Adsorption properties and mechanism of Cu(II) on virgin and aged microplastics in the aquatic environment

“Plastic fragments or particles < 5 mm in diameter are generally referred to as MPs (Thompson et al. 2004).”

“According to the different formation conditions, MPs can be divided into primary MPs and secondary MPs(Cole et al. 2011, Oni and Sanni 2022).”

“The aging process changes the physical and chemical properties of MPs, such as their surface morphology, functional group composition, crystallinity and hydrophobicity (Wright et al. 2013), thus affecting the adsorption capacity and adsorption mechanism of MPs for other pollutants.”

“Despite their huge production, only 6 to14% of plastics are recycled (Alimi et al. 2018), and other plastics enter the environment in different ways.”

“MPs are pollutants that are widely distributed in environmental media such as oceans, rivers, lakes, sediments, and soils (Fiore et al. 2022; Hu et al. 2021; Li et al. 2018, 2021; Shen et al. 2018), and are even found in polar areas (Berg-mann et al. 2019; Ding et al. 2023).”

“Humans ingest MPs through diet, respiration, or skin contact, which can harm human health (Carbery et al. 2018; Rubio et al. 2020), which also presents an immense risk to ecological environmental security and biodiversity (Rahman et al. 2021).”

“…2019), the SSA and pore structure of particles increase (Fan et al. 2021b), and the oxygen functional groups on the surface of MPs also increase (Brennecke et al. 2016; Kalcíková et al. 2020), thereby increasing the binding sites on the surface of MPs (Wang et al. 2023), enhancing the…”

“In the natural environment, UV irradiation, thermal radiation, physical wear, chemical oxidation and biodegradation can cause different degrees of aging of MPs (Lang et al. 2020; Liu et al. 2020; Wang et al. 2021c).”

“PA and PLA MPs have been detected in several aquatic environments (Jang et al. 2020; Naji et al. 2021; Obbard et al. 2014; Yan et al. 2019).”

“Primary MPs are mainly micron and nano-scale plastic particles produced during the production, use and discharge of cosmetics and personal care products(Napper et al. 2015; Zhang et al. 2017).”

“The main types of MPs in the environment are polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), polyethylene terephthalate (PET), polylactic acid (PLA), polyurethane (PU) and nylon (Rayon) (Guo and Wang 2019, Rochman et al. 2013, Zhao et al. 2018).”

“Secondary MPs are mainly produced by the crushing of large plastic fragments(Kataoka et al. 2019; Li et al. 2020).”

“…decrease in crystallinity may be due to the fact that the oxidation of UV produces more oxygen-containing groups, so that some ordered structures in the polymer chains of MPs crystals are destroyed by UV light during aging, and some molecular chains undergo oxidative damage (Velzeboer et al. 2014).”

“Heavy metals have the characteristics of environmental persistence, biological concentration, undegrada-bility and toxicity (Sheng et al. 2022; Velusamy et al. 2021), which can cause harm to human health and ecosystems at very low concentrations (O'Connor et al. 2020).”

“For example, studies have found that after aging, the surface of MPs becomes rough and cracks and gullies appear (Liu et al. 2019), the SSA and pore structure of particles increase (Fan et al. 2021b), and the oxygen functional groups on the surface of MPs also increase (Brennecke et al. 2016;…”

“Humans ingest MPs through diet, respiration, or skin contact, which can harm human health (Carbery et al. 2018; Rubio et al. 2020), which also presents an immense risk to ecological environmental security and biodiversity (Rahman et al. 2021).”

“It was found that the peak area of the oxygen-containing groups increased after the aging of PA and PLA, while (Lang et al. 2020; Li et al. 2022b; Mao et al. 2020), which is consistent with the previous FTIR analysis results.”

“The main types of MPs in the environment are polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), polyethylene terephthalate (PET), polylactic acid (PLA), polyurethane (PU) and nylon (Rayon) (Guo and Wang 2019, Rochman et al. 2013, Zhao et al. 2018).”

“Their adsorption capacity is affected by their own physical and chemical properties, such as morphology, SSA and aging degree (Luo et al. 2022).”

“The adsorption of heavy metal ions by MPs may enhance their environmental mobility, bioaccumulation and ecological risk (Khalid et al. 2021).”

