Estimation of the uptake rate constants for polycyclic aromatic hydrocarbons accumulated by semipermeable membrane devices and triolein-embedded cellulose acetate membranes

π-π stack driven competitive /complementary adsorption of aromatic compounds on MIL-53(Al)

In this study, the selective adsorption of aromatic compounds on mesoporous MIL-53(Al) was investigated, and followed the order: Biphenyl (Biph) > Triclosan (TCS) > Bisphenol A (BPA) > Pyrogallol (Pyro) > Catechol (Cate) > Phenol (Phen), and exhibited high selectivity toward TCS in binary compounds. In addition to hydrophobicity and hydrogen bonding, π-π interaction/stacking predominated, and more evidently with double benzene rings. TCS-containing halogens could increase π interaction on the benzene rings via forming Cl-π stacking with MIL-53(Al). Moreover, site energy distribution confirmed that complementary adsorption mainly occurred in the Phen/TCS system, as evidenced by ΔQ^pri (the decreased solid-phase TCS concentration of the primary adsorbate) < Q^sec (the solid-phase concentrations of the competitor (Phen)). In contrast, competitive sorption occurred in the BPA/TCS and Biph/TCS systems within 30 min due to ΔQ^pri = Q^sec, followed by substitution adsorption in the BPA/TCS system, but not for the Biph/TCS system, likely attributed to the magnitude of energy gaps (E_g) and bond energy of TCS (1.80 eV, 362 kJ/mol) fallen between BPA (1.74 eV, 332 kJ/mol) and Biph (1.99 eV, 518 kJ/mol) according to the density-functional theory of Gaussian models. Biph with a more stable electronic homeostasis than TCS lead to the occurrence of substitution adsorption in the TCS/BPA system, but not in the TCS/Biph system. This study provides insight into the mechanisms of different aromatic compounds on MIL-53(Al).

Exploring the influence of concentration fluctuation and matrix effects on a passive sampler of triolein-embedded cellulose acetate membrane measuring polychlorinated biphenyls in water

A membrane of triolein-embedded cellulose acetate membrane (TECAM), as an integrative passive sampler, was applied to adsorb 28 polychlorinated biphenyls (PCBs) from pure water and sea water in order to probe into the influence of concentration fluctuation and water matrix. The results demonstrated the temporal variations of PCBs concentrations in TECAM followed the first-order kinetics model. The periodic refreshment of solution and matrix effects of sea water significantly prolonged the time that PCBs reached equilibrium stage. The refreshment facilitated the uptake mass in TECAM. On the contrary, the matrix effects of sea water and dissolved organic matter (DOM) declined the PCBs absorption to TECAM. The average logK_P values of PCBs in pure water were about 1.2 log unit higher than those in sea water in the experiments that the solution was not refreshed, while the difference of average logK_P values narrowed to 0.3 log unit if the PCBs solutions were periodically refreshed. The correlation between logK_P and logK_OW values fitted the quadratic curve well, which was similar to semi-permeable membrane device (SPMD). The appropriate sampling times (t_94%) ranged from 98.8 to 819 h (mean 500 h) for pure water with refreshment, much longer than those in sea water with refreshment (80.1~410 h, mean 189 h). The t_94% values in the solution with high DOM content increased significantly, up to 409 h. Furthermore,  comparing the two experiments that the spiked pure water and sea water solution were refreshed frequently, the estimated sampling rates (R_s) in pure water (0.154~2.06 L/day with a mean value of 0.605 L/day) were slightly lower than those in sea water (0.292~3.84 L/day with a mean value of 1.69 L/day). However, the R_s values in sea water with DOM declined sharply to 0.042 L/day. Therefore, concentration fluctuation, matrix effect, and DOM contents of sea water evidently posed significant influence on dynamic parameters of TECAM absorption, which would be screened and probed detailed in future.

