Fast and Effective Decontamination of Aqueous Mercury by a Highly

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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

Fast and Effective Decontamination of Aqueous Mercury by a Highly Stable Zeolitic-like Chalcogenide Bo Zhang,*,†,‡ Jun Li,† Dan-Ni Wang,† Mei-Ling Feng,‡ and Xiao-Ying Huang*,‡ †

College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, P. R. China State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China

‡

Inorg. Chem. Downloaded from pubs.acs.org by EAST CAROLINA UNIV on 03/11/19. For personal use only.

S Supporting Information *

ABSTRACT: Highly efficient and effective removal of mercury from water, especially at very low ionic concentration, remains a grand challenge for ecosystem protection and human health. Herein, we present the synthesis, crystal structure, and mercury uptake performance of a new heterometallic chalcogenidometalate, namely, [TAEAH][TAEAH2]0.6Ga2.2Sn1.8S8·H2O (GaSnS-1; TAEA = Tris(2-aminoethyl)amine). GaSnS-1 features a three-dimensional (3D) zeolite-typed (RWY) framework structure of [Ga 2.2Sn 1.8S 8 ] n2.2n− that is constructed by corner-sharing of supertetrahedral [Ga2.2Sn1.8S10]6.2− T2 clusters. The equilibrium model study indicated that the maximum Hg2+ saturation capacity of GaSnS-1 was 213.9 mg/g. GaSnS-1 possessed extremely rapid adsorption kinetics following the pseudo-second-order model with a k2 of 5.65 × 102 g· mg−1·min−1. Particularly, GaSnS-1 exhibited excellent selectivity for Hg2+ ions with a high distribution coefficient Kd value of 1.62 × 107 mL/g and high removal efficiency of close to 100%. The superior Hg2+ ion adsorption performance was also impressive despite the presence of excessive competing cations and the acidic/basic conditions. Furthermore, a simple chromatographic column loaded with GaSnS-1 microcrystals is capable of rapidly and effectively capturing Hg2+ ions far below the upper limit (2 ppb, USA-EPA) of drinking water. These advantages of GaSnS-1 make it a promising candidate for the fast and efficient remediation of Hg2+-contaminated water sources.

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INTRODUCTION The contamination of water caused by toxic heavy metal ions is one of the most serious worldwide environmental and sanitary issues.1 As one of the most toxic heavy metal ions, mercury is considered a major pollutant in natural water sources and industrial wastewater, posing a great threat to ecosystem and human health.2 Even at very low ionic concentration, it can cause irreversible damage to living organisms, especially the central nervous system.3 Therefore, the efficient and effective removal of mercury from contaminated water is of urgent need. In this regard, various water purification technologies and methods have been adopted to deal with mercury from polluted water, including ion exchange, membrane separation, chemical precipitation, adsorption, and so forth.4 Among them, adsorption stands out and holds great promise due to its relatively inexpensive cost, good performance, facile operation, and easy regeneration.5 Conventional adsorption materials such as clay, zeolite, and activated carbon generally suffered from low adsorption capacity, slow adsorption kinetics, and narrow pH operating range.6 Worse yet, it is extremely difficult for above-mentioned adsorption materials to get rid of Hg2+ ions far below the acceptable limits (i.e., the upper limit of 2 ppb for Hg in potable water, the United States Environmental Protection Agency (USA-EPA)).7 Some leading adsorbents qualified for mercury ion sequestration are mainly limited to © XXXX American Chemical Society

some thiol-/thio-functionalized materials. Nevertheless, the preparation of these functionalized adsorbents normally requires expensive reagents, complicated experimental processes, and harsh operating conditions.8 Another common and important limitation existing in most materials is their hydrolytic instability, especially in acidic and basic environments.9 Thus, these weaknesses and handicaps necessitate the development of new types of stable adsorbents that are capable of efficient and effective remediation of aqueous mercury. In recent years, metal chalcogenides have received considerable attention due to the good water stability, high saturation capacity, and excellent selectivity for heavy metal ions (e.g., Pb2+ and Hg2+)10 and ions with respect to nuclear waste (e.g., Cs+ and UO22+).11 The unique properties of chalcogenides stem from their own soft S2− ligands, which endow them with innate affinity for soft or relatively soft Lewis acid ions.12 It has been found that some layered pure inorganic sulfides, such as KMS-1,10a LHMS-1,13 and KTS-3,10b show great potential in the decontamination of toxic aqueous mercury. Comparatively speaking, the exploration of organically templated chalcogenides to challenge current serious mercury pollution issues has been rarely pursued.14 Received: October 20, 2018

