Sorption of two common antihypertensive drugs onto polystyrene microplastics in water matrices

Implications of polystyrene and polyamide microplastics in the adsorption of sulfonamide antibiotics and their metabolites in water matrices

Microplastics (MP) and antibiotics coexist in the environment and their combined exposure represents a source of increasing concern. MP may act as carriers of antibiotics because of their sorption capacity. Knowledge of the interactions between them may help improve understanding of their migration and transformation. In this work, the adsorption behaviour of a group of sulfonamides and their acetylated metabolites on different sizes of polyamide (PA) and polystyrene (PS) MP were investigated and compared. Sulfonamides were adsorbed on both MP (qmax up to 0.699 and 0.184 mg/g, for PA and PS, respectively) fitting to a linear isotherm model (R2 > 0.835). A low particle size and an acidic and salinity medium significantly enhances the adsorption capacity of sulfonamides (i.e. removal of sulfamethoxazole increased from 8 % onto 3 mm PA pellets to 80 % onto 50 mm of PA pellets). According to characterization results, adsorption mechanism is explained by pore filling and hydrogen bonds (for PA) and hydrophobic interactions (for PS). After adsorption, surface area was increased in both MP as result of a potential ageing of the particles and the intensity of XRD peaks was higher denoting a MP structure more amorphized. Metabolites were adsorbed more efficiently than their parent compounds on PS while the opposite effect was observed on PA explained by the acetylation of the amine group and, subsequently the reduction of hydrogen bond interactions. Although the dissolved organic matter inhibits sulfonamides adsorption, removal up to 65.2 % in effluent wastewater and up to 72.1 % in surface water were observed in experiments using real matrices denoting the role of MP as vectors of sulfonamide antibiotics in aquatic media.

Aging of plastics in aquatic environments: Pathways, environmental behavior, ecological impacts, analyses and quantifications

The ubiquity of plastics in our environment has brought about pressing concerns, with their aging processes, photo-oxidation, mechanical abrasion, and biodegradation, being at the forefront. Microplastics (MPs), whether originating from plastic degradation or direct anthropogenic sources, further complicate this landscape. This review delves into the intricate aging dynamics of plastics in aquatic environments under various influential factors. We discuss the physicochemical changes that occur in aged plastics and the release of oxidation products during their degradation. Particular attention is given to their evolving environmental interactions and the resulting ecotoxicological implications. A rigorous evaluation is also conducted for methodologies in the analysis and quantification of plastics aging, identifying their merits and limitations and suggesting potential avenues for future research. This comprehensive review is able to illuminate the complexities of plastics aging, charting a path for future research and aiding in the formulation of informed policy decisions.

Dialdehyde modified and cationic aerogel for efficient microplastics adsorption from environmental waters

Recent reports had shown that microplastics could be transferred to organisms through various channels, severely and adversely affecting organisms' health and their physiological functions. Therefore, there remained an urgency to adopt an effective and environmentally friendly method to extract microplastics from water. In this paper, a cationic-modified d-DCPG aerogel with a three-dimensional network structure was successfully prepared by a directional freeze-drying technology in which double-aldehyde-modified cellulose nanofiber (CNF) was used as the matrix, betaine chloride hydrazide (GT) provided modification, and polyvinyl alcohol (PVA) provided cross-linking function. Aerogels had an excellent adsorption capacity (145.05 mg/g) for microplastics in aqueous environment, and when the pH was from 10 to 4, it exhibited an excellent adsorption efficiency from 90.01 % to 97.61 %; an excellent adsorption efficiency after 8 cycles (>89 %); pseudo-second-order kinetics and Freundlich adsorption isotherm had a high fitting effects on the adsorption process and adsorption results, respectively. And ultraviolet analysis also verified the occurrence of adsorption behavior. These results showed that d-DCPG aerogels had an excellent application prospects in microplastics removal in river, lake, reservoir, and marine environments.

