Adsorption Of Phthalate Esters Research Articles

Influencing factors and risk assessment of phthalate ester pollution in the agricultural soil on a tropical island

Phthalate esters (PAEs) are widely prevalent in agricultural soil and pose potential risks to crop growth and food safety. However, the current understanding of factors influencing the behavior and fate of PAEs is limited. This study conducted a large-scale investigation (106 sites in 18 counties with 44 crop types) of 16 types of PAEs on a tropical island. Special attention was given to the impacts of land use type, soil environmental conditions, agricultural activity intensity, and urbanization level. The health risks to adults and children from soil PAEs via multiple routes of exposure were also evaluated. The results showed that the mean concentration of PAEs was 451.87 ± 284.08 μg kg−1 in the agricultural soil. Elevated agricultural and urbanization activities contributed to more pronounced contamination by PAEs in the northern and southern regions. Land use type strongly affected the concentration and composition of PAEs in agricultural soils, and the soil PAE concentration decreased in the order of vegetable fields, orchards, paddy fields, and woodlands. In paddy fields, di-isobutyl phthalate and di-n-butyl phthalate made more substantial contributions to the process through which the overlying water inhibited volatilization. Soil microplastic abundance, pesticide usage, crop yield, gross domestic product, and distance to the nearest city were calculated to be the major factors influencing the concentration and distribution of PAEs. Soil pH, organic matter content, microplastic abundance and the fertilizer application rate can affect the adsorption of PAEs by changing the soil environment. A greater risk was detected in the northern region and paddy fields due to the higher soil PAE concentrations and the dietary structure of the population. This study reveals important pathways influencing the sources and fate of PAE pollution in agricultural soils, providing fundamental data for controlling PAE contamination.

The effects of salinity, temperature, and UV irradiation on leaching and adsorption of phthalate esters from polyethylene in seawater.

In this study, the leaching of six phthalic acid esters (PAEs) from three common consumer plastics was investigated: low and high density polyethylene (LDPE, HDPE) and recycled polyethylene (RP). The effects of salinity, temperature, and ultraviolet irradiation (UVR) on leaching were investigated. The study of leaching of phthalates in aqueous environments in batch experiments is challenging due to their readsorption by the high hydrophobicity of PAEs, and there are no standard methods to study release processes. Here with the experiments, leaching (A) and spiking (B) using six PAEs to study the readsorption in the leaching process. PAEs were identified and quantified using GC-MS. Dibutyl phthalate (DBP) and benzyl butyl phthalate (DEHP) showed considerable leaching during the 5-day incubation: 14 ± 1 to 128 ± 14 and 25 ± 2 to 79 ± 5 ng/cm2, respectively, under UVR, corresponding approximately to (1.9-13%) and (12.4-22.4%) of the solvent extracted mass. The highest Kd values were measured for RP polymers (0.3-9.4), followed by LDPE (0.5-5.4) and HDPE (0.2-2.2) polymers. Thus, readsorption of PAEs at the surface removed 30-80% of the leached PAEs in the dissolved phase. For example in LDPE, the calculated total release of DBP was up to 54 ± 4 ng/cm2, while the dissolved amount was 8.5 ± 1 ng/cm2 during the 5-day incubation under freshwater conditions. Increasing salinity negatively affected the leaching rate, which decreased for DBP from 54 ± 4 ng/cm2 in freshwater to 44 ± 3 and 38 ± 3 ng/cm2 at salinity of 20 and 40 g/L, respectively, from LDPE during the 5-day incubation. Temperature and UVR had a positive effect on the leaching rate, with the release of DBP from LDPE increasing from 44 ± 3 ng/cm2 at room temperature (25 °C) to 60 ± 6 and 128 ± 14 ng/cm2 at high temperature (40 °C) and UVR, respectively. Overall, this study highlights the positive relationship between temperatures, UVR on the extent of leaching and surface adsorption on the leaching measurements.

