Carboxylate Complexes Research Articles

Solid-State NMR, X-Ray Diffraction, and Theoretical Studies of Neutral Mononuclear Molecular Bis(triphenylphosphine)silver(I) Mono-Carboxylate and -Nitrate Systems

Neutral mononuclear molecular silver(i) carboxylate complexes of the form [(Ph3P)2Ag(O2XY)] with O2XY=O2CCH2Ph, O2CCHPh2, O2CC(CH3)3, O2CCH2C(CH3)3, and O2CCF3 (compounds 1–4 and 5β) have been investigated in the solid state using single-crystal X-ray structure determinations, 1D 31P CPMAS NMR and 2D 31P–31P CPCOSY NMR measurements, and ab initio computational modelling. The results show that these complexes contain P2AgO2 molecular cores with four-coordinate silver in which the carboxylate ligands are weakly bound to the silver atoms via the two oxygen atoms giving rise to unsymmetrical chelate units. Crystal structure determinations and solid-state NMR spectra have also been analysed for the mononuclear molecular silver(i) nitrate complex [(Ph3P)2Ag(O2NO)] (9α) and two polymorphs of its toluene monosolvate (11α, β). In 9α, the two PPh3 ligands are of the same chirality, whereas in 11α, β, they are opposed. The crystalline environments in the polymorphs have been explored by way of Hirshfeld surface analyses, after quantum-mechanical isolated-molecule calculations had shown that although the molecular energies of the experimental geometries of 9α, and 11α, β are significantly different from each other and from the energies of the optimized geometries, the latter, in contrast, do not differ significantly from each other despite the conformational isomerism. It has further been shown using 9α as an example that the energy dependence on variation of the P–Ag–P angle over a range of ~15° is only ~5 kJ mol−1. All this indicates that the forces arising from crystal packing result in significant perturbations in the experimental geometries, but do not alter the stereoisomerism caused by the donor atom array around the Ag atom. In the NMR study, a strong inverse correlation has been found between 1J(107/109Ag,31P) and the Ag–P bond length across all carboxylate and nitrate compounds.

Synthesis, characterization, structural elucidation, electrochemistry, DNA binding study, micellization behaviour and antioxidant activity of the Cu(II) carboxylate complexes

New dimeric paddlewheel copper(II) mixed ligand complexes were synthesized having general formulae [(py)Cu(L)4Cu(py)] (1), [(clpy)Cu(L*)4Cu(clpy)] (2) and [(py)Cu(L°)4Cu(py)] (3) where HL = 4-bromophenylacetic acid, HL* = phenyl acetic acid, HL° = 2-nitrophenylacetic acid, py = pyridine, clpy = 2-chloropyridine and characterized via FT-IR, powder and single crystal XRD, electrochemical solution studies and electron spin resonance spectroscopy. The resultant structures are dimeric paddlewheel where the carboxylate ligands act as bridges between two copper ions and pyridine acts as apical ligand leading to a square pyramidal geometry around each copper. The purity and crystalline nature of the complexes was checked by powder XRD technique. ESR spectra of the copper(II) complexes gave a sharp peak with g values = 1.443 (1) 1.512 (2) and 1.391 (3). The electrochemical studies showed diffusion controlled processes with diffusion co-efficient Do values = 3.68 × 10−6 cm2s−1 (1) and 3.63 × 10−6 cm2s−1 (3). Moreover, the complex-DNA interaction was studied by viscosity measurement, spectrofluorometry, cyclic voltammetry and UV–Visible spectrophotometry, the latter two yielding binding constant, Kb values = 4.0497 × 104 M−1 and 1.703 × 104 M−1 (1) and 4.117 × 104 M−1 and 1.743 × 104 M−1 (3), respectively. The complexes 1 and 2 showed moderate scavenging activity for the radical 2,2-diphenyl-1-picryl-hydrazil. Micellization behaviour was studied with cationic surfactant CTAB using conductivity meter and UV–Visible spectrophotometer showing that all the complexes have increased solubility with the addition of surfactant. These initial studies heralded good biological potential of the complexes.

