Mahmoud Sunjuk

Selective removal of dibenzothiophene from commercial diesel using manganese dioxide-modified activated carbon: a kinetic study

With a total concentration of 7055 mgS/kgfuel, the content of organosulphur compounds (OSCs) in local diesel is 20 times higher than the regulated value. Analysis revealed that 30% of OSC is originated from dibenzothiophene (DBT). It is known that DBT is a hardly removable compound and selective adsorbents are often needed for its removal with low affinity for other diesel components. In this work, a selective adsorbent based on surface modification of activated carbon (AC) by MnO2 is prepared for DBT removal from diesel. The porous nature of AC enabled carrying large amounts of MnO2 particles to end up with a selective adsorber for DBT. The best performance was observed at a surface loading of 26.8% of Mn and DBT is favourably removed over mono- and diaromatics hydrocarbons in diesel. Adsorption kinetics of DBT is studied under a high initial concentration of 835–11,890 mg/kg and at a ratio of 11 cm3/g (diesel:carbon). The results indicated a fast removal process after surface modification where 96% of the surface is occupied within 30 min of interaction. Kinetic data were best presented by reaction-based models with low prediction error sum of squares values 0.5–47.0, while, diffusion-based models showed limited application for modelling DBT adsorption. Accordingly, adsorption process is controlled by surface reactions and pore diffusion has a minor role in the overall process. The modified adsorbent is satisfactorily regenerated using n-hexane at 65°C.

A simple and accurate analytical method for determination of three commercial dyes in different water systems using partial least squares regression

A simple analytical procedure is proposed for simultaneous determination of three common dyes (Basic Blue 9, Brilliant Blue E-4BA, and Reactive Blue 2) in natural waters without prior separation of the solutes. A popular chemometric method, partial least squares regression PLS-1, was effectively applied for spectral resolution of a highly overlapping system. At the best modeling conditions, mean recoveries and relative standard deviations (RSD) for dyes quantification by PLS-1 were found to be 102.1 (4.4), 95.7 (8.4), and 98.9 (6.2) for Basic Blue, Brilliant Blue, and Reactive Blue, respectively. The estimated limits of detection (LOD) were estimated using net-analyte signal concept and were 0.11, 0.52, 0.49 mg L(-1) for Basic Blue, Brilliant Blue, and Reactive Blue, respectively. The quantitative determination of dyes spiked in real water samples was carried out successfully by PLS-1 with satisfactory recoveries for dyes (90-106%).

Solvent Extraction of Li+ using Organophosphorus Ligands in the Presence of Ammonia

In this work, the selective extraction of Li+ with the aid of organophosphorus ligands (H-OP) including phenylphosphonic (H-PHO), phenylphosphinic (H-PHI) and bis(2-ethylhexyl) phosphoric (H-BIS) acids in the absence and presence of ammonia was studied. Adding NH3 to the aqueous phase resulted in significant improvement in the % extraction of Li+ into the organic phase containing H-OP ligands. The highest % extraction values obtained in the case of H-PHO, H-PHI, and H-BIS were 43.2%, 45.7%, and 90.0%, respectively. Two mechanisms were inferred; the first was that the extraction equilibrium reaction of LiCl + H-OP ↔ Li-OP + HCl shifted forward due the reaction of the produced HCl with NH3. The second mechanism was that the Li+/NH4+ exchange of NH4-OP (produced from the reaction of H-OP with NH3) was easier than Li+/H+ exchange of H-OP itself. Competitive extraction experiments indicated that the selectivity factors of Li+ over Na+ and K+ were strongly dependent on the concentration of H-OP ligands which suggested that aggregation of ligand molecules via hydrogen bonding is the limiting factor for selectivity.

Synthesis of Phosphorus, Arsenic and Antimony Ylides Containing the 1,3- Dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione Fragments

The ylides Ph3E-C6H6N2O3 (7, E = P (a), As (b), Sb (c)) have been prepared through the reaction of Ph3E and 5- bromo-1,3-dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione (5-bromo-1,3-dimethylbarbituric acid) 6 in the presence of trieth- ylamine. Their characterisation was performed by nuclear magnetic resonance (NMR), mass spectrometry (MS) and ele- mental analysis.

Evidences for Chelating Complexes of Lithium with Phenylphosphinic and Phenylphosphonic Acids: A Spectroscopic and DFT Study

Abstract Lithium complexes were prepared with phenylphosphinic and phenylphosphonic acids. The complexes were studied in the solid state using Fourier transform infrared spectroscopy spectroscopy and in solution (methanol) using 1H, 13C, and 31P Nuclear magnetic resonance spectroscopy (NMR) spectroscopy; the most preferred structures of the complexes were determined by density functional theory (DFT) computational method. Although methanol has a strong solvation effect on lithium ions and ligands, which causes dissociation of the complexes, significant changes of the NMR spectra of the complexes (relative to those of the free ligands) were observed. The new spectroscopic results indicate the presence of the phenylphosphinic acid tautomer (I: C6H5PH(˭O)OH) rather than that of phenyl-phosphorous acid (II: C6H5P(OH)2) in deuterated methanol showing PH/PD exchange. On the other hand, tautomer I predominates in the complex with lithium without showing PH/PD exchange. The DFT calculations predict that tautomer I is the preferred structure in the case of free ligand and lithium complex. The absence of a PH/PD exchange in the complex is due to the formation of a chelating complex, rather than of a simple salt between lithium ion and the two oxygen atoms of I, which prevent tautomerization of I into II. DFT calculations support the formation of lithium chelating complexes. The lithium ion was found to affect the spectroscopic properties of phenylphosphinic acid more dramatically than those of phenylphosphonic acid. GRAPHICAL ABSTRACT

Crystal structure of 1,3-di-cyclo-hexyl-4,5-dimethyl-1H-imidazol-3-ium-2-carbodi-thio-ate chloro-form monosolvate.

The title compound, C18H28N2S2·CHCl3, crystallizes as a zwitterion. The C—S bonds are almost equivalent, with lengths of 1.666 (3) and 1.657 (3) Å. The S—C—S bond angle is expanded to 129.54 (16)° and the N—C—N angle is reduced to the tetrahedal value of 108.8 (2)°. In the crystal, adjacent molecules are linked via C—H⋯S hydrogen bonds, forming chains along [100]. The chloroform solvent molecule, which is disordered over two positions [occupancy ratio = 0.51 (2):0.49 (2)], is linked to the chain by bifurcated C—H⋯(S,S) hydrogen bonds.