Integrated passive sampling and fugacity model to characterize fate and removal of organophosphate flame retardants in an anaerobic-anoxic-oxic municipal wastewater treatment system

It is crucial to deeply understand the fate and removal mechanism of various organophosphate flame retardants (PFRs) in specified wastewater treatment processes. However, concentration fluctuation and matrix effect in wastewater challenge quantification of PFR flux for both field observation and model validation. We present measured seasonal distribution profiles of time-weighted average (TWA) concentrations by in situ hydrophobic and polar passive samplers and modeled mass transport and transformation by means of fugacity for 11 PFRs with varied structures in an anaerobic-anoxic-oxic (A-A-O) municipal wastewater treatment system, and provided a systematic approach to characterize fate and removal mechanism of PFRs in major compartments via various treatment processes. We find evidence that PFRs have a unique structural-dependent fate and removal in the A-A-O system. Hydrophilic chlorinated-PFRs present persistent in all major compartments and dominate in effluents with significant variations; alkyl-PFRs are majorly reduced by biodegradation; whereas hydrophobic aryl-PFRs have the highest removal percentage, contributed by both sorption on solids and biotransformation. Sensitive analysis shows the most influential operation parameters on removal efficiency varied among the PFRs with different properties. We also conclude passive sampling can be effectively applied to estimate TWA wastewater concentrations and to validate fugacity model prediction.

Remobilization and bioavailability of polycyclic aromatic hydrocarbons from estuarine sediments under the effects of Nereis diversicolor bioturbation

The effects of Nereis diversicolor bioturbation on the remobilization and bioavailability of polycyclic aromatic hydrocarbons from estuarine sediment were determined after 60 d in a laboratory experiment. The release fluxes and mass transfer coefficients showed that bioturbation by N. diversicolor can lead to a significant remobilization of polycyclic aromatic hydrocarbons (PAHs) from estuarine sediments. Bioturbation enhanced the release of PAHs from sediment to water by accelerating the transport of sediment particles to the sediment-water interface followed by PAHs desorption to the water. The bioavailability of PAHs was described by SPMD-sediment accumulation factors (SSAF). The SSAF of low molecular weight PAHs with bioturbation was significantly higher than that of PAHs without bioturbation, and there were no significant variations in high-molecular-weight PAHs. Our results revealed that N. diversicolor bioturbation significantly increased PAHs release from sediment to water but only increased the bioavailability of low-molecular-weight PAHs.

Application of triolein-embedded cellulose acetate membrane (TECAM) passive sampler to study phase distribution of hexabromocyclododecanes (HBCDs) in sediment

Hexabromocyclododecanes (HBCDs) are a class of widely used brominated flame retardants (BFRs) that exhibit strong hydrophobicity. The ubiquity and persistence of HBCDs in sediment have attracted significant attention because of public health concerns. The environmental fate and ecological risks of HBCDs closely depend on their phase distribution in sediments. However, little information is available regarding the freely dissolved concentrations (C_free) of HBCDs in sediment porewater. In this study, we developed a method to measure C_free of HBCDs in sediment porewater using triolein-embedded cellulose acetate membranes (TECAM). The TECAM-to-water partitioning coefficient (log K_TECAM) was 4.69, 4.77, and 4.63 for α-HBCD, β-HBCD, and γ-HBCD, respectively. In sediments, HBCDs sorbed to the sediment solid phase accounted for more than 99% of the total chemical mass. The dissolved organic carbon (DOC)-water partition coefficient (K_DOC) values were derived from TECAM measurements, and the log K_DOC values ranged from 5.77 to 6.23 for the three HBCD diastereomers, suggesting a strong tendency for HBCDs to sorb to DOC. The high sorption of HBDCs for DOC implies a potential for DOC-facilitated transport which may enhance the environmental mobility of HBCDs.

Aquatic passive sampling of perfluorinated chemicals with polar organic chemical integrative sampler and environmental factors affecting sampling rate

A modified polar organic chemical integrative sampler (POCIS) could provide a convenient way of monitoring perfluorinated chemicals (PFCs) in water. In the present study, the modified POCIS was calibrated to monitor PFCs. The effects of water temperature, pH, and dissolved organic matter (DOM) on the sampling rate (R s) of PFCs were evaluated with a static renewal system. During laboratory validation over a 14-day period, the uptake kinetics of PFCs was linear with the POCIS. DOM and water temperature slightly influenced POCIS uptake rates, which is in consistent with the theory for uptake into POCIS. Therefore, within a narrow span of DOM and water temperatures, it was unnecessary to adjust the R s value for POCIS. Laboratory experiments were conducted with water over pH ranges of 3, 7, and 9. The R s values declined significantly with pH increase for PFCs. Although pH affected the uptake of PFCs, the effect was less than twofold. Application of the R s value to analyze PFCs with POCIS deployed in the field provided similar concentrations obtained from grab samples.

