Phenolic Oxime Research Articles

Sequential recovery of copper, nickel, gold, silver and zinc from WPCBs of obsolete mobile phones through hydrometallurgical recycling

Waste printed circuit board (WPCB) of an obsolete mobile phone is a valuable source of base and precious metals. Alternatively, WPCBs also contain various lethal and toxic constituents which introduce ecological impacts while landfilling and incineration. Recycling WPCB is essential to reduce the environmental effects and to recover valuable metals. This article employs a hydrometallurgical route for the sequential recovery of copper, nickel, gold, silver and zinc from WPCBs through leaching, solvent extraction and cementation processes. Initially, the metal clads of WPCBs are used for the leaching of copper, nickel and other base metals without any selective dissolution of gold and silver. Optimal results revealed that dilute nitric acid at room temperature provides effective leaching (99.9%) of copper, nickel and zinc by leaving precious metals gold and silver in the residue. The utilization of phenolic oxime as a solvent extraction reagent revealed the selective recovery of copper and nickel from the leach liquor individually. The availed residue is dissolved in the halide salts in the presence of acidic conditions showing the quantitative dissolution of gold and silver. Solvent extraction with amide-based reagents recovered gold by leaving the silver-rich raffinate. A cementation technique with copper powder is implemented for the precipitation of silver. The proposed approach delivers an effective, eco-friendly and economically feasible process for the sequential recovery of metallic values from WPCBs of obsolete mobile phones.

Liquid–liquid separation of copper and nickel ammine complexes using phenolic oxime mixture with tributyl phosphate

ABSTRACT In the present study, a complete separation of copper over nickel has been studied from an ammoniacal leach liquor of nickel laterite ore generated via the Caron process. For this purpose, a phenolic oxime (LIX 84-IC) used as the extractant molecule was mixed with tributyl phosphate (TBP) to inhibit the co-extraction of nickel with copper loading into the organic phase. The antagonistic effect of TBP was confirmed by the distribution coefficients to be D mix << D LIX 84-IC + D TBP and negative values of ∆D. The highest separation (β Cu/Ni) of >1329 was yielded using the molar ratio of organic mixture at LIX 84-IC:TBP = 0.4:0.6 at an organic-to-aqueous phase ratio of 1. The thermodynamic properties of copper extraction exhibited an endothermic nature with ΔH° value of 5.4 kJ∙mol−1, indicating the formation of inner-sphere coordination between metal ions and the organic mixture. Further, the stripping of copper from the loaded organic phase was quantitatively achieved by contacting with 1.0 mol∙L−1 H2SO4 solution at the unit phase ratio.

Spectrophotometric Determination of Fe(II) and Fe(III) Using 5-(4-Ethylphenyl azo ) 2-Hydroxybenzaldehyde Oxime Reagent

Spectrophotometric Determination of Fe(II) and Fe(III) Using 5-(4-Ethylphenyl azo ) 2-Hydroxybenzaldehyde Oxime Reagent

Efficient Extraction of Metal Ions Using a Recirculating Two‐Stage Flow Reactor

AbstractWe report a simple flow reactor for the selective extraction of target metal ions from an aqueous solution, using passive mixers and liquid‐liquid separators. The extraction takes place in two stages. In the first stage, target metal ions are selectively transferred to an organic phase containing extractant molecules; and, in the second stage, an acid solution strips the metal ions from the organic phase and regenerates the (uncomplexed) extractant molecules, thereby allowing them to be recirculated through the reactor. Using aqueous mixtures of copper sulphate and nickel sulphate as test solutions, copper ion extraction rates of 98 % are achieved, using the copper‐selective phenolic oxime ligand 5‐(tert‐butyl)‐2‐hydroxybenzaldehyde oxime as a molecular extractant. The two‐stage, recirculating nature of the reactor minimises the use of both the extractant molecules and the supporting organic solvent, resulting in a greener, more economical process.

Copper‐Catalyzed Chemoselective O‐Aroylation of Phenolic Oxime Ethers with Aryl Aldehydes

AbstractCopper‐catalyzed oxidative O‐aroylation of phenolic oxime ethers with a wide range of aromatic aldehydes are described. This approach offers an efficient synthesis of phenolic oxime ether esters in good to excellent yields.