Construction of mesoporous Cu/ZrO2-Al2O3 as a ternary catalyst for efficient synthesis of γ-valerolactone from levulinic acid at low temperature

A ternary base metal catalyst, which contained metallic Cu, oxygen deficiencies derived from ZrO2, and acidic Al2O3, was constructed for the efficient synthesis of γ-valerolactone by levulinic acid hydrogenation under mild conditions. Excellent catalytic performance was obtained by fine tuning the proportion of these three active components. The optimized Cu/Zr-Al-3 catalyst achieved superior catalytic activity with a high mass activity of 220.5 mmol GVL·h−1·g−1 surf. Cu at 130 °C, which was nearly eight times higher than Cu/Al and nine times higher than Cu/Zr. More importantly, Cu/Zr-Al-3 also possessed excellent recycling stability, making it as a potential catalyst for industrial applications. The presence of ZrO2 in the ternary catalysts weakened the Cu–Al2O3 interaction and formed Zr–O–Al interaction in the form of Al2O3–ZrO2 solid solution, which facilitated the reduction of CuO species and in turn enhanced the formation of more Cu0 active sites on the catalyst surface. The existence of a large number of oxygen vacancies and acid sites on the optimized ternary catalysts was also demonstrated by XPS and NH3 temperature-programmed desorption results. Levulinic acid can be adsorbed strongly on oxygen vacancies by its carboxylic or carbonyl groups and then readily attached by active H atoms dissociated on Cu0 sites to form active intermediates, while the acid sites presented on the ternary catalyst surface promote subsequent dehydration and intramolecular esterification of adsorbed active intermediates and consequently facilitate the formation of γ-valerolactone. The adsorption of levulinic acid onto oxygen vacancies also avoided the leaching of active Cu metal via the formation of soluble Cu metal carboxylate complexes, resulting in outstanding recycling stability for the optimized ternary catalysts. The intimate synergies of these ternary active sites mainly accounted for the superior catalytic activity and excellent recycling stability of the Cu/Zr-Al-3 catalyst.

In vivo antitumour properties of tribenzyltin carboxylates in a 4T1 murine metastatic mammary tumour model: Enhanced efficacy by PLGA nanoparticles

This study reports the in vivo performance of two tribenzyltin carboxylate complexes, tri(4-fluorobenzyl)tin[(N,N-diisopropylcarbamothioyl)sulfanyl]acetate (C1) and tribenzyltin isonicotinate (C9), in their native form as well as in a poly(lactic-co-glycolic acid) (PLGA)-based nanoformulation, to assess their potential to be translated into clinically useful agents. In a 4T1 murine metastatic mammary tumour model, single intravenous administration of C1 (2.7 mg/kg) and C9 (2.1 mg/kg; 2.1 mg/kg C9 is equivalent to 2.7 mg/kg C1) induced greater tumour growth delay than cisplatin and doxorubicin at equivalent doses, while a double-dose regimen demonstrated a much greater tumour growth delay than the single-dose treated groups. To improve the efficacy of the complexes in vivo, C1 and C9 were further integrated into PLGA nanoparticles to yield nanosized PLGA-C1 (183.7 ± 0.8 nm) and PLGA-C9 (163.2 ± 1.2 nm), respectively. Single intravenous administration of PLGA-C1 (2.7 mg C1 equivalent/kg) and PLGA-C9 (2.1 mg C9 equivalent/kg) induced greater tumour growth delay (33% reduction in the area under curve compared to that of free C1 and C9). Multiple-dose administration of PLGA-C1 (5.4 mg C1 equivalent/kg) and PLGA-C9 (4.2 mg C9 equivalent/kg) induced tumour growth suppression at the end of the study (21.7 and 34.6% reduction relative to the size on day 1 for the double-dose regimen; 73.5 and 79.0% reduction relative to the size on day 1 for the triple-dose regimen, respectively). Such tumour growth suppression was not observed in mice receiving multiple-dose regimens of free C1 and C9. Histopathological analysis revealed that metastasis to the lung and liver was inhibited in mice receiving PLGA-C1 and PLGA-C9. The current study has demonstrated the improved in vivo antitumour efficacies of C1 and C9 compared with conventional chemotherapy drugs and the enhancement of the efficacies of these agents via a robust PLGA-based nanoformulation and multiple-drug administration approach.

