•We developed a novel adsorbent chitosan/Al2O3/magnetic iron oxide NPs composite.•It showed high adsorption capacity for removing Methyl Orange as a model anionic dye.•The kinetics, thermodynamics, ...isotherm and desorption were comprehensively studied.•MO adsorption kinetics followed a pseudo-second-order kinetic model.•The adsorption kinetic was controlled by film diffusion and intra-particle diffusion.
In this study we developed a novel chitosan/Al2O3/magnetic iron oxide nanoparticle composite acting as an adsorbent for removing Methyl Orange (MO), a model anionic dye, from aqueous solution. The new adsorbent was characterized by Scanning Electron Microscope (SEM), Thermo Gravimetric Analysis (TGA), Brunauer–Emmett–Teller (BET) specific surface area, Energy Dispersive spectrometer (EDAX), powder X-ray Diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) methods.
The MO removal by the developed adsorbent was investigated using batch adsorption technique and all parameters influencing the removal efficiency such as: dose of adsorbent, pH and initial MO concentration were considered. The optimum adsorbent amount was determined to be 0.4gL−1 and adsorption process was found to be optimal in the wide pH range of 4–10.
Also, the adsorption activity of synthesized adsorbent including kinetics, thermodynamics, isotherm and desorption were comprehensibly studied. The adsorption isotherm was well described by the Langmuir model and showed high MO adsorption capacity (1.27mmolg−1, i.e., 417mgg−1 at 25°C). MO adsorption kinetics followed a pseudo-second-order kinetic model, indicating that adsorption was the rate-limiting step. At 10mgL−1, only 14min was required to reach 93% adsorption and about 50% of the MO was adsorbed in 2min. The fitting of experimental data with Weber and Morris model indicates that the adsorption kinetic was controlled simultaneously by film diffusion and intra-particle diffusion. Furthermore, the desorption studies of MO using 0.1M HCl showed the reusability of the adsorbent.
The study of the structures and properties of atomically precise gold nanoclusters is the object of active research worldwide. Recently, research has been also focusing on the doping of metal ...nanoclusters through introduction of noble metals, such as platinum, and less noble metals, such as cadmium and mercury. Previous studies, which relied extensively on the use of mass spectrometry and single-crystal X-ray crystallography, led to the assignment of the location of each of these foreign-metal atoms. Our study provides new insights into this topic and, particularly, compelling evidence about the actual position of the selected metal atoms M = Pt, Pd, Hg, and Cd in the structure of Au24M(SR)18 0. To make sure that the results were not dependent on the thiolate, for SR we used both butanethiolate and phenylethanethiolate. The clusters were prepared according to different literature procedures that were supposed to lead to different doping positions. Use of NMR spectroscopy and isotope effects, with the support of mass spectrometry, electrochemistry, and single-crystal X-ray crystallography, led us to confirm that noble metals indeed dope the cluster at its central position, whereas no matter how the doping reaction is conducted and the nature of the ligand, the position of both Cd and Hg is always on the icosahedron shell, rather than at the central or staple position, as often reported. Our results not only provide a reassessment of previous conclusions, but also highlight the importance of NMR spectroscopy studies and cast doubts on drawing conclusions mostly based on single-crystal X-ray crystallography.
Iron oxide (Fe3O4) and iron oxide/activated carbon (Fe3O4/AC) were fabricated by co-precipitation method for the removal of Cr(VI), Cu(II) and Cd(II) ions from aqueous solution in batch mode. These ...nanoparticles were characterized by BET, FTIR, XRD, SEM/TEM and VSM. The optimum conditions for the removal of ions were pH = 2 for Cr(VI) and 6 for Cu(II) and Cd(II), initial metal ion concentration = 50 mg L−1, nanoparticle dose = 50 mg/10 mL, temperature = 25 ± 1 °C, shaking speed = 180 rpm and contact time = 3 h. The equilibrium data of ions sorption were well described by Langmuir, Freundlich, Redlich-Peterson and Intraparticle Diffusion model. The R2 values obtained by Langmuir model were highest by Fe3O4/AC for Cr(VI) = 0.9994,Cu(II) = 0.9998 and Cd(II)= 0.9750. The temperature dependent study in the range of 288–328 K confirmed that the adsorption process was endothermic in nature. Desorption studies with 0.1 M HCl stated that these nanoparticles can be regenerated effectively and can be used after four adsorption-desorption cycles without any mass loss.
