Soil and sludge are important pools for microplastics (MPs), however standard separation methods for MPs from these pools are still missing. We tested the widely used methods for MPs extraction from ...water and sediment to six agriculture surface soils and three sewage sludges from municipal wastewater treatment plants and included an additional pre-digestion procedure with 30% H2O2 before floatation to remove soil or sludge organic matter (OM). Extraction efficiency of MPs were evaluated under different separation conditions, including floatation solution (NaCl, ZnCl2, and NaI), filtration membrane, and oxidation solution. Results showed that H2O2 pre-digestion significantly increased MPs extraction in soil and sludge, especially the samples with high OM contents, particularly sludge. Floatation solution with higher densities recovered more MPs. The extra released MPs were mainly small fibrous MPs, probably because they are easily retained by aggregates. Our results provide an feasible separation method for MPs in soil and sludge, i.e., pre-digestion with 30% H2O2 at 70 °C, floatation with NaI solution, filtration through nylon membrane, and further oxidation with 30% H2O2 + H2SO4 or 30% H2O2 at 70 °C. About 420–1290 MP items/kg soil were detected in soil samples, while much higher numbers (5553–13460 MP items/kg) were found in sludge samples. The dominate morphology of MPs was white fiber with a size of 0.02–0.25 mm, while the main types of MPs, identified by a micro-Fourier transformed infrared spectroscopy (μ-FTIR), were polyethylene and polypropylene in soil samples and polyethylene, polyethylene terephthalate, and polyacrylonitrile in sludge samples.
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•Extraction methods for aquatic MPs are not applicable to soil and sludge samples.•Floatation alone cannot extract all MPs from soil and sludge.•Pre-digestion with H2O2 releases more small fibrous MPs from soil and all shapes' MPs from sludge.•High-density floatation solution helps to extract more small MP fibers with high-density.
An optimal separation and identification method of microplastic from soil and sludge were proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The adsorption of five toxic metallic cations, Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II), onto montmorillonite was investigated as a function of pH and ionic strength and a two-site surface ...complexation model was used to predict the adsorption data. The results showed that in the lower pH range, 3∼6 for Cd, Cu, Ni and Zn, and 3∼4.5 for Pb, the adsorption was greatly affected by ionic strength, while in the higher pH range, the adsorption was not. In the lower pH range, the metallic cations were mainly bound through the formation of outer-sphere surface on the permanently charged basal surface sites (≡X
−), while in the higher pH range the adsorption occurred mainly on the variably charged edge sites (≡SOH) through the formation of inner-sphere surface complexes. Acid-base surface constants and metal binding constants for the two sites were optimized using FITEQL. The adsorption affinity of the five metallic cations to the permanently charged sites of montmorillonite was Pb
>
Cu
>
Ni
≈
Zn
≈
Cd, while that to the variable charged sites was Pb
≫
Cu
>
Zn
>
Cd
>
Ni.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Birnessite is one of the most common manganese oxides in the environment and an important scavenger of trace metals. This study investigated the adsorption of seven divalent metal cations (Cd2+, ...Co2+, Cu2+, Mn2+, Ni2+, Pb2+ and Zn2+) on birnessite at different pH conditions, ionic strengths and initial concentrations. The adsorption data were used to formulate a self-consistent, two-site surface complexation model consisting of a triple-corner-sharing (TCS) complex at interlayer vacancies and a double-corner-sharing (DCS) complex at mineral edge sites. Unlike the other metals, Ni2+ had a relatively low adsorption capacity on birnessite, attributable to its tendency to incorporate within Mn vacancies (INC); hence a two-site model with INC and DCS complexes was used to describe Ni2+ adsorption on birnessite. The model well described all the adsorption data and was verified by data from the literature. In addition, a linear free energy relationship (LFER) was developed between the TCS binding constants and metal electronegativity and hydrous ionic radii, which can be used to estimate the binding constants of other trace metals. The proposed model contributes to a better understanding of the adsorption mechanisms of trace metals by manganese oxides. Furthermore, the data set can be included in geochemical assemblage models to predict the dissolution and mobility of metals in the environment.