A

DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry In this paper, we report the synthesis, crystal structure, and mercury capture properties of a new amine-directed Ga−Sn−S compound, namely, [TAEAH][TAEAH2]0.6Ga2.2Sn1.8S8·H2O (GaSnS-1; TAEA = Tris(2-aminoethyl)amine). GaSnS-1 features a 3D zeolite-like (RWY) framework structure of [Ga2.2Sn1.8S8]n2.2n−, exhibiting impressive structural stability.10g,14b GaSnS-1 displays extremely fast mercury adsorption kinetics, with a high saturation capacity of 213.9 mg/g. Remarkably, GaSnS-1 shows high selectivity for Hg2+ ions even when a large amount of alkali/alkaline earth metal ions as well as heavy metal ions are present, with the highest Kd value up to 1.62 × 107 mL/g. The Hg2+ ion uptake efficiency of GaSnS-1 is prominent within a broad pH range (pH = 1.92−11.84). Also, GaSnS-1 displays good remediation ability for other individual heavy metal ions such as Ag+ and Pb2+ ions, and a rapid and effective removal of mercury from continuous water has been successfully realized by a column loaded with GaSnS-1 microcrystals.

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Figure 1. (a) {M4S10} T2 cluster formed by four [MS4] tetrahedra via corner-sharing (M = 0.55Ga + 0.45Sn). (b) The supersodalite cage built up of 24 {M4S10} T2 clusters via vertex-sharing. (c) Packing diagram of GaSnS-1 viewed along the [1 1 1] direction. (d) Schematic view of the topology of GaSnS-1, in which the {M4S10} T2 clusters are shown as green balls. Organic parts and guest molecules are omitted for clarity.

EXPERIMENTAL SECTION

Materials. Ga(NO3)3·9H2O (99.9%, Longjin Chemical Reagent), S (99.99%, Kelong Chemical Reagent), tris(2-aminoethyl)amine (>98.0%, TCI), HgCl2 (99.5%, Sigma-Aldrich). Other reagents, such as Sn (99.9%), NaCl (99.9%), and KCl (99.9%), were of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Synthesis of GaSnS-1. A total of 0.418 g of Ga(NO3)3·9H2O, 0.118 g of Sn, 0.256 g of S, and 3.0 mL of tris(2-aminoethyl)amine was mixed and sealed in a Teflon-lined stainless steel autoclave (23 mL). The resulting mixture was heated at 190 °C for 9 days and then cooled to ambient condition naturally. By filtration, pale-yellow blockshaped crystals were obtained, which are then washed with deionized water and anhydrous ethanol, and subsequently selected by hand (74.6% yield based on Ga(NO3)3·9H2O). Anal. Calcd (%) for [TAEAH][TAEAH2]0.6Ga2.2Sn1.8S8·H2O: C, 13.13; H, 3.78; N, 10.21%. Found: C, 13.12; H, 3.59; N, 9.86%. Mercury Capture Experiments. The typical mercury uptake experiment of GaSnS-1 was performed by a batch equilibration technique at ambient condition (∼25 °C). In a glass bottle, 10 mg of GaSnS-1 were mixed with 10 mL of HgCl2 solution, which was stirred mechanically for a period of time. Then, the solid material was isolated by centrifugation, and the resultant supernatant was analyzed with the help of inductively coupled plasma-atomic emission spectrometry (ICP-AES); for an extra low ion concentration, inductively coupled plasma-mass spectroscopy (ICP-MS) was utilized. More experimental details including isotherm, kinetics, pH, competition and column studies are provided in the Supporting Information (SI).

