Optimization of ilmenite flotation process in the presence of microwave irradiation

In the present study, the effect of parameters, including microwave irradiation power, pH, dosage of chemical reagents (collector, depressant and activator) were studied by microflotation (in Hallimond tube) process. The mechanical flotation tests were carried out on optimum parameters obtained from microflotation tests. The software based on experimental design method (DX7) with the two-level full factorial design was applied to determine the parameter effects and to optimize the microflotation recovery. The optimum conditions were determined by analysis of variance (ANOVA), indicating that the irradiation power was the most effective parameter. The optimum values of parameters in the microflotation process are as follows: power of microwave (1000 W), pH (6.3), dosage of chemical reagents (sodium oleate 3.65 × 10^-4 M as a collector, acidified sodium silicate 2 g L^–1 as a depressant, and lead(II) nitrate 2.1 × 10^–5 M as an activator). By applying these optimized parameters, a product with ilmenite recovery of 83.26% was predicted by the software. The results of microflotation tests indicated that an ilmenite recovery of 82.35% was achieved being very close to the predicted value. The results of mechanical flotation based on optimized condition showed that the recovery and separation efficiency of irradiated ilmenite were improved up to 86.03% and 48.61%, respectively, indicating the positive effect of irradiation on ilmenite floatability.     

Experimental and theoretical study of some <Emphasis Type="Italic">N</Emphasis>-pyridinium salt derivatives as corrosion inhibitors for mild-steel in acidic media

N-pyridinium salt derivatives (1–5) were prepared and investigated as corrosion inhibitors for mild steel in 1 M H₂SO₄ solution at 30°C for 24 h. The corrosion inhibiting action was studied using weight loss measurements. The results demonstrated that the corrosion rate decreases, inhibition efficiencies increase, and surface coverage degree increases with increasing inhibitor concentration. Inhibition efficiencies for prepared N-pyridinium salt derivatives have highest inhibiting efficiency for even low concentration. The values of ΔG_ads^° showed physisorption effect for all prepared compounds. Molecular modeling systems were achieved for suggested inhibitors 1–5. Theoretical calculations could be used as a useful tool to obtain information for explaining the mechanism and nature of interaction between the metal surface and the organic molecule as a corrosion inhibitor.     

Preparation,Characterization and Electrochemical Application of ZnS/ZnAl2S4 Nanocomposite for Voltammetric Determination of Methionine and Tryptophan Using Modified Carbon Paste Electrode

ZnS/ZnAl₂S₄ nanocomposite and 2‐chlorobenzoyl ferrocene, were synthesized and used to construct a modified carbon paste electrode. The electrooxidation of methionine at the surface of the modified electrode was studied. Under the optimized conditions, the square wave voltammetric (SWV) peak current of methionine increased linearly with methionine concentration in the range of 5.0×10^?8 to 8.0×10^?4 M and detection limit of 10.0 nM was obtained for methionine. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of methionine and tryptophan which makes it suitable for the detection of methionine in the presence of tryptophan in real samples.     

An ab initio investigation of chalcogen–hydride interactions involving HXeH as a chalcogen bond acceptor

This work presents an ab initio study on chalcogen–hydride interactions in several binary complexes of chalcogen-containing molecules with HXeH. The geometries, H–Xe stretching frequencies and interaction energies of XCY···HXeH binary complexes are investigated at MP2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels of theory, where X = O, S, Se, Te and Y = S, Se, Te. For each XCY···HXeH complex, a chalcogen–hydride bond is formed between the negatively charged hydrogen atom of the HXeH molecule and the most positive electrostatic potential region (σ-hole) on the surface of the interacting atom Y. Upon complex formation, a notable blue shift is found for the H–Xe stretch vibration. This result reveals that there is a stronger H^?(XeH)⁺ ion-pair character in XCY···HXeH complexes than in free HXeH molecule. In order to shed light on the origin of the chalcogen–hydride interactions, molecular electrostatic potential, quantum theory of atoms in molecules and interaction energy decomposition analyses are performed. Cooperative effects between a conventional chalcogen bond and the chalcogen–hydride interaction in OCY···OCY···HXeH complexes are also investigated.     

Synthesis,single crystal structure determination,and solution behavior of an 8-hydroxyquinoline derivative of niobium(V) ethoxide

An 8-hydroxyquinoline derivative of niobium(V) ethoxide was synthesized and characterized by elemental analysis, mass spectrometry, infrared, electronic, and ¹H, ¹³C, and ⁹³NMR spectroscopies. Tetraethoxy(8-quinolinato)niobium(V), as shown by the single crystal structure determination, exists as an octahedral compound in the solid state in which the 8-quinolinato group chelates to the metal atom. In solution, this group partially becomes unidentate; the six-coordinate species is in equilibrium with the five-coordinate species, as shown by ⁹³Nb and variable-temperature ¹H NMR spectroscopy.     