Sulphate Ion Interference on Oil Recovery Mechanism of Low Salinity Waterflooding in Dolomite Reservoirs

This study focused on the sulphate ion concentration interference with different divalent cations ratio, used in low salinity water flooding in dolomite reservoirs by comparing the oil recovery with the altered amount of divalent cations dissolved in brine, occurred from rock surface equilibrium shifting. The oil recovery from injecting different potential determining ions concentration is measured by core flood experiment. The process of detecting the amount of divalent cations begins with establishing oil adsorption on the dolomite grain surface. Then, the grain is stirred in brine with different formula, which is later titrated in order to gather the desired data. Finally, the phenomena occurred during flooding with different potential determining ion concentration is described by combining the result of oil recovery with altered amount of divalent ions. The results showed that at high temperature (70°C), the oil recovery from each case is not much different because high amount of calcium sulphate precipitation can be compensated by high rate of rock dissolution and magnesium carboxylate complex formation. However, at low temperature (30°C), the oil recovery tends to be lower when the sulphate concentration is higher because calcium ion tends to form or precipitate with sulphate ion rather than forming the carboxylate complex. Due to low dissolution rate, the amount of calcium ion is insufficient for oil recovery mechanism, especially when the sulphate ion concentration exceeds the solubility limit. Furthermore, for the case that the ratio of magnesium to calcium ion is high, it is observed that some amount of magnesium ion can form the carboxylate complex to compensate the lost amount of calcium ion. From the result, it can be concluded that at low temperature, which the dissolution reaction occurs slowly, the effect of changing the divalent cation ratio, including sulphate concentration, is large because the formation of magnesium carboxylate complex is not much at this temperature, however calcium sulphate precipitation reduces the number of active calcium ions in oil recovery mechanism. On the other hand, because the dissolution reaction occurs faster and the formation of magnesium carboxylate complex is more favourable at high temperature, therefore the values of oil recovery, even at different concentration of potential determining ions, are not much different at this temperature. Furthermore, it is also found that the carboxylate complex formation can be induced by high concentration of either type of divalent ions when the sulphate ion concentration is not too high.

Synthesis and thermal characterization of luminescent hybrid composites based on bisphenol A diacrylate and NVP

The synthesis and characterization of luminescent hybrid composites based on bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BPA-Acr) as a cross-linking monomer and N-vinylpyrrolidone (NVP) as an active diluent, in the presence of UV initiator (Irgacure 651), are presented. Eu(III) and Tb(III) carboxylate complexes were added as luminescent components of composites. In their preparation, a constant concentration of the initiator (1%) and the BPA-Acr to NVP (10:3) ratio were applied. The structures of the obtained materials were confirmed by the infrared spectra (ATR-FTIR). Thermal properties of the cross-linked products were determined by different thermal analysis methods in air and nitrogen (TG–DTG–DSC and TG–FTIR). Thermal stability, pathways of thermal decomposition and volatile products of degradation were determined. Photoluminescence properties of the lanthanide complexes and the obtained composites were established. These materials can have the potential application as coatings filtering harmful UV radiation.

Synthesis and Structures of 1,3-Dicarbonyl Compounds Based on 9,10-Phenanthrenequinone. Crystal and Molecular Structure of the Lantern-Type Binuclear Copper(II) Complex Cu2[μ2-OOCCH2(C14H8)(CO)2OC2H5]4(NCCH3)2

1,3-Dicarbonyl compounds were synthesized by the reaction of 9,10-phenanthrenequinone with acetylacetone and acetoacetic ester followed by the reduction and were characterized by spectroscopic and quantum-chemical methods. In the crystalline state and in solution, these compounds were found to exist in the keto form. The molecular and crystal structure of the binuclear lantern-type copper(II) carboxylate complex Cu2[μ2-OOCCH2(C14H8)(CO)2OC2H5]4(NCCH3)2, which was formed through the oxidation of the starting 1,3-dicarbonyl compound upon the complexation, was determined by X-ray diffraction. The coordination polyhedron of each copper atom can be described as a (4 + 1) square pyramid with four O atoms of four carboxyl groups at the base and the acetonitrile N atom in the apical position. The formation of the lantern-type dimer is attributed to the μ2-O,O' bidentate-bridging coordination mode of carboxyl groups.