Microplastics release phthalate esters and cause aggravated adverse effects in the mouse gut

Increasing evidence shows that microplastics (MPs) have the potential to act as carriers and transport contaminants into organisms, as well as induce serious health risks. Here we endeavored to address for the first time whether MPs could transport and release phthalate esters (PAEs) into mouse gut and the consequential toxic effects. As a result, MPs could adsorb PAEs, transport PAEs into the gut and cause intestinal accumulation. The accumulation of PAE in the gut followed the order of DEHP > DBP > DEP > DMP, which was the same order for the adsorption of PAEs on MPs. After exposed to DEHP-contaminated MPs for 30 days, significantly increased intestinal permeability and enhanced intestinal inflammation were induced compared with individual MPs and DEHP according to biochemical and histological analysis. Transcriptomic analysis found that 703 genes were differentially regulated and these genes are involved in oxidative stress, immune response, lipid metabolism, and hormone metabolism. Moreover, gut microbiota analysis found that the combined exposure of MPs and DEHP also caused alterations in gut microbiota composition, especially some energy metabolism and immune function related bacteria were significantly changed in the relative abundance. The aggravated effects on intestinal inflammation and metabolic disorders caused by DEHP-contaminated MPs may attribute to increased DEHP accumulation, changed exposure pathway, and shared toxic mechanisms. Our results provide valuable information for the health risk of MPs and plastic additives.

Screening the main factors affecting phthalate esters adsorption on soils, humic acid, and clay organo-mineral complexes

Phthalate esters (PAEs) are one of the most frequently detected organic pollutants in soils. In this work, the adsorption behaviors of di-ethyl phthalate (DEP) and dibutyl phthalate (DBP) on soils, humins (HM) and Clay organo-mineral complexes (Clay-OM) from four regions in China, Changchun (CC), Cangzhou (CZ), Yinchuan (YC), and Changsha (CS) were studied. The surface and structural properties of these sorbents were characterized using Brunauer-Emmett-Teller specific surface area, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and 13C nuclear magnetic resonance methods. The results showed that the CC soil has the largest pore volume (PV) and specific surface area (SSA). PV, SSA, and aliphatic carbon content of the samples ranked as Clay-OM>HM>soil. Adsorption experiments indicated that the Clay-OM exhibited the strongest adsorption affinity for both DBP and DEP, followed by HM, and then the soil samples. Furthermore, DEP and DBP adsorption amounts on the samples declined as follows: CC>CS>CZ>YC. To illustrate the dominant mechanisms for PAEs adsorption onto soil, the soil organic carbon content normalized adsorption coefficient (LogKoc) was correlated with several possible parameters using multiple parameter linear regression and significance testing. The R2 values of the DBP and DEP in multi-regression equations were 0.825 and 0.741 respectively, and the significance test suggested that pore structure and specific surface area had crucial influences on the adsorption progress.

Magnetic solid phase extraction of phthalate products from bottled, injectable and tap waters using graphene oxide: Effect of oxidation method of graphene

Phthalate esters (PAEs) are considered as an endocrine disrupting chemicals which cause harm on human and environment. Therefore, PAEs concentration should be determined and evaluated. In the present work, graphene (G) was oxidized with either nitric acid, ammonium persulfate or hummer method, to produce the corresponding graphene oxides (GO): GO-NA, GO-APS and GO-HUM, respectively. Magnetite was deposited on graphene and oxidized graphene to produce the magnetic sorbents: MG, MGO-NA, MGO-APS and MGO-HUM. These were used for optimization of simultaneous magnetic solid -phase extraction (MPSE) method of five phthalate products (DMP, DEP, BBP, DIBP, and DBP) from bottled, injectable and tap water. The highest recoveries were achieved using 40 mg of MGO-APS at pH5, sample volume 50 ml, elution with 5 ml ethyl acetate, shaking time 45 min, and elution time 15 min. The following figures of merits were achieved: detection limits range (0.004-0.013 mg.L-1), %RSD range(0.62–6.02)%, %bias range ((-16.6)-(-7.0))%, and sensitivity range (79–149)L-1.mg. Application of the optimum MSPE on bottled, injectable, and tap water showed that DEP, BBP, DIBP, and DBP were present in bottled and injectable water. The adsorption of PAEs on graphene oxide was best fitted with Langmuir model.

