Exploring the adsorption behavior of benzotriazoles and benzothiazoles on polyvinyl chloride microplastics in the water environment

Investigation of interaction mechanism between polyvinyl chloride microplastics and phthalate acid esters using APGC-MS/MS

Phthalate acid esters (PAEs) are a kind of typical endocrine disruptors chemicals (EDCs). PAEs can be enriched, migrated and released into organisms through microplastics (MPs), causing high toxicological risks. This study presented an atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS) method for 10 PAEs trace analysis. Based on this method, the interaction mechanism between polyvinyl chloride microplastics (PVC MPs) and PAEs was explored. The established APGC-MS/MS method achieved 10 PAEs analysis in 14 min with the satisfied detection limit as low as 0.0025 μg/L and excellent linearity (R2 = 0.99868-0.99996). The interaction mechanism investigation showed that PVC MPs had high adsorption and desorption capacities for PAEs. The adsorption mechanism involves adsorption distribution, surface adsorption, hydrophobic interaction and intermolecular van der Waals force. Temperature, diffusion channels, pore filling, hydrophobicity and solubilization may be potential desorption mechanisms. Moreover, the intestinal environment of warm-blood organisms has the highest bioavailability of PAEs. Overall, this APGC-MS/MS method of PAEs had the virtue of simplicity, efficiency, reliability and sensitivity, and could serve as a potential tool for risk analysis of MPs and PAEs exposure.

Practical guidelines and challenges in the isolation and characterization of microplastics/microfibers by Raman microscopy

We address some challenges usually encountered in the analysis of microplastics (MPs) and microfibers (MFs) using Raman microscopy. Those issues are examined considering that the researchers that carry out the collection and analysis of MP contamination may not have necessarily specialized expertise in Raman microscopy or polymer chemistry. Topics such as effective particle isolation or the use of adequate substrates are approached on the base of the impact they have on the spectroscopic characterization. Issues as the control of background signal, the influence of sample digestion, and the presence of internal interferences such as pigments, dyes, and fillers, are discussed. Spectral features of the polymer families found as MP/MF contaminants are presented based upon polymer structure, properties, and applications. The use of open-source libraries to complement chemical identification is also discussed. Overall, this work aims to enhance the practice and understanding of Raman microscopy for researchers engaged in characterizing MP/MF contaminants.

Comprehensive analysis of benzothiazoles (BTHs), benzotriazoles (BTRs), and benzotriazole ultraviolet absorbers (BUVs) in the western South China Sea: Spatial distributions, migration tendencies and ecotoxicological relevance

Benzothiazoles (BTHs), benzotriazoles (BTRs), and benzotriazole ultraviolet absorbers (BUVs) have garnered significant attention owing to their persistent nature in the environment and adverse impacts on aquatic organisms. However, there remains a dearth of investigations and studies conducted in tropical marine environments. In this study, we undertook the inaugural distributional survey and ecotoxicological relevance of BTHs, BTRs, and BUVs in seawater and sediments of the western South China Sea (WSCS). Elevated concentrations of BTHs, BTRs, and BUVs in the seawater and suspended particulate matter (SPM) were primarily observed in the Pearl River Estuary (PRE) and the western region of the WSCS, attributed to terrestrial runoff and hydrodynamic processes. Moreover, the transport of these compounds at the seawater-SPM interface was influenced by both the intrinsic properties of the contaminants and temperature variations. Spatially, concentrations of BTHs, BTRs, and BUVs in surface sediments exhibited a diminishing trend with increasing distance from the coast to offshore areas, reflecting notable anthropogenic impacts. Concentration profiles of these compounds in sediment cores displayed a bottom-up increasing trend, with total organic carbon (TOC) identified as the primary determinant governing their accumulation within sediment cores in the WSCS. Terrestrial runoff inputs and atmospheric deposition as major contributors to the occurrence of BTHs, BTRs, and BUVs in the WSCS. Simultaneously, the study underscores the non-negligible moderate mixture risk quotient associated with BTHs, BTRs, and BUVs in the sediments.

