A Universal Synergistic Rule of Cd(II)-Sb(V) Coadsorption to Typical Soil Mineral and Organic Components

Abstract

Heavy metals and metalloids are common cooccurrence in contaminated soils, making their behaviors more complex than their individual presences. Adsorption to soil minerals and organic components determines the solubility and mobility of heavy metals. However, little information is available regarding coadsorbing metals (e.g., Cd) and metalloids (e.g., Sb) to soil components, and whether there is a universal coadsorption rule needs to be illuminated. This study investigated the coadsorption behaviors of Cd(II) and Sb(V) to goethite, kaolinite, and bacteria (Bacillus cereus) at both acidic (pH 4.5) and alkaline pH (pH 8.5). Equilibrium adsorption experiments, coupled with scanning electron microscopy- (SEM-) energy-dispersive X-ray spectrum (EDS) and X-ray photoelectron spectroscopy (XPS), were applied to determine the batch adsorption phenomena and possible mechanisms. Batch results showed that Cd(II) adsorption was greater at pH 8.5 whereas Sb(V) adsorption was greater at pH 4.5. The presence of Cd or Sb promoted each other’s adsorption to goethite, kaolinite, and bacteria, but slight differences were that Sb(V) preferred to enhance Cd(II) adsorption at acidic pH, whereas Cd(II) was more able to increase Sb(V) adsorption at alkaline pH. SEM-EDS analyses further showed that the distribution of Cd and Sb was colocalized. The surface FeOH, AlOH, and COOH groups participated in the binding of Cd(II) and Sb(V), probably through the formation of inner-sphere complexes. Two possible ternary complexes, i.e., sorbent-Cd²⁺-Sb(OH)₆ ^– and sorbent-Sb(OH)₆ ^–-Cd²⁺, were possibly formed. Both the charge effect and the formation of ternary complexes were responsible for the collaborative coadsorbing of Cd-Sb. The universal synergistic rule obtained suggests that current models for predicting Cd(II) or Sb(V) sequestration based on single systems may underestimate their solid-to-liquid distribution ratio in a coexistence situation. The results obtained have important implications for understanding the chemical behavior of Sb and Cd in contaminated soils.

1. Introduction

Soils contaminated with both elevated concentrations of heavy metals (e.g., Cd and Pb) and metalloids (e.g., As and Sb) are common in mining and smelting-impacted regions. For example, Sb/As-Cd combined pollution often occurs in soils surrounding mines due to the concomitant presence of Cd in Sb/As-containing ores [1–4]. The chemical properties of metals and metalloids are distinctly different; i.e., Sb and As commonly exist as oxyanion whereas Cd presents as cation, which makes a big difference in their reactivity, bioavailability, mobility, and fate in the environment. Moreover, the coexistence of metal cations and anions poses a higher risk to biologic organisms and ecological safety than their individual presences [5]. Unfortunately, studies focusing on the behaviors of coexisting metals-metalloids in soils are rare.

Adsorption-desorption is an important process determining the solubility and partitioning of metal pollutants between the solid and aqueous interfaces. The most important interfaces include phyllosilicates, metal (oxyhydr)oxides, organic matter, and microbes [6–11]. Metal cations and metalloids show quite different affinities towards soil components [12]. For metal cations, favorable adsorption is commonly observed on organic colloids such as humus, microbes, and extracellular secretions at environmentally relevant pH [13–18]. These organic constituents exhibit negative surface charge and abundant functional groups including carboxyl, phosphate, amino, phenolic hydroxyl, and sulfhydryl [19–22], showing a strong ability to complex metal cations to form stable inner-sphere-type complexes. As for metalloids, they are inclined to bind to metal (oxyhydr)oxides [23–26] rather than the organic constituents. Strong inner-sphere surface complexes and structural incorporation were observed during As and Sb adsorption to Fe/Al/Mn (oxyhydr)oxides [27–34]. Several studies also demonstrated that pH is a dominant influencing factor; i.e., lower pH favors metalloid adsorption whereas higher pH favors metal cation adsorption.

There is an increasing number of studies investigating the coadsorption characteristics of metal-metalloid to soil metal (oxyhydr)oxides. For example, Jiang et al. [30] showed that the adsorption of Cd(II) on goethite was enhanced in the presence of As(V), which could be interpreted by the decreased electrostatic potential with adsorbed AsO₄ ^3– and the formation of a Cd-As-goethite complex. In contrast, Cd(II) did not affect As(V) adsorption quantity but changed its coordination environments such as the As-Fe distance [30]. Carabante et al. [35] discovered that Zn(II) had no effect on As(V) adsorption to ferrihydrite at pH 4 but significantly enhanced adsorption at pH 8, possibly due to the formation of arsenate-zinc hydroxide carbonate complexes. For the Cd(II)-Sb(V) system, Liu et al. [36] observed a positive effect of Cd(II) on Sb(V) adsorption to Fe-Mn binary oxides, owing to the increased $ζ$ -potential and the formation of Cd(II)-Sb(V) precipitates. Similar metal-metalloid-mineral precipitates were also observed such as Cu(II)-As(V)-goethite [37] and Zn(II)-As(V)-goethite [38].