Using linoleic acid embedded cellulose acetate membranes to in situ monitor polycyclic aromatic hydrocarbons in lakes and predict their bioavailability to submerged macrophytes

To date no passive sampler has been used to predict bioavailability of contaminants to macrophytes. Here a novel passive sampler, linoleic acid embedded cellulose acetate membrane (LAECAM), was developed and used to in situ measure the freely dissolved concentrations of ten polycyclic aromatic hydrocarbons in the sediment porewaters and the water columns of two lakes in both winter and summer and predict their bioavailability to the shoots of resident submerged macrophytes (Potamogeton malainus, Myriophyllum spicata, Najas minor All., and Vallisneria natans (Lour.) Hara). PAH sampling by LAECAMs could reach equilibrium within 21 days. The influence of temperature on LAECAM-water partition coefficients was 0.0008-0.0116 log units/°C. The method of LAECAM was comparable with the active sampling methods of liquid-liquid extraction combined with fDOC adjustment, centrifugation/solid-phase extraction (SPE), and filtration/SPE but had several advantages. After lipid normalization, concentrations of the PAHs in LAECAMs were not significantly different from those in the macrophytes. In contrast, concentrations of the PAHs in the triolein containing passive sampler (TECAM) deployed simultaneously with LAECAM were much higher. The results suggest that linoleic acid is more suitable than triolein as the model lipid for passive samplers to predict bioavailability of PAHs to submerged macrophytes.

Application of the triolein-embedded cellulose acetate membrane passive sampler for monitoring of polycyclic aromatic hydrocarbons in water

Triolein-embedded cellulose acetate membrane (TECAM) can be used as a passive sampler to measure hydrophobic organic contaminants in water. Uptake constant rates (k u ) for polycyclic aromatic hydrocarbons (PAHs) by TECAM sampling were measured under different hydrodynamic conditions. The measured k u values were modeled to enable the quantification of time weighed average (TWA) concentrations of PAHs in the field. An empirical relationship that enables the calculation of in situ k u values of chemicals using performance reference compounds (PRCs) was derived and its application was demonstrated in a field study. The results showed that freely dissolved concentrations of hydrophobic organic compounds (HOCs) can be accurately measured in the field using TECAM method based on empirical uptake models calibrated with PRCs.

Estimating pesticide sampling rates by the polar organic chemical integrative sampler (POCIS) in the presence of natural organic matter and varying hydrodynamic conditions

The polar organic chemical integrative sampler (POCIS) was calibrated to monitor pesticides in water under controlled laboratory conditions. The effect of natural organic matter (NOM) on the sampling rates (R(s)) was evaluated in microcosms containing <0.1-5 mg L(-1) of total organic carbon (TOC). The effect of hydrodynamics was studied by comparing R(s) values measured in stirred (SBE) and quiescent (QBE) batch experiments and a flow-through system (FTS). The level of NOM in the water used in these experiments had no effect on the magnitude of the pesticide sampling rates (p > 0.05). However, flow velocity and turbulence significantly increased the sampling rates of the pesticides in the FTS and SBE compared to the QBE (p < 0.001). The calibration data generated can be used to derive pesticide concentrations in water from POCIS deployed in stagnant and turbulent environmental systems without correction for NOM.

Triolein embedded cellulose acetate membrane as a tool to evaluate sequestration of PAHs in lake sediment core at large temporal scale

Although numerous studies have addressed sequestration of hydrophobic organic compounds (HOCs) in laboratory, little attention has been paid to its evaluation method in field at large temporal scale. A biomimetic tool, triolein embedded cellulose acetate membrane (TECAM), was therefore tested to evaluate sequestration of six PAHs with various hydrophobicity in a well-dated sediment core sampled from Nanyi Lake, China. Properties of sediment organic matter (OM) varying with aging time dominated the sequestration of PAHs in the sediment core. TECAM-sediment accumulation factors (MSAFs) of the PAHs declined with aging time, and significantly correlated with the corresponding biota-sediment accumulation factors (BSAFs) for gastropod (Bellamya aeruginosa) simultaneously incubated in the same sediment slices. Sequestration rates of the PAHs in the sediment core evaluated by TECAM were much lower than those obtained from laboratory study. The relationship between relative availability for TECAM (MSAF(t)/MSAF(0)) and aging time followed the first order exponential decay model. MSAF(t)/MSAF(0) was well-related to the minor changes of the properties of OM varying with aging time. Compared with chemical extraction, sequestration reflected by TECAM was much closer to that by B. aeruginosa. In contrast to B. aeruginosa, TECAM could avoid metabolism and the influences from feeding and other behaviors of organisms, and it is much easier to deploy and ready in laboratory. Hence TECAM provides an effective and convenient way to study sequestration of PAHs and probably other HOCs in field at large temporal scale.

