INHIBITING EFFECT OF CRYSTAL VIOLET DYE ON ALUMINUM CORROSION IN ACIDIC AND ALKALINE MEDIA

Crystal violet dye (CV) was studied as a corrosion inhibitor for aluminum in hydrochloric acid (1 mol dm^?3) and potassium hydroxide (0.5 mol dm^?3) solutions in the temperature range 30°–60°C using the gravimetric technique. The effect of iodide ions on the inhibiting efficacy of CV was also assessed. CV was found to inhibit Al corrosion in both aggressive media, exhibiting greater inhibition efficiency in 1 M HCl (83.6%) than in 0.5 M KOH (23.0%). Inhibition efficiency in 0.5 M KOH was, however, synergistically increased in the presence of iodide ions to attain values up to 85.3%. Inhibition efficiency in the acidic and alkaline solutions increased with CV concentration but decreased with rise in temperature, suggesting physical adsorption of CV on the Al surface. The calculated values of activation energy (E_a), free energy of adsorption (ΔG_ads), and heat of adsorption (Q_ads) confirm the physisorption mechanism. The inhibitor adsorption characteristics were approximated by the Freundlich adsorption isotherm.     

Synergistic Effect of Mixed Surfactant Systems on Foam Behavior and Surface Tension

Foam and surface tension behaviors of different ionic/nonionic surfactant solutions along with their different combinations have been investigated. Among different surfactants, sodium dodecyl sulfate showed the highest foamability over other surfactants. Mixed surfactant systems were always found to have higher foamability than the individual surfactant. It was also noticeable that nonionic surfactants show good foamability when they combine with anionic and cationic surfactants. In the case of mixed surfactant systems, nonionic/cationic surfactant mixtures showed lower surface tension than nonionic/anionic surfactant mixture due to a synergistic effect.     

Synthesis, Surface Properties, Synergism Parameter and Inhibitive Performance of Novel Cationic Gemini Surfactant on Carbon Steel Corrosion in 1 M HCl Solution

Electrochemical and gravimetric measurements were performed to investigate the effectiveness of a synthesized cationic gemini surfactant as corrosion inhibitor for carbon steel in 1 M HCl solution. The inhibition efficiency obtained from all methods are in good agreement. Potentiodynamic polarization measurements showed that, the prepared surfactant hinders both anodic and cathodic processes, i.e. acted as mixed-type inhibitor. It was found that the adsorption of the synthesized inhibitor followed the Langmuir adsorption isotherm and showed a mixed physical and chemical adsorption. Kinetic parameters were calculated and discussed. The inhibitor exhibited a synergistic effect with Sn²⁺ more than with Cu²⁺. The synthesized cationic gemini surfactant exhibited good surface properties.     

Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Study

The interaction of cationic gemini and cationic conventional surfactants by conductivity was systematically overviewed, paying attention to synergism observed in micellization. These mixed systems were found to show remarkable synergism in micelle formation. The experimental critical micelle concentration values being lower than the value predicted by ideal solution theory indicate that the mixed micellization is due to attractive interaction between the two components. Gemini/conventional systems form mixed micelle due to attractive interactions (negative β values). The values of micellar mole fraction of constituent 1 (X ₁) in surfactant mixtures are more than in the ideal state (X ₁ ^ideal ), which means that, the mixed micelles are rich in conventional surfactants in comparison to that in the ideal state.     

Combustion Study of Synergism of Urea-Sodium Polymetaphosphate on the Flame-Retardancy of a Cotton Fabric Monitored by TG

The synergism of sodium polymetaphosphate- urea on the flammability of a cotton fabric (woven, plain 144 g/m², the number of yarns 21 per 10 mm) has been investigated in this study. After impregnation with suitable individual additives and/or their appropriate admixed formulation onto the fabrics, their flammability has been assessed by using the described procedure. In this study the flame spread tests comply with thermogravimetry's data. Explanation of the synergism with regard to the thermal analysis illustrated moderately effect of sodium polymetaphosphate to show flame-retardancy due to the confinement of phosphate's activity in the polymeric inorganic chain, however this effect increased by using urea.     

