Enhanced heavy metal adsorption on microplastics by incorporating flame retardant hexabromocyclododecanes: Mechanisms and potential migration risks.
Graphical abstract
Introduction
The COVID-19 pandemic emphasized the indispensable role of plastic products in our daily lives. Due to their excellent properties such as lightweight, flexibility, durability, and chemical stability, plastics are used in personal protective equipment, packaging applications, and commercial products, which saw unprecedented growth during the pandemic (Patrício Silva et al., 2021; Prata et al., 2020; Roberts et al., 2021). However, the deterioration of the environmental situation due to poor management of plastic waste has further reinforced the widespread perception of plastic as a harmful pollutant (Parashar and Hait, 2021). More seriously, these plastics are subjected to physical, chemical, and biological degradation into smaller plastic fibers, known as microplastics (MPs, particle size < 5 mm), that pose a serious environmental pollution problem (Guan et al., 2020; Thompson et al., 2004).
As an abundant and persistent pollutant, MPs not only pose a direct or indirect threat to ecological environments (Ya et al., 2021; Zhang et al., 2022) and organisms (Li et al., 2022b; Liu et al., 2022a), but also tend to adsorb some pollutants and migrate easily, thus causing even more severe ecological and toxicological effects (Ouyang et al., 2022; Pestana et al., 2021; Wang et al., 2021). In fact, most commercial plastics contain inherent chemical additives that are required to meet the process and application requirements for better use in life (Do et al., 2022; Fauser et al., 2022; Yan et al., 2021). These chemical additives may be released into the environment together with MPs (Fauser et al., 2022). Tun et al. (2022) found that about half of the additives (e.g., phthalates and antioxidants) in a study of drainage field soils were sourced from MPs. Cao et al. (2022) revealed that MPs were a potential source of phthalate esters in the water environment and estimated their release to be approximately 57.8 to 16,100 kg of phthalate esters per year. Several recent studies have also demonstrated that the inclusion of chemical additives in MPs could cause greater ecological risks and toxicity to organisms compared to virgin MPs (Jang et al., 2021; Na et al., 2021). However, most previous studies focused on pure MPs acting as carriers of heavy metals, and information on the role of chemical additives in the migration and fate of MPs and pollutants was highly lacking. This knowledge gap has emerged as one of the central uncertainties in our understanding of the role of MPs in the migration and fate of heavy metals.
Hexabromocyclododecane (HBCD), a typical brominated flame retardant, is extensively applied as insulation material for building materials, decorative textiles, and electronics (Covaci et al., 2006; Fromme et al., 2014; Lee et al., 2019). Generally, HBCD is mixed with polystyrene (PS) plastics through extrusion and high-impact methods (Duan et al., 2016), which produces PS plastics containing HBCD (HBCD/PS) that are frequently detected in the environment (Covaci et al., 2006; Lee et al., 2019; Lin et al., 2021a). For example, HBCD was detected in substantial amounts in PS plastics (up to 14.5 mg/g) collected in the coastal region of South Korea, Hong Kong, Canada, and Japan, implying that HBCD/PS composite contamination was a common and global environmental problem (Jang et al., 2017). Additionally, HBCD has attracted worldwide attention due to its potential persistence, toxicity, and bioaccumulation (Jang et al., 2021; Liu et al., 2018). This has led to the fact that the addition of HBCD to MPs can therefore cause more serious toxic effects on organisms in the environment than virgin MPs (Lackmann et al., 2022). In our previous study, we found that HBCD could significantly promote the enrichment behavior of Pb(II) onto PS MPs (Lin et al., 2021b), which greatly enhanced the ability of MPs to serve as contaminants carriers in the environment. Therefore, it is necessary to further investigate the potential roles of HBCD in the adsorption of other heavy metals onto MPs and their potential migration risks, especially in the land-sea migration process.