The effect of microplastics on the depuration of hydrophobic organic contaminants in Daphnia magna: A quantitative model analysis

Microplastics are emerging pollutants that can absorb large amounts of hydrophobic organic contaminants (HOCs). However, no biodynamic model has yet been proposed to estimate their effects on HOC depuration in aquatic organisms, where the HOC concentrations are time-varying. In this work, a microplastic-inclusive biodynamic model was developed to estimate the depuration of HOCs via ingestion of microplastics. Several key parameters of the model were redefined to determine the dynamic HOC concentrations. Through the parameterized model, the relative contributions of dermal and intestinal pathways can be distinguished. Moreover, the model was verified and the vector effect of microplastics was confirmed by studying the depuration of polychlorinated biphenyl (PCB) in Daphnia magna (D. magna) with different sizes of polystyrene (PS) microplastics. The results showed that microplastics contributed to the elimination kinetics of PCBs because of the fugacity gradient between the ingested microplastics and the biota lipids, especially for the less hydrophobic PCBs. The intestinal elimination pathway via microplastics would promote overall PCB elimination, contributing 37-41 % and 29-35 % to the total flux in the 100 nm and 2 μm polystyrene (PS) microplastic suspensions, respectively. Furthermore, the contribution of microplastic uptake to total HOC elimination increased with decreasing microplastic size in water, suggesting that microplastics may protect organisms from HOC risks. In conclusion, this work demonstrated that the proposed biodynamic model is capable of estimating the dynamic depuration of HOCs for aquatic organisms. The results can shed light on a better understanding of the vector effects of microplastics.

Investigation of the adsorption-desorption behavior of antibiotics by polybutylene succinate and polypropylene aged in different water conditions

Microplastics (MPs) are widely present in aqueous environments and aged by natural components of complex water environments, such as salinity (SI) and dissolved organic matter (DOM). However, the effects of multicondition aging on the physicochemical properties and environmental behavior of MPs have not been completely investigated. In this study, the degradable MP polybutylene succinate (PBS) was used to investigate the environmental behavior of sulfamethoxazole (SMZ) and was compared with polypropylene (PP). The results showed that the single-factor conditions of DOM and SI, particularly DOM, promoted the aging process of MPs more significantly, especially for PBS. The degrees of MP aging under multiple conditions were lower than those under single-factor conditions. Compared with PP, PBS had greater specific surface area, crystallinity, and hydrophilicity and thus a stronger SMZ adsorption capacity. The adsorption behavior of MPs fitted well with the pseudo-second-order kinetic and Freundlich isotherm models, indicating multilayer adsorption. Compared with PP, PBS showed relatively a higher adsorption capacity, for example, for MPs aged under DOM conditions, the adsorption of SMZ by PBS was up to 5.74 mg/g, whereas that for PP was only 3.41 mg/g. The desorption experiments showed that the desorption amount of SMZ on MPs in the simulated intestinal fluid was greater than that in Milli-Q water. In addition, both the original PBS and the aged PBS had stronger desorption capacities than that of PP. The desorption quantity of PBS was 1.23-1.84 times greater than PP, whereas the desorption rates were not significantly different. This experiment provides a theoretical basis for assessing the ecological risks of degradable MPs in complex water conditions.

Removal of drug dexamethasone from aqueous matrices using low frequency ultrasound: Kinetics, transformation products, and effect of microplastics

