of 8400 K, and T o d is the equilibrium dissolution temperature. The value of T o d is determined to be 200°C by differential scanning calorimetry. In these high supercoolings, the nucleation theory of polymer crystallization loses its validity; in fact, the slope of the plot of log( G η ) versus 1 TΔT is four times as large as the value predicted by nucleation theory. Possible growth mechanisms at high supercoolings are discussed on the basis of the morphology.

Surface controlled crystallization of poly(tetramethylene terephthalate)

Epitaxial crystallization of poly(tetramethylene terephthalate) from dimethyl phthalate solution on alkali halide crystals has been studied using electron microscopy and electron diffraction techniques. Rod-like crystals oriented in the 〈110〉 directions of the substrate were found to form at short crystallization times. At longer times, however, lamella-like crystals, which were nucleated at the sides of the rod-like crystals, grew in directions dictated by the substrate. Besides the normal bidirectional orientations induced by the substrate, the polymer crystals showed twinning which was found to be due to the triclinic lattice structure of the polymer.

Kinetics of free‐radical copolymerization of α‐methylstyrene and styrene

AbstractThe free‐radical copolymerization of α‐methylstyrene and styrene has been studied in toluene and dimethyl phthalate solutions at 60°C. Gas chromatography was used to monitor the rate of consumption of monomers. For styrene alone, the measured rate of polymerization Rp and M̄n of the polymer coincided with values expected from previous studies by other workers. Solution viscosity η affected Rp and M̄n of styrene homopolymers and copolymers as expected on the basis of an inverse proportionality between η1/2 and termination rate. The rate of initiation by azobisisobutyronitrile appears to be independent of monomer feed composition in this system. Molecular weights of copolymers can be accounted for by considering combinative termination only. The effects of radical chain transfer are not significant.A theory is proposed in which the rate of termination of copolymer radicals is derived statistically from an ideal free‐radical polymerization model. This simple theory accounts quantitatively for Rp and M̄n data reported here and for the results of other workers who have favored more complicated reaction models because of the apparent failure of simple copolymer reactivity ratios to predict polymer composition. This deficiency results from systematic losses of low molecular weight copolymer species in some analyses. Copolymer reactivity ratios derived with the assumption of a simple copolymer model and based on rates of monomer loss can be used to predict Rp values measured in other laboratories without necessity for consideration of depropagation or penultimate unit effects. The 60°C rate constants for propagation and termination in styrene homopolymerization were taken to be 176 and 2.7 × 107 mole/l.‐sec, respectively. The corresponding figures for α‐methylstyrene are 26 and 8.1 × 108 mole/l.‐sec. These constants account for the sluggish copolymerization behavior of the latter monomer and the low molecular weights of its copolymers. The simple reaction scheme proposed here suggests that high molecular weight styrene–α‐methylstyrene copolymers can be produced at reasonable rates at 60°C by emulsion polymerization. This is shown to be the case.