Polyamide 6 microplastics as carriers led to changes in the fate of bisphenol A and dibutyl phthalate in drinking water distribution systems: The role of adsorption and interfacial partitioning

Microplastics (MPs) co-exist with plastic additives and other emerging pollutants in the drinking water distribution systems (DWDSs). Due to their strong adsorption capacity, MPs may influence the occurrence of additives in DWDSs. The article investigated the occurrence of typical additives bisphenol A (BPA) and dibutyl phthalate (DBP) in DWDSs under the influence of polyamide 6 (PA6) MPs and further discussed the partitioning of BPA/DBP on PA6s, filling a research gap regarding the impact of adsorption between contaminants on their occurrence within DWDSs. In this study, adsorption experiments of BPA/DBP with PA6s and pipe scales were conducted and their interaction mechanisms were investigated. Competitive adsorption experiments of BPA/DBP were also carried out with site energy distribution theory (SEDT) calculations. The results demonstrated that PA6s might contribute to the accumulation of BPA/DBP on pipe scales. The adsorption efficiencies of BPA/DBP with both PA6s and pipe scales were 26.47 and 2.61 times higher than those with only pipe scales. It was noteworthy that BPA had a synergistic effect on the adsorption of DBP on PA6s, resulting in a 26.47 % increase in DBP adsorption. The article provides valuable insights for the compounding effect of different types of additives in water quality monitoring and evaluation.

Comparing the adsorption of methyl orange and malachite green on similar yet distinct polyamide microplastics: Uncovering hydrogen bond interactions

Microplastics (MPs) and dye pollutants are widespread in aquatic environments. Here, the adsorption characteristics of anionic dye methyl orange (MO) and cationic dye malachite green (MG) on polyamide 6 (PA6) and polyamide 66 (PA66) MPs were investigated, including kinetics, isotherm equilibrium and thermodynamics. The co-adsorption of MO and MG under different pH was also evaluated. The results reveal that the adsorption process of MO and MG is suitably expounded by a pseudo-second-order kinetic model. The process can be characterized by two stages: internal diffusion and external diffusion. The isothermal adsorption equilibrium of MO and MG can be effectively described using the Langmuir model, signifying monolayer adsorption. Furthermore, the thermodynamic results indicated that the adsorption was spontaneous with exothermic and endothermic properties, respectively. The results of binary systems reveal that MO dominates the adsorption at low pH (2-5), while MG dominates at high pH (8-10). Strong competitive adsorption was observed between MO and MG in neutral conditions (pH 6-8). The desorption experiments confirm that PA6 and PA66 could serve as potential carriers of MO and MG. The interaction between dyes and polyamide MPs is primarily mediated through hydrogen bonds and electrostatic attraction. The results reveal that PA6 formed more hydrogen bonds with the dyes, resulting in higher adsorption capacity than that of PA66. This difference can be attributed to the disparities in the synthesis process and polymerization method. Our study uncovered the adsorption mechanism of dye pollutants on PA6 and PA66, and provided a more comprehensive theoretical basis for the risk assessment concerning different types of polyamide MPs in aquatic environments.

Rapid adsorption of benzotriazole onto oxidized carbon cloth as an easily separable adsorbent

A commercial carbon cloth (CC) was oxidized by HNO3 acid and the features of the plain and oxidized CC were evaluated. The results of characterization illustrated that HNO3 oxidization duplicated the oxygen-containing functional groups and the surface area of the CC. The adsorption performance of the plain and oxidized CC (Oxi-CC) toward benzotriazole (BTR) was compared. The results disclosed that the uptake of BTR by oxidized CC was greater than the plain CC. Thence, the affinity of oxidized CC toward BTR was assessed at different conditions. It was found that the adsorption was quick, occurred at pH 9 and improved by adding NaCl or CaCl2 to the BTR solution. The kinetic and isotherm studies revealed that the surface of Oxi-CC is heterogeneous and the adsorption of BTR follows a physical process and forms multilayer over the Oxi-CC surface. The regenerability and reusability study illustrated that only deionized water can completely regenerate the Oxi-CC and that the Oxi-CC can be reused for five cycles without any loss of performance. The high maximum adsorption capacity of Dubinin-Radushkevich isotherm model (252 mg/g), ease of separation and regeneration, and maintaining the adsorption capacity for several cycles revealed the high efficiency and economical and environmental feasibility of Oxi-CC as an adsorbent for BTR.