Although coadsorbing metal-metalloids to metal (oxyhydr)oxides have been well documented, information regarding clay mineral systems is rare. Clay minerals, a group of hydrous aluminum silicates, are also an important mineral host for heavy metals/metalloids in soils [6]. Clay minerals have completely different surface charge characteristics compared to metal (oxyhydr)oxides, which might show different impacts on coadsorbing metals-metalloids. In addition to minerals, soil organic constituents such as humus and microbes also play an important role in metal sequestration [39]. There is also an urgent need to investigate the behaviors of coadsorbing metal-metalloids in organo systems.

This investigation was aimed at elucidating whether there is a universal coadsorption rule of Cd-Sb to typical soil mineral and organic components and how this coadsorption behavior affects the mobility and fate of Cd and Sb in contaminated soils. We selected two kinds of minerals, i.e., kaolinite, a typical clay mineral, and goethite, a typical iron oxide, and one representative organic component, i.e., bacteria (Bacillus cereus), under both acidic and alkaline pH. Batch adsorption coupled with various spectroscopic tools was applied. The results of this study will provide a new perspective for realizing how Sb(V)-Cd(II) cointeracts with soil components, which helps predict their mobility and fate in contaminated soils and sediments.

2. Materials and Methods

2.1. Materials

Goethite was synthesized following the procedures described in Schwertmann et al. [40], by hydrolyzing a Fe(NO₃)₃ solution to pH 12, and aged at 60°C for 24 h. Kaolinite was purchased from the Clay Minerals Society. The <2 μm clay-sized fractions were separated via a sedimentation procedure reported in Rong et al. [41]. The Bacillus cereus is an autochthonous Gram-positive soil bacterium (GenBank accession number is MH34583). Bacterial cells were cultured in a Luria-Bertani nutrient medium at 28°C. The biomass was obtained by centrifugation, and the cells were suspended in the electrolyte (0.1 M KNO₃) to form a parent solution and stored at 4°C before use.

2.2. Batch Experiments

Adsorption experiments were conducted in a batch process at room temperature (25°C). Sb(V) and Cd(II) stock solutions were prepared from KSb(OH)₆ and Cd(NO₃)₃, respectively. Adsorption samples, containing 0.05 g/L sorbent (goethite/kaolinite/Bacillus cereus) and 0.2 mM adsorbate (Cd and/or Sb), were prepared in a 0.1 M KNO₃ electrolyte. Three different systems were considered: single Cd, single Sb, and binary Cd-Sb (1 : 1 molar ratio). The pH of the adsorption suspension was adjusted to either pH 4.5 or 8.5 using dilute NaOH or HNO₃, and the suspension was placed on an end-over-end shaker for 24 h. Adsorption suspensions were then centrifuged at 4500 g. The supernatants were filtered through a 0.45 μm syringe filter, acidified with 1% HNO₃, and analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The residual thick pastes left in the adsorption experiments were freeze-dried for SEM-EDS and XPS analyses. All batch experiments were conducted in triplicate.

2.3. Characterization

Scanning electron microscopy was recorded on a field emission scanning electron microscope (FE-SEM, Quanta 250, USA), equipped with a Flat QUAD probe (Bruker Quantax) for energy-dispersive spectroscopy (EDS) analysis. The $ζ$ -potentials of goethite, kaolinite, and Bacillus cereus cell were determined using a $ζ$ -potential analyzer (Zetaplus90, Brookhaven). X-ray photoelectron spectroscopy (XPS) was recorded using an X-ray photoelectron spectrometer (Thermo Fisher Scientific, USA) with a KRATOS Axis Ultra X-ray source (1486.7 eV). An energy range of 0–1100 eV was used with a step size of 1 eV for a wide-scan spectrum, and the high-resolution scans were recorded with a step size of 0.05 eV. The C 1s peak at 284.8 eV was used as an internal standard calibration peak for charge correction. The Shirley background and Gaussian/Lorentzian were set up to 20%.

3. Results and Discussion

3.1. Synergistic Coadsorption of Cd(II)-Sb(V) to Goethite, Kaolinite, and Bacteria

In goethite systems, Sb(V) adsorption was larger at pH 4.5 than at pH 8.5, with an equilibrium Sb(V) adsorption of 1.42 and 1.17 mmol/g, respectively (Table 1, batches 1 and 4). The uptake of Cd(II) was greater at pH 8.5 than at pH 4.5, with the final Cd adsorption of ~1.64 and 0.4 mmol/g, respectively (Table 1, batches 5 and 2). Our findings agree with previous observations [14, 34]. Goethite normally has a pH_pzc (zero point of charge) around 7.5 [42]. At pH 4.5, goethite is positively charged ( $ζ ‐ potential = 17.33 mV$ , Table 2); an electrostatic attraction between Sb(V) oxyanions and goethite could facilitate adsorption, whereas a strong electrostatic repulsion between Cd(II) and the surface would inhibit adsorption. The opposite is true at pH 8.5. In binary systems, both Sb(V) and Cd adsorptions were greater than those in single systems. Specifically speaking, Sb(V) removal increased to 1.60 and 2.28 mmol/g, respectively, at pH 4.5 and 8.5 (Table 1, batches 3 and 6); Cd adsorption raised to 0.70 and 1.99 accordingly. It is therefore concluded that Cd-Sb coadsorption on goethite is a synergistic process. Notably, the increment in Sb(V) adsorption was much greater (~120%) at pH 8.5 than at pH 4.5 (~13%), whereas the enhancement in Cd(II) removal was greater (~75%) at pH 4.5 than at pH 8.5 (~21%).