[Mn(dien) 2 ] 4 Mn 2 Ga 4 Sn 4 S 20 ·2H 2 O, 15 UCR-21 GaSnSTAEA,16 and UCR-22 GaSnS-AEP.16 Each {M4S10} T2 cluster further connects four neighboring ones through sharing the S(3) atoms to give rise to a 3D [Ga2.2Sn1.8S8]n2.2n− anionic framework, generating large supersodalite cages that are filled by template cations and guest molecules (Figure 1b, 1c). If each {M4S10} T2 unit is considered as a 4-connected node, the anionic framework in GaSnS-1 can be classified as a zeolite-typed SOD topology (Figure 1d). The effective void volume is found to be 64.7%, calculated by the PLATON program.17 Mercury Capture by GaSnS-1. The unique zeolite-type structure and its innate S2− ligands endowed GaSnS-1 with better thermal and chemical stability, and potential application in highly toxic aqueous mercury remediation. To demonstrate the performance of GaSnS-1 in thermal stability, TGA and variable temperature PXRD experiments were conducted. As shown in Figure S7, GaSnS-1 exhibits two periods of weight loss in the region 30−800 °C and begins to lose organic amines at about 150 °C. Variable temperature PXRD indicated GaSnS-1 could maintain its structural integrity when heated to at least 200 °C for 3 h in the N2 flow (Figure 2a). Subsequently, we have also studied the chemical stability of GaSnS-1 in 0.05 M H3PO4, Hg2+-contaminated solution, and aqueous solution with different pH values. During the soak and uptake process, as expected, almost no gallium and tin leached out of the GaSnS-1 sample and its robust framework was still completely preserved, which were confirmed by the ICP-AES and PXRD results (Figures 2b and S8). The energy dispersive X-ray (EDX) analyses indicated that Hg2+ ions were adsorbed in the surface of the materials, but not entered (Figure 2c). XPS experiments performed on a mercury-loaded sample of GaSnS-1 show peaks at 101.0 and 104.9 eV (Figure 2d), which are characteristic of 4f7/2 and 4f5/2 of the Hg2+ ion.18 Additionally, the Raman spectrum of Hg@ GaSnS-1 displays the peak at about 391 cm−1, associated with the Hg−S stretching vibrations (Figure S9).19 The TGA curve

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RESULTS AND DISCUSSION Crystal Structure Description of GaSnS-1. GaSnS-1 belongs to the cubic space group of I4̅3m and features a 3D [Ga2.2Sn1.8S8]n2.2n− anionic framework (Figure 1). The fundamental structure feature of GaSnS-1 is the supertetrahedral {M4S10} T2 cluster (Figure 1a), which consists of one M site (M = 0.55Ga(1) + 0.45Sn(1), 48h) and three S sites (S(1) in 48h site, S(2) in 24f site with 2.. symmetry, S(3) in 24g site with mirror symmetry), Figure S1. In the open framework of [Ga2.2Sn1.8S8]n2.2n−, the M site adopts a distorted tetrahedral coordination geometry. The M−S bond distances and S−M−S angles in [MS4] tetrahedra scatter from 2.231(9)−2.412(9) Å and 97.7(2)°−118.9(3)° (Table S2), respectively, which are comparable with those of some related compounds, for instance, [Mn2(en)5]2Mn2Ga4Sn4S20·4H2O,15 B

DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

metal ion at equilibrium, q (mg/g) is the removal quantity at Ce, qm (mg/g) is the saturation capacity of the material, and b (L/mg) is the constant of the Langmuir equation. The equilibrium model study indicated that the maximum mercury saturation capacity of GaSnS-1 was 213.9 mg/g. This value is significantly larger than that of some widely studied sulfide-based and oxide-based materials, such as LHMS-1 (87 mg/g),13 polypyrrole multilayer-laminated cellulose (32 mg/ g),20 magnetic graphenes composite material (23 mg/g),21 and polymer-brush-grafted magnetic nanoparticles (48 mg/g).22 In addition to the relatively large mercury adsorption capacity, the kinetics of mercury capture by GaSnS-1 is extremely fast. As shown in Figure 4 and Figure S11, it was