“These provide more adsorption sites for Cu(II) attachment to the MPs surface, which is beneficial for the adsorption behavior of Cu(II) on MPs surface (Ammala et al. 2011).”

“Primary MPs are mainly micron and nano-scale plastic particles produced during the production, use and discharge of cosmetics and personal care products(Napper et al. 2015; Zhang et al. 2017).”

“The main types of MPs in the environment are polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), polyethylene terephthalate (PET), polylactic acid (PLA), polyurethane (PU) and nylon (Rayon) (Guo and Wang 2019, Rochman et al. 2013, Zhao et al. 2018).”

“PA and PLA MPs have been detected in several aquatic environments (Jang et al. 2020; Naji et al. 2021; Obbard et al. 2014; Yan et al. 2019).”

“Secondary MPs are mainly produced by the crushing of large plastic fragments(Kataoka et al. 2019; Li et al. 2020).”

“…the adsorption rate of MPs on heavy metal ions, and the quantity of available adsorption sites determines the adsorption rate (Han et al. 2021; Wang et al. 2020), which is similar to the SEM and SSA analysis results for MPs. Aged MPs generally have a higher adsorption rate constant than…”

“…high hydrophobicity, are difficult to degrade (Leng et al. 2023; Liu et al. 2018; Oni et al. 2020), and readily serve as carriers to adsorb and enrich various organic compounds, heavy metals, and microorganisms from external phases (Ahechti et al. 2022; Torres et al. 2021; Upadhyay et al. 2022).”

“In the natural environment, UV irradiation, thermal radiation, physical wear, chemical oxidation and biodegradation can cause different degrees of aging of MPs (Lang et al. 2020; Liu et al. 2020; Wang et al. 2021c).”

“There are three stages of Cu(II) adsorption on both virgin and used PA and PLA (Ma et al. 2019; Sun et al. 2023).”

“The increase in pore volume indicates that the structure of the aged MPs was more developed and could provide more internal adsorption sites, which is consistent with previous research related to UV aging (Fan et al. 2021a).”

“The reason may be that the oxygen-containing groups react with Cu(II) to form metal oxides (Arp et al. 2021; Zhou et al. 2019).”

“According to statistics, global plastic manufacturing will reach 367 million tons by 2020 (Chen et al. 2023), and by 2050, the global plastic output is expected to reach 34 billion tons (Petersen and Hubbart 2021).”

“After Cu(II) adsorption, new Cu 2p3 / 2 and Cu 2p1 / 2 peaks and satellite peaks appeared on the aged PA and PLA (Huang et al. 2017, 2024 involved in the adsorption process of Cu(II).”

“In the natural environment, UV irradiation, thermal radiation, physical wear, chemical oxidation and biodegradation can cause different degrees of aging of MPs (Lang et al. 2020; Liu et al. 2020; Wang et al. 2021c).”

“Humans ingest MPs through diet, respiration, or skin contact, which can harm human health (Carbery et al. 2018; Rubio et al. 2020), which also presents an immense risk to ecological environmental security and biodiversity (Rahman et al. 2021).”

“…structure of particles increase (Fan et al. 2021b), and the oxygen functional groups on the surface of MPs also increase (Brennecke et al. 2016; Kalcíková et al. 2020), thereby increasing the binding sites on the surface of MPs (Wang et al. 2023), enhancing the adsorption capacity of…”

“PA and PLA MPs have been detected in several aquatic environments (Jang et al. 2020; Naji et al. 2021; Obbard et al. 2014; Yan et al. 2019).”

“PLA is a transparent and environmentally friendly biodegradable material with high strength, high modulus, and excellent formability and has great application value in various fields (Geng et al. 2020; Sun et al. 2022).”

“This indicates that the cracks and pits on the surface of MPs caused by the aging process increased their SSA, thereby increasing the number of adsorption sites on their surfaces of MPs and improving their ability to adsorb contaminants (Fu et al. 2021).”

“These pollutants also enter the food chain with MPs, and are transmitted and enriched between food chains, posing a serious risk to human wellness (Luo et al. 2023, Zhuang and Wang 2023).”

“…the adsorbent particles in the solution to be over-crowded, resulting in the overlapping of adsorption binding sites and the unsaturated utilization of active binding sites during the adsorbent process (Chaturvedi et al. 2020), causing the adsorption capacity of the unit to gradually decline.”