Table 1

Summary of experimental conditions and final adsorption of Sb(V) and Cd(II) for the batch experiments.

	Batch experiment	Initial concentration (mmol/L)		pH	Adsorption (mmol/g)
	Batch experiment	Sb(V)	Cd(II)	pH	Sb(V)	Cd(II)
Goethite	1	0.2			$1.42 \pm 0.04$
	2		0.2	4.5		$0.40 \pm 0.01$
	3	0.2	0.2		$1.60 \pm 0.03$	$0.70 \pm 0.07$
	4	0.2			$1.17 \pm 0.01$
	5		0.2	8.5		$1.64 \pm 0.02$
	6	0.2	0.2		$2.58 \pm 0.14$	$1.99 \pm 0.02$

Kaolinite	7	0.2			$1.14 \pm 0.03$
	8		0.2	4.5		$0.29 \pm 0.01$
	9	0.2	0.2		$1.50 \pm 0.02$	$1.17 \pm 0.01$
	10	0.2			$0.64 \pm 0.01$
	11		0.2	8.5		$1.23 \pm 0.06$
	12	0.2	0.2		$1.74 \pm 0.01$	$1.99 \pm 0.01$

Bacteria	13	0.2			$0.28 \pm 0.01$
	14		0.2	4.5		$1.03 \pm 0.01$
	15	0.2	0.2		$0.59 \pm 0.03$	$1.63 \pm 0.03$
	16	0.2			$0.20 \pm 0.01$
	17		0.2	8.5		$2.33 \pm 0.01$
	18	0.2	0.2		$1.05 \pm 0.01$	$2.67 \pm 0.07$

Table 2

The zeta potentials (mV) of goethite, kaolinite, and bacteria at different pH.

	pH	Zeta potential (mV)
Goethite	4.5	17.33
Goethite	8.5	-23.73

Kaolinite	4.5	-6.12
Kaolinite	8.5	-25.01

Bacteria	4.5	-16.68
Bacteria	8.5	-56.79

In kaolinite systems, the removal of Sb(V) was greater at pH 4.5 than at pH 8.5 (Table 1, batches 7 and 10); the opposite was true for Cd(II) (Table 1, batches 8 and 11). This adsorption trend with pH is similar to that in goethite systems and agrees with previous observations in literature [43, 44]. Kaolinite is negatively charged at both pH 4.5 and 8.5 (Table 2); the increased negative charge with increasing pH may explain the different adsorption properties for Sb(V) and Cd(II). In binary systems, Sb(V) adsorption was increased to 1.50 and 1.75 mmol/g, respectively, at pH 4.5 and 8.5 (Table 1, batches 9 and 12), corresponding to an increment of ~32% and 173%, respectively. The uptake of Cd(II) was increased by ~315% and 62%, respectively, at pH 4.5 and 8.5. The presence of Cd(II) was more able to promote Sb(V) adsorption at alkaline pH, while Sb(V) was more capable of facilitating Cd(II) adsorption at acidic pH, which is consistent with the trend in goethite systems.

In bacteria systems, the uptake of Sb(V) was larger at pH 4.5 than at pH 8.5, with a final Sb(V) adsorption of 0.28 and 0.20 mmol/g, respectively (Table 1, batches 13 and 16). The much lower Sb(V) adsorption on bacteria than those on goethite and kaolinite is mainly because of the stronger repulsion between Sb(V) oxyanions and more negatively charged bacterial cells (see $ζ$ -potentials in Table 2). The adsorption of Cd(II) was much larger at pH 8.5 than at pH 4.5 (Table 1, batches 14 and 17). In binary systems, Sb(V) uptake was increased by ~111% and 425%, respectively, at pH 4.5 and 8.5, compared to those in single systems. The adsorption of Cd had increased by ~58% and 15%, respectively, at pH 4.5 and 8.5. Similar to goethite and kaolinite systems, the promotion in Sb(V) adsorption was more pronounced at higher pH, whereas lower pH was more favorable to promote Cd(II) adsorption.

Overall, the batch results demonstrate a synergistic coadsorption behavior of Cd(II)-Sb(V) to typical soil clay minerals, iron (oxyhydr)oxides, and bacteria. The presence of Sb(V) significantly enhances Cd(II) adsorption at acidic pH, whereas Cd(II) prominently facilitates Sb(V) adsorption at alkaline pH.