Cu(II), Ni(II), and Zn(II) are heavy metals widely used in multiple industries, such as agriculture, the electroplating industry, and the dyestuff industry (Wang et al., 2020; Yildirim et al., 2020). When released into water bodies without proper treatment, these heavy metals can cause damage to human health and ecosystems due to their toxicity and biodegradability. Notably, these metals can be highly toxic to lower and higher organisms when exceeding certain concentrations (Li et al., 2022a; Tang et al., 2021b), and are thus included in the Water Framework Directive (Quevauviller, 2009). Moreover, Cu, Zn, and Ni are concerned heavy metals in estuaries due to their historical and humanistic residues (Hong et al., 2020). In this regard, we selected these three heavy metals as the target pollutants. Overall, the aims of this work are to i) reveal the potential roles and mechanisms of HBCD inherent in PS MPs with Cu(II), Ni(II), and Zn(II) adsorption; ii) investigate the influence of water chemistry (e.g., solution pH, salinity, dissolved organic matter (DOM)) on the adsorption processes; and iii) evaluate the potential migration risks of HBCD/PS MPs associated with the metals desorption in river water and seawater media.
Section snippets
Materials and Chemicals
The PS MPs and HBCD/PS MPs (HBCD: 2% of total weight) were obtained from a local material plant (Lianyungang Qihang Flame Retardant Material Co., Ltd, Lianyungang, China). The detailed production process of the HBCD/PS is shown in Fig. S1. The main difference between the PS MPs and HBCD/PS MPs is that the latter have an additional step in the preparation process that involves the addition of HBCD. Comparison of FTIR and XRD spectra of PS, HBCD, and HBCD/PS demonstrates that HBCD and PS were
Comparison of adsorption capacity
In the control experiments, while the HBCD or treated HBCD only accounted for 2% of the mass fraction of the HBCD/PS MPs, it contributes 41.59–57.68 %, 46.53–56.61 %, and 38.64–54.70 % to the Cu(II), Ni(II), and Zn(II) adsorption by HBCD/PS MPs, respectively (Fig. S3). However, the treated PS only contributes 2.15–7.71 % to the metals adsorption by HBCD/PS MPs. There results imply that HBCD plays an important role in the metals adsorption by HBCD/PS MPs. Furthermore, the adsorption ability of
Conclusions
Herein, the potential roles and risks of HBCD inherent in PS MPs associated with Cu(II), Ni(II), and Zn(II) adsorption/desorption were investigated. The results showed that the addition of HBCD greatly promoted the adsorption of Cu(II), Ni(II), and Zn(II) onto the MPs. The SEM-EDS, FTIR, and XPS analyses as well as density functional theory well explained that the metals were mainly adsorbed on the –O and –Br groups of the HBCD/PS MPs through electrostatic interactions and surface complexation.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
In memory of our best friend, Dr. John Merefield. We gratefully acknowledge the support of this work by National Natural Science Foundation of China (31870483, 31530008) and National Important Scientific Research Programme of China (2018YFC1406600). We thank TopEdit (www.topeditsci.com) for its linguistic assistance during the preparation of this manuscript. The authors would like to acknowledge the editors and anonymous reviewers whose comments and advice greatly improved the quality of this
References (80)
- et al.
Adsorption kinetics and thermodynamics of β-carotene on silica-based adsorbent
Chem. Eng. J.
(2009) - et al.
Inorganic arsenic species removal from water using bone char: A detailed study on adsorption kinetic and isotherm models using error functions analysis
J. Hazard. Mater.
(2021) - et al.
Removal of Zn(II) and Ni(II) heavy metal ions by new alginic acid-ester derivatives materials
Carbohydr. Polym.
(2021) - et al.
Microplastics: A major source of phthalate esters in aquatic environments
J. Hazard. Mater.
(2022) - et al.
Synthesis of magnetic Fe3O4/CFA composites for the efficient removal of U(VI) from wastewater
Chem. Eng. J.
(2017) - et al.
Competitive sorption of Pb(II), Cu(II) and Ni(II) on carbonaceous nanofibers: A spectroscopic and modeling approach
J. Hazard. Mater.
(2016) - et al.
Leaching of microplastic-associated additives in aquatic environments : A critical review ☆
Environ. Pollut.
(2022) - et al.
As(III) adsorption onto different-sized polystyrene microplastic particles and its mechanism
Chemosphere
(2020) - et al.
Adsorption mechanism of As(III) on polytetrafluoroethylene particles of different size
Environ. Pollut.
(2019) - et al.
Characterization of brominated flame retardants in construction and demolition waste components: HBCD and PBDEs
Sci. Total Environ.