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Tripodal N‐donor ligands are used to form halogen‐bonded assemblies via structurally analogous Ag+‐complexes. Selective formation of discrete tetrameric I6L4 and dimeric I3L2 halonium cages, wherein ...multiple N⋅⋅⋅I+⋅⋅⋅N halogen bonds are used in concert, can be achieved by using sterically rigidified cationic tris(1‐methyl‐1‐azonia‐4‐azabicyclo2.2.2octane)‐mesitylene ligand, L1(PF6)3, and flexible ligand 1,3,5‐tris(imidazole‐1‐ylmethyl)‐2,4,6‐trimethylbenzene, L2, respectively. The iodonium cages, I6L14(PF6)18 and I3L22(PF6)3, were obtained through the N⋅⋅⋅Ag+⋅⋅⋅N→ N⋅⋅⋅I+⋅⋅⋅N cation exchange reaction between the corresponding Ag6L14(PF6)18 and Ag3L22(PF6)3 coordination cages, prepared as intermediates, and I2. The synthesized metallo‐ and halonium cages were studied in solution by NMR, in gas phase by ESI‐MS and in the solid‐state by single crystal X‐ray diffraction.
My body is a cage: Applying the robust N⋅⋅⋅Ag+⋅⋅⋅N→N⋅⋅⋅I+⋅⋅⋅N cation exchange reaction to silver metallocages from tripodal N‐donor halogen ligands results in the corresponding halonium cages (see figure).
Halogen bonding has increasingly facilitated the assembly of diverse host-guest solids. Here, we show that a well-known class of organic salts, bis(trimethylammonium) alkane diiodides, can reversibly ...encapsulate α,ω-diiodoperfluoroalkanes (DIPFAs) through intermolecular interactions between the host's I⁻ anions and the guest's terminal iodine substituents. The process is highly selective for the fluorocarbon that forms an I⁻···I(CF₂)mI···I⁻ superanion that is matched in length to the chosen dication. DIPFAs that are 2 to 12 carbons in length (common industrial intermediates) can thereby be isolated from mixtures by means of crystallization from solution upon addition of the dissolved size-matched ionic salt. The solid-state salts can also selectively capture the DIPFAs from the vapor phase, yielding the same product formed from solution despite a lack of porosity of the starting lattice structure. Heating liberates the DIPFAs and regenerates the original salt lattice, highlighting the practical potential for the system in separation applications.
In the last decades, synthesis and design of low molecular weight organogelators has gained increasing attention due to their versatile use in, for example, cosmetics, biomedicine and oil spill ...remediation. In this work, three potential gelators have been prepared from allylated d-mannose. Both the gelators and the corresponding gels formed were thoroughly characterized by crystallography, FTIR spectroscopy, SEM, rheometry and NMR spectroscopy, in solution and in solid state. The results showed that two of the compounds phase-selectively form gels with hydrocarbon solvents. The most promising gelator compound is alkene terminated, with the unsaturated end functionality not critical for gel formation, tentatively providing the possibility for customizing the gelation properties by further chemical modification. Alternatively, the alkene group could possibly be utilized as a linker for future coupling to carrier materials or surfaces to further increase the mechanical strength of the gel.
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•Low-molecular weight gelator compounds were prepared from d-mannose.•Compounds are phase-selective.•Characterized with FTIR, rheometry, and both solution and solid-state NMR spectroscopy.•End-functionalization makes further modification possible.
Neodymium-iron-boron (NdFeB) has become the most prominent permanent magnet alloy, with a wide variety of applications and an ever-increasing demand. Their recycling is important for securing the ...supply of critical raw materials used in their manufacturing. The use of organic acids such as acetic acid has been of recent interest for the recycling of waste NdFeB magnets. Despite achieving good leaching efficiencies, the published literature has not properly investigated the effects of key factors influencing the acetic acid leaching process and their respective interactions, which has led to conflicting findings as to what conditions are optimal. The present work goes to show that no such optimum exists by taking a look at the major factors (concentration, solid-to-liquid ratio, time, and temperature) and their interactions. The results show that leaching efficiencies >95% and even up to 100% can be achieved using a variety of different conditions showing that the leaching reaction is quite flexible, which is helpful for a potential upscaling of the process. The separation of the leached elements presents another problem in NdFeB magnet processing. As a novel application, this work investigated iron separation from the acetic acid leachate by the means of simple and inexpensive aeration. It was found that up to 99% of iron could be precipitated as FeO(OH) (goethite) within 2 h at pH 5 and 80 °C, while only minor neodymium co-precipitation was observed (5%). Separation of iron from the leachate can help obtain purer REE products in further processing.