3.2. SEM-EDS Analyses

Typical morphology pictures of goethite, kaolinite, and Bacillus cereus are shown in Figure 1. The synthesized goethite comprises <2 μm needle-type crystal. Kaolinite shows a layered hexagonal shape with a size mostly smaller than 2 μm. Bacillus cereus cells yield a rod shape with cell length and width of ~3.0 μm and 1 μm, respectively.

Figure 1

SEM images of (a) goethite, (b) kaolinite, and (c) Bacillus cereus cell.

(b)

(c)

Two-color SEM-EDS elemental maps of the distribution of Sb (yellow) and Cd (red) in goethite, kaolinite, and Bacillus cereus are shown in Figure 2. There are few separated red or yellow areas (mostly orange, red+yellow), indicating that the distribution of Sb and Cd is positively correlated. This could be due to the formation of the ternary sorbent-Sb-Cd complexes at the same coordinated sites. The elemental mass percentage results (Figure 3) show clearly that kaolinite, goethite, and bacteria adsorb much more Cd/Sb at pH 8.5 than at pH 4.5 in the coexisting situation. This may indicate that Cd(II) and Sb(V) could be more easily coadsorbed by soil components in an alkaline environment.

Figure 2

SEM-ED mapping of goethite, kaolinite, and Bacillus cereus cell after the sorption of Cd(II) and Sb(V) at pH 4.5 and 8.5.

Figure 3

Mass percentage of Cd(II) and Sb(V) in goethite, kaolinite, and Bacillus cereus cell. Data are produced from Figure 2.

3.3. XPS Analyses

To reveal the underlying mechanisms, goethite, kaolinite, and Bacillus cereus before and after the binding of Cd and/or Sb were characterized by XPS (Figures 4–7). XPS is a powerful tool for surface functional group analyses. For goethite, the O 1s spectrum can be subdivided into Fe–O–Fe (529.67 eV) and Fe–O–H (531.04 eV) [45]. The peak intensity of Fe-O-H is much higher (65.49%) than that of Fe–O–Fe (34.51%) (Figure 4), indicating the presence of abundant hydroxyl functional groups on the surface. For kaolinite, the O 1s spectrum can be subdivided into O atoms of silanol (≡SiOH) and aluminol (≡AlOH) on the basal/edge surface and O atoms bridging Si and Al (Si–O–Al) [44]. The Si/Al–O–H is located at ~531.91 eV while the Si–O–Al is located at ~530.94 eV, and the proportions are 65.47% and 34.53%, respectively (Figure 4). For bacteria, the peak of C 1s can be decomposed into three peaks which are assigned to the C–C/C–H (284.1 eV), C–O/N (286.5 eV), and O–C=O (288.2 eV), respectively [46].

Figure 4

High-resolution O 1s XPS spectra of goethite and kaolinite and C 1s XPS spectrum of the Bacillus cereus cell.

Figure 5

High-resolution O 1s XPS spectra of goethite after the sorption of Cd(II) and/or Sb(V).

Figure 6

High-resolution O 1s XPS spectra of kaolinite after the sorption of Cd(II) and/or Sb(V).

Figure 7

High-resolution C 1s XPS spectra of the Bacillus cereus cell after the sorption of Cd(II) and/or Sb(V).

When Sb(V) and/or Cd(II) adsorb on goethite, there is a significant increase in the Fe–O–H fraction (Figure 5). Specifically, the proportion of Fe–O–H is increased to 80.63%, 67.01%, and 78.14%, respectively, after Sb(V), Cd(II), and Sb(V)-Cd(II) adsorption at pH 4.5 and 75.13%, 73.69%, and 82.03%, respectively, at pH 8.5. These observations demonstrate that the ferric hydroxyl groups of goethite participate in the binding of Sb(V) and/or Cd(II), possibly through the formation of inner-sphere complexes, i.e., Fe–O–Cd/Sb [34, 47, 48]. These newly formed species would contribute to the increased peak intensity of the surface Fe–O–H. It is also interesting that the changes of Sb(V)-loaded spectra are more evident at pH 4.5, whereas the changes of Cd(II)-loaded spectra are more pronounced at pH 8.5. This again agrees with the batch results that Sb(V) adsorption increases with decreasing pH whereas Cd(II) sorption increases with elevated pH.

When Sb(V) and/or Cd(II) adsorb on kaolinite, the component of Si/Al–O–H is increased to 75.54%, 67.91%, and 80.59%, respectively, after Sb(V), Cd(II), and Sb(V)-Cd(II) adsorption at pH 4.5 (Figure 6). At pH 8.5, the component of Si/Al–O–H is enhanced to 73.68%, 78.24%, and 85.94%, respectively. Therefore, the Si/Al–O–H groups participate in the binding of Cd(II) and/or Sb(V) on kaolinite [49]. The gibbsite basal planes of kaolinite can have variable charges [50], which can complex Cd(II) and Sb(V) to form various inner-sphere complexes. However, it cannot rule out the presence of outer-sphere complexes from XPS, and a previous study showed that Cd(II) can adsorb both as an outer-sphere complex at the negatively charged basal sites and as an inner-sphere complex at the edges of the clay [44, 51].