Removal of persistent organic pollutants from micro-polluted drinking water by triolein embedded absorbent

A new biomimetic absorbent, cellulose acetate (CA) embedded with triolein (CA-triolein), was prepared and applied for the removal of persistent organic pollutants (POPs) from micro-polluted aqueous solution. The comparison of CA-triolein, CA and granular activated carbon (GAC) for dieldrin removal was investigated. Results showed that CA-triolein absorbent gave a lowest residual concentration after 24 h although GAC had high removal rate in the first 4 h adsorption. Then the removal efficiency of mixed POPs (e.g. aldrin, dieldrin, endrin and heptachlor epoxide), absorption isotherm, absorbent regeneration and initial column experiments of CA-triolein were studied in detail. The linear absorption isotherm and the independent absorption in binary isotherm indicated that the selected POPs are mainly absorbed onto CA-triolein absorbent by a partition mechanism. The absorption constant, K, was closely related to the hydrophobic property of the compound. Thermodynamic calculations showed that the absorption was spontaneous, with a high affinity and the absorption was an endothermic reaction. Rinsing with hexane the CA-triolein absorbent can be regenerated after absorption of POPs. No significant decrease in the dieldrin removal efficiency was observed even when the absorption-regeneration process was repeated for five times. The results of initial column experiments showed that the CA-triolein absorbent did not reach the breakthrough point at a breakthrough empty-bed volume (BV) of 3200 when the influent concentration was 1-1.5 microg/L and the empty-bed contact time (EBCT) was 20 min.

Polymer coating of paramagnetic particulates for in vivo oxygen-sensing applications

Crystalline lithium phthalocyanine (LiPc) can be used to sense oxygen. To enhance biocompatibility/stability of LiPc, we encapsulated LiPc in Teflon AF (TAF), cellulose acetate (CA), and polyvinyl acetate (PVAc) (TAF, previously used to encapsulate LiPc, was a comparator). We identified water-miscible solvents that don't dissolve LiPc crystals, but are solvents for the polymers, and encapsulated crystals by solvent evaporation. Oxygen sensitivity of films was characterized in vitro and in vivo. Encapsulation did not change LiPc oximetry properties in vitro at anoxic conditions or varying partial pressures of oxygen (pO2). EPR linewidth of encapsulated particles was linear with pO2, responding to pO2 changes quickly and reproducibly for dynamic measurements. Encapsulated LiPc was unaffected by biological oxidoreductants, stable in vivo for four weeks. Oximetry, stability and biocompatibility properties of LiPc films were comparable, but both CA and PVAc films are cheaper, and easier to fabricate and handle than TAF films, making them superior.

Assessing accumulation and biological effect of hydrophobic organic contaminants in water using caged Japanese medaka and deployed triolein-embedded cellulose acetate membranes

Applicability of triolein-embedded cellulose acetate membrane (TECAM) to accumulation and potential biological effect assessment for hydrophobic organic contaminants (HOCs) was investigated compared with Japanese medaka. The results of field exposure showed that medaka and TECAMs accumulated contaminants in a similar pattern with good correlations between concentrations in medaka and TECAMs based on lipid weight for OCPs (r=0.96, p=0.01, n=9) and PAHs (r=0.73, p=0.01, n=13). Meanwhile, 2,3,7,8-TCDD equivalents (TEQs) of TECAM extracts detected by in vitro H4IIE cell bioassay corresponded well to hepatic EROD activities of exposed fish and TEQs of water samples. We concluded that TECAM could be utilized as a surrogate for biomonitoring organisms to assess the bioaccumulation of HOCs and potential biological effect.

