Dichromate Anions Research Articles

Novel Anthracene-Appended Calix[4]triazacrown-5 as an Effective Fluorescence Probe for Co2+ and Hazardous Cr2O7 2- Ions.

A new calix[4]triazacrown-5-derived fluorescence chemosensor (AntUr-AzClx) at cone conformation was synthesized to afford an effective fluorescent probe, which enables an enhancement in the fluorescence intensity specifically in the presence of Co2+ metal ions as well as a turnoff response for hazardous dichromate anions. 1H-NMR, 13C-NMR, ESI-MS, and elemental analysis techniques were used to characterize the structure of the anthracene-appended calix[4]triazacrown-5 (AntUr-AzClx). The metal ion-binding ability of AntUr-AzClx was evaluated against Co2+, Ba2+, Ni2+, Pb2+, and Zn2+ ions. On the basis of various metal ion recognition phenomena, AntUr-AzClx exhibited outstanding selectivity for only the Co2+ ion among other metal ions. Also, the calix[4]triazacrown-5-derived fluorescence chemosensor showed high sensitivity towards the Co2+ ion with a very low limit of detection (LOD) 0.142 μmol L-1. In addition, anion binding abilities of AntUr-AzClx against various anions such Cr2O7 2-, HCO3 -, CO3 2-, NO3 -, SO3 2-, SO4 2-, N3 -, F-, and I- demonstrated that AntUr-AzClx enables selective and highly sensitive detection of the Cr2O7 2- anion with an excellent LOD of 4.182 nmol L-1 in DMF/PBS (1/1, v/v; pH: 7.05). Furthermore, the calix[4]triazacrown-5-derived fluorescence chemosensor displayed a significant sensing behavior to detect the presence of dichromate anions even in real samples.

A portable Eu-MOF-loaded paper-based probe integrated with smartphone for the visual and on-site detection of Cr2O72− in aqueous media

The high toxicity of dichromate anion (Cr2O72−) its accurate necessitates its sensitive and effective detection to safeguard human health. The study introduces a Eu-MOF fluorescent probe, named as Eu-TDCA, synthesized using 2,5-thiophenedicarboxylic acid (H2TDCA) as a bridging ligand for the detection of Cr2O72− in aqueous media. The probe suspension can detect Cr2O72− through fluorescence quenching, and the detection process exhibits a wide linear range (0–85 and 85–230 mg/L), low limit of detection (LOD, 5.1 μg/L) and rapid response speed (2 min). Furthermore, a portable Eu-TDCA-loaded paper-based probe, integrated with a smartphone color recognition app, was developed for the visual, sensitive and quantitative detection of Cr2O72− in real lake and river water samples, achieving satisfactory recoveries of 99.72%–103.75 %. Additionally, an advanced logic gate device was designed to simplify the detection process, providing a new direction for intelligent on-line detection of analytes.

Polyaniline-Based Cationic Porous Organic Polymers for Fast and Efficient Anion-Exchange-Driven Capture of Cr2O7 2.

Efficient treatment of wastewater contaminated with carcinogenic Cr(VI) has been a long-term challenge for both academic and industrial research efforts. Removal of Cr(VI) species by ion exchange is a relatively simple and efficient method, and its combination with highly tailorable nanomaterials is promising for the treatment of such wastewater. Here, we report a type of cationic porous organic polymer (POP), namely, PTPA-PIP, which can be prepared simply by converting the corresponding aromatic polyamine PTPA to its protonated form, thereby significantly increasing its hydrophilicity and ability to disperse homogeneously in water, crucial for application in water treatment. In addition to detailed characterization of the physicochemical properties of PTPA-PIP (including using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and solid-state NMR techniques), adsorption experiments demonstrate that PTPA-PIP removes low-concentration dichromate anions with very high performance, including excellent exchange capacity (maximum capacity of 230 mg Cr2O7 2-/g PTPA-PIP), ultrafast removal (initial adsorption rate of 83 mg g-1 min-1), excellent selectivity (∼10% loss of adsorption capacity in the presence of 40-fold concentration of competing anions), as well as superior reusability (reusable for at least 5 cycles without compromised performance). These results demonstrate that PTPA-PIP is an outstanding candidate for application in industrial settings for the effective removal of harmful Cr(VI) pollutants in wastewater.

