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Öğe Adsorption and contact angle of single and binary mixtures of surfactants on apatite(Pergamon-Elsevier Science Ltd, 2003) Sis, H; Chander, SAdsorption and contact angle of single and binary mixtures of sodium oleate and ethoxylated nonylphenol type nonionic surfactants on apatite minerals were studied. The effect of Ca2+ ions was investigated in the absence and presence of nonionic surfactants. The results showed that multilayers of oleate adsorbed on apatite surface and the presence of Ca2+ ions increased the adsorption by causing surface precipitation of oleate salt as calcium oleate. However, the presence of nonionic surfactant decreased oleate adsorption due to competition between the surfactants and prevention of oleate ions from precipitation as calcium oleate. Ethoxylated surfactants adsorbed on apatite as multilayers and the amount of adsorption decreased with increasing EO segments per molecule. When tested separately, the contact angle in oleate solutions was significantly larger than in nonionic surfactant solutions. The presence of a nonionic surfactant, NP-4, increased the contact angle of oleate solutions at relatively low concentrations of both the reagents. (C) 2003 Elsevier Ltd. All rights reserved.Öğe Improving froth characteristics and flotation recovery of phosphate ores with nonionic surfactants(Pergamon-Elsevier Science Ltd, 2003) Sis, H; Chander, SThe beneficial effect of a series of nonylphenol polyethylene glycol ether surfactants were tested in the flotation of phosphate ores in which the mixtures of sodium oleate and dodecane were used as collectors. In order to elucidate the flotation results, equilibrium surface tension of single and binary surfactant solutions prepared with sodium oleate and nonionic surfactants were investigated. Synergism between surfactants was determined by observing the change in surface tension of solutions and by the calculation of interaction parameter from surface tension data. The lowering of surface tension of sodium oleate solutions was observed in the presence of nonionic surfactants. The interaction parameter between sodium oleate and a nonionic surfactant (i.e., NP-4) was calculated to be -0.21, showing attraction between the two surfactant molecules. The nonionic surfactant NP-4 was then tested in batch flotation of phosphate ores. The beneficial effect of nonionic surfactant was obtained at different collector dosages and surfactant combinations. (C) 2003 Elsevier Science Ltd. All rights reserved.Öğe Kinetics of drop breakage in stirred vessels under turbulent conditions(Taylor & Francis Inc, 2005) Sis, H; Kelbaliyev, G; Chander, SThe emulsification of dodecane oil was studied in a standard stirred vessel filled with distilled water. The in situ size distribution of the drops was measured at certain time intervals by using a particle size analyzer while stirring. The results showed that an increase in the stirring time and stirring rate resulted in a decrease in the mean drop size of drops and shifted the drop size distribution toward smaller sizes. The minimum droplet size in the turbulent flow was found to be proportional to a(min) similar to (WD)(-1.75). Normalization of data exhibited that the size distribution of drops is self-preserving. The distribution of mean drop size and distribution functions of drops were determined by using models developed from the Focker-Plank equation regarding size distribution of particles in turbulent flows. The evaluation of droplet breakage with time in isotropic turbulent flow showed that the size distribution can be represented by the summation of log-normal distribution function in series. It was found that the experimental data could be represented well by the empirical models.Öğe Kinetics of emulsification of dodecane in the absence and presence of nonionic surfactants(Elsevier Science Bv, 2004) Sis, H; Chander, SThe effect of a nonylphenol polyethylene glycol ether (Tergitol NP-4) and a PEO/PPO/PEO type triblock copolymer (Pluronic L-61) surfactants on the emulsification of dodecane oil was investigated. The oil was emulsified in a standard mixing tank at different stirrer speeds. Kinetics of emulsification of dodecane with nonionic surfactants was measured by droplet size distribution of dodecane as a function of time. A phenomenological model was used to analyze the kinetics of emulsification. The results showed that the breakage of oil droplet in the mixing tank was accelerated in the presence of nonionic surfactants acting as emulsifiers. The mechanism of the breakage was explained in terms of reduction of interfacial tension by the adsorption of surfactants the liquid/oil interface. (C) 2004 Elsevier B.V. All rights reserved.Öğe Reagents used in the flotation of phosphate ores: a critical review(Pergamon-Elsevier Science Ltd, 2003) Sis, H; Chander, SPhosphate rock needs processing to reduce the content of gangue minerals such as silicates, carbonates, and clays to meet the requirements of the phosphate industry. Froth flotation method has been an important part of the concentration process since the 1920s and today, more than half of the world's marketable phosphate is produced by froth flotation. The literature on the processing of phosphate rocks by flotation is critically reviewed. Commonly used collectors, depressants, auxiliary reagents, and their mixtures in the flotation of the phosphate ores were tabulated. The advantages and disadvantages of the reagent type and structure (e.g., ionic and nonionic) on flotation were criticized. Based on the literature it was concluded that using surfactant mixtures has certain advantages over single surfactant as synergistic effect between surfactant mixtures were observed at different experiments such as surface tension, contact angle, adsorption, and flotation. (C) 2003 Elsevier Science Ltd. All rights reserved.Öğe Synergism in sodium oleate/ethoxylated nonylphenol mixtures(Taylor & Francis Inc, 2005) Sis, H; Chander, G; Chander, SThe adsorption of sodium oleate and various ethoxylated nonylphenol surfactants and their mixtures at air/liquid interface was investigated by equilibrium and dynamic surface tension experiments. Synergism was determined by observing the lowering of surface tension of water by single surfactants and their mixtures. The results showed that the addition of nonionic surfactant reduced both the equilibrium and dynamic surface tension of sodium oleate solutions. The effect of molecular weight, HLB, and degree of ethoxylation of the surfactant was studied. Interaction between anionic and nonionic surfactant mixtures was calculated by using an interaction parameter. The interaction parameter between oleate and NP-4 (a nonionic surfactant) was calculated to be -0.21, showing attraction between the two surfactant molecules.