FORMATION AND FUNCTIONING OF SYMBIOTIC SYSTEMS OF SOYA – BRADYRHIZOBIUM JAPONICUM FOR THE INFLUENCE OF COMPLEXES OF NANOPARTICLES OF CARBOXYLATES OF MICROELEMENTS

Objective. To study the effect of combined preparations based on highly active strains of Brad-yrhizobium japonicum and complexes of carboxylates of trace elements germanium, molybdenum, and ferrum on a symbiotic apparatus of soybean plants, in order to increase the efficiency of bacte-rial inoculants. Methods. Gas chromatography, microbiological, physiological. Results. The com-bination of a microbiological preparation based on efficient strains of nodule bacteria with complexes of nanoparticles of carboxylates Mo, Fe, Ge was found to promote the enhancement of nodulation activity, provide growth of mass of root nodules, activate the nitrogen-fixing activity of symbiotic soybean systems. When use the preparation combined with germanium and molyb-denum compounds, nitrogenase activity increases by 23–63 %, in combination with inoculum with germanium and ferrum nanocarboxylates — by 14–21 % depending on the phases of soybean or-ganogenesis. The complex application of biological and abiotic factors influencing the formation and functioning of symbiotic nitrogen-fixing systems contributes to the improvement of plant mor-phometric parameters and provides high yields of this crop. At the same time, it was established that germanium carboxylate complexes with molybdenum carboxylate, as well as germanium nanocarboxylates, should be used as effective stimulants for the formation of seed productivity of soybean plants and nitrogen-fixing activity of symbiotic systems created with their participation. In the experiment, soybean yield under the combination of B. japonicum with germanium and molyb-denum nanocarboxylates increased by 10 %, and by 13 % — under the complex application of bac-terial inoculum with germanium and ferrum carboxylate nanoparticles. Conclusion. Application of these complexes of nanocomponents in microbiological production technologies will allow plants to be supplied with additional nutritional elements, forming effective plant-microbial systems and ob-taining high and stable crops of environmentally safe food and feed protein.

Rhizosphere modifications of iron-rich minerals and forms of heavy metals encapsulated in sulfidic tailings hardpan

Hardpan caps formed after extensive weathering of the top layer of sulfidic tailings have been advocated to serve as physical barriers separating reactive tailings in depth and root zones above. However, in a hardpan-based root zone reconstructed with the soil cover, roots growing into contact with hardpan surfaces may induce the transformation of Fe-rich minerals and release potentially toxic elements for plant uptake. For evaluating this potential risk, two representative native species, Turpentine bush (Acacia chisholmii, AC) and Red Flinders grass (Iseilema vaginiflorum, RF), of which pre-cultured root mats were interfaced with thin discs of crushed hardpan minerals in the rhizosphere (RHIZO) test. After 35 days, the surface dissolution of hardpan minerals occurred and Fe-rich cement minerals were transformed from ferrihydrite-like minerals to goethite-like and Fe(III)-carboxylic complexes, as revealed by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and synchrotron-based X-ray absorption fine structure spectroscopy (XAFS) analysis. This transformation may result from the functions of root exudates. The transformation of hardpan cement minerals caused the co-dissolution of Cu and Zn initially encapsulated in the cements and their uptake by plants. Nevertheless, only was the minority of the plant Cu and Zn transported into shoots.

Separation of europium using graphene oxide supported membranes

Spectroscopic and morphological properties of graphene oxide (GO)-europium (Eu(III)) composite sheets prepared at different Eu(III) concentrations and pH are examined to ascertain interaction mechanism of Eu(III) ions with diverse oxygen functionalities of GO. Incorporation of Eu(III) ions deteriorates absorption characteristics of GO, quenches GO luminescence, originates irregular wrinkles on GO sheets, which infer reorganization in structure of GO in composites. Preparation of composites at large Eu(III) concentrations and sufficiently ionized ambience results in formation of Eu(III) hydroxide and/or carboxylate complexes and consequent aggregation of composite sheets. Based on these inferences, conditions for optimum Eu(III) uptake together with perseverance of GO characteristics are derived. Further, membrane filters are prepared using different size/multiple layers of GO and their Eu(III) adsorption abilities are examined by percolation of aqueous Eu(III) solutions. These membranes displayed enhancement in Eu(III) filtration efficiency with increase in number of GO layers, attributed to formation of uninterrupted and multiple filtration layers for improved Eu(III) ion adsorption. These studies also emphasize significance of larger surface area and availability of un-aggregated GO sheets for superior adsorption of Eu(III) ions. In the present work, GO membranes showed an optimum Eu(III) removal efficiency of ∼35% and average Eu(III) adsorption capacity of ∼115 mg/g.