Insight into effects of citric acid on adsorption of phthalic acid esters (PAEs) in mangrove sediments

The adsorption of phthalate esters (PAEs) in mangrove sediment greatly influences their availability to aquatic organisms, however, the adsorption processes of PAEs in mangrove sediment, as well as the effects of root exudates, are poorly understood. In this study, dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP) was used as model PAEs to determine the effects and mechanism of citric acid on the adsorption kinetics and isotherms of PAEs in the mangrove sediments. The adsorption kinetics followed pseudo-second order model, describing the characteristics of heterogeneous chemisorption of PAEs in mangrove sediments. The adsorption isotherms of DMP and DEP followed Freundlich model, implying the characteristics of surface multilayer heterogeneous adsorption; while the Henry model better described the adsorption isotherms of DBP, suggesting that hydrophobic partition accounted for DBP adsorption in the mangrove sediments. Inter-chemical variability was observed in adsorption capacity (qe) with the sequence of DBP > DEP > DMP. Surface polarity index ((C-O + COOH + C˭O)%) of particulate organic matter (POM) regulated the adsorption capacity of DMP and DEP in mangrove sediments, while different POM content among mangrove sediments explained the difference in the sorption strength for DBP. The presence of citric acid enhanced the qe of the three PAEs by 6.4–12.6%. These findings are of great significance to reveal that the root exudates play a crucial role in the PAEs adsorption in mangrove sediments, and provide valuable information for availability of PAEs in mangrove ecosystem.

SOC Effects on Diethyl Phthalate Sorption to Four Soils in China

Purpose: Phthalate esters (PAEs) are commonly detected in agricultural soils of China, which can post potential threats to human health. Understanding their sorption to soils is important in assessing their transport and bioavailability in environment. Limited research focuses on the influence of soil organic carbon (SOC) on PAEs adsorption to soils at different depths and increased dissolved organic carbon (DOC) after adsorption. Materials and Methods: Batch sorption experiments of diethyl phthalate (DEP) to four types of soils were conducted in this study, including black soil, fluvo-aquic soil, paddy soil, and red soil. Total concentration of solute DEP and the concentration of free DEP not sorbed to DOC were measured with HPLC. The UV absorbance of supernatant was measured and specific UV absorbance at 254 nm was calculated for DOC aromaticity. Sorption isotherms of DEP to soil particles were fitted to the Langmuir model and the Freundlich model. Results and Discussion: Partial SOC can dissolve to DOC in solution, and 47.4- 89.4% of total DEP can be sorbed to DOC. Increasing DEP in solution can enhance aliphatic SOC dissolving. The sorption coefficients of DEP are higher to fluvo-aquic soils (Koc for surface soils 1820 L kg-1 and subsurface soils 1388 L kg-1) than to other soils (<520 L kg-1), which indicates that SOC fractions of different soils have varied affinity to DEP. Conclusions: SOC plays an important role in DEP sorption to soil particles. Soil samples from surface layers have higher affinity than those from subsurface layers. DOC from SOC in solution is important for DEP transport in soil, and organic pollution can accelerate SOC dissolving.

Competitive adsorption of phthalate esters on marine surface sediments: kinetic, thermodynamic, and environmental considerations.

In this study, the sorption behavior of six widely used phthalate esters (PEs) on marine sediments was investigated. The adsorption of PEs was fast and reached the equilibrium within 6h. The forward and backward rate constants of all PEs on sediments were calculated. Several kinds of kinetic and thermodynamic models have been investigated; the pseudo-second-order model and the partition isotherm model were best fitted to the adsorption behavior of PEs. The rate-limiting step of sorption was controlled by the film diffusion mechanism. After treating sediments with H2O2, the partition coefficients of all PEs were significantly reduced and indicated that the amorphous organic carbon has a major role in adsorption process. The negative values of ΔH° and ΔG° for these compounds showed that the sorption process is exothermic and spontaneous. The adsorption capacities of all PEs were slightly influenced by increasing the salinity from 0 to 40gL-1. These research findings have a prime importance on assessment of the fate and transport of PEs in seawater-sediment systems.

Fate and transport modeling of phthalate esters from biosolid amended soil under corn cultivation

Phthalate esters (PAEs) are prevalent in the environment due to the broad range of industrial, agriculture and domestic applications. The ubiquitous use of PAEs has resulted in their potential to reach groundwater sources through application of agri-chemicals and municipal biosolids. A study was conducted to monitor the fate and transport of seven commonly detected PAEs in the environment including: dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP), bis(di-ethyl hexyl) phthalate (DEHP), di-n-octyl phthalate (DnOP), dipentyl phthalate (DPP), and di-n-butyl phthalate (DnBP). Biosolids sourced from the Halifax Regional Municipality were applied at three rates on field-based lysimeter cells which were cropped to corn (Zea mays) for one growing season. In the present study, breakthrough curves (BTCs) were established for phthalates leaching from a corn-cultivated agricultural soil profile. The HYDRUS-1D model and a two-site sorption model were applied to predict transport parameters of PAEs using an inverse solution approach. Results of our research revealed that higher PAE adsorption was observed based on increasing carbon chain number. In addition, higher values of F (i.e. the fraction of type-1 sorption sites assumed to be in equilibrium with the solution phase) and lower values of D (i.e. dispersion coefficient) were observed for PAEs with large carbon chains which was validated both through the empirical dataset and the model simulations.