Recycling copper and gold from e-waste by a two-stage leaching and solvent extraction process

The recycling of metals such as gold and copper from discarded end-of-life electronic waste (e-waste or WEEE) is an important aspect to the development of environmentally benign manufacturing processes that exhibit circularity in materials flow. Global e-waste production is increasing at a 3–5% rate, so it is concerning that only 30% is recycled using regulated processes. We present here a new hydrometallurgical route for the technically feasible recycling of copper and gold from waste printed circuit boards (WPCBs) of mobile phones. This process comprises the liberation of the metallic fractions from downsized WPCBs, a two-stage acid leaching process to provide a bulk separation of copper and gold from the other metals present, and subsequent purification of the copper and gold-containing solutions by solvent extraction using highly selective phenolic oxime and amide extractants, respectively. Complete dissolution of the base metals was seen using 3 M nitric acid at 30 °C and the selective separation of copper from this leach liquor was achieved by solvent extraction using ACORGA M5640 dissolved in kerosene. The residues from base-metal leaching were treated with a mixture of 3 M sulfuric acid and 3 M sodium bromide at 70 °C, resulting in greater than 95% gold dissolution. The selective separation of gold from this precious metal leachate was achieved by solvent extraction using 0.1 M tertiary amide extractant dissolved in toluene. This process delivers complete copper and gold recycling from WPCBs under relatively benign laboratory conditions and represents a proof of concept for liberating valuable and critical metals back into active service from end-of-life electronic devices.

A simple Cu(II) complex of phenolic oxime: synthesis, crystal structure, supramolecular interactions, DFT calculation and catecholase activity study

A copper (II) complex [Cu(4-MeO-salox)2](1) based on saloxime ligand was synthesized and characterized using single crystal X-ray diffraction studies. The geometry was further emphasized by DFT optimization. The complex was found to be pseudo-macrocyclic mononuclear having square planer geometry. The complex 1 shows two types of supramolecular hydrogen bonding interactions and forms the multi-dimensional framework with the help of CH∙∙∙O, OH∙∙∙O and π∙∙∙π(chelate) interactions. The complex 1 performs as efficient catalyst in catecholase activiy having good turnover number (TON), kcat = 22.97 h−1 where TON is the number of catechol molecules converted into quinone by catalyst molecule i.e 1 in a unit time.

Synthesis, characterization and structural study of new vanadium complexes with phenolic oxime ligands

In this work, three new vanadium complexes are reported. Their synthesis, crystallization and characterization are detailed. The complex (1) [VO(C7H6NO2)2] is a mononuclear and crystallizes in the monoclinic P21/n space group exhibiting a square pyramidal geometry around the vanadium. Dissolved in p-xylene (1–4 dimethylbenzene), this complex gives a binuclear complex (2) [V2O2(C7H6NO2)2(C7H5NO2)2]·C8H10 with a triclinic P-1 space group and an octahedral geometry around the vanadium. The complex (3) [VO2(C9H9N2O3)] was obtained using the new iminoacylated oxime ligand (the result of the nucleophilic attack of 4-hydroxysalicylaldoxime with acetonitrile), it crystallizes in the triclinic P-1 space group with a trigonal bipyramidal geometry around the vanadium. All complexes were characterized by single crystal X-ray diffraction, FT-IR, NMR, UV–visible and TGA.

New diazo-containing phenolic oximes: structural characterization, computationalstudies, and solvent extraction of Cu(II), Ni(II), and Zn(II) ions

In the current study, four new phenolic oxime ligands (HL1ox-HL4ox) containing diazo groups (-N$=$N-) were synthesized and used for liquid-liquid extraction of heavy metal ions [Cu(II), Ni(II), and Zn(II)]. The new compounds were characterized by analytical and spectroscopic methods. Solid-state structures of HL1ox-HL3ox were determined by single-crystal X-ray diffraction studies. Hirshfeld surface analysis of the compounds was performed to determine the contribution of different intermolecular contacts to the stability of the structures. The HL1ox-HL4ox ligands showed higher extraction performance for Cu(II) ion than Ni(II) and Zn(II) ions. The effect of pH on extraction capacity was investigated and the oxime compounds showed high extraction capacity at low pH values. The effects of the substitute groups (at the meta position of the phenol ring) on the extraction were investigated. Within the oxime ligands, the HL3ox compound exhibited higher extraction capacity for Cu(II) ions. The better extraction value of HL3ox is attributed to the weak hydrogen bond type interactions, which result in more stable complexes.