When Sb(V) and/or Cd(II) adsorb to bacteria, the component of the O–C=O fraction is increased to 28.09–32.62% at pH 4.5 and 26.42–34.61% at pH 8.5 (Figure 7). The O–C=O fraction is commonly assigned to the carbonyls, carboxylate, and/or aldehydes [52], which make up the peptidoglycan, phospholipid bilayer, lipopolysaccharides, and protein of the cell walls. The increase in this component suggests that carboxylic groups are responsible for the binding of Sb and/or Cd(II) on bacterial surfaces.

It is worth noting that for all sorbents (goethite, kaolinite, and bacteria), the changes of the Fe/Si/Al–O–H and O–C=O components are more evident in binary Sb-Cd systems than in single systems. On the one hand, this may be due to the higher adsorption of Cd-Sb in binary systems. On the other hand, the formation of a ternary sorbent-Cd-Sb or sorbent-Cd-Sb complexes may play a role.

3.4. Possible Mechanisms and Implications

Goethite, kaolinite, and Bacillus cereus, represented by the most ubiquitous soil components, play a crucial role in the sequestration of both metals and metalloids. Our results show that Cd(II)-Sb(V) coadsorption is a synergistic process that their sorption in binary systems is larger than that in single systems. Two possible explanations are as follows: (1) one is the charge effect. Because Cd(II) is positively charged whereas Sb(V) is negatively charged, therefore the adsorption of Cd(II) on the surface will facilitate the electrostatic attraction between Sb(V) and the surface and vice versa. (2) The second is the formation of the ternary complexes. As for the studied systems, two types of ternary complexes are possibly formed, one where the adsorbed Cd is near the surface (type A, sorbent-Cd²⁺-Sb(OH)₆ ^–) and the other where the adsorbed Sb is near the surface (type B, sorbent-Sb(OH)₆ ^–-Cd²⁺). For example, the structure of type A complexes on the goethite and kaolinite surface is shown in Figures 8(a) and 8(c), while that for type B is shown in Figures 8(b) and 8(d). The fact that Cd(II) and Sb(V) play a promoting role in each other’s adsorption onto soil clay minerals and organic constituents is a nice addition to previous findings only concerning Fe (oxyhydr)oxide systems. Collectively, our results combined with previous findings demonstrate a universal synergistic effect regarding the coadsorbing Cd-Sb to soil components. In this scenario, current thermodynamic models for predicting Cd(II) or Sb(V) behaviors based on single-solute systems may underestimate their binding to soil solid phases in a coexistence situation. Our results also show that the promotion effects are dependent on pH; i.e., Sb(V) enhances Cd(II) adsorption more pronouncedly at acidic pH, whereas Cd(II) prominently facilities Sb(V) adsorption at alkaline pH. This reminds us that soil pH must be taken into consideration when evaluating the coadsorption behaviors of Cd-Sb. As soil components commonly interact with each other, it is therefore important to consider mineral-organo interaction when studying Cd-Sb coadsorbing behaviors in the future.

Figure 8

The structures of two possible ternary complexes on (a, b) goethite and (c, d) kaolinite.

(b)

(c)

(d)

4. Conclusions

This study provides the first systematic evidence for coadsorbing Cd(II)-Sb(V) to typical mineral and organic components. The results show that Cd(II) and Sb(V) adsorption to goethite, kaolinite, and bacterial cells is greater in binary Cd-Sb systems than in their individual presences at both acidic and alkaline pH. Sb(V) is more able to enhance Cd(II) adsorption at acidic pH, whereas Cd(II) is more capable of increasing Sb(V) adsorption at alkaline pH. The distribution of Sb and Cd is colocalized. The ferric hydroxy groups (FeOH) of goethite, the aluminol (AlOH) of kaolinite, and the carboxyl groups of bacteria are responsible for the binding of Cd(II) and Sb(V), via the formation of inner-sphere-type complexes. Two possible ternary complexes are formed when coadsorption occurs, one where Cd is near the surface and the other where Sb is near the surface. All our observations have important implications for predicting Sb and Cd mobility and fate in contaminated soils.

Footnotes

Data Availability

All data, models, and code generated or used during the study appear in the submitted article.

Conflicts of Interest

The authors declare no conflicts of interest.

Authors’ Contributions

Min Zhou and Ruijia Yang contributed equally to this work.

Acknowledgments

We acknowledge the National Natural Science Foundation of China (NSFC, No. 41907015) and the National Key Research and Development Program of China (2017YFD0801505) for the financial support.