Synergistic effect using vermiculite as media with a bacterial biofilm of Arthrobacter sp. for biodegradation of di-(2-ethylhexyl) phthalate

Vermiculite is one of matrix material used for constructed wetland (CW) for the treatment of municipal wastewater. Arthrobacter sp. strain C21 (CGMCC No. 7671), isolated from a constructed wetland receiving municipal wastewater, forms biofilm on the surface of vermiculite. Di-(2-ethylhexyl) phthalate (DEHP), a typical phthalate pollutant in environment, can be degraded by the biofilm of strain C21 formed on vermiculite. Results of laboratory studies indicated that DEHP was removed from aqueous phase via biodegradation, adsorption by vermiculite, and adsorption by biofilm biomass. Synergistic effect of these three reactions enhanced the overall DEHP removal efficiency. During a batch incubation test with vermiculite and the cell suspension, bacterial adhesion to the media surface occurred within 5h and the phthalate esters (PEs) removal was due to both biodegradation and vermiculite adsorption. As the biofilm developed on surface of vermiculite (5–36h), biodegradation became the predominance for PEs removal. As mature biofilm was formed (36–54h), the adsorption of PEs by biofilm biomass became a main driving force for the removal of PEs from aqueous phase. The content of extracellular polymers (EPS) of the biofilm and DEHP removal performance showed a significant positive correlation (rp>0.86).

Adsorption of PAEs from aqueous solution by modified zeolites

Natural zeolites (NZ), zeolites modified with hexadecyl trimethylammonium bromide (CTMZ), and zeolites modified with hexadecyl trimethyl ammonium bromide/sodium dodecyl sulfate (CSMZ) were prepared and used for the adsorption of phthalate esters (PAEs). The adsorbents were characterized using scanning election microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric, Brunauer–Emmett–Teller, and organic carbon analyses. Adsorption characteristics, such as kinetics, isotherms, thermodynamics, and renewability, were also evaluated. The amount of PAEs adsorbed followed the order of CSMZ > CTMZ > NZ at all adsorption times. The kinetic data were fitted into three kinetic models, namely, pseudo-first-order, pseudo-second-order, and intra-particle diffusion. The pseudo-second-order model was the most suitable in describing the experimental process. The adsorption isotherms were also correlated using four different models. The equilibrium adsorption data of PAEs fitted better with the linear isotherm model for CTMZ and CSMZ and with the non-linear isotherm model for NZ. Hence, partition primarily contributes to PAEs adsorption onto CTMZ and CSMZ. PAEs adsorption onto NZ, CTMZ, and CSMZ was spontaneous and exothermic in nature, and was not affected by pH. The regeneration experiment results showed that CTMZ and CSMZ are potential adsorbents because of their low cost and reusability.

Elucidating Adsorption Mechanisms of Phthalate Esters upon Carbon Nanotubes/Graphene and Natural Organic Acid Competitive Effects in Water by DFT and MD Calculations

Simulations at multiple levels were performed to investigate the aqueous adsorption of phthalate esters (PAEs) on carbon nanoparticles and to find the competitive effect of a low molecular weight natural organic acid (benzoic acid) on the adsorption process. Six PAEs of varying alkyl side chain lengths and three carbon‐based nanomaterials including a single‐walled carbon nanotube (SWNT), double‐walled carbon nanotube (DWNT), and graphene (G) were studied. Results showed that the adsorption energies calculated using density functional theory increase with increasing length of the PAE alkyl chain. G exhibits higher adsorption capacity for the PAEs than SWNT and DWNT. The absolute adsorption energies of these systems also display a positive linear correlation with the hydrophobicity of the PAE molecules. Molecular dynamics simulations indicate that the presence of neutral/anionic benzoic acid in water alleviates the PAE adsorption. Furthermore, anionic benzoic acid exerts more impact on the PAE adsorption than the neutral form.