Figure 2. (a) Variable temperature PXRD patterns of GaSnS-1 (N2 flow, 3 h). (b) PXRD patterns of the pristine GaSnS-1, Hg2+-loaded product of GaSnS-1, GaSnS-1 soaked in 0.05 M H3PO4 aqueous solution, and the simulated one of GaSnS-1 (C0 ≃ 400 ppm). (c) The EDX spectrum of Hg@GaSnS-1 (the surface of the crystal). (d) XPS of mercury for Hg2+-loaded product of GaSnS-1.

showed that there is no obvious weight loss of organic amines after the mercury adsorption regardless of the more adsorbed water molecules (Figure S7), which was further confirmed by the EA and FT−IR results (Figure S10). These results revealed that the mercury capture mechanism may mainly be attributed to the surface adsorption instead of cation exchange. Adsorption Isotherm and Kinetics Studies. To demonstrate the great potential of GaSnS-1 in capturing the mercury, the sorption isotherm experiments were first investigated. The Hg2+ ion adsorption−equilibrium data are presented in Figure 3, which is well fitted with the Langmuir

Figure 4. Kinetics curve of Hg2+ ion adsorption plotted as the ion concentration (ppb) vs the contact time (min). Inset: the plot of t/qt (min·g·mg−1) vs t (min).

able to achieve 99.89% of the adsorption capacity within 2 min with a decrease of the concentration of Hg2+ ions from 1841 to 1.99 ppb. Especially, the concentration of Hg2+ ions can be further reduced far below the acceptable limit of drinking water within 5 min of contact, achieving nearly 100% removal. The kinetic data of GaSnS-1 were further processed and fitted with the pseudo-second-order adsorption kinetics model that is represented in the eq 3. t 1 t = + 2 qt qe k 2qe (3) Here, k2 (g·mg−1·min−1) is the pseudo-second-order adsorption rate constant, and qe (mg/g) and qt (mg/g) are the amount of mercury adsorbed at equilibrium and at time t (min), respectively. Fitting the experimental data reveals an extremely high correlation coefficient (∼1; the inset in Figure 4), verifying that the model can adequately describe the kinetic data of mercury sorption. This result further implies that chemical adsorption is the determining step of the adsorption processes and its major uptake mechanism.9b,23 The derived adsorption rate constant k2 was calculated to be 5.65 × 102 g·mg−1·min−1, which is 1−3 orders of magnitude better than those of most high-performance mercury adsorbents to date, for example, PTMT,23a PAF-1-SH,23b and thiol-functionalized HKUST.9b To the best of our knowledge, such extremely rapid adsorption kinetics found in GaSnS-1 can be attributed to the homogeneous distribution of its soft S2− ions, and the strong affinity of the basic anionic framework for soft acidic Hg2+ ions.

Figure 3. Hg2+ equilibrium curve of GaSnS-1.

model with a correlation coefficient of 0.971. The calculation of q and the expression of the Langmuir model equation are given in the following eqs 1 and 2. q = qm q=

bCe 1 + bCe

(C0 − Ce)V m

(1)

(2)

wherein m (g) is the dosage of material, V (mL) is the volume of metal ion solution, C0 (ppm) is the initial metal ion concentration, Ce (ppm) represents the concentration of the C

DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

soaking, the PXRD of Hg2+-laden products exhibited a shift of the basal Bragg peaks around 48° to higher 2θ angles. This may be attributed to the smaller proton cations entering the structure, which were often observed in the metal ions capture process of other sorbents.11a,13,14a To check the performance of GaSnS-1 in capturing mercury under a competing environment, simulated groundwater was intentionally contaminated by a trace concentration of Hg2+ ions. In accordance with the expectation, GaSnS-1 was able to remove more than 98% of the Hg2+ ions even in the presence of excess competitive alkali/alkaline earth metal ions, demonstrating its strong preference and high affinity for Hg2+ ion (Figure 6a). In the case of competitive adsorption

pH-Dependent and Competitive Mercury Adsorption Studies. Following the isotherm and kinetics experiments, we have also tested the effect of pH on Hg2+ ion adsorption (Figure 5). The distribution coefficient Kd, an important factor