References

Liu

Luo

Tie

Liu

Lei

The long-term effectiveness of ferromanganese biochar in soil Cd stabilization and reduction of Cd bioaccumulation in rice

Biochar 2021 3

9131597

4 499 509

10.1007/s42773-021-00113-2

Long

Tan

Deng

Lei

Pollution and ecological risk assessment of antimony and other heavy metals in soils from the world's largest antimony mine area, China

Human and Ecological Risk Assessment 2018 24

9131597

3 679 690

10.1080/10807039.2017.1396531

2-s2.0-85035117772

Loska

Wiechuła

Korus

Metal contamination of farming soils affected by industry

Environment International 2004 30

9131597

2 159 165

10.1016/S0160-4120(03)00157-0

2-s2.0-0347135734

Williams

P. N.

Lei

Sun

Huang

Deacon

Meharg

A. A.

Zhu

Y. G.

Occurrence and partitioning of cadmium, arsenic and lead in mine impacted paddy rice: Hunan, China

Environmental Science & Technology 2009 43

9131597

3 637 642

10.1021/es802412r

2-s2.0-63149177303

19244995

Huang

Choi

Kim

N. Y.

Park

C. H.

Kim

D. S.

Park

Song

J. S.

Kim

Choi

B. S.

I. J.

Park

J. D.

Risk assessment of low-level cadmium and arsenic on the kidney

Journal of Toxicology and Environmental Health, Part A 2009 72

9131597

21-22 1493 1498

10.1080/15287390903213095

2-s2.0-75749085401

20077223

Bradl

H. B.

Adsorption of heavy metal ions on soils and soils constituents

Journal of Colloid and Interface Science 2004 277

9131597

1 1 18

10.1016/j.jcis.2004.04.005

2-s2.0-3242660172

15276031

Cai

Liu

Zhang

Tie

Lei

Wei

Peng

Silicate-modified oiltea camellia shell-derived biochar: A novel and cost- effective sorbent for cadmium removal

Journal of Cleaner Production 2021 281

9131597

10.1016/j.jclepro.2020.125390

Zhang

Peacock

Liu

Nie

Xue

Lei

Tie

Natural organic matter decreases uptake of W(VI), and reduces W(VI) to W(V), during adsorption to ferrihydrite

Chemical Geology 2020 540

9131597

10.1016/j.chemgeo.2020.119567

Kurek

Czaban

Bollag

J. M.

Sorption of cadmium by microorganisms in competition with other soil constituents

Applied and Environmental Microbiology 1982 43

9131597

5 1011 1015

10.1128/aem.43.5.1011-1015.1982

16346002

10.

Lair

G. J.

Gerzabek

M. H.

Haberhauer

Sorption of heavy metals on organic and inorganic soil constituents

Environmental Chemistry Letters 2007 5

9131597

1 23 27

10.1007/s10311-006-0059-9

2-s2.0-33846798337

11.

Ledin

Krantz-Rülcker

Allard

Microorganisms as metal sorbents: comparison with other soil constituents in multi-compartment systems

Soil Biology and Biochemistry 1999 31

9131597

12 1639 1648

10.1016/S0038-0717(99)00073-5

2-s2.0-0344631714

12.

Nie

Rao

W. K.

Lei

Tie

Ferrihydrite-organo composites are a suitable analog for predicting Cd(II)-As(V) coexistence behaviors at the soil solid-liquid interfaces

Environmental Pollution 2021 290

9131597

10.1016/j.envpol.2021.118040

34454194

13.

Huang

Zhou

Tie

Lei

Wei

Liu

Yang

Sorption of Cu(II) by Al hydroxide organo-mineral coprecipitates: microcalorimetry and NanoSIMS observations

Chemical Geology 2018 499

9131597

165 171

10.1016/j.chemgeo.2018.09.026

2-s2.0-85053938612

14.

Peacock

C. L.

Chen

Huang

Binding of Cd by ferrihydrite organo-mineral composites: implications for Cd mobility and fate in natural and contaminated environments

Chemosphere 2018 207

9131597

404 412

10.1016/j.chemosphere.2018.05.092

2-s2.0-85063247320

29803890

15.

Lei

Tie

Liu

Wei

Yang

Insights into Pb(II) binding by Fe/Al hydroxide-microbe composite: XAFS spectroscopy and isothermal titration calorimetry study

Chemical Geology 2019 510

9131597

84 90

10.1016/j.chemgeo.2019.02.024

2-s2.0-85061800909

16.

Rao

Nie

Binding of Cd(II) by amorphous aluminum hydroxide-organophosphorus coprecipitates: from macroscopic to microscopic investigation

Adsorption Science & Technology 2021 2021, article 9943663

9131597

10.1155/2021/9943663

17.

Moon

E. M.

Peacock

C. L.

Adsorption of Cu(II) to ferrihydrite and ferrihydrite-bacteria composites: importance of the carboxyl group for Cu mobility in natural environments

Geochimica et Cosmochimica Acta 2012 92

9131597

203 219

10.1016/j.gca.2012.06.012

2-s2.0-84864409924

18.

Templeton

A. S.

Spormann

A. M.

Brown

G. E.

Speciation of Pb(II) sorbed by Burkholderia cepacia/goethite composites

Environmental Science & Technology 2003 37

9131597

10 2166 2172

10.1021/es026081b

2-s2.0-0037955888

12785522

19.

Christl

Metzger

Heidmann

Kretzschmar

Effect of humic and fulvic acid concentrations and ionic strength on copper and lead binding

Environmental Science & Technology 2005 39

9131597

14 5319 5326

10.1021/es050018f

2-s2.0-22344454762

16082962

20.