Rational design of self-assembled copper oxide nanoparticles into hierarchical nanorods with high-surface-area for environmental remediation of wastewater

The coordinated generation of hierarchical structures is a difficult task that necessitates accurate control over a number of variables such as assembly shape, array dimensions, peripheral spacing, and uniformity. In this study, we successfully synthesized self-assembled copper oxide nanomaterials using hydrothermal processes. By aggregating copper oxide nanoparticles (diameter 4–6 nm), we were able to create a hierarchical rod-like morphology with highly homogeneous particle morphology and feature sizes ranging from 50 to 200 nm. We thoroughly investigated the methods of self-assembly of CuO nanorod formations, as well as the influence of templates on the materials' structure. Our analysis included powder X-ray diffraction (XRD), TEM, N2 sorption, and X-ray photoelectron spectroscopic (XPS) methods. N2 adsorption–desorption isotherm indicated high surface areas (125–190 m2/g) and limited pore diameter (less than 5 nm) for different samples. Furthermore, XPS examination demonstrated that the materials have a high concentration of Cu2+ groups, which serve as active sites for dichromate anion adsorption. We further investigated the adsorption process using Langmuir, Freundlich and Weber–Morris models and found that these CuO nanorods can perform as a highly powerful and recyclable adsorbent for hazardous dichromate from wastewater. Our findings have significant implications for the progress of new materials for environmental remediation and other applications.

A bifunctional imidazolium-based porous organic polymer for efficient detection of Cr2O72− and adsorptive separation of Cr2O72− and MO in water

The presence of heavy metal ions and organic dyes in aqueous solutions has a significant impact on the ecological environment and human health. Herein, a novel bifunctional imidazolium-based porous organic polymer (IMSPF-Br-C=C) was prepared successfully via quaternization reaction of spirobifluorene and 1,4-dibromo-2-butene. The synthesized material was characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infra-red spectra (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD), N2 adsorption-desorption analysis and solid-state 13C CP/MAS NMR spectroscopy, confirming its structure and stability. Owing to the conjugated structure of spirobifluorene, IMSPF-Br-C=C showed excellent recognition performance for dichromate anion (Cr2O72−) with the limit of detection (LOD) of 1.58 μmol/L. In addition, IMSPF-Br-C=C with the abundant imidazolium cations showed the outstanding adsorption performance in the removal of Cr2O72− and methyl orange (MO). Removal efficiencies and adsorption capacities of IMSPF-Br-C=C were 98.3 % and 99.4 %, 452.8 and 1304.2 mg/g in 6 min, respectively. The results show that the electrostatic interactions and π-π stacking play crucial roles in the fluorescence detection of Cr2O72− and adsorptive separation of Cr2O72− and MO. Furthermore, physico-chemical techniques, density functional theory (DFT) calculation and frontier molecular orbital theory (FMO) were used to explain action mechanism. This work provides a cost-effective IMSPF-Br-C=C as a bifunctional platform for sensing Cr2O72− and adsorptive separation of Cr2O72− and MO in aqueous solution.

Fluorophore molecule loaded in Tb-MOF for dual-channel fluorescence chemosensor for consecutive visual detection of bacterial spores and dichromate anion

Developing multifunctional luminescent switches for detecting various poisons are urgent given the continuous deterioration of the environment. Herein, a new porous fluorescent metal–organic framework [Tb2(TPTC)(DMA)4(NO3)2]n(HPU-25) was initially designed. Then, fluorophore molecule tris(2,2′-bipyridine) dichlororuthenium(II) hexahydrate (Ru(bpy)32+) was loaded onto HPU-25 by a simple post-synthesis strategy to prepare a new ratio fluorescence sensor Ru(II)@HPU-25. As a sensor, it can detect 2,6-pyridinedicarboxylic acid (DPA) content in real-time, with high sensitivity and selectivity, without being disturbed by probe concentration and environment. Evident changes in fluorescence color and intensity are observed in distinguishing DPA contents. In addition, after detecting DPA, it can be used for consecutive visual detection of dichromate anion (Cr2O72−) in water. This multifunctional fluorescence sensor could make up for the defects of single fluorescence and single function of the traditional fluorescence sensor by using the dual strategies of ratio sensing and cascade sensing. Interestingly, DPA and Cr2O72− in samples can be visually detected rapidly in real-time through the chroma acquisition APP on smartphone. More importantly, we also designed the combination of two logic gate operations for sensing the two targets. In the poison detection in daily life, these intelligent applications of fluorescence sensors have a broad development space.