Figure 5. (a) Kd values of Hg2+ ion in pH-dependent adsorption studies (C0 = 2.16−7.06 ppm). (b) PXRD patterns of GaSnS-1 and corresponding Hg@GaSnS-1 at various pH values.

that determines the affinity and selectivity of GaSnS-1 for the Hg2+ ion, is defined in eq 4. The ion removal efficiency R was calculated by eq 5. The physical meanings of V, m, C0, and Ce are the same as previously mentioned and call for no further comments. Kd =

R=

V (C0 − Ce) m Ce (C0 − Ce) × 100% C0

Figure 6. (a) Ion removal rate in competitive alkali/alkaline earth metal ions adsorption experiments (C0(Na+) = 44.32 ppm, C0(K+) = 25.19 ppm, C0(Mg2+) = 11.08 ppm, C0(Ca2+) = 15.03 ppm, C0(Hg2+) = 5.12 ppm). (b) The ion removal rate in mixed heavy metal ions adsorption experiments (C0(Mn2+) = 9.47 ppm, C0(Zn2+) = 15.86 ppm, C0(Co2+) = 10.39 ppm, C0(Cd2+) = 11.28 ppm, C0(Ni2+) = 8.83 ppm, C0(Pb2+) = 16.16 ppm, C0(Cu2+) = 12.94 ppm, C0(Hg2+) = 4.00 ppm).

(4)

experiments containing eight mixed heavy metal ions, GaSnS-1 also displays good remediation capacity, especially for Cu2+, Pb2+, and Hg2+. As demonstrated in Figure 6b, the relative amount of Mn2+, Zn2+, Co2+, and Ni2+ ions removed were less than 2%, whereas the Cd2+ ion removal rate reached 98.5%. For Hg2+, Cu2+, and Pb2+, three heavy metal ions, it is worth noting that GaSnS-1 can attain close to 100% uptake efficiency at equilibrium and decrease the concentrations of these three ions below the detection limit of ICP-AES. These results show that GaSnS-1 is still an efficient and effective Hg2+ ion scavenger despite the complex competing systems. Individual Heavy Metal Ions Adsorption Experiments. The adsorption results of GaSnS-1 for 10 individual heavy metal ions are shown in Table 1. After 24 h of contact time, GaSnS-1 can attain 85.57−99.60% of the adsorption capacity for the other nine heavy metal ions except for Hg2+, with the Kd values in the range of 5.93 × 103 to 2.48 × 105

(5)

From Figure 5a, we can see that the Hg2+ ion uptake by GaSnS-1 remained very effective over a broad pH range (1.92−11.84). It was capable of maintaining large Kd values varying from 2.04 × 103 to 1.41 × 106 mL/g, with the prominent Hg2+ ion removal efficiency, especially in a mildly acidic environment (close to 100%). The highest Kd value was able to reach up to 1.41 × 106 mL/g at pH = 2.43, which is less or slightly better than the most efficient crystalline chalcogenido Hg2+ sorbents, such as KMS-1,10a LHMS-1,13 and K6MS.24 PXRD characterization indicated that the stability of GaSnS-1 is impressive (Figure 5b), which is rare and better than most oxide-based materials, such as activated carbons,6d natural zeolites,6b and some functionalized nanocomposites or metal−organic framework materials.9,25 In addition, compared with the pristine compound GaSnS-1 without aqueous solution D

DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

volumes, happily, the Hg2+ ion concentration in the outlet solution was reduced to less than the limit of detection of ICPAES, well below the acceptable limit in potable water.7 These properties, coupled with its extremely rapid adsorption kinetics and high selectivity, render GaSnS-1 a promising trapper for the efficient purification of industrial wastewater and drinking water polluted by Hg2+ ions.