Removal of benzotriazole derivatives by biochar: Potential environmental applications

Benzotriazole and its derivatives (BTAs) are commonly present in wastewater due to their extensive use in industrial processes, yet their removal is still unexplored. Here, we test the removal of these pollutants using two functionalised biochars, synthesised from wild plum (WpOH) and apricot (AsPhA) kernels. The aim of this work was to optimise the adsorption process against various BTAs (i.e., benzotriazole (BTZ), 4-hydroxy-1H-benzotriazole (OHBZ), 4-methyl-1H-benzotriazole (4 MBZ), 5-methyl-1H-benzotriazole (5 MBZ), 5-chloro-1H-benzotriazole (ClBZ), 5,6-dimethyl-1H-benzotriazole (DMBZ)), and determine the adsorption mechanisms at play, using real wastewater matrices. Batch studies showed that the optimal adsorption pH ranged between 4 and 6 for WpOH and AsPhA, respectively, and equilibrium was reached after 240 min. The kinetic models that best described the adsorption process were in the following order: Elovich model > pseudo-second order model > pseudo-first order model. The equilibrium data showed the highest correlation with the Freundlich isotherm, indicating multilayer adsorption. The maximum adsorption capacity obtained in mixtures was 379 mg/g on WpOH and 526 mg/g on AsPhA. The mechanistic work revealed that the BTAs became bound to the biochar primarily through H-bonding, n-π and π-π EDA interactions. In wastewater, obtained before and after conventional treatment, the concentration of OHBZ and BTZ was reduced by >40%, while the concentration of the other compounds studied fell below the detection limit (∼2.0-90 ng/L). Finally, using a Vibrio fischeri assay, we showed that adsorption onto AsPhA significantly reduced the relative toxicity of both raw and treated wastewater.

Sorption of representative organic contaminants on microplastics: Effects of chemical physicochemical properties, particle size, and biofilm presence

Microplastic pollution has attracted mounting concerns worldwide. Microplastics may concentrate organic and metallic contaminants; thus, affecting their transport, fate and organismal exposure. To better understand organic contaminant-microplastic interactions, our study explored the sorption of selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), α-hexabromocyclododecane (α-HBCDD), and organophosphate flame retardants (OPFRs) on high-density polyethylene (HDPE) and polyvinylchloride (PVC) microplastics under saline conditions. Sorption isotherms determined varied between chemicals and between HDPE and PVC microplastics. Log Freundlich sorption coefficients (Log K_F) for the targeted chemicals ranged from 2.01 to 5.27 L kg^-1 for HDPE, but were significantly lower for PVC, i.e., ranging from Log K_F data (2.84 - 8.58 L kg^-1). Significant correlations between chemicals' Log K_F and Log K_ow (octanol-water partition coefficient) indicate that chemical-dependent sorption was largely influenced by their hydrophobicity. Sorption was evaluated using three size classes (< 53, 53 - 300, and 300 - 1000 µm) of lab-fragmented microplastics. Particle size did not significantly affect sorption isotherms, but influenced the time to reach equilibrium and the predicted maximum sorption, likely related to microplastic surface areas. The presence of biofilms on HDPE particles significantly enhanced contaminant sorption capacity, indicating more complex sorption dynamics in the chemical-biofilm-microplastic system. Our findings offer new insights into the chemical-microplastic interactions in marine environment.