Physical and Chemical Methods Used for Determination of Structures of Some Imines Derived from Different Carbonyl Compounds

The project is concerned with the preparation of fifteen imines derived from 2-acetyl pyridine ,3 or 4 –hydroxy benzaldehyde and m-anisaldehyde with aromatic primary amines by standard method . These imines include namely ,hydroxylamine hydrochloride,o,m,p-amino phenols ,4-amino naphthol ,bromo or chloro aniline and p-anisidine . The main aims of the study is the determination of structures of these imines by the available physical method ,namely ,the melting points ,boiling points , U.V and IR spectra . Some chemical tests for functional groups are also included .This seems important from chemistry point of view as in the elucidation of tautomerism reactions happen in some oximes and phenolic oximes . Finally ,the influence of inter molecular hydrogen bonding on association (polymerization) of imines was also discussed

Paramagnetic NMR of Phenolic Oxime Copper Complexes: A Joint Experimental and Density Functional Study.

1 H and 13 C pNMR properties of bis(salicylaldoximato)copper(II) were studied in the solid state using magic-angle-spinning NMR spectroscopy and, for the isolated complex and selected oligomers, using density-functional theory at the PBE0-1/3 //PBE0-D3 level. Large paramagnetic shifts are observed, up to δ(1 H)=272 ppm and δ(13 C)=1006 ppm (at 298 K), which are rationalised through spin delocalisation from the metal onto the organic ligand and the resulting contact shifts arising from hyperfine coupling. The observed shift ranges are best reproduced computationally using exchange-correlation functionals with a high fraction of exact exchange (such as PBE0-1/3 ). Through a combination of experimental techniques and first-principles computation, a near-complete assignment of the observed signals is possible. Intermolecular effects on the pNMR shifts, modelled computationally in the dimers and trimers through effective decoupling between the local spins via A-tensor and total spin rescaling in the pNMR expression, are indicated to be small. Addition of electron-donating substituents and benzannelation of the organic ligand is predicted computationally to induce notable changes in the NMR signal pattern, which suggests that pNMR spectroscopy can be a sensitive probe for the spin distribution in paramagnetic phenolic oxime copper complexes.

ChemInform Abstract: A Review of Manganese‐Based Molecular Magnets and Supramolecular Architectures from Phenolic Oximes

AbstractReview: 94 refs.

EPR/ENDOR and Computational Study of Outer Sphere Interactions in Copper Complexes of Phenolic Oximes.

Copper complexes of the phenolic oxime family of ligands (3-X-salicylaldoximes) are used extensively as metal solvent extractants. Incorporation of electronegative substituents in the 3-position, ortho to the phenol group, can be used to buttress the interligand H-bonding, leading to an enhancement in extractant strength. However, investigation of the relevant H-bonding in these complexes can be exceedingly difficult. Here, we have combined EPR, ENDOR, DFT, and X-ray crystallography to study this effect. Analysis of the (1)H ENDOR data revealed a variation in the Cu···H(16) (oxime proton) distance from 2.92 Å for the unsubstituted complex [Cu(L(2))2] to 3.65 Å for the X = CH2N(C6H13)2 substituted complex [Cu(L(3))2]. DFT calculations showed that this variation is caused by changes to the length and strength of the H-bond between the oximic hydrogen and the phenolate oxygen. Noticeable changes to the Cu···H(15) (azomethine proton) distances and the Cu···N bonding parameters were also observed in the two complexes, as revealed through the (N)A and (N)Q ENDOR data. Distortions in the structure of the complex and variations in the oximic proton to phenolate oxygen H-bond strength caused by the substituent (X) were confirmed by DFT and X-ray crystallography. DFT directly evidenced the importance of the interaction between H(16) and the amine nitrogen of CH2N(C6H13)2 in the buttressed complex and indicated that the high strength of this interaction may not necessarily lead to an enhancement of copper extraction, as it can impose an unfavorable geometry in the inner coordination sphere of the complex. Therefore, ENDOR, DFT, and X-ray structural data all indicate that the aminomethyl substituent (X) ortho to the phenolic oxygen atom provides a particularly strong buttressing of interligand H-bonding in these copper complexes and that these outer sphere interactions can significantly influence structure and stability.

Turning a "useless" ligand into a "useful" ligand: a magneto-structural study of an unusual family of Cu(II) wheels derived from functionalised phenolic oximes.