“It was found that the peak area of the oxygen-containing groups increased after the aging of PA and PLA, while (Lang et al. 2020; Li et al. 2022b; Mao et al. 2020), which is consistent with the previous FTIR analysis results.”

“The increase in pore volume indicates that the structure of the aged MPs was more developed and could provide more internal adsorption sites, which is consistent with previous research related to UV aging (Fan et al. 2021a).”

“In general, similar to previous studies, the morphology of MPs was dramatically altered by UV aging (Gao et al. 2021).”

“…and the oxygen functional groups on the surface of MPs also increase (Brennecke et al. 2016; Kalcíková et al. 2020), thereby increasing the binding sites on the surface of MPs (Wang et al. 2023), enhancing the adsorption capacity of pollutants and causing greater ecological and environmental risks.”

“MPs have high affinity for heavy metals in the aquatic environments and are good carriers of heavy metal ions (Foshtomi et al. 2019; Marsic-Lucic et al. 2018).”

“These pollutants also enter the food chain with MPs, and are transmitted and enriched between food chains, posing a serious risk to human wellness (Luo et al. 2023, Zhuang and Wang 2023).”

“PA and PLA MPs have been detected in several aquatic environments (Jang et al. 2020; Naji et al. 2021; Obbard et al. 2014; Yan et al. 2019).”

“…with large plastics, MPs have a small particle size, high SSA, and high hydrophobicity, are difficult to degrade (Leng et al. 2023; Liu et al. 2018; Oni et al. 2020), and readily serve as carriers to adsorb and enrich various organic compounds, heavy metals, and microorganisms from external phases…”

“In addition, Na + near the MPs may compete compete with free Cu(II) for adsorption sites on the surface of the MPs, thereby inhibiting the adsorption of Cu(II) (Wang et al. 2022b).”

“The reason may be that the oxygen-containing groups react with Cu(II) to form metal oxides (Arp et al. 2021; Zhou et al. 2019).”

“…mining, paper manufacture, and other industries, heavy metal ion-containing wastewater is being released into the environment in increasing amounts (Dong et al. 2019; He et al. 2020a; Wu et al. 2020; Xie et al. 2022), which makes the combined pollution of heavy metal ions and MPs serious.”

“…and the oxygen functional groups on the surface of MPs also increase (Brennecke et al. 2016; Kalcíková et al. 2020), thereby increasing the binding sites on the surface of MPs (Wang et al. 2023), enhancing the adsorption capacity of pollutants and causing greater ecological and environmental risks.”

“MPs are pollutants that are widely distributed in environmental media such as oceans, rivers, lakes, sediments, and soils (Fiore et al. 2022; Hu et al. 2021; Li et al. 2018, 2021; Shen et al. 2018), and are even found in polar areas (Berg-mann et al. 2019; Ding et al. 2023).”

“Heavy metals have the characteristics of environmental persistence, biological concentration, undegrada-bility and toxicity (Sheng et al. 2022; Velusamy et al. 2021), which can cause harm to human health and ecosystems at very low concentrations (O'Connor et al. 2020).”

“In the natural environment, UV irradiation, thermal radiation, physical wear, chemical oxidation and biodegradation can cause different degrees of aging of MPs (Lang et al. 2020; Liu et al. 2020; Wang et al. 2021c).”

“Among them, Cu(II) is the most common heavy metal pollutant discharged into water (Cherono et al. 2021; Wang et al. 2021b).”

“This may be mainly due to the formation of large particle clusters due to the interaction between MP particles, hindering the normal diffusion of Cu(II) to the MPs' surfaces (He et al. 2020b).”

“Most of the plastics that enter the environment will gradually break into smaller plastic fragments due to weathering, mechanical crushing, ultraviolet radiation, chemical reactions, microbial degradation and other environmental effects (De Gisi et al. 2022; Lionetto et al. 2023).”

“…high hydrophobicity, are difficult to degrade (Leng et al. 2023; Liu et al. 2018; Oni et al. 2020), and readily serve as carriers to adsorb and enrich various organic compounds, heavy metals, and microorganisms from external phases (Ahechti et al. 2022; Torres et al. 2021; Upadhyay et al. 2022).”