Spherical TiO2 /Cr2O3 Composites Synthesized Using Ion-Exchange Resins as a Template

Two samples of TiO2 /Cr2O3 composites were synthesized as spherical grains by stepwise thermal treatment of ion-exchange resins, which were preliminarily saturated with chromium cations Cr3+ and dichromate anions Cr2O7 2– and covered with a film-forming solution of titania. The modes of calcination were based on thermal analysis and determined by the type of ion-exchange resin chosen as a template. The obtained composites consist mostly of the α-Cr2O3 phase, while the content of the TiO2 phase does not exceed 4 %. The composites retain the spherical grain shape of the initial ion-exchange resins with the size from 370 to 660 μm. Grains of the sample based on cationite, which adsorbs Cr3+ ions, have a pore structure with swells and voids. Grains of the sample based on anionite have fractures and cracks over the entire surface due to nonuniform distribution of adsorbed Cr2O72– anions in the initial anionite. The composites exhibit the catalytic activity in the complete oxidation of p-xylene. The sample based on cationite is more active. This may be related to a smaller accessible specific surface area of titania in the anionite-based sample due to formation of the Ti3+ solid solution in α-Cr2O3.

Schiff Base-functionalized Metal-organic Frameworks for Selective Sensing of Chromate and Dichromate in Water.

In this research, Zn- or Cd-based metal-organic frameworks (coded ZnMOF-1 and CdMOF-1) containing benzene-1,4-dicarboxylic acid (H2bdc) and pyridyl-based Schiff base (4-pyridylcarboxaldehydeisonicotinoylhydrazone (L)) dual ligands were successfully assembled via a conventional solvothermal method. The photoluminescence quenching response of ZnMOF-1 and CdMOF-1 and their sensing sensitivity and selectivity towards various inorganic anions were evaluated in aqueous media. Crystallographic and thermogravimetric studies confirm the formation of both MOFs with good crystallinity and thermal stability. Photoluminescence studies also verify the selectivity of ZnMOF-1 and CdMOF-1 for efficient sensing of inorganic oxyanions (like chromate/dichromate: CrO42- and Cr2O72-). Further, it was noted that only chromate/dichromate (CrO42-/Cr2O72-) anions showed a significant turn-off quenching effect while other anions (like F-, Br-, I-, Cl-, ClO4-, SCN-, SO42-, NO3-, and NO2-) have a low/negligible effect on the photoluminescence intensity of both MOFs. The limit of detection (LOD) of chromate/dichromate by ZnMOF-1 and CdMOF-1 was 9.79/10.94µM and 2.68/1.48µM, respectively. A probable mechanism for turn-off quenching response towards chromate and dichromate anions could be attributed to the spectral overlap of both excitation and emission spectra of ZnMOF-1/CdMOF-1 with the absorption spectra ofchromate/dichromate anions. As a result, the energy transfer from ZnMOF-1 or CdMOF-1 to the target chromate and dichromate anions decreased fluorescence intensity (i.e., fluorescence quenching effect).

Preparation of Two Calix[4]arene-Functionalized Biopolymers and Evaluations of Their Extraction Abilities Against Cr(VI)/As(V) Anions

Two calixarene-functionalized biopolymers (calixarene-functionalized chitosan and calixarene-functionalized cellulose) have been synthesized and duly characterized using FTIR, TGA and elemental analysis techniques. Furthermore, their anion extraction behaviors at various pH values have been evaluated toward dichromate and arsenate anions. Results indicated that calixarene-functionalized chitosan against dichromate ion exhibited higher extraction capability than calixarene-functionalized cellulose. Intriguingly, although a less extraction efficiency against dichromate anion was obtained by calixarene-functionalized cellulose, the arsenate anion extraction results showed that calixarene-functionalized cellulose is more effective ionophore than calixarene-functionalized chitosan.

