Volume 49, Issue 4

The kinetics of nucleophilic substitution of dimethylsulfoxide by chloride ion in bis-dimethyl sulfoxide dimethyltin(IV) dichloride and bis-dimethyl sulfoxide diphenyltin(IV) dichloride in micellar microenvironment (1.0 × 10 –2 M SDS in aqueous solution of ethanol (1:1, v/v) has been studied conductometrically. The reactions have been carried out at 25°C. Substitution follows first order path with respect to chloride ion concentration. A millimolar solution of the complexes in ethanolic solution of 1.0 × 10 –2 M SDS shows an increase in conductance with time due to solvation of the molecule. Sn(CH 3 ) 2 Cl 2 · 2 DMSO shows high conductance as compared to Sn(C 6 H 5 ) 2 Cl 2 · 2 DMSO. In the presence of the nucleophilic reagents, C 6 H 5 COCl and CH 3 COCl there is a greater enhancement in conductance due to substitution of DMSO by chloride ion. The data of rate constant for solvation (K S ) and for nucleophilic substitution (K 1 and K 2 ) have been calculated. It was found that the solvation is a slower process compared to the substitution by chloride ions i.e., K 1 , K 2 > Ks. A possible mechanism has been suggested.

The minerals application in polymer industry is one of the solutions towards the modification of polymer properties. In this study, the micronized silica was used as filler into the polypropylene (PP) matrix to enhance its mechanical properties. Two compatibilizers; namely: styrene-ethylene/butylene-styrene (SEBS) triblock copolymer and its grafted maleic anhydride (SEBS-g-MA) were used and evaluated using statistical design of experiments. The results showed that the addition of silica to the PP matrix substantially improves the mechanical properties of the composite with a drop in strain measures. On the other hand, the addition of the compatibilizer enhances the interfacial bonding and smoothen the stresses transfer between filler particles and the polymeric matrix. Consequently, a remarkable improvement in impact strength and strain was noticed. The statistical analysis showed that the interaction between silica and compatibilizer plays a crucial role in determining the mechanical properties of the final composite.

Vanadium(V) oxidation of ethanol follows a first order dependency on the concentration of ethanol, vanadium(V), H + and HSO 4 – . These observations remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant (i.e., N-cetylpyridinium chloride [CPC]), anionic surfactant (i.e., sodium dodecyl sulphate [SDS]) and neutral surfactant (i.e., Triton X-100 [TX-100]) has been studied. CPC inhibits the reactions, whereas SDS and TX-100 accelerate the reaction to different extents. Observed effects have been justified by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and TX-100 can be used as catalysts in the production of acetaldehyde from ethanol.

The heavy metals such as manganese (Mn), cadmium (Cd), zinc (Zn), chromium (Cr), lead (Pb), nickel (Ni), copper (Cu) and iron (Fe) were determined in domestic, commercial and industrial soot samples via atomic absorption spectrophotometer. The vehicle soot samples showed highest concentration of investigated heavy metals as compared to other soot samples. It was also found that the concentration of Fe was high in the soot samples (range 5.75–1105 mg/Kg) followed by Cu (70–990 mg/Kg) while the concentration of Ni was lower (range 0.5–3 mg/Kg). It was also found that the concentration of Mn and Fe was decreased as decreased the size of the soot samples while the concentration of other investigated heavy metals increased as decreased the size fraction.

Natural cellulosic fiber derived from Ficus carica, was used as eco-friendly biosorbent after alkali treatment for methylene blue dye remediation from aqueous system. The biosorbent was characterized by instrumental techniques such as Fourier transform infrared spectroscopy and scanning electron microscopy. The equilibrium behavior of the biosorbent was investigated in presence of electrolyte and surfactants by batch adsorption experiments. It was observed that in presence of ionic surfactants such as sodium dodecylbenzenesulfonate (SDS) and cetyltrimethyl ammonium bromide (CTABr), the adsorption capacity decreased from 38.97 mg g –1 to 35.64 mg g –1 and 36.75 mg g –1 respectively. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm models and were best represented by the Langmuir isotherm model. The pseudo second order kinetic model adequately describes the kinetic data in comparison to first order model. Thermodynamic studies indicated that the adsorption was endothermic and spontaneous. The desorption studies illustrated that the removal of methylene blue dye at optimized condition was 64.95%, out of which 41.53% of methylene blue dye can be recovered by desorption in first cycle. Thus, the biosorbent used in this work proved to be effective materials for the treatment of dye contaminated aqueous systems.