Organoplatinum(II) complexes with phosphite ligands

The phosphite complexes cis-[PtMe₂L(SMe₂)] in which L = P(OⁱPr)₃, 1a, or L = P(OPh)₃, 1b, were synthesized by the reaction of cis,cis-[Me₂Pt(μ-SMe₂)₂PtMe₂] with 2 equiv. of L. If 4 equiv. of L was used the bis-phosphite complexes cis-[PtMe₂L₂] in which L = P(OⁱPr)₃, 2a, or L = P(OPh)₃, 2b, were obtained. The reaction of cis-[Pt(p-MeC₆H₄)₂(SMe₂)₂] with 2 equiv. of L gave the aryl bis-phosphite complexes cis-[Pt(p-MeC₆H₄)₂L₂] in which L = P(OⁱPr)₃, 2a′, or L = P(OPh)₃, 2b′. Use of 1 equiv. of L in the latter reaction gave the bis-phosphite complex along with the starting complex in a 1:1 ratio.The complexes failed to react with MeI. The reaction of cis,cis-[Me₂Pt(μ-SMe₂)₂PtMe₂] with 2 equiv. of the phosphine PPh₃ gave cis-[PtMe₂(PPh₃)₂] and cis-[PtMe₂(PPh₃)(SMe₂)] along with unreacted starting material. Reaction of cis-[PtMe₂L(SMe₂)], 1a and 1b with the bidentate phosphine ligand bis(diphenylphosphino)methane, dppm = Ph₂PCH₂PPh₂, gave [PtMe₂(dppm)], 8, along with cis-[PtMe₂L₂], 2. The reaction of cis-[PtMe₂L(SMe₂)] with 1/2 equiv. of the bidentate N-donor ligand NN = 4,4′-bipyridine yielded the binuclear complexes [PtMe₂L(μ-NN)PtMe₂L] in which L = P(OⁱPr)₃, 3a, or L = P(OPh)₃, 3b.The complexes were fully characterized using multinuclear NMR (¹H, ¹³C, ³¹P, and ¹⁹⁵Pt) spectroscopy.     

Synthesis of a functionalized tetrahydro-1,4-thiazepine in water as the solvent and theoretical investigation of its tautomeric structures

Reaction of sodium 2,2-dicyanoethene-1,1-bis(thiolate) with 2-chloroethylamine hydrochloride in water afforded the novel (Z)-5-amino-7-thioxo-2,3,4,7-tetrahydro-1,4-thiazepine-6-carbonitrile. The molecular geometry of the most stable tautomeric structure was investigated with DFT and AIM at the B3LYP level of theory using the standard 6-31G** basis set. Correspondence: Mehdi Bakavoli, Department of Chemistry, School of Science, Ferdowsi University, 91775-1436 Mashhad, Iran.     

Synthesis of pyrido[3′,2′:4,5]thieno[2,3-e][1,2,4]triazolo[4,3-a]pyrimidin-5(4H)-one derivatives

Some new pyrido[3′,2′:4,5]thieno[2,3-e]-[1,2,4]triazolo[4,3-a] pyrimidin-5(4H)-ones were prepared through heterocyclization of ethyl 3-aminothieno[2,3-b]pyridine-2-carboxylate with phenyl or ethyl isothiocyanate followed by nucleophilic displacement with hydrazine, and finally cyclocondensation with orthoesters. Correspondence: Abolghasem Davoodnia, Department of Chemistry, School of Sciences, Islamic Azad University, Mashhad Branch, Mashhad 91735-413, Iran.     

Triumfettamide and Triumfettoside Ic,Two Ceramides and Other Secondary Metabolites from the Stems of Wild Triumfetta cordifolia A. Rich. (Tiliaceae)

Two new ceramides, triumfettamide ( 1 ) and triumfettoside Ic ( 2 ), characterized as (2R,6Z)‐2‐hydroxy‐N‐[(2S,3S,4R)‐1,3,4‐trihydroxyhexacosan‐2‐yl]heptadec‐6‐enamide and (2R)‐N‐{(1S,2R,3E,6Z, 9Z,12Z,15Z)‐1‐[(β‐D ‐glucopyranosyloxy)methyl]‐2‐hydroxyheneicosa‐3,6,9,12,15‐pentaen‐1‐yl}‐2‐hydroxytetradecanamide, respectively, were isolated from the stems of Triumfetta cordifolia A. Rich. besides eight known secondary metabolites identified as heptadecanoic acid, β‐sitosterol glucopyranoside, friedelin, lupeol, betulin, maslinic acid, 2‐hydroxyoleanolic acid and the mixture of stigmasterol and β‐sitosterol. Their structures were determined on the basis of spectroscopic methods as well as HR‐MALDI‐FT‐ICR‐MS analysis, chemical transformation, and by comparison of their physical and spectral data with those reported in the literature and with authentic specimens for some known compounds. Five pentacyclic triterpenoids, friedelin, lupeol, betulin, maslinic acid, and 2‐hydroxyoleanolic acid, have been isolated from Triumfetta genus for the first time.     

Fe(HSO4)3: An efficient, heterogeneous and reusable catalyst for the synthesis of 14-aryl- or alkyi-14H-dibenzo[a.j]xanthenes

Fe(HSO4)3 has been used as an efficient and reeyclable catalyst for the one-pot synthesis of 14-aryl- or alkyl-14H-dibenzo[a,j]xanthene derivatives by the reaction of 2-naphtol and aldehydes. Different types of aromatic and aliphatic aldehydes are used in the reaction and in all cases the products were obtained in good to excellent yields.