Face-Directed Construction of a Metal-Organic Isohedral Tetrahedron for the Highly Efficient Capture of Environmentally Toxic Oxoanions and Iodine.

Geometric analysis has been guiding the design and construction of metal-organic polyhedra. Here, a series of isohedral tetrahedra ZrIT-1 and -2 and VIT-1 and -2 were synthesized by a one-pot method relying on trivalent molecular building blocks. Structural analysis shows that the isohedral tetrahedra constructed with {V6(SO4)(CO2)3} have three different sets of prism lengths, while those constructed with {Zr3O(CO2)3} have two different sets of prism lengths. Comparison of two types of polyhedra reveals that the different sizes and coordination flexibilities of the two MBBs result in different cavity volumes. The environmentally toxic oxoanion trapping ability of ZrIT-1 was explored due to its structural stability and cation cage properties. The results show that ZrIT-1 can capture permanganate and dichromate anions in water with high efficiency and selectivity. Notably, the permanganate adsorption capacity can reach ∼276.6 mg/g, which exceeds those of most metal-organic framework materials. In addition, the adsorption and desorption of iodine showed that ZrIT-1 has a reversible adsorption capacity for iodine.

Calixarene-tethered textile fabric for the efficient removal of hexavalent chromium from polluted water

This study describes the tethering of dimethylamionomethyl bonded calixarene (DMAM-calixarene) onto cotton fabric surface functionalized with poly(glycidyl methacrylate) (PGMA) linker layer using initiated chemical vapor deposition (iCVD) technique and the efficient adsorption capability of DMAM-calixarene functional textiles for the toxic hexavalent chromium from polluted water. The characterization of DMAM-calixarene-tethered textile fabric was performed by FTIR and XPS spectroscopy. Cr(VI) solutions was passed over packed DMAM-calixarene-tethered textile fabric adsorbent and the highest adsorption was observed at pH 2 in dichromate anion form of COS. The regeneration and selectivity studies indicate that the DMAM-calixarene-tethered textile fabric has outstanding adsorbent features in used experimental conditions for hexavalent chromium. Moreover, it was observed that both H-bonding and electrostatic interactions were significant factors in the dichromate anion adsorption process. Thus, this study clearly revealed that any DMAM-calixarene-tethered textile fabric can be easily used as a selective hexavalent chromium capture filter in geographic regions lacking appropriate wastewater purification systems.

EQUILIBRIA PROCESSES IN AQUEOUS SOLUTIONS OF K2CrO4 – HNO3 – KNO3 – H2O AND K2Cr2O7 – NaOH – KNO3 – H2O SYSTEMS

The equilibria processes in aqueous solutions of CrO42– – H+ – H2O and Cr2O72– – OH– – H2O systems were studied by pH‑potentiometric titration, mathematical modeling and UV–Vis. spectroscopy. It was established that in the CrO42– – H+ – H2O systems with acidity ZН = ν(H+)/ν(Cr(VI)) = 0–2.5 the processes of dichromate and hydrochromate anion formation and hydrolytic conversion of dichromate to hydrochromate take place, for which the logarithms of the equilibrium concentration constants were calculated by the quasi-Newton method (CLINP 2.1 software; 95 % confidence probability). The calculated values of the logarithms of the concentration equilibrium constants lgKC reliably agree with the literature data. The calculated lgKC were used to build of chromium(VI) anions distribution diagrams depending on ZH, and ZOH in solutions. For the first time, by the Pitzer method the thermodynamic equilibria constants of hydrochromate HCrO4– (lgK10 = 6,94), the dichromate anion Cr2O72– (lgK20 = 15,49) formation processes from the CrO4 2– and H+ ions, and the logarithm of equilibrium constant of the interconversion of the dichromate anion to the hydrochromate anion (lgK30 = –1,61) were calculated. Mathematical modeling and UV–Vis. spectroscopy show that the composition of anions in Cr2O72– – OH– – H2O solutions with alkality ZOH = ν(OH–)/ν(Cr(VI)) = 0–2.5 is identical to CrO42– – H+ – H2O systems. It is established that the experimental dependencies pH = f(Z) for the Cr2O72– – OH– – H2O system can be reliably reproduced by hydrolysis reactions of dichromate anion to hydrochromate anion and by subsequent neutralization to chromate anion with equilibrium constants calculated for processes in CrO42– – H+ – H2O solutions with same ionic strengths. The quantitative composition of chromium(VI) solutions was confirmed qualitatively by UV–Vis. spectroscopy.