Corrosion Potential Measurement to Investigate Copper Dissolution in Simulated Pore Environment on Ant Nest Corrosion

Refrigerant leakage due to the occurrence of formicary corrosion, also called ant nest corrosion, has been serious problem in copper piping used for the heat exchangers 1, 2). Because the ant nest corrosion begins at small pit and progresses rapidly in the depth direction, it is difficult to detect the occurrence of the ant nest corrosion. Notoya 2) reported that the progress of the ant nest corrosion in the depth direction was related to the repetition of the proportional reaction composed of copper and divalent carboxylic acid copper complex. In the present study, the corrosion potential measurement was performed to investigate the influence of proportional reaction composed of copper and divalent copper ions on the progress of the ant nest corrosion. A silicon sheet and two copper plates were used to simulate the pore environment on the ant nest corrosion. The small hole was drilled on the silicon sheet and copper plates. The diameter of the holes was 1 mm. The silicon sheet was sandwiched between copper plates, and the small hole penetrated into the silicon sheet and coper plates. This hole, which simulates the pore on ant nest corrosion, was filled with an aqueous solution of 100 ppm formic acid. In this case, the upper and lower copper plates were defined as working electrode 1 and 2 (WE1 and WE2), respectively. The corrosion potential measurement of the WE2 was carried out during the galvanostatic polarization of the WE1. A phosphor-deoxidized copper plates were used as the WE1 and WE2, and the electrochemical measurement was performed by a four-electrode system using a dual potentiostat. The corrosion potential of the WE2 was measured during the applying the constant current of 20 μA to the WE1. The corrosion potential of WE2 was shifted to noble potential because of the dissolution of the divalent copper ions on the WE1. This implies that the cathodic reaction rate of WE2 was increased due to the increase of the divalent copper ions concentration near the electrode interface of WE2, leading to the repetition of the proportional reaction composed of copper and divalent copper ions.

Chondroitin-Sulfate-A-Coated Magnetite Nanoparticles: Synthesis, Characterization and Testing to Predict Their Colloidal Behavior in Biological Milieu.

Biopolymer coated magnetite nanoparticles (MNPs) are suitable to fabricate biocompatible magnetic fluid (MF). Their comprehensive characterization, however, is a necessary step to assess whether bioapplications are feasible before expensive in vitro and in vivo tests. The MNPs were prepared by co-precipitation, and after careful purification, they were coated by chondroitin-sulfate-A (CSA). CSA exhibits high affinity adsorption to MNPs (H-type isotherm). We could only make stable MF of CSA coated MNPs (CSA@MNPs) under accurate conditions. The CSA@MNP was characterized by TEM (size ~10 nm) and VSM (saturation magnetization ~57 emu/g). Inner-sphere metal–carboxylate complex formation between CSA and MNP was proved by FTIR-ATR and XPS. Electrophoresis and DLS measurements show that the CSA@MNPs at CSA-loading > 0.2 mmol/g were stable at pH > 4. The salt tolerance of the product improved up to ~0.5 M NaCl at pH~6.3. Under favorable redox conditions, no iron leaching from the magnetic core was detected by ICP measurements. Thus, the characterization predicts both chemical and colloidal stability of CSA@MNPs in biological milieu regarding its pH and salt concentration. MTT assays showed no significant impact of CSA@MNP on the proliferation of A431 cells. According to these facts, the CSA@MNPs have a great potential in biocompatible MF preparation for medical applications.

Evaluation of amicarbazone toxicity removal through degradation processes based on hydroxyl and sulfate radicals

The herbicide amicarbazone (AMZ), which appeared as a possible alternative to atrazine, presents moderate environmental persistence and is unlikely to be removed by conventional water treatment techniques. Advanced oxidation processes (AOPs) driven by •OH and/or SO4•− radicals are then promising alternatives to AMZ-contaminated waters remediation, even though, in some cases, they can originate more toxic degradation products than the parent-compound. Therefore, assessing treated solutions toxicity prior to disposal is of extreme importance. In this study, the toxicity of AMZ solutions, before and after treatment with different •OH-driven and SO4•−-driven AOPs, was evaluated for five different microorganisms: Vibrio fischeri, Chlorella vulgaris, Tetrahymena thermophila, Escherichia coli, and Bacillus subtilis. In general, the toxic response of AMZ was greatly affected by the addition of reactants, especially when persulfate (PS) and/or Fe(III)-carboxylate complexes were added. The modifications of this response after treatment were correlated with AMZ intermediates, which were identified by mass spectrometry. Thus, low molecular weight by-products, resulting from fast degradation kinetics, were associated with increased toxicity to bacteria and trophic effects to microalgae. These observations were compared with toxicological predictions given by a Structure-Activity Relationships software, which revealed to be fairly compatible with our empirical findings.