Transport of emerging organic ultraviolet (UV) filters in ceramic membranes: Role of polyethylene (PE) microplastics

Microplastics can be considered potential carriers of emerging organic ultraviolet (UV) filters due to their considerable adsorption capacity in wastewater treatment. The adsorption behavior of organic UV filters, which are commonly contained in personal care products to preserve the skin against UV radiation, onto polyethylene (PE) microplastics were systematically studied to investigate their combined effects. Kinetics and isotherm analyses revealed that the adsorption of four organic UV filters onto PE microplastic surfaces followed a multi-rate and a heterogeneous multi-layer pattern. Several factors including salinity, microplastic size, and dosage also influenced the adsorption efficiency due to hydrophobic interactions. A bench-scale cross-flow ceramic membrane filtration experiment was investigated to evaluate the role of PE microplastics on the retention performance of organic UV filters. The retentions for organic UV filters were 34.2%-37.8% in the non-existence of PE microplastics. Conversely, organic UV filter retentions were significantly increased up to 82.2%-97.9% when they were adsorbed onto the PE microplastics, which were almost completely retained by the ceramic membrane. Therefore, organic UV filters can likely migrate and eventually be carried by PE microplastics, thus increasing the retention of both emerging organic UV filters and microplastics prior to discharge from wastewater treatment facilities.

Enhanced adsorption of tetracycline using modified second pyrolysis oil-based drill cutting ash

In this work, second pyrolysis oil-based drill cutting ash (OBDCA-sp) was modified using NaOH and cetyltrimethylammonium bromide (CTAB), respectively. The modified OBDCA-sp was used as the novel adsorbent for adsorption of tetracycline (TC) in aqueous solutions. The original and modified OBDCA-sp were characterized by SEM, XRD, FTIR, zeta potential analysis, contact angle, and BET. The maximum theoretical adsorption quantity (45 ℃) for TC was calculated as 1.7 mg/g using CTAB-OBDCA-sp as the adsorbent. The adsorption isotherm of TC on OBDCA-sp was fitted well with Freundlich model and the adsorption kinetic was illustrated by pseudo-second-order model. Neutral condition was favorable for the adsorption of TC. The result of regeneration experiment indicated the reusability of OBDCA-sp. The hydrogen bonding was the possible mechanism for TC adsorption. This paper developed the novel surface modification methods of OBDCA-sp and provided an approach for the resource utilization of OBDCA-sp as an environmental functional material.

Synthesis and Biological Importance of 2-(thio)ureabenzothiazoles

The (thio)urea and benzothiazole (BT) derivatives have been shown to have a broad spectrum of biological activities. These groups, when bonded, result in the 2-(thio)ureabenzothizoles (TBT and UBT), which could favor the physicochemical and biological properties. UBTs and TBTs are compounds of great importance in medicinal chemistry. For instance, Frentizole is a UBT derivative used for the treatment of rheumatoid arthritis and systemic lupus erythematosus. The UBTs Bentaluron and Bethabenthiazuron are commercial fungicides used as wood preservatives and herbicides in winter corn crops. On these bases, we prepared this bibliography review, which covers chemical aspects of UBTs and TBTs as potential therapeutic agents as well as their studies on the mechanisms of a variety of pharmacological activities. This work covers synthetic methodologies from 1935 to nowadays, highlighting the most recent approaches to afford UBTs and TBTs with a variety of substituents as illustrated in 42 schemes and 13 figures and concluded with 187 references. In addition, this interesting review is designed on chemical reactions of 2-aminobenzothiazoles (2ABTs) with (thio)phosgenes, iso(thio)cyanates, 1,1′-(thio)carbonyldiimidazoles [(T)CDI]s, (thio)carbamoyl chlorides, and carbon disulfide. This topic will provide information of utility for medicinal chemists dedicated to the design and synthesis of this class of compounds to be tested with respect to their biological activities and be proposed as new pharmacophores.