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•An environmentally friendly acetic acid leaching process for NdFeB magnets.•Main effects and interactions of key factors illuminated - flexible leaching process.•Iron precipitated as FeO(OH) using a simple and inexpensive aeration method.
The synthesis, structural, thermal, and magnetic properties of a series of simple binary organic salts based on the radical anion of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and ...4-(N-alkylpyridinium-3-yl)-1,2,3,5-dithiadiazolyl (DTDA), 1 R (R = Et, Pr, Bu), radical cations and their heavier selenium analogues (DSDA), 2 R , are described. Single-crystal X-ray structural analyses reveal that short alkyl substituents on the pyridinium moiety of DTDA/DSDA cations lead to crystallization of isostructural acetonitrile (MeCN) solvates 1 Et ·MeCN, 1 Pr ·MeCN, 2 Et ·MeCN, and 2 Pr ·MeCN with trans-cofacial DTDA radical cation and eclipsed-cofacial TCNQ radical anion dimers. A slight increase in the substituent chain length to butyl affords the solvate 1 Bu ·0.5MeCN or the nonsolvate 1 Bu . The nonsolvate 1 Bu can be exclusively isolated using propionitrile (EtCN), whereas the isostructural selenium analogue 2 Bu crystallizes from MeCN. The crystal packing in 1 Bu ·0.5MeCN and 1 Bu /2 Bu is distinctively different: rare one-dimensional (1D) columnar π-stacks of evenly spaced TCNQ radical anions with periodic distortions along the vertical stacking direction and cis-cofacial DTDA dimers in 1 Bu ·0.5MeCN vs discrete, non-eclipsed-cofacial TCNQ dimers and trans-antarafacial DTDA/DSDA dimers in 1 Bu /2 Bu . The nonsolvated structure 1 Pr with trans-cofacial DTDA and non-eclipsed-cofacial TCNQ dimers can be isolated from EtCN. Single-crystal and powder X-ray diffraction methods confirmed a thermally driven, irreversible, single-crystal-to-single-crystal structural transformation between 1 Pr ·MeCN and 1 Pr . Thermogravimetric analyses of all nonsolvated salts show varied, yet robust, thermal behavior, while the thermal behavior of the solvates is consistent with more facile lattice solvent loss from structures with longer N-alkyl chains. Variable-temperature magnetic susceptibility measurements indicate that all structures are diamagnetic at low temperatures. However, thermally populated magnetic states could be observed for 1 Et ·MeCN, 1 Et ·EtCN, 1 Pr ·MeCN, 1 Bu ·0.5MeCN, 1 Bu , and 2 Bu at higher temperatures. This can be correlated with desolvation and structural changes that lead to the generation of weakly antiferromagnetically coupled non-eclipsed-cofacial TCNQ dimers, in agreement with results from density functional theory (DFT) calculations.
As the mining industry spreads to new areas in the arctic regions, the need for re-useable efficient methods for mine chemicals’ recycling increases. Especially in the case of xanthates, which are ...used as collectors for many metals from ore. Xanthates are very toxic to aquatic life either directly or indirectly and cause potentially severe health problems to humans after long-term exposure. In the present work, potassium ethyl xanthate (KEX) was observed to coordinate into metal organic frameworks (MOFs). HKUST-1 and its post-synthetically modified forms were observed to behave most effectively of the studied MOFs at low concentrations of KEX. Differences in the uptake of KEX were detected regarding the synthesis method in the case of MIL-100(Fe) synthetized by solvothermal and mechanochemical methods. Other studied MOFs, UiO-66 and MIL-100(Al)/MIL-96(Al), were not observed to be effective in KEX uptake.
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