Rabah Khalil

Publications (19) View all

• Article: Use of Acetic Acid as an Electrolyte in Lead Electrorefining

  Rabah A. Khalil, Alla H. Jalil
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  ABSTRACT: As the scrap of lead is locally available and the pure lead is quite needful particularly if refined by green process. Therefore, an aqueous solution of acetic acid has been employed as an electrolyte instead of common industrial complex electrolytes that used in lead electrorefining. The results indicate that the optimum concentration of acetic acid is 2.5M using gelatin as an adhesive material. The effect of amount of gelatin as additive has been explored giving 2g/l as a typical amount. The optimum working temperatures for the presented process was found within the range of 40-50oC. It has been concluded that the acetic acid is suitable as an electrolyte for lead refining which produces lead electrodes with purity of 99.79% and current efficiency of 98.76%.
  (Mu’tah Lil-Buhuth wad-Dirasat: Natural & Applied Series). 02/2011; 26(2):27-42.
• Article: Application of Lee-Wheaton Equation for some Ionic Surfactants in Aqueous Solution

  Rabah A. Khalil, Ahlam M. Jameel, Abdussamed M. A. Saeed
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  ABSTRACT: This paper reports conductmetric investigations of some ionic surfactants using Lee-Wheaton equation. Two sets of electrical conductivities of aqueous solutions of anionic sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfate (SDBS) and cationic cetyltrimethylammonium bromide (CTAB), below and above critical micelle concentrations (CMC) have been measured at different temperatures. At concentrations below than CMC application of Kohlrausch's model show abnormal relationships for all surfactants and application of Lee-Wheaton equation cannot proceed. While, at concentrations over CMC, Lee-Wheaton model is applicable with no logical results. It was concluded that Lee-Wheaton equation does not recognizes the formation of micelles and care should be taken for treating self assembly compounds using this equation.
  Physical Chemistry: An Indian Journal. 01/2011; 6(3).
• Article: The Role of Organic Additives in Changing the Sign of Standard Enthalpy of Micellization

  Rabah A. Khalil, Alaa M. Hashim
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  ABSTRACT: The phenomenon of changing the sign of standard enthalpy of micellization ( ) from negative to positive for anionic surfactant [sodium dodecyl sulfate (SDS)]; due to presence of hydrocortisone acetate (HA) as an additive has been recently detected by Khalil and Hassan (J. Dispersion Science & Technology, 31:1195–1201, 2010). No such observation for cationic cetyltrimethylammonium bromide (CTAB) surfactant has been noticed by those authors. The reason for this phenomenon has been doubtfully attributed to the hydrogen bond between anionic polar head group of SDS with hydrogen of HA hydroxyl group. In order to investigate a certain reason for this problem, the effect of four organic additives (methyl salicylate (MS), benzene, toluene and cyclohexane) on the critical micelle concentration (CMC) of SDS and CTAB has been examined. The results exhibit that the effect of the presented additives on the sign of was in a similar manner to that of HA. It was concluded that the hydrophobic effect through iceberg formation which resulted from the presence of hydrophobic additives plays a major role in changing the sign of and increasing the CMC of both anionic and cationic surfactants. CTAB surfactant does not show such changes in the sign of which attributed to competitive between the hydrophobic effect with its high tendency towards forming micelle in contrast with that of SDS.
  Physical Chemistry: An Indian Journal. 01/2011; 6(3).
• Article: Exploration for micelles driving force from determination of critical micelle concentration of ionic surfactants in presence of hydrocortisone acetate

  Rabah A. Khalil, Mohammad Q. Hassan
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  ABSTRACT: It is well known that the hydrophobic group of surfactants is the main driving force for forming micelles. Chemists some times suspect by this phenomenon and, therefore, it requires further confirmations. The hydrophobic characteristics of hydrocortisone acetate (HA) may aid for understanding the latter phenomenon when use it as an additive in determinations of critical micelle concentrations (CMC) of surfactants. The effect of HA as an additive on the CMCs of anionic (sodium dodecyl sulfate, SDS, and cationic cetyltrimethylammonium bromide, CTAB) surfactants at different pH and temperatures using electrical conductivity has been investigated. It was found that the CMCs of anionic and cationic surfactants increased with increasing HA concentration at their natural media. This phenomenon is opposite to that found in the recent investigations using polar amino substituents as additives. Interestingly, it has been found that the presence of HA changes the negative sign of standard enthalpy of micellization (DH°) of anionic SDS to positive. It has been concluded that the addition of HA causes unfavorable factor for micellar formation and the hydrophobic interactions should not be considered as the main driving force for micellization process. © Taylor & Francis Group, LLC.
  Journal of Dispersion Science and Technology 01/2010; 31:1195. · 0.56 Impact Factor
• Article: Micellar catalysis in reactions of some β-lactam antibiotics with p -dimethylaminobenzaldehyde

  Rabah A. Khalil, Rawya Z. Al-Khayat
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  ABSTRACT: Kinetic study of the reactions of amoxicillin (I), ampicillin (II) and cephlaxin (III) with p-dimethylaminobenzaldehyde (DAB) in weakly acidic EtOH/H2O solution has been investigated using spectrophotometric method. Relatively slow reversible reactions of first order with respect to the antibiotic have been found. A derived equation for detecting the existence of reversibility from the linearity has been introduced. The effect of anionic surfactants (sodium dodecyl sulfate, SDS) on the kinetic of these reactions in aqueous solution has been studied. The presence of 0.005 M of SDS increases the rate constants by 4.3, 2 and 3.3 times for I, II and III, respectively. The consequence of the rate constants have a similar order in absence and presence of SDS; III > II > I. The rate constants pass through maxima with increasing SDS concentration followed by a gradual but steady decrease in the rate as the surfactant concentration increases further. Multiple linear regression method has been performed to evaluate the binding constants of each drug and DAB with SDS from the resulted kinetic data. The results suggest using multiple linear correlation method for such calculations, which is more accurate, reliable and less time consuming. The calculated binding constants between these drugs with SDS are following the consequence I > II > III which is related to the differences in their substitutions. The kinetic results were employed for spectrophotometric microdetermination of these drugs (I–III) in aqueous solution. The method was based on the reaction of β-lactam with an excess of DAB in presence of SDS and HCl (pH 2) at a wavelength 410 nm. The results indicate that the presented method is simple, precise and accurate. This method is applied to bulk antibiotics and some of their pharmaceutical preparations.
  Physics and Chemistry of Liquids 02/2008; 46(1):34-46. · 0.60 Impact Factor