Syntheses, crystal structures and DNA binding potential of copper(II) carboxylates

Copper(II) carboxylate complexes [Cu2{CH3CH(C6H5)CH2COO}4]n (1) and [Cu2{CH3CH(C6H5)CH2COO}4(3-MePy)2] (2) were synthesized and characterized by FT-IR and single crystal X-ray analyses. Bridging bidentate binding modes of the carboxylate ligands were first suggested by FT-IR spectra and later on confirmed by x-ray diffraction. Complexes 1 and 2 exhibited polymeric and discrete molecular units, respectively, with a paddle wheel arrangement of the bridging carboxylate ligands around the copper centers with octahedral coordination geometry. Both the complexes have shown hypochromism with no (complex 2) or a very small red shift of 3 nm (complex 1) on addition of SSDNA suggesting a mixed binding mode consisting of partial intercalation of the complexes into the base pairs of DNA together with groove binding.Molecular docking studies have shown increase in steric descriptors including octanol-water partition coefficient (slogP), molar refractivity (MR), and surface volume (Vsurf) with increasing binding strength of the complexes.

Mono and Dinuclear Cu(II) Carboxylate Complexes with Pyridine and 1‐methylimidazole as Co–Ligands: Synthesis, Structure, Antibacterial Activity and Catalytic Nitroaldol Reactions

AbstractA new series of Cu(II) carboxylate complexes [Cu2(RCOO)4(Py)2] (1 & 2) and [Cu(RCOO)2(MIm)2] (3 & 4) {RCOO=p–FBA (p‐fluorobenzoic acid), BA (benzoic acid), Py (Pyridine), MIm (1–methylimidazole)} have been synthesized. The composition of complexes (1–4) has been established by spectral (FTIR, UV/Vis & EPR) methods and elemental analysis. Molecular structures of copper(II) carboxylate complexes [Cu2(p–FBA)4(Py)2] (1) and [Cu(p–FBA)2(MIm)2] (3) were established by X–ray diffraction. These copper(II) carboxylate complexes 1–4 exhibit a very good catalytic activity towards nitroaldol (Henry) reaction of various aldehydes with nitromethane. The ligands and copper(II) complexes were also screened for their antibacterial activity against microorganisms Staphylococcus aureus and Escherichia coli.

Synthesis and Crystal Structure of a New Binuclear Copper(II) Carboxylate Complex as a Precursor for Copper(II) Oxide Nanoparticles

A paddle-wheel copper(II) carboxylate complex of the type [Cu2(2-nb)4(EtOH)2] (1), where 2-nb = 2-nitrobenzoate, is synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The results show that the complex has a square pyramidal geometry around the metal center. Combustion of copper(II) carboxylate gives copper(II) oxide nanoparticles which were characterized by powder XRD, SEM, EDX, and IR analyses. This study indicates that the coordination compound represents a suitable single precursor for the synthesis of CuO nanoparticles.

Methods for Synthesis of Molecular Materials with Unique Physical Properties

The authors discovered and investigated new types of stable heterometallic carboxylate complexes in which divalent transition metal atoms of the 4th period of the Periodic Table of Chemical Elements (V, Co, Ni, Cu, Zn) combine with atoms of lithium, magnesium, calcium or rare earth elements. These polynuclear heterometallic compounds retain their structure under conditions when the homometallic compounds of these transition metals decompose to mononuclear complexes. The different metals combination in one molecule allows us to use the obtained heterometallic compounds for producing disperse and film oxide materials, and bimetallic oxide catalysts. The stability of the complexes allows to immobilize them in various matrices and to assemble 3D polymer structures on their base. Since the metal ions under consideration (V, Co, Ni, Cu, Zn) are capable to form isostructural heterometallic compounds, it becomes possible to obtain compounds within a single structural type with a given combination of physical properties, determined by the nature of the metal ions.