Predicting bioavailability of PAHs in field-contaminated soils by passive sampling with triolein embedded cellulose acetate membranes

Triolein embedded cellulose acetate membrane (TECAM) was used for passive sampling of the fraction of naphthalene, phenanthrene, pyrene and benzo[a]pyrene in 18 field-contaminated soils. The sampling process of PAHs by TECAM fitted well with a first-order kinetics model and PAHs reached 95% of equilibrium in TECAM within 20 h. Concentrations of PAHs in TECAM (C(TECAM)) correlated well with the concentrations in soils (r(2)=0.693-0.962, p<0.001). Furthermore, concentrations of PAHs determined in the soil solution were very close to the values estimated by C(TECAM) and the partition coefficient between TECAM and water (K(TECAM-w)). After lipid normalization nearly 1:1 relationships were observed between PAH concentrations in TECAMs and earthworms exposed to the soils (r(2)=0.591-0.824, n=18, p<0.01). These results suggest that TECAM can be a useful tool to predict bioavailability of PAHs in field-contaminated soils.

Biomimetic accumulation of PAHs from soils by triolein-embedded cellulose acetate membranes (TECAMs) to estimate their bioavailability

A new passive sampling device (PSD), a triolein-embedded cellulose acetate membrane (TECAM), was used to biomimetically accumulate naphthalene, phenanthrene, pyrene and benzo[a]pyrene from ten spiked soils and a soil spiked with different concentrations of these polycyclic aromatic hydrocarbons (PAHs). TECAM exposure conditions were optimized. The quantities of PAHs accumulated by TECAMs were positively and linearly related to their concentrations in the soil. PAHs accumulated by TECAMs were negatively related to soil organic matter (SOM) and positively related to the dissolved organic carbon (DOC) according to the results obtained from ten spiked soils. Aging time (1-150 days) had a significant effect on accumulation of PAHs by TECAMs. A good linear relationship (R2=0.970-0.993) was observed between TECAM-accumulated PAHs and PAHs accumulated by earthworms (Eisenia andrei). The data indicate that TECAM represents a useful surrogate to estimate the bioavailability of PAHs and perhaps other hydrophobic organic contaminants (HOCs) in soils.

Research progress of novel adsorption processes in water purification: a review

As an effective, efficient, and economic approach for water purification, adsorbents and adsorption processes have been widely studied and applied in different aspects for a long time. In the recent years, a lot of novel adsorption processes have been developed for enhancing the efficiency of removing the organic and inorganic contaminants from water. This article reviews some new adsorbents and advanced adsorption methods that specialize in their compositions, structures, functions, and characteristics used in water treatment. The review emphasizes adsorption/catalytic oxidation process, adsorption/catalytic reduction process, adsorption coupled with redox process, biomimetic sorbent and its sorption behaviors of POPs, and modified adsorbents and their water purification efficiency.

Accurate quantification of freely dissolved organochlorine pesticides in water in the presence of dissolved organic matter using triolein-embedded cellulose acetate membrane

A novel method is described using triolein-embedded cellulose acetate membrane (TECAM) for accurate determination of the freely dissolved fraction of organochlorine pesticides (OCPs) in waters rich in dissolved organic matter (DOM). The performance of the method was tested with an air-bridge system for extracting OCPs from aqueous solutions with and without humic acid. In addition, the partition coefficients between humic acid and water (K (doc)s) for 20 OCPs were determined by TECAM with negligible depletion extraction. Results show that TECAM predominantly extracts the freely dissolved compounds and its extraction efficiency decreases significantly with an increase in concentration of humic acid in water. The proposed methodology is suitable for facile laboratory K (doc) measurement for moderate to high hydrophobic compounds (log K (ow) > 4). The linear relationship between log K (ow) and log K (doc) obtained in this study agrees well with the results reported earlier. The kinetic uptake rate constants (k (u)s) and TECAM-water partition coefficients (K (TECAM)s) for the 20 OCPs were obtained using the controlled laboratory continuous-flow and static exposure system, respectively. These calibration parameters were used in the field experiment to estimate the freely dissolved concentrations of OCPs in the water of Taihu Lake in China. Our results show that TECAM can be used successfully to determine the freely dissolved OCPs in aquatic environments containing DOM, and the method is particularly suited for long-term water sampling. Figure Schematic diagram of water sampling with a triolein-embedded cellulose acetate membrane (TECAM).