Synthesis of new anthracene-substituted calix[4]triazacrown-5 as highly sensitive fluorescent chemosensor and extractant against hazardous dichromate anion.

A new fluorogenic anthracene functionalized calix[4]triazacrown-5 (Ant-AzClx) was successfully synthesized using a simple Schiff's base reaction. The 1 H-NMR, 13 C-NMR, ESI-MS, and elemental analysis techniques were performed to characterize its structure. Excited at 370 nm, Ant-AzClx reveals excimer emission at 418 nm. Therefore, its anion binding properties were investigated against F- , HCO3 - , H2 PO4 - , NO3 - , Cr2 O7 2- , and SO4 2- ions. When hazardous dichromate anion was introduced into medium, the fluorescence intensity of Ant-AzClx was markedly quenched. The binding constant, stoichiometry, the detection limits and Stern-Volmer equation for the complex formed between Ant-AzClx and Cr2 O7 2- ion were determined. Furthermore, the 1 H-NMR technique was also performed to assess the mechanism of the complex (Ant-AzClx@Cr2 O7 2- ). Apart from its excellent fluorescent chemosensor properties for selective and sensitive recognition of Cr2 O7 2- ion, Ant-AzClx was used as an efficient extractant towards dichromate anion. The extraction results indicated that Ant-AzClx exhibited high extraction capability, leading to it being a promising extractant for the removal of dichromate anions from water.

New Mn(II) coordination polymer constructed from a semi-rigid tricarboxylate acid ligand: Synthesis, structure, and fluorescence recognition of acetylacetone and dichromate anion

We herein report a new manganese(II) coordination polymer (CP), [Mn(HL)(H2O)2]·(bpe)0.5 (1), which is incorporated with semi-rigid tricarboxylate 4-(2′,3′-dicarboxylphenoxy) benzoic acid (H3L) and 1,2-bis(4-pyridyl) ethylene (bpe) as organic linkers through self-assembly strategy. Single crystal X-ray diffraction indicates that compound 1 contains a one-dimensional (1D) chain structure, which self-assembles into a final three-dimensional (3D) supramolecular framework via the interchain hydrogen bondings. Noticeably, bpe molecules have no practical contribution to the construction of 1D chain structure of 1, which only act as the guest molecules improving the stability of the 3D supramolecular network. More remarkably, the fluorescence signals feature a highly selective and sensitive “turn-off” response toward Cr2O72− and acetylacetone (Hacac) highlighted with the low detection limits of 4.44 μM and 6.11 ppm, respectively. The linear range for Hacac detecting is 0–5.0 mM, while 0–100 μM for Cr2O72−. Therefore, the exceptional sensing performance render compound 1 a potential platform for dually probe Hacac and oxo-anion Cr2O72− in wastewater. The crystal structure, selective sensing behavior and probable sensing mechanism of 1 toward both analytes are discussed in detail.

Viologen-Based Cationic Metal-Organic Framework for Efficient Cr2O72- Adsorption and Dye Separation.