Sonochemical oxidation was employed for the degradation of the drug dexamethasone (Dex). The oxidation at 20 kHz followed pseudo-first-order kinetics and increased with applied ultrasound power density. Acoustic cavitation at 71 W/L was able to eliminate 500 μg/L of dexamethasone from ultrapure water at inherent pH in less than 60 min. The oxidation was enhanced at pH 3 and decreased at increased Dex concentration. Scavenging experiments with tert-butanol showed that hydroxyl radicals play a crucial role in decomposition, where the reaction mainly occurs on the gas-liquid interface of the formed cavities. The addition of chloride did not affect Dex removal, while in the presence of 10 mg/L of humic acid or bicarbonate, the apparent kinetic constant decreased from 0.0423 ± 0.004 min^-1 to about 0.03 ± 0.002 min^-1. The rate in secondary effluent was 3.3 times lower than in ultrapure water due to the complexity of the actual matrix. Six transformation products were identified via high resolution LC-MS during the sonochemical oxidation of 3 mg/L Dex in ultrapure water. The presence of polyethylene or polystyrene microplastics slightly enhanced DEX sonodegradation. The effect of ultrasound irradiation at 71 W/L for 60 min on the microplastics surfaces was inconsiderable.

New insights into the adsorption behavior of thiacloprid at the microfibers/water interface: Role of humic acid

Dissolved organic matter regulates the interaction between microplastics (MPs) and organic pollutants. Here, this paper investigated the effect and mechanism of humic acid (HA) on the adsorption behavior of thiacloprid at two microfibers (MFs)/water interface, and compared the differences in the performance of MFs and pure MPs. The results showed that 10 mg L^-1 HA decreased the adsorption capacity and the partition coefficient K_D of thiacloprid on MFs and pure MPs. Spectral analysis showed that HA could form hydrogen bonds and van der Waals forces with both MPs and thiacloprid, ultimately affecting the adsorption behavior of thiacloprid at MPs/water interface via competitive adsorption and bridging effect. Furthermore, two-dimensional correlation spectroscopy demonstrated that thiacloprid was preferentially adsorbed onto MPs compared with HA. Finally, density functional theory calculation demonstrated that phenolic-OH, -COOH, and alcoholic-OH played critical roles in competing adsorption and bridging effect. This study offers a theoretical foundation for a better comprehension of the adsorption behavior of organic pollutants at the MPs/water interface.

Adsorption of perfluoroalkyl substances on polyamide microplastics: Effect of sorbent and influence of environmental factors

Microplastics (MPs) and perfluoroalkyl substances (PFASs) are two types of pollutants coexisting in the environment. Their co-exposure is a source of increasing concern. MPs present in the natural environment suppose an ideal surface for the sorption of hazardous contaminants. This study investigates the adsorption behaviour of six PFASs on polyamide (PA) MPs. Adsorption experiments under various internal (PA and PFASs dosage, PA particle size) and environmental (pH, ionic strength, dissolved organic matter) factors were carried out. Isotherm results (from 0.1 to 25 mg/L of PFASs) showed that the maximum adsorption capacity of the selected PFASs on the PA was as follows: perfluorooctanesulfonic acid (PFOS, 0.873 mg/g) > perfluorooctanoic acid (0.235 mg/g) > perfluoroheptanoic acid (0.231 mg/g) > perfluorohexanoic acid (0.201 mg/g) > perfluoropentanoic acid (0.192 mg/g) > perfluorobutanoic acid (0.188 mg/g) (pH 5.88, 0% salinity and 0% of dissolved organic matter). The PFOS has more tendency to be sorbed onto PA than perfluorocarboxilic acids. The MP characterization by scanning electron microscopy, X ray diffraction and Fourier transform infrared spectroscopy showed changes in the PA surface after adsorption assays. Pore filling, hydrophobic interactions and hydrogen bonds governed sorption process. The sorption capacity of PFASs was crucially affected by the PA size (from 19.6% to 99.9% for 3 mm and 50 μm particle size, respectively). The process was not significantly influenced by salinity while the dissolved organic matter exerted a negative effect (decrease from 100% to 26% for PFOS in presence of 25 mg/L of humic acid). Finally, adsorption rates of PFASs were quantified in real water matrices (influent and effluent wastewater, surface and tap water samples). The results revealed interactions between PA and PFASs and evidenced the role of PA as a vector to transport PFASs in the aquatic environment.