Synergistic Antiproliferative Effects of γ-Tocotrienol and Statin Treatment on Mammary Tumor Cells

Statins are potent inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase and display anticancer activity, but their clinical use is limited by their high-dose toxicity. Similarly, γ-tocotrienol, an isoform of vitamin E, also reduces HMGCoA reductase activity and displays potent anticancer activity. Studies were conducted to determine if combined low dose treatment of γ-tocotrienol with individual statins resulted in a synergistic antiproliferative effect on neoplastic mouse +SA mammary epithelial cells. Treatment with 3–4 μM γ-tocotrienol or 2–8 μM simvastatin, lovastatin or mevastatin alone resulted in a significant decrease, whereas treatment with 10–100 μM pravastatin had no effect on +SA cell growth. However, combined treatment of subeffective doses (0.25 or 10 μM) of individual statins with 0.25–2.0 μM γ-tocotrienol resulted in a dose-responsive synergistic inhibition in +SA cell proliferation. Additional studies showed that treatment with subeffective doses of individual statins or γ-tocotrienol alone had no effect, whereas combined treatment of these compounds resulted in a relatively large decrease in intracellular levels of phosphorylated (activated) MAPK, JNK, p38, and Akt. These findings strongly suggest that combined low dose treatment of γ-tocotrienol with individual statins may have potential value in the treatment of breast cancer without causing myotoxicity that is associated with high dose statin treatment.     

Photoinitiated polymerization in ionic liquids: Kinetics and viscosity effects

The photo-induced polymerization of poly(ethylene glycol) dimethacrylate and poly(ethylene glycol) monomethacrylate (crosslinking and linear, resp.) in four imidazolium-based ionic liquids (ILs) containing the same cation or the same anion in pairs is reported. The kinetic studies were accompanied by detailed viscosity measurements, which showed the occurrence of an interesting phenomenon - a viscosity synergism in monomer/IL mixtures (i.e. the viscosity of the mixture is higher than the simple additive combination of viscosities of the two components). Viscosity synergism, very important for kinetic considerations, is especially strong for ILs of low viscosity and its magnitude depends on the monomer structure. The polymerization conducted in ILs was considerably faster than in a reference solvent. The propagation rate coefficients were influenced mainly by the anion structure whereas the termination rate coefficients by viscosity of the initial monomer/IL mixture (taking into account the synergistic effect). FTIR studies showed the existence of specific interactions between the carbonyl group in the monomer and C₂-H of the imidazolium ring; the polymerization rates were directly related to the magnitude of the monomer/IL interaction.     

Synergistic antioxidant effect of α-tocopherol and myricetin on the autoxidation of triacylglycerols of sunflower oil

The synergistic antioxidant effect of different concentrations (50–250 ppm) of α-tocopherol and myricetin during autoxidation of triacylglycerols of sunflower oil (TGSO) at 100 °C was studied. The process was followed by monitoring the peroxide values and the formation of conjugated dienes. It was established that myricetin is a more effective and stronger antioxidant than α-tocopherol. All mixtures investigated exhibited a synergistic effect. The best synergistic effect was achieved with an equal molar ratio of α-tocopherol and myricetin, and at total concentration of the mixtures lower than 10 × 10⁻⁴ M. The kinetic analysis of the results demonstrated that α-tocopherol regenerates myticetin during autoxidation of TGSO at 100 °C.     

The roles of Cu, Zn and Mn in Cu0.5Zn0.5Mn2O4 spinel-lattice catalyst for methanol decomposition

Cu_0.5Zn_0.5Mn₂O₄ spinel-lattice catalyst has been studied for methanol decomposition by in situ infrared (IR) spectroscopy analysis and micro reactor study. Methoxy species is formed by dissociative adsorption of methanol which subsequently converts into formate species via step-wise dehydrogenation process. The activities of surface intermediates on reduced CuO, ZnO and Mn₂O₃ catalysts are strongly affected by the ease of hydrogen desorption from the site, the strength of C–H bonding and the availability of oxygen. A synergism between Cu and MnO whereby the Cu serves as a sink for reverse hydrogen atoms spillover from MnO has been proposed. The micro reactor analysis correlates well with the IR results.     

二(2-乙基己基)二硫代磷酸对镅和稀土元素协同萃取的研究

研究了二(2-乙基己基)二硫代磷酸(DEHDTP)和三辛基氧磷(TOPO)、4,7-二苯基-1,10-邻二氮菲(DPPHEN)、三辛基硫磷(TOPS)三种协萃剂对Am^3 、Nd^3 、Eu^3 、Tm^3 的协同(混合)萃取行为。TOPO和DPPHEN有很强的协萃能力,并提高了镅和稀土元素之间的分离系数,前者β(Am/Eu)=3．9,后者β(Am/Eu)=2,而TOPS几乎没有协萃作用。在常量稀土离子存在时分离系数进一步提高,TOPO的β(Am/Eu)=71,DPPHEN的β(Am/Eu)=3。