A novel cationic metal-organic framework composed of {Cu2(COO)4} paddle-wheel units and a tetracarboxylic viologen derivative, namely, {[Cu2(bdcbp)(H2O)2]·2NO3·2H2O}n (Cu-CMOF, H4bdcbpCl2 = 1,1'-bis(3,5-dicarboxyphenyl)-4,4'-bipyridinium dichloride), has been successfully synthesized and structurally characterized. In Cu-CMOF, the {Cu2(COO)4} unit and viologen derivative both act as four-connected nodes forming an ssb-type cationic network with 42.84 topology, in which the positive charges are distributed on the organic viologen moieties. Deeper insight of the structure indicates that the 3D architecture of Cu-CMOF can be seen as packing of a 26-faceted polyhedral cage and two cuboid cages. Notably, Cu-CMOF displays a highly efficient anion exchange ability for capture and removal of anionic pollutants. UV-vis absorption spectra and digital images demonstrate that Cu-CMOF is capable of adsorbing the dichromate anion and anionic dyes effectively, such as methyl orange (MO-), Congo red (CR2-), and New Coccine (NC3-). Meaningfully, anionic dyes (MO-, CR2-, and NC3-) can be efficiently and selectively removed by Cu-CMOF in the presence of cationic dye methylene blue (MLB+). Such behaviors of anionic pollutant adsorption and dye separation are mainly caused by an ion-exchange process facilitated by the large cavity and decentralized distribution of positive charge in Cu-CMOF.

Dichromate and arsenate anion removal by PEI microgel, cryogel, and bulkgel

Among the various metal ions, chromate (Cr(VI)) and arsenate (As(V)) are the two most hazardous toxic ion species and are found in nature in the form of dichromate and arsenate anions. In this investigation, polyethyleneimine (PEI)-based hydrogels were prepared with microgel, cryogel, and bulkgel morphologies employing glycerol diglycidyl ether as a crosslinker. The prepared PEI-based hydrogels were used to remove dichromate and arsenate anions from aqueous media. PEI microgel, cryogel, and bulkgels weighing 50 mg of each adsorbed 84.7 ± 0.8, 76.5 ± 5.2, and 108.9 ± 2.4 mg.g−1 of dichromate anions and 15.9 ± 0.7, 45.4 ± 1.9, and 79.2 ± 11.6 mg.g−1 of arsenate anions in 30, 120, and 240 min, respectively. The dichromate and arsenate anions adsorption of PEI-based hydrogels were found to fit to the pseudo-second-order kinetic, and nonlinear Langmuir isotherm models, respectively with higher R2 values. The highest distribution coefficient (Kd) value of PEI-based hydrogels for dichromate adsorption was obtained on the cryogel forms of PEI as 1.89 ± 0.05. Likewise, the highest Kd value for the arsenate adsorption was calculated on PEI-based bulkgels as 0.46 ± 0.01. The thermodynamic parameters of PEI based hydrogels in the adsorption of dichromate and arsenate anions e.g., ΔG (all negative (except for the arsenate adsorption by PEI microgels), and ΔH that is around 2−10 kJ.mol−1, and ΔS what is around 0.01−0.02 kJ.mol−1. K−1 were calculated. The reusability studies showed that PEI-based hydrogels can be used for at least 5 consecutive adsorption-desorption cycles with almost 70 % anion removal efficiency after the fifth cycle.

Mg-Al-Cr<sub>2</sub>O<sub>7</sub> Hydrotalcite-Like Catalysts Synthesized at Different pH Values for Styrene Oxidation

Dichromate anions were intercalated between two consecutive hydroxide layers of [Mg0.6Al0.4(OH)2]0.40+ via co-precipitation at different pH conditions. The physico-chemical properties of the obtained solids were examined by physical methods such as X-ray diffraction (XRD), Infrared (IR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) and Energy-Dispersive Spectroscopy (EDS). The experimental results indicated that the amount of dichromate anions in the catalysts varies with the pH media. Also, the morphology, structure and chemical composition of the materials depends strongly on the preparation conditions. The Mg-Al-Cr2O7 hydrotalcite-like compounds are used as heterogeneous catalysts for the styrene oxidation with H2O2 at mild conditions. The styrene conversion is about 20-50% while styrene selectivity remains rather high.