Performance of biochar-based filtration bed for the removal of Cr(VI) from pre-treated synthetic tannery wastewater

ABSTRACT In the present study, the performance of biochar-based filtration bed was assessed to enhance the removal efficiency of Cr(VI), from the pre-treated synthetic tannery wastewater. The pre-treatment of wastewater was carried out with aluminium formate (AF) as a coagulant and 80% Cr(VI) removal was observed which might be due to the formation of carboxylic complexation reaction. The purity of coagulant and the sludge components were validated with XRD analysis and the results revealed the formation of pure aluminium formate compound as well as a clear change in the crystalline structure in the treated sludge. FT-IR spectra demonstrated the carboxylic compound participated in the removal of Cr(VI) during the coagulation process. The pre-treated wastewater having 20 mg/L (residual) Cr(VI) was passed through a three-layered filtration bed containing biochar, which showed complete removal of Cr(VI) ∼ 99.99% by precipitating into bind form under the influence of CaCO3 and formate ions. The possible mechanistic approach might be due to the presence of formate ions in the pre-treated wastewater, the precipitation of Cr(VI) occurred in the form of Cr(OH)2 by the release of bicarbonate (HCO3−), carbonate ion (CO3 2−) and hydroxide (OH−) ions in the filtration bed. The properties of the biochar were investigated by XRD and FTIR analysis and the results revealed the existence of hydroxyl, carboxyl and carbonyl groups, which participated during the removal of Cr(VI). The results suggest that biochar-based filtration bed could be a promising method for the treatment of pre-treated tannery wastewater.

Preparation and characterization of CuCr2O4/SiO2 and Cu2Cr2O4/SiO2 nanocomposites obtained from carboxylate complex combinations

This study reports the preparation and characterization of CuCr2O4/SiO2 and Cu2Cr2O4/SiO2 nanocomposites. In order to obtain 50 mass% CuCr2O4/SiO2 and Cu2Cr2O4/SiO2 nanocomposites, we have used a method based on the thermal decomposition of the precursors Cu(II) and Cr(III) carboxylate type complexes inside the SiO2 matrix. The precursors were formed inside the gels during the redox reaction between Cu(II) and Cr(III) metal nitrates and 1,3-propanediol (1,3PD). As a result of the gels heating, the precursors decomposed at ~ 300 °C leading to the amorphous metal oxides CuO and Cr2O3+x. Cr2O3+x turned to crystalline α-Cr2O3 (crystalline) at 400 °C which subsequently interacted with CuO. Well crystallized Cu2Cr2O4 was obtained at 1000 °C as a result of the interaction between CuCr2O4 and residual CuO formed at 800 °C. In both samples the oxides were homogenously distributed within the amorphous silica matrix. The nanocomposite samples CuCr2O4/SiO2 and Cu2Cr2O4/SiO2 obtained at different annealing temperatures were characterized by thermal analysis, FT-IR spectrometry and powder x-ray diffraction. The results showed that the silica matrix plays a crucial role for the preparation of the desired chromite nanoparticles.

Validation of a combined Fe(III)/UV/NaOH process for efficient removal of carboxyl complexed Ni from synthetic and authentic effluents

Nickel, massively used in plating industry but detrimental to ecosystem, tends to form stable complexes with organic additives in industrial effluents. Currently, most of the available processes aim at water decontamination from free toxic metal ions and thus, could not effectively remove nickel-carboxyl complexes from water. Herein, we employed a proprietary combined process Fe(III)/UV/NaOH, namely Fe(III) displacement and UV irradiation followed by alkaline precipitation, to validate its feasibility on the efficient removal of nickel-carboxyl complexes from synthetic and authentic effluents. Fe(III)/UV/NaOH outperformed other commonly used processes including NaOH precipitation, UV/NaOH, Fe(III) coagulation, and Fenton/NaOH. Each unit of the combined process was optimized, and the underlying mechanism was elucidated. Fe(III) displacement favored the stoichiometric release of free nickel ions and formation of Fe(III)-carboxyl complexes, which could be decarboxylated via ligand-metal charge transfer under UV irradiation. The precipitation unit aims at simultaneously removing the released Ni along with Fe species. Attractively, the presence of other organic species (ethylene glycol, ethyl acetate and humic acid) and anions (chloride and sulfate) exerted very slight effect on the final Ni removal, whereas greatly adverse effect occurred on the Fenton process under similar conditions. The feasibility of the combined process was validated by testing on an authentic electroplating effluent, resulting in the residual Ni below 0.1 mg/L, the most stringent discharge standard for Ni in electroplating effluent in China.