Table 1. Sorption Results of GaSnS-1 for Individual Heavy Metal Ions Single ions 3+

Cr Co2+ Mn2+ Zn2+ Ni2+ Cu2+ Ag+ Pb2+ Cd2+ Hg2+ Hg2+

C0 (ppm)

Ce (ppm)

Mn+ Removal (%)

9.44 11.50 8.53 9.16 9.37 9.27 4.69 7.87 10.95 16.17 6.24

0.64 1.66 0.254 1.06 0.855 0.171 0.0188 0.043 0.488 0.001 −a

93.22 85.57 97.02 88.43 90.88 98.16 99.60 99.45 95.54 99.99 ∼100

Kd (mL/g) 1.38 5.93 3.26 7.64 9.96 5.32 2.48 1.82 2.14 1.62 −a

× × × × × × × × × ×

104 103 104 103 104 104 105 105 104 107

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CONCLUSIONS In summary, a new and highly stable zeolitic-like chalcogenide, namely GaSnS-1, with the potential for remediation of highly toxic mercury has been solvothermally obtained. GaSnS-1 shows extremely fast mercury adsorption kinetics, high saturation capacity, and wide pH resistance. Particularly, GaSnS-1 exhibits outstanding selectivity for Hg2+ ions with a Kd value up to 1.62 × 107 mL/g. In addition, the Hg2+ ion adsorption properties in complex competing environments, as well as the uptake ability for other individual heavy metal ions (e.g., Ag+, Pb2+), are also impressive. Specifically, residual Hg2+ in chromatographic column experiments can be reduced far below the acceptable levels of potable water. These advantages render GaSnS-1 a promising material for decontamination of highly toxic aqueous mercury.

− = Not detected by ICP-AES.

a

mL/g. By contrast, GaSnS-1 displayed an extraordinary affinity and high selectivity for the Hg2+ ion, with an observed maximum Kd value up to 1.62 × 107 mL/g. It deserves to be mentioned that this value is 1−3 orders of magnitude greater than that of the other nine heavy metal ions and matches or significantly exceeds that of some existing high-performance sulfide-based and oxide-based mercury adsorbents,13,26 such as KMS-2,26a LHMS-1,13 and chalcogel-1.26b We also note that when the starting value of Hg2+ ion was 6.24 ppm, the concentration of Hg2+ ion was reduced below the limit of detection of ICP-AES, reaching approximately 100% removal. The general selectivity and preference order of these ions was Co2+, Zn2+ < Cr3+, Mn2+, Ni2+, Cu2+, Cd2+ < Pb2+, Ag+ < Hg2+. This consequence is well consistent with some previous work.14a,25 In addition, PXRD measurements confirm that the skeletal structure of GaSnS-1 was entirely preserved during the uptake process of different individual heavy metal ions, further indicating its good water stability (Figure S12). Chromatographic Column Experiment. A chromatographic column is commonly used in the actual wastewater treatment process,27 so we carried out an applied chromatographic column study for the simulated adsorption of Hg2+ ions from the flowing water. The scheme is illustrated in Figure 7a. After the treatment of 24 bed volumes of mercurycontaining solutions, the Hg2+ ion removal efficiency is up to 96.34% (Figure 7b). By prolonging the treatment to 42 bed

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b02981. Crystallographic data for GaSnS-1 (CCDC No. 1585127), more experimental details, structural analyses and comparisons, ICP-AES, EDX, PXRD, TGA, Raman and FT−IR results (PDF) Accession Codes

CCDC 1585127 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Bo Zhang: 0000-0002-7766-0467 Mei-Ling Feng: 0000-0003-2524-0994 Xiao-Ying Huang: 0000-0002-3514-216X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We acknowledge the Natural Science Foundation of Shandong Province (No. ZR2018LB001), the Foundation of State Key Laboratory of Structural Chemistry (No. 20180034), the National Natural Science Foundations of China (Nos. 21521061 and 11847124), and the 973 program (No. 2014CB845603).

Figure 7. (a) Schematic representation of separation column packed with GaSnS-1 microcrystals. (b) Chromatographic column studies plotted as Hg2+ ion removal rate vs bed volumes (C0(Hg2+) = 3.31 ppm, V/m = 500 mL/g). Inset in Figure 7b: the ion concentration (ppb) vs the bed volumes. E

DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

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DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.inorgchem.8b02981 Inorg. Chem. XXXX, XXX, XXX−XXX