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•The adsorption of Cd, Co, Cu, Mn, Ni, Pb and Zn on birnessite was investigated.•A two-site surface complexation model was developed to describe the adsorption.•The model included a TCS complex at vacancies and a DCS complex at edge sites.•The model is self-consistent and was verified using data from the literature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The adsorption of tetracycline (TC) on a Na-montmorillonite was studied as a function of five background electrolyte cations (Li+, Na+, K+, Mg2+ and Ca2+), one transitional metal cation (Cu2+) and ...humic acid (HA) over a pH range from 3 to 9 using batch experiments combined with XRD and FTIR measurement. Results showed that pH had great effect on the TC adsorption and acidic condition is more favored. Monovalent (Li+, Na+ and K+) and divalent (Mg2+, Ca2+ and Cu2+) cations showed very different effects on the TC adsorption onto montmorillonite. In the presence of monovalent cations, the adsorption edge curves were little affected by the types of cations. They presented a great decrease at pH<6, then an increase to a local maximum at about pH 8, followed by a gradual decrease (8<pH<9), which might resulted from cation exchange at the interlayer surface sites and surface complexation at the basal or edge sites. In the presence of divalent cations, the adsorption of TC was enhanced compared to the ones in the presence of monovalent cations, indicating other mechanism might involve. The enhanced TC adsorption has an order: Cu2+≫Ca2+>Mg2+, which might be due to the capability of “bridge” effect of divalent cations. The difference of enhancing TC adsorption in the presence of Ca2+ and Mg2+ might be a result of different ionic radii and different interacting groups in TC molecular. XRD results showed that TC was intercalated into interlayers of montmorillonite since the interlayer expansion was observed. The band changes of amide carbonyl and amino groups in tricarbonyl methane group and the carbonyl group in phenolic deketone group in the FTIR spectra of TC equilibrated with montmorillonite confirmed that TC was adsorbed to the clay via cation exchange and surface complexation. It was also found that the effect of HA on the TC adsorption was pH-dependent and the presence of HA significantly reduced the mobility of TC in solution especially under acidic condition due to the complexation between cationic or zwitterionic TC species and the deprotonated sites on HA (mainly carboxylic groups) via electrostatic attraction. These results suggested that coexistence of divalent cations and HA would reduce TC's mobility in soil environment, especially at acidic condition.
► Tetracycline adsorption to montmorillonite by ion exchange and surface complexation. ► Divalent cations improved adsorption via ion bridging: Cu2+≫Ca2+>Mg2+. ► Humic acid reduced the mobility of tetracycline in solution under acidic condition. ► Cations and humic acid have great effects on tetracycline mobility in soils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Tetracycline (TC), a common antibiotic, can behave as an efficient ligand with cations, but the effect of its interaction with heavy metal cations on the mobility of both species in soils has not ...been well evaluated. In this study, the complexation affinities of TC with Cd (II), Cu (II) and Pb (II) were examined using potentiometric titration and spectroscopic methods. The cosorption behavior of TC and metal ions onto three selected Chinese soils was evaluated using batch adsorption experiments. The presence of metal cations promoted TC adsorption through an ion bridging effect in the order Cu (II) > Pb (II) > Cd (II), which is in accordance with their complexation ability with TC. The addition of TC affects metal adsorption differently depending on the solution pH and metal type. Therefore, it is necessary to consider the complexation ability of TC and divalent metal cations when evaluating their mobility in soils.
•The complex affinity with TC has an order of Cu(II) > Pb(II) > Cd(II).•The complexation constants of TC with the three metals are obtained.•The cosorption behavior in soils greatly depends on the complexation affinity.