Mishra

Boyanov

Bunker

B. A.

Kelly

S. D.

Kemner

K. M.

Fein

J. B.

High- and low-affinity binding sites for Cd on the bacterial cell walls of Bacillus subtilis and Shewanella oneidensis

Geochimica et Cosmochimica Acta 2010 74

9131597

15 4219 4233

10.1016/j.gca.2010.02.019

2-s2.0-77953958393

21.

Sutton

Sposito

Molecular structure in soil humic substances: the new view

Environmental Science & Technology 2005 39

9131597

23 9009 9015

10.1021/es050778q

2-s2.0-28444458433

16382919

22.

Fein

J. B.

Sulfhydryl binding sites within bacterial extracellular polymeric substances

Environmental Science & Technology 2016 50

9131597

11 5498 5505

10.1021/acs.est.6b00347

2-s2.0-84973644331

27177017

23.

Lei

Tao

Yang

Tie

Liu

Wei

Binding of Sb (III) by Sb-tolerant Bacillus cereus cell and cell-goethite composite: implications for Sb mobility and fate in soils and sediments

Journal of Soils and Sediments 2019 19

9131597

6 2850 2858

10.1007/s11368-019-02272-z

2-s2.0-85061282652

24.

Rao

Song

Lei

Tie

Natural dissolved organic matter (DOM) affects W(VI) adsorption onto Al (hydr)oxide: mechanisms and influencing factors

Environmental Research 2022 205

9131597

10.1016/j.envres.2021.112571

34919961

25.

Tian

Geng

Lin

Dang

Defective magnesium ferrite nano-platelets for the adsorption of As(V): the role of surface hydroxyl groups

Environmental Pollution 2018 235

9131597

11 19

10.1016/j.envpol.2017.12.050

2-s2.0-85038817305

29274533

26.

Xue

Ran

Tan

Peacock

C. L.

Arsenite and arsenate binding to ferrihydrite organo-mineral coprecipitate: implications for arsenic mobility and fate in natural environments

Chemosphere 2019 224

9131597

103 110

10.1016/j.chemosphere.2019.02.118

2-s2.0-85062383694

30818188

27.

Adra

Morin

Ona-Nguema

Brest

Arsenate and arsenite adsorption onto Al-containing ferrihydrites. Implications for arsenic immobilization after neutralization of acid mine drainage

Applied Geochemistry 2016 64

9131597

2 9

10.1016/j.apgeochem.2015.09.015

2-s2.0-84956966582

28.

Bolanz

R. M.

Wierzbicka-Wieczorek

Caplovicova

Uhlik

Gottlicher

Steininger

Majzlan

Structural incorporation of As⁵⁺ into hematite

Environmental Science & Technology 2013 47

9131597

16 9140 9147

10.1021/es305182c

2-s2.0-84882677195

23909875

29.

Guo

Meng

Jin

Qiu

Zhang

Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure

Journal of Hazardous Materials 2014 276

9131597

339 345

10.1016/j.jhazmat.2014.05.025

2-s2.0-84901911168

24910911

30.

Jiang

Luo

Yang

Lin

Zhang

Arsenate and cadmium co-adsorption and co-precipitation on goethite

Journal of Hazardous Materials 2013 262

9131597

22 55 63

10.1016/j.jhazmat.2013.08.030

2-s2.0-84883526107

24007999

31.

Sowers

T. D.

Harrington

J. M.

Polizzotto

M. L.

Duckworth

O. W.

Sorption of arsenic to biogenic iron (oxyhydr)oxides produced in circumneutral environments

Geochimica et Cosmochimica Acta 2017 198

9131597

194 207

10.1016/j.gca.2016.10.049

2-s2.0-85007364750

32.

Sun

Cui

P. X.

Liu

Peng

S. M.

Alves

M. E.

Zhou

D. M.

Shi

Z. Q.

Wang

Y. J.

Antimony oxidation and sorption behavior on birnessites with different properties (δ-MnO₂ and triclinic birnessite)

Environmental Pollution 2019 246

9131597

990 998

10.1016/j.envpol.2018.12.027

2-s2.0-85060349995

31159148

33.

Sun

S. P.

Xiao

Chen

X. D.

W. D.

As(V) and Sb(V) co-adsorption onto ferrihydrite: synergistic effect of Sb(V) on As(V) under competitive conditions

Environmental Science and Pollution Research 2018 25

9131597

15 14585 14594

10.1007/s11356-018-1488-2

2-s2.0-85043483222

29532371

34.

Yang

Tao

Huang

Tie

Lei

Yang

Co-adsorption of Cd(II) and Sb(III) by ferrihydrite: a combined XPS and ITC study

Journal of Soils and Sediments 2019 19

9131597

3 1319 1327

10.1007/s11368-018-2140-y

2-s2.0-85053749819

35.

Carabante

Grahn

Holmgren

Kumpiene

Hedlund

Influence of Zn(II) on the adsorption of arsenate onto ferrihydrite

Environmental Science & Technology 2012 46

9131597

24 13152 13159

10.1021/es300729m

2-s2.0-84871287800

23170764

36.