Solvation of potential stable cations and anions originating from the Martian regolith in select ionic liquids

Element recovery from the Martian regolith using ionic liquids (ILs) is an active area of research within the field of in-situ resource utilization. In this work, we performed a classical molecular dynamics (MD) simulation study to better understand the solvation thermodynamics and structures of potential cationic and anionic species originating from the Martian regolith in two select ILs, i.e., 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) and 1-ethyl-3-methylimidazolium hydrogen sulfate ([emim][HSO4]), at two temperatures of 298.15 and 473.15 K. The studied cationic and anionic species represent the stable ions, i.e., a series of tetra-, tri-, di-, and monovalent cations, as well as several silicate, phosphate, chromate, titanate, and select halide anions, based on the mineral composition of the Martian regolith. We calculated the solvation free energies (SFEs) of these ionic species in the ILs using the free energy perturbation method. Moreover, we investigated the solvation environment of these ionic solutes by generating the relevant radial distribution functions and calculating the running coordination numbers of ILs' anions and cations surrounding the solutes. Overall, the average absolute values of the SFEs for cationic solutes increase with increasing ion valency (charge) and size of the solute at both temperatures. For anionic solutes, a more complex effect of anion molecular size and charge is responsible for the trends observed in the absolute values of the SFEs. For example, we found orthosilicate to be the most soluble anionic species in both ILs. On the other hand, the dichromate anion was found to be essentially insoluble in both ILs. Comparing between the solvation efficiencies of the ILs, [emim][Ac] shows larger negative SFE values than [emim][HSO4] for all cationic solutes at both temperatures. While the temperature effect on the solvation of cationic solutes is mixed, higher temperatures generally favor the dissolution of the anionic solutes in both ILs. Our results provide molecular insights into the solvation thermodynamics of various potential ionic species that may be extracted from the Martian regolith using suitable ILs.

A colloid chemistry route for the preparation of hierarchically ordered mesoporous layered double hydroxides using surfactants as sacrificial templates

An efficient synthetic route was developed to prepare hierarchically ordered mesoporous layered double hydroxide (LDH) materials. Sodium dodecyl sulfate (SDS) was used as a sacrificial template to tune the interfacial properties of the LDH materials during the synthetic process. The SDS dose was optimized to obtain stable dispersions of the SDS-LDH composites, which were calcined, then rehydrated to prepare the desired LDH structures. Results of various characterization studies revealed a clear relationship between the colloidal stability of the SDS-LDH precursors and the structural features of the final materials, which was entirely SDS-free. A comparison to the reference LDH prepared by the traditional co-precipitation-calcination-rehydration method in the absence of SDS shed light on a remarkable increase in the specific surface area (one of the highest within the previously reported LDH materials) and pore volume as well as on the formation of a beneficial pore size distribution. As a proof of concept, the mesoporous LDH was applied as adsorbent for removal of nitrate and dichromate anions from aqueous samples, and excellent efficiency was observed in both sorption capacity and recyclability. These results make the obtained LDH a promising candidate as adsorbent in various industrial and environmental processes, wherever the use of mesoporous and organic content-free materials is required.

Mn2Cl4 Cluster Based Two-Dimensional Coordination Polymer for Dichromate Sensing Property

The new coordination polymer of {Mn2Cl4(L1)2}n (1, 1′ and 1′′ for different synthesis conditions) [L1 = 1,3,5-tris(4′-pyridyloxadiazole)-2,4,6-triethylbenzene] has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy and powder X-ray diffraction. As revealed by the single crystal X-ray diffraction, there exist two kinds of L1 ligands and one kind of Mn2Cl4 dimer cluster in complex {Mn2Cl4(L1)2}n. L1 and the Mn2Cl4 dimer form a 3 × 6 two-dimensional layer structure. Each 2D net is composed of Mn2Cl4 linking Mn2-organic cycles. The 2D nets are packed into 3D frameworks through kinds of weak interactions including C-H···N and C-H···Cl hydrogen bonds in the AB fashion. As the assembly reaction can be conducted at room temperature or 90 °C giving rise to 1 and 1′ respectively, the micro-sized products 1′′ can be easily obtained under open solvothermal condition. Finally, the photo-luminescence of the coordination polymer is applied to the harmful dichromate anion sensing in aqueous media. And a fast respond to Cr2O72− at low concentration is realized. The CCDC number of 1 and 1′ are 1977023 and 1977024, respectively.