“MPs are pollutants that are widely distributed in environmental media such as oceans, rivers, lakes, sediments, and soils (Fiore et al. 2022; Hu et al. 2021; Li et al. 2018, 2021; Shen et al. 2018), and are even found in polar areas (Berg-mann et al. 2019; Ding et al. 2023).”

“MPs have high affinity for heavy metals in the aquatic environments and are good carriers of heavy metal ions (Foshtomi et al. 2019; Marsic-Lucic et al. 2018).”

“The adsorption of Cu(II) by MPs before and after aging is mainly chemical, and the adsorption process is a monolayer adsorption (Loncarski et al. 2021).”

“Compared with large plastics, MPs have a small particle size, high SSA, and high hydrophobicity, are difficult to degrade (Leng et al. 2023; Liu et al. 2018; Oni et al. 2020), and readily serve as carriers to adsorb and enrich various organic compounds, heavy metals, and microorganisms from…”

“Linear, Freundlich, and Langmuir isotherm models were used to fit the isotherm data on adsorption (Sackey et al. 2021; Zhao et al. 2013), and the expressions are shown in Eqs.”

“This may be mainly due to the formation of large particle clusters due to the interaction between MP particles, hindering the normal diffusion of Cu(II) to the MPs' surfaces (He et al. 2020b).”

“MPs are pollutants that are widely distributed in environmental media such as oceans, rivers, lakes, sediments, and soils (Fiore et al. 2022; Hu et al. 2021; Li et al. 2018, 2021; Shen et al. 2018), and are even found in polar areas (Berg-mann et al. 2019; Ding et al. 2023).”

“Linear, Freundlich, and Langmuir isotherm models were used to fit the isotherm data on adsorption (Sackey et al. 2021; Zhao et al. 2013), and the expressions are shown in Eqs.”

“…the value, the slower the adsorption rate of MPs on heavy metal ions, and the quantity of available adsorption sites determines the adsorption rate (Han et al. 2021; Wang et al. 2020), which is similar to the SEM and SSA analysis results for MPs. Aged MPs generally have a higher adsorption rate…”

“In solution, H + competes with Cu(II) for adsorption, and H + occupies the adsorption sites of the MPs, resulting in a low Cu(II) adsorption effect (Allouss et al. 2020).”

“There are three stages of Cu(II) adsorption on both virgin and used PA and PLA (Ma et al. 2019; Sun et al. 2023).”

“…high hydrophobicity, are difficult to degrade (Leng et al. 2023; Liu et al. 2018; Oni et al. 2020), and readily serve as carriers to adsorb and enrich various organic compounds, heavy metals, and microorganisms from external phases (Ahechti et al. 2022; Torres et al. 2021; Upadhyay et al. 2022).”

“MPs help pollutants migrate into the environment through water transport or atmospheric flow, and can also interact with pollutants to produce combined effects, causing joint toxicity to organisms and eco-systems (Lv et al. 2022; Mejías et al. 2023).”

“To investigate the adsorption behavior of MPs on Cu(II), pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to fit the kinetic data (Betianu et al. 2020; Zhang et al. 2023).”

“MPs are pollutants that are widely distributed in environmental media such as oceans, rivers, lakes, sediments, and soils (Fiore et al. 2022; Hu et al. 2021; Li et al. 2018, 2021; Shen et al. 2018), and are even found in polar areas (Berg-mann et al. 2019; Ding et al. 2023).”

“After Cu(II) adsorption, new Cu 2p3 / 2 and Cu 2p1 / 2 peaks and satellite peaks appeared on the aged PA and PLA (Huang et al. 2017, 2024 involved in the adsorption process of Cu(II).”

“According to statistics, global plastic manufacturing will reach 367 million tons by 2020 (Chen et al. 2023), and by 2050, the global plastic output is expected to reach 34 billion tons (Petersen and Hubbart 2021).”

“Cu(II) is mostly chemically adsorbed onto MPs by methods such as surface adsorption and exter-nal liquid film diffusion (Liu et al. 2022a).”

“Changes in MPs morphology after aging may be caused by UV photooxidation degradation (Bao et al. 2022; Guo et al. 2023).”

“MPs are pollutants that are widely distributed in environmental media such as oceans, rivers, lakes, sediments, and soils (Fiore et al. 2022; Hu et al. 2021; Li et al. 2018, 2021; Shen et al. 2018), and are even found in polar areas (Berg-mann et al. 2019; Ding et al. 2023).”