Adsorption of Phthalate Esters from Aqueous Solution by Mg–Al Layered Double Hydroxide

Mg–Al layered double hydroxide (Mg–Al LDH) was investigated for adsorption of dimethyl phthalate (DMP), di-(2-ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP) from water samples. The adsorption capability of the Mg–Al LDH was compared with that of activated carbon. Adsorption of the three phthalate esters (PAEs) fitted pseudo-second-order kinetics, and the Langmuir or Freundlich equations described the adsorption isotherms. Adsorption of the PAEs was exothermic, and was mainly dominated by physical interactions including dispersion, induction, orientation and hydrogen bond forces. Compared with activated carbon, the Mg–Al LDH removal efficiency of the relatively small PAE, DMP, was about 20 % lower. The removal efficiencies of the larger PAEs, DEHP and DOP, were about the same on both sorbents. After three regeneration cycles of the Mg–Al LDH at 300 °C for 2 h, its adsorption capacity remained above 90 %. The infrared (IR) spectra and the X-ray diffraction (XRD) patterns for the Mg-Al-LDH before and after regeneration showed no large differences, which indicates that the structure of the Mg–Al LDH does not change after regeneration.

Adsorption of Phthalate Esters from Aqueous Solution by Mg–Al Layered Double Hydroxide

Mg–Al layered double hydroxide (Mg–Al LDH) was investigated for adsorption of dimethyl phthalate (DMP), di-(2-ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP) from water samples. The adsorption capability of the Mg–Al LDH was compared with that of activated carbon. Adsorption of the three phthalate esters (PAEs) fitted pseudo-second-order kinetics, and the Langmuir or Freundlich equations described the adsorption isotherms. Adsorption of the PAEs was exothermic, and was mainly dominated by physical interactions including dispersion, induction, orientation and hydrogen bond forces. Compared with activated carbon, the Mg–Al LDH removal efficiency of the relatively small PAE, DMP, was about 20 % lower. The removal efficiencies of the larger PAEs, DEHP and DOP, were about the same on both sorbents. After three regeneration cycles of the Mg–Al LDH at 300 °C for 2 h, its adsorption capacity remained above 90 %. The infrared (IR) spectra and the X-ray diffraction (XRD) patterns for the Mg-Al-LDH before and after regeneration showed no large differences, which indicates that the structure of the Mg–Al LDH does not change after regeneration.

Removal of Phthalate Esters from Aqueous Solutions by Chitosan Bead

Removal of phthalate esters (PAEs) by chitosan bead in aqueous solution was studied. The adsorption isotherms of PAEs by chitosan bead were well described by Freundlich isotherm equations. Results of kinetic experiments indicated that diheptyl phthalate (DHpP) had the highest adsorption capacity (1.52 mg/g) among six PAEs in our research. PAE adsorption efficiency by chitosan bead was examined in both batch and continuous systems, and DHpP attained 74.9% recovery efficiency from chitosan bead by shaking with an equal volume mixture of methanol and water. The recovered chitosan bead was reusable as an adsorbent. The influences of temperature, pH, Ca+2, and NaCl on PAE adsorption were also evaluated to determine performance in different water environments (e.g., groundwater, surface water, and sea water). The results showed that PAE adsorption decreased as temperature increased. From pH experiments it appeared that pH 8.0 was optimal for adsorption. The effect of Ca+2 showed that adsorption efficiency did not change by increasing the concentrations of Ca+2 until 400 mg/L. NaCl coexistence showed an insignificant effect on PAE adsorption. Furthermore, the chitosan bead was also applied to treating the discharge of a plastics plant, and the treatment results resembled those of a laboratory continuous system. This is the first report to use chitosan bead as an adsorbent to adsorb phthalate esters from aqueous solution. These results indicate that the application of chitosan bead is feasible in the aqueous environments of Taiwan.

Adsorption of phthalate esters on soil at near saturation conditions

Batch studies were performed to determine the adsorption behavior of dimethyl phthalate ester and diethyl phthalate ester on two sandy New Jersey soils at near saturation conditions. One soil had a very low organic matter content (<0.012%) while the other was quite higher (1.33%). Both esters displayed BET type adsorption to the high organic content soil, while little adsorption was displayed to the low organic matter soil. Linear, Langmuir, Freundlich, BET, and a composite isotherm proposed by Marinas and Li were fitted to the data. The composite isotherm fir best in all cases. The diethyl phthalate evidence a greater tendency to adsorb than the dimethyl phthalate.