(2016)
Residual additives in marine microplastics and their risk assessment – A critical review
Mar. Pollut. Bull.
Polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and ‘novel’ brominated flame retardants in house dust in Germany
Environ. Int.
Behaviors and influencing factors of the heavy metals adsorption onto microplastics: A review
J. Clean. Prod.
Surface complexation modelling of Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) adsorption onto kaolinite
Geochim. Cosmochim. Acta
Microplastics as an emerging anthropogenic vector of trace metals in freshwater: Significance of biofilms and comparison with natural substrates
Water Res
Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model
J. Colloid Interface Sci.
Capturing hormones and bisphenol A from water via sustained hydrogen bond driven sorption in polyamide microfiltration membranes
Water Res
The legacy of trace metal deposition from historical anthropogenic river management: A regional driver of offshore sedimentary microbial diversity
J. Hazard. Mater.
Adsorption thermodynamics of Methylene Blue onto bentonite
J. Hazard. Mater.
Adsorption of hydrolyzable metal ions at the oxide-water interface. III. A thermodynamic model of adsorption
J. Colloid Interface Sci.
Relative importance of aqueous leachate versus particle ingestion as uptake routes for microplastic additives (hexabromocyclododecane) to mussels
Environ. Pollut.
Widespread detection of a brominated flame retardant, hexabromocyclododecane, in expanded polystyrene marine debris and microplastics from South Korea and the Asia-Pacific coastal region
Environ. Pollut.
Dietary exposure and risk assessment of exposure to hexabromocyclododecanes in a Taiwan population
Environ. Pollut.
Adsorption of three pesticides on polyethylene microplastics in aqueous solutions: Kinetics, isotherms, thermodynamics, and molecular dynamics simulation
Chemosphere
Release of sediment metals bound by glomalin related soil protein in waterfowls inhabiting mangrove patches
Environ. Pollut.
Fulvic acid anchored layered double hydroxides: A multifunctional composite adsorbent for the removal of anionic dye and toxic metal
J. Hazard. Mater.
Microplastics increase the accumulation of phenanthrene in the ovaries of marine medaka (Oryzias melastigma) and its transgenerational toxicity
J. Hazard. Mater.
Chemosphere Adsorption behaviour of microplastics on the heavy metal Cr (VI) before and after ageing
Chemosphere
Adsorption of ibuprofen on organo-sepiolite and on zeolite/sepiolite heterostructure: Synthesis, characterization and statistical physics modeling
Chem. Eng. J.
Interpretation of the adsorption mechanism of Reactive Black 5 and Ponceau 4R dyes on chitosan/polyamide nanofibers via advanced statistical physics model
J. Mol. Liq.
Sorption of tetracycline onto hexabromocyclododecane/polystyrene composite and polystyrene microplastics: Statistical physics models, influencing factors, and interaction mechanisms
Environ. Pollut.
Hexabromocyclododecane alters malachite green and lead(II) adsorption behaviors onto polystyrene microplastics: Interaction mechanism and competitive effect
Chemosphere
Uncovering the disposable face masks as vectors of metal ions (Pb(II), Cd(II), Sr(II)) during the COVID-19 pandemic
Chem. Eng. J.
The protective layer formed by soil particles on plastics decreases the toxicity of polystyrene microplastics to earthworms (Eisenia fetida)
Environ. Int.
Microplastics as a vehicle of heavy metals in aquatic environments: A review of adsorption factors, mechanisms, and biological effects
J. Environ. Manage.
Sorption behaviors of tris-(2,3-dibromopropyl) isocyanurate and hexabromocyclododecanes on polypropylene microplastics
Mar. Pollut. Bull.
Combined statistical physics models and DFT theory to study the adsorption process of paprika dye on TiO2 for dye sensitized solar cells
J. Mater. Res. Technol.
Adsorption-desorption behavior of heavy metals in aquatic environments: Influence of sediment, water and metal ionic properties
J. Hazard. Mater.
Synergistic effect of microplastic fragments and benzophenone-3 additives on lethal and sublethal Daphnia magna toxicity
J. Hazard. Mater.
Plastics in the time of COVID-19 pandemic: Protector or polluter?
Sci. Total Environ.
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