Liu

Simultaneous removal of Cd(II) and Sb(V) by Fe-Mn binary oxide: positive effects of Cd(II) on Sb(V) adsorption

Journal of Hazardous Materials 2015 300

9131597

847 854

10.1016/j.jhazmat.2015.08.020

2-s2.0-84940510436

26340552

37.

Gräfe

Beattie

D. A.

Smith

Skinner

W. M.

Singh

Copper and arsenate co-sorption at the mineral-water interfaces of goethite and jarosite

Journal of Colloid and Interface Science 2008 322

9131597

2 399 413

10.1016/j.jcis.2008.02.044

2-s2.0-43049154796

18423478

38.

Gräfe

Sparks

D. L.

Kinetics of zinc and arsenate co-sorption at the goethite-water interface

Geochimica et Cosmochimica Acta 2005 69

9131597

19 4573 4595

10.1016/j.gca.2005.04.016

2-s2.0-26844467690

39.

Reuter

J. H.

Perdue

E. M.

Importance of heavy metal-organic matter interactions in natural waters

Geochimica et Cosmochimica Acta 1977 41

9131597

2 325 334

10.1016/0016-7037(77)90240-X

2-s2.0-0000586427

40.

Schwertmann

Cornell

R. M.

Schwertmann

Cornell

R. M.

Iron oxides in the laboratory: preparation and characterization

Clay Minerals 2000 27

9131597

3 393 393

41.

Rong

Huang

Chen

Microcalorimetric investigation on the metabolic activity of Bacillus thuringiensis as influenced by kaolinite, montmorillonite and goethite

Applied Clay Science 2007 38

9131597

1-2 97 103

10.1016/j.clay.2007.01.015

2-s2.0-36749012342

42.

Juang

R. S.

W. L.

Adsorption of sulfate and copper(II) on goethite in relation to the changes of zeta potentials

Journal of Colloid and Interface Science 2002 249

9131597

1 22 29

10.1006/jcis.2002.8240

2-s2.0-0036353227

16290565

43.

Rakshit

Sarkar

Datta

Surface complexation of antimony on kaolinite

Chemosphere 2015 119

9131597

349 354

10.1016/j.chemosphere.2014.06.070

2-s2.0-84919740693

25046527

44.

Vasconcelos

I. F.

Haack

E. A.

Maurice

P. A.

Bunker

B. A.

EXAFS analysis of cadmium(II) adsorption to kaolinite

Chemical Geology 2008 249

9131597

3-4 237 249

10.1016/j.chemgeo.2008.01.001

2-s2.0-41349100663

45.

Hao

Ouyang

Lai

Liu

Chen

Chang

Wang

Temperature effects on arsenate adsorption onto goethite and its preliminary application to arsenate removal from simulative geothermal water

RSC Advances 2014 4

9131597

94 51984 51990

10.1039/C4RA08318K

2-s2.0-84908231533

46.

Naskar

Guha

A. K.

Mukherjee

Ray

Adsorption of nickel onto Bacillus cereus M116: a mechanistic approach

Separation Science and Technology 2016 51

9131597

3 427 438

10.1080/01496395.2015.1115069

2-s2.0-84960440154

47.

Collins

C. R.

Ragnarsdottir

K. V.

Sherman

D. M.

Effect of inorganic and organic ligands on the mechanism of cadmium sorption to goethite

Geochimica et Cosmochimica Acta 1999 63

9131597

19-20 2989 3002

10.1016/S0016-7037(99)00226-4

2-s2.0-0033368254

48.

Leuz

A. K.

Mönch

Johnson

C. A.

Sorption of Sb(III) and Sb(V) to goethite: influence on Sb(III) oxidation and mobilization

Environmental Science & Technology 2006 40

9131597

23 7277 7282

10.1021/es061284b

2-s2.0-33845312282

17180978

49.

Ilgen

A. G.

Trainor

T. P.

Sb (III) and Sb (V) sorption onto Al-rich phases: hydrous Al oxide and the clay minerals kaolinite KGa-1b and oxidized and reduced nontronite NAu-1

Environmental Science & Technology 2012 46

9131597

2 843 851

10.1021/es203027v

2-s2.0-84855927731

22136137

50.

Coppin

Berger

Bauer

Castet

Loubet

Sorption of lanthanides on smectite and kaolinite

Chemical Geology 2002 182

9131597

1 57 68

10.1016/S0009-2541(01)00283-2

2-s2.0-0036149681

51.

Gräfe

Singh

Balasubramanian

Surface speciation of Cd(II) and Pb(II) on kaolinite by XAFS spectroscopy

Journal of Colloid and Interface Science 2007 315

9131597

1 21 32

10.1016/j.jcis.2007.05.022

2-s2.0-34548762972

17714722

52.

Ahimou

Boonaert

C. J.

Adriaensen

Jacques

Thonart

Paquot

Rouxhet

P. G.

XPS analysis of chemical functions at the surface of Bacillus subtilis

Journal of Colloid and Interface Science 2007 309

9131597

1 49 55

10.1016/j.jcis.2007.01.055

2-s2.0-33947328539

17316673