The interaction between tetracycline and metal cations can influence the adsorption behavior of these species in soils, depending on their complexation ability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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In this study, a charge distribution multisite surface complexation model (CD–MUSIC) for adsorption of chromate onto goethite was carefully developed. The adsorption of Cr(VI) on ...goethite was firstly investigated as a function of pH, ionic strength and Cr(VI) concentration. Results showed that an inner-sphere complexation mechanism was involved because the retention of Cr(VI) was little influenced by ionic strength. Then two surface species: a bidentate complex (Fe2O2CrOOH) and a monodentate complex (FeOCrO3−3/2), which is constrained by prior spectroscopic evidence were proposed to fit the macroscopic adsorption data. Modeling results showed that the bidentate complex was found to be the dominant species at low pH, whereas, with increasing pH, monodentate species became more pronounced. The model was then verified by prediction of competitive adsorption of chromate and phosphate at various ratios and ionic strengths. The model successfully predicted the inhibition of chromate with the presence of phosphate, suggesting phosphate has higher affinity to goethite surface than Cr(VI). Results showed that the model developed in this study for Cr(VI) onto goethite was applicable for various conditions. It is a useful supplement for the surface complexation model database for oxyanions onto goethite surfaces.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Tumor-targeting nanomaterial-based chemotherapeutic drug delivery systems have been shown to represent an efficacious approach for the treatment of cancer because of their stability in blood ...circulation and predictable delivery patterns, enhanced tumor-selective drug accumulation, and decreased toxicity to normal tissues. The cell-surface transmembrane glycoprotein CD44 binds to the extracellular domain of hyaluronic acid (HA), and is overexpressed in breast, ovarian, lung, and stomach cancer. In this study, an HA-based nano-carrier incorporating doxorubicin (DOX) and cisplatin (CDDP) was synthesized as a CD44-targeting anti-cancer drug delivery system, and its tumor inhibition effects against CD44
+
breast cancer cells were evaluated
in vitro
and
in vivo
. These dual drug-loaded HA micelles (HA-DOX-CDDP) exhibited significantly enhanced drug release under acidic conditions, and showed higher cellular uptake and stronger cellular growth inhibition than free drugs against 4T1 (CD44
+
) breast cancer cells. In contrast, no significant differences in growth inhibition and cellular uptake were observed between HA-DOX-CDDP and free drugs in NIH-3T3 (CD44
-
) control cells. Furthermore, HA-DOX-CDDP micelles exhibited stronger inhibitory effects and lower systemic toxicity than free drugs in a 4T1 mammary cancer-bearing mouse model, as determined using immunofluorescence and histological analyses. Therefore, HA-DOX-CDDP micelles represent a promising drug delivery system that exhibits acid-sensitive drug release, CD44-targeted delivery, and excellent biocompatibility and biodegradation. These properties resulted in excellent tumor accumulation and reduced adverse effects, indicating that HA-DOX-CDDP micelles have promising potential applications in chemotherapy for breast cancer.
Copper (II) significantly enhanced tetracycline adsorption via acting as a bridge ion to form goethite–Cu2+–tetracycline complex because Cu2+ could form strong and specific inner-sphere surface ...complexes. Display omitted
► Background electrolyte cations showed almost no effect on tetracycline adsorption onto goethite. ► Copper (II) and humic acid enhanced the adsorption to different extent. ► Tetracycline was adsorbed by goethite through inner-sphere complextion. ► Copper (II) and humic acid have great effects on tetracycline mobility in soils.