“Subsequently, the MPs' surface adsorption sites were progressively filled, the adsorption rate slows down (Leng et al. 2023), and the adsorption reaches equilibrium at 36 h.”

“They are widely used in aerospace, military, agriculture, industry, daily life and other fields (Tan et al. 2020).”

“In the natural environment, UV irradiation, thermal radiation, physical wear, chemical oxidation and biodegradation can cause different degrees of aging of MPs (Lang et al. 2020; Liu et al. 2020; Wang et al. 2021c).”

“H, the characteristic peak at 3000 cm −1 was the stretching vibration of-CH 2 , and the characteristic peak at 1755 cm −1 was attributed to the stretching vibration of C = O (Fan et al. 2023; Liang et al. 2023).”

“According to the different formation conditions, MPs can be divided into primary MPs and secondary MPs(Cole et al. 2011, Oni and Sanni 2022).”

“The above results show that under the action of photooxidation, the SSA of MPs increases, and the pore diameter becomes larger, which was more beneficial for the ions of heavy metals on the surface of MPs, leading to adsorption (Wang et al. 2022a).”

“Cu(II) is mostly chemically adsorbed onto MPs by methods such as surface adsorption and exter-nal liquid film diffusion (Liu et al. 2022a).”

“The position of the characteristic diffraction peak of PA MPs did not change after aging; however, the intensity of the diffraction peak decreased (Li et al. 2024, 2022a).”

“PLA is a transparent and environmentally friendly biodegradable material with high strength, high modulus, and excellent formability and has great application value in various fields (Geng et al. 2020; Sun et al. 2022).”

“MPs help pollutants migrate into the environment through water transport or atmospheric flow, and can also interact with pollutants to produce combined effects, causing joint toxicity to organisms and eco-systems (Lv et al. 2022; Mejías et al. 2023).”

“…mining, paper manufacture, and other industries, heavy metal ion-containing wastewater is being released into the environment in increasing amounts (Dong et al. 2019; He et al. 2020a; Wu et al. 2020; Xie et al. 2022), which makes the combined pollution of heavy metal ions and MPs serious.”

“To investigate the adsorption behavior of MPs on Cu(II), pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to fit the kinetic data (Betianu et al. 2020; Zhang et al. 2023).”

“Most of the plastics that enter the environment will gradually break into smaller plastic fragments due to weathering, mechanical crushing, ultraviolet radiation, chemical reactions, microbial degradation and other environmental effects (De Gisi et al. 2022; Lionetto et al. 2023).”

“…mining, paper manufacture, and other industries, heavy metal ion-containing wastewater is being released into the environment in increasing amounts (Dong et al. 2019; He et al. 2020a; Wu et al. 2020; Xie et al. 2022), which makes the combined pollution of heavy metal ions and MPs serious.”

“H, the characteristic peak at 3000 cm −1 was the stretching vibration of-CH 2 , and the characteristic peak at 1755 cm −1 was attributed to the stretching vibration of C = O (Fan et al. 2023; Liang et al. 2023).”

“These are the characteristic bands of PA (Du et al. 2022; Liu et al. 2023).”

“1a, b, c, and d), which may have been due to the oxidation of MPs during this process, resulting in the generation of chromogenic group substances (Li et al. 2023; Liu et al. 2022b).”

“Due to its good mechanical properties, heat resistance and chemical stability, it is widely used in automobiles, electronic appliances, machinery, rail transit, and sports equipment (Crespo et al. 2019; Rein-aldo et al. 2020).”

“…C values of the aged MPs in the three stages of adsorption were greater than those of the virgin MPs, which was mostly caused by the MPs' surfaces exhibiting more adsorption sites as they aged, increasing the mass transfer driving force of Cu(II) in MPs intra-particle diffusion (Fan et al. 2022).”

“Similarly, the adsorption ability of MPs for Cu 2+ decreased as salinity increased due to competition from Na + with free Cu 2+ for adsorption sites on the MP surface (Hu et al., 2024).”

“The increase in Q max values of photoaged PP suggests the significant enhancement in adsorp - tion capacity resulting from the surface modifi - cation caused by photoaging (Hu et al., 2024).”