While the phenolic oximes (R-saoH2) are well known for producing monometallic complexes of the type [M(II)(R-saoH)2] with Cu(II) ions in near quantitative yield, their derivatisation opens the door to much more varied and interesting coordination chemistry. Here we show that combining the complimentary diethanolamine and phenolic oxime moieties into one organic framework (H4L1 and H4L2) allows for the preparation and isolation of an unusual family of [Cu(II)]n wheels, including saddle-shaped, single-stranded [Cu(II)8] wheels of general formula [Cu8(HL1)4(X)4](n)[Y] (when n = 0, X = Cl(-), NO3(-), AcO(-), N3(-); when n = 2+ X = (OAc)2/(2,2'-bpy)2 and Y = [BF4]2) and [Cu8(HL2)4(X)4] (X = Cl(-), Br(-)), a rectangular [Cu6(HL1)4] wheel, and a heterometallic [Cu4Na2(HL1)2(H2L1)2] hexagon. Magnetic studies show very strong antiferromagnetic exchange between neighbouring metal ions, leading to diamagnetic ground states in all cases. DFT studies reveal that the magnitude of the exchange constants are correlated to the Cu-N-O-Cu dihedral angles, which in turn are correlated to the planarity/puckering of the [Cu(II)]n rings.

Phenolic oxime based receptors for selective detection of fluoride

The possibilities to employ phenol and oxime functionalities as fluoride recognition motif are investigated. The recognition involves H-bonding followed by deprotonation.

Combining Complementary Ligands into one Framework for the Construction of a Ferromagnetically Coupled [MnIII12] Wheel

Phenolic oxime and diethanolamine moieties have been combined into one organic framework, resulting in the formation of a novel ligand type that can be employed to construct a rare and unusual dodecametallic Mn wheel, within which nearest neighbours are coupled ferromagnetically.

A truncated [Mn(III)₁₂] tetrahedron from oxime-based [Mn(III)₃O] building blocks.

The use of the novel pro-ligand H4L combining the complimentary phenolic oxime and diethanolamine moieties in one organic framework, results in the formation of the first example of a [Mn(III)12] truncated tetrahedron and an extremely rare example of a Mn cage conforming to an Archimedean solid.

From antiferromagnetic to ferromagnetic exchange in a family of oxime-based MnIII dimers: a magneto-structural study

The reaction of Mn(ClO4)2·6H2O, a derivatised phenolic oxime (R-saoH2) and the ligand tris(2-pyridylmethyl)amine (tpa) in a basic alcoholic solution leads to the formation of a family of cluster compounds of general formula [Mn(III)2O(R-sao)(tpa)2](ClO4)2 (1, R = H; 2, R = Me; 3, R = Et; 4, R = Ph). The structure is that of a simple, albeit asymmetric, dimer of two Mn(III) ions bridged through one μ-O(2-) ion and the -N-O- moiety of the phenolic oxime. Magnetometry reveals that the exchange interaction between the two Mn(III) ions in complexes 1, 3 and 4 is antiferromagnetic, but that for complex 2 is ferromagnetic. A theoretically developed magneto-structural correlation reveals that the dominant structural parameter influencing the sign and magnitude of the pairwise interaction is the dihedral Mn-O-N-Mn (torsion) angle. A linear correlation is found, with the magnitude of J varying significantly as the dihedral angle is altered. As the torsion angle increases the AF exchange decreases, matching the experimentally determined data. DFT calculations reveal that the dyz|π*|dyz interaction decreases as the dihedral angle increases leading to ferromagnetic coupling at larger angles.

A 1-D coordination polymer based on a Mn40 octagonal super-structure

A 1-D coordination polymer, constructed using a combination of diols and phenolic oximes, contains a novel [Mn(9)] sub-unit, a nanosized [Mn(40)] octagonal super-structure and a [Mn(21)] repeating unit.

Linking [MIII3] triangles with “double-headed” phenolic oximes

Strapping two salicylaldoxime units together with aliphatic α,Ω-aminomethyl links in the 3-position gives ligands which allow the assembly of the polynuclear complexes [Fe(7)O(2)(OH)(6)(H(2)L1)(3)(py)(6)](BF(4))(5)·6H(2)O·14MeOH (1·6H(2)O·14MeOH), [Fe(6)O(OH)(7)(H(2)L2)(3)](BF(4))(3)·4H(2)O·9MeOH (2·4H(2)O·9MeOH) and [Mn(6)O(2)(OH)(2)(H(2)L1)(3)(py)(4)(MeCN)(2)](BF(4))(5)(NO(3))·3MeCN·H(2)O·5py (3·3MeCN·H(2)O·5py). In each case the metallic skeleton of the cluster is based on a trigonal prism in which two [M(III)(3)O] triangles are tethered together via three helically twisted double-headed oximes. The latter are present as H(2)L(2-) in which the oximic and phenolic O-atoms are deprotonated and the amino N-atoms protonated, with the oxime moieties bridging across the edges of the metal triangles. Both the identity of the metal ion and the length of the straps connecting the salicylaldoxime units have a major impact on the nuclearity and topology of the resultant cluster, with, perhaps counter-intuitively, the longer straps producing the "smallest" molecules.