In order to predict percolation temperature of AOT-Based microemulsions (AOT/iC 8 /H 2 O w/o microemulsions) in the presence of small organic molecules (ureas and thioureas), different Artificial Neural Network architectures (ANN) have been carried out using a Perceptron Multilayer Artificial Neural Network with three entrance variables (W = value of the microemulsion, additive concentration, logP value). Best ANN architecture consists in three input neurons, one middle layer (with two neurons) and one output neuron. Correlation values were R = 0.9251 for the training set and R = 0.9719 for the prediction set.

The self-association of benzethonium chloride (BZCl) in aqueous solution has been analyzed as a function of temperature. The critical micelle concentration (CMC.), the degree of counterion binding (β) and thermodynamic parameters of micellization (molar Gibbs energy, enthalpy and entropy of micellization) were determined using six experimental methods (conductometry, potentiometry, UV spectrophotometry, spectrofluorimetry, NMR and densitometry) within the temperature range 20–50°C. All methods used gave very similar values for CMC. Changes in the thermodynamic parameters on micellization were determined by applying a mass action model.

Significant change in the cloud point of the nonionic surfactant solutions is observed by adding foreign substance. The aqueous solutions of these surfactants show complex phase behaviour including liquid-liquid separation at higher temperature. Electrolytes as well as nonelectrolytes have a large effect on the cloud point (CP) of C 12 EO 6 and C 12 EO 8 nonionic surfactants, because of their effect on water structure and their hydrophilicity. The presence of NaI and KI in the systems leads to a substantial increase in the cloud point of 2 wt% of the C 12 EO 6 and C 12 EO 8 solutions, but the increase is relatively less with KI than with NaI. Moreover, the cloud point decreases in the presence of NaF, NaCl and NaBr, and also similar identical observation was seen in the cloud point with KF, KCl and KBr, respectively. Furthermore, the results show that the addition of the tetramethyl ammonium bromide (TMABr) decreases the cloud point of the C 12 EO 6 and C 12 EO 8 , whereas the addition of tetrabutyl ammonium iodide (TBAI) increases the cloud point of the above systems. The clouding phenomenon of the aqueous C 12 EO 6 and C 12 EO 8 systems in the presence of various additives is discussed.

In this study palmitoyl piperidinium chloride and stearoyl piperidinium chloride surfactants were synthesized by two steps. The synthesized products in each step were analyzed by Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectrometry (FTIR), and elemental analysis. The properties of two surfactants were investigated, including surface tension (γ), critical micelle concentration (CMC), effectiveness (π cmc ), efficiency (pC 20 ), and anti-static properties. It was found that the number of methylene groups (-CH 2 -) in the hydrophobic chain has important effect on the properties of surfactants. Increasing the methylene groups enhances the ability of surfactant to act as effective surface tension agents in many applications. Furthermore, stearoyl piperidinium chloride showed that it can be used as a good capping agent in the microemulsion synthesis of MnS nanoparticles.

The synthesis of a series of sodium mono-alkylamide maleate surfactants was described, and the surface activity properties of the surfactants were studied. The mono-alkylamide maleic acids were synthesized by amidation using primary aliphatic amine (lauryl, myristyl, cetyl) and maleic anhydride as starting material. They were structurally characterized by IR, 1 H-NMR and MS. The sodium mono-alkylamide maleate surfactants were prepared by neutralization of the precursor mono-alkylamide maleic acids with sodium hydroxide. They reduced the surface tension of water to 32–34 mN · m –1 at concentration levels of 10 –4 –10 –3 mol · L –1 .