Adsorption of tetracycline, one of the most widely used antibiotics, onto goethite was studied as a function of pH, metal cations, and humic acid (HA) over a pH range 3–10. Five background electrolyte cations (Li+, Na+, K+, Ca2+, and Mg2+) with a concentration of 0.01M showed little effect on the tetracycline adsorption at the studied pH range. While the divalent heavy metal cation, Cu2+, could significantly enhance the adsorption and higher concentration of Cu2+, stronger adsorption was found. The results indicated that different adsorption mechanisms might be involved for the two types of cations. Background electrolyte cations hardly interfere with the interaction between tetracycline and goethite surfaces because they only form weak outer-sphere surface complexes. On the contrary, Cu2+ could enhance the adsorption via acting as a bridge ion to form goethite–Cu2+–tetracycline surface complex because Cu2+ could form strong and specific inner-sphere surface complexes. HA showed different effect on the tetracycline sorption under different pH condition. The presence of HA increased tetracycline sorption dramatically under acidic condition. Results indicated that heavy metal cations and soil organic matters have great effects on the tetracycline mobility in the soil environment and eventually affect its exposure concentration and toxicity to organisms.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Current models for inorganic ion transport in porous media describe the adsorption–desorption processes mostly based on empirical adsorption isotherms or simple thermodynamic mechanisms, often ...overlooking the adsorption kinetics. This study introduces a novel unified reactive solute transport model framework that incorporates well-established surface complexation models to describe the adsorption–desorption of ions in the transport process and takes into full consideration the non-equilibrium adsorption, enabling the use of the same set of thermodynamic-kinetic parameters to accurately describe ion transport under different chemical conditions. To evaluate the constructed model, Cr(VI), P(V), and As(V) column transport experiments were carried out using goethite-coated sand as the porous medium. Kinetic constants derived from single-ion transport experiments accurately predicted the cotransport behaviors of Cr(VI), P(V), and As(V) under various flow chemistry conditions, especially the overshooting phenomena of Cr(VI) under P(V) and As(V) competition. The model framework can be easily incorporated into solute transport models with various surface complexation reactions to predict the fate and transport of ions under complexed chemical conditions without extensive parameterization, and thus is a useful complement to the current reactive transport model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Birnessite minerals help control the fate of Zn in surface environments and readily fractionate Zn isotopes through adsorption reactions, yet little is known about the role played by various reactive ...sites in stable isotopic fractionation. Here we present the Zn isotope fractionation data cause by adsorption on birnessite under different reaction times, pH values, and Zn concentrations. We observe that isotopic equilibrium of Zn is attained after ∼120 h of reaction time at pH 6. At pH 3–5 and Zn concentrations of 0.05–0.3 mM, the isotopic fractionation (Δ66Znadsorbed-aqueous) is around −0.46 ± 0.04‰, and gradually increases to −0.09 ± 0.05‰ at pH 6–8 and Zn concentrations of 0.2 mM. The change in Zn isotopic compositions as a function of pH and Zn concentration is well described using the surface complexation model, where two binding sites are involved: external edge sites and interlayer vacancies. According to this model, two different isotopic fractionation factors of Zn are calculated: Δ66Znadsorbed-aqueous = −0.46 ± 0.04‰ for adsorption on vacancy sites and Δ66Znadsorbed-aqueous = 0.52 ± 0.04‰ for binding to edge sites. Extended X-ray absorption fine structure spectroscopy (EXAFS) demonstrates that Zn forms triple-corner-sharing (TCS) octahedral complex on birnessite vacancies at pH 3 and Zn concentrations of 0.05–0.2 mM, where Zn is coordinated on one side to three oxygen atoms of the Mn vacancy (∼2.03 Å) and to three water molecules on the other side (∼2.15 Å), suggesting the formation of distorted ZnO octahedra (average bond length: ∼2.09 Å). At pH 6 and 8, double-corner-sharing (DCS) complexes on layer edges formed in addition to the TCS octahedral complex on vacancies. Density functional theory (DFT) optimisations suggest that DCS Zn complex exist in tetrahedral coordination. Based on EXAFS spectroscopy, DFT optimisations and surface complexation modeling, the distinct isotopic fractionation of Zn is related to the differences in Zn local structure at different reactive sites of birnessite. Our results provide a molecular-scale understanding of Zn isotopic fractionation in natural birnessite-containing settings, as well as new insights into predicting the links between adsorption and fractionation of other similar metals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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