By Okonkwo, NA; Onuchukwu, AI; Ikeh, OA; Anarado, IL; Ejidike, LC (2024). Greener Journal of Physical Sciences, 10(1): 1-16.
Return to Issue
Full text – PDF
Full text – HTML
Full text – EPUB
Table of Contents
Greener Journal of Physical Sciences
Vol. 10(1), pp. 1-16, 2024
ISSN: 2276-7851
Copyright ©2024, Creative Commons Attribution 4.0 International.
https://gjournals.org/GJPS
1 Department of Industrial Chemistry, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria, West Africa.
2 Department of Pure and Industrial Chemistry, Chukwuemeka Odumegwu Ojukwu University, Uli Campus, Anambra State, Nigeria, West Africa.
Article No.: 032024038
Type: Research
Full Text: PDF, PHP, HTML, EPUB, MP3
Surface tension is the tendency of a liquid to resist surface penetration. The values of the surface tension of Ethane-1, 2-diol, 2-Aminoethan-1-o1 and Ethane-1, 2-diamine were determined in this work by the capillary-liquid rise method in aqueous solution as the solvent. The values of the surface excess concentration were obtained by plotting the changes of surface tension with concentrations of these surfactants. This work is meant to assess the film coverage of these surfactants from the values of the surface concentration. The values of the surface tensions of these surfactants showed the order Ethane-1,3-diol (52,60,48, 70, 43, 10, 37.05 and 32.35 Nm-1) < 2-Aminoethan-1ol (59.50, 55.15, 52.60, 48.50 and 44.40 Nm-1) < Ethane -1,2 –diamine (66.40, 62.25, 59.91. 57.76 and 54.31 Nm-1). Thus, the positive values of the surface excess concentration, Гi (mole/m2) obtained from these changes in the values of surface tension, dγ with respect to changes in concentrations, dC (mole/m2) from the relation: Гi (mole/m2) –(1/RT dy/dc) in water as a solvent indicated that the values of dy/dc were of negative values which implied that (i) these surfactants were miscible with water in all concentrations and (ii) the molecules of the surfactants deposited substantially more on the air/water interface than within the bulk solution. These interactions between the surfactant in each case with air/water interface reduced drastically the surface tension of water. Further elucidation of the results herein showed that this occlusion of the air/solution interface by these surfactants produced a considerable decrease in the surface tension with increase in surface excess concentration in the order; Ethane -1, 2-diol (16.2 x 10-2) > 2-Aminoethan-1-ol (12.33 x 10-2) > Ethane -1,2-diamine (8.28 x 10-2). The findings based on the occlusion of the air/solution interface by the surfactants elicit interest for their use as surface-active suppressants against the volatility of perfumes in pyrogen-free water in perfume industry. In this work, these amphiphilic surfactants have proven to be more effective as suppressants than the previously used mono-alcohols.
Published: 08/04/2024
Okonkwo, N.A.
E-mail: na.okonkwo@ unizik.edu.ng
Phone: +2348069162912, +2348130530583
Keywords: Surface tension, surfactants, surface excess concentration, interface, bulk, Ethane-1, 2-diol, 2-Aminothan-1-ol, Ethane-1, 2-diamine.
Liquid surfaces tend to contract inwards, manifesting either an invisible surface film or as if an invisible membrane is covering the liquid surface [1,2]. This surface film phenomenon is exhibited by all liquids in their natural forms. This surface film or an invisible surface membrane resists surface penetration into a liquid. In consequence, this surface film by its resistance to surface penetration exhibits the flotation of most substances on liquid surfaces such as hydrophobic dust, foils, pollen grain, etc. Thus, the manifestation of this surface film formation by a liquid that resists surface penetration is termed surface tension [3,4,17] with the symbol γ Nm-1 and is further elucidated here under.
These forces that manifest as surface tension on liquid surfaces resisting surface penetration may be explained by considering a vessel (beaker) containing water as shown in Figure 1. By considering a molecule of water at the position “B” with radial forces acting and maintaining the molecule at a static equilibrium of the molecule at “B”, the forces acting on the molecule “B” in the bulk are equal in all directions and therefore maintaining a static equilibrium of the molecule at “B”. However, let us consider the molecule in position “A” at the water/air interface. The molecule at “A” requires an upward force to balance the force pulling it inwards [11].
Therefore, the surface tension phenomenon of inward pull of the molecules of a liquid, is responsible for the following: (i) the spherical shape of falling liquid droplets, such as observed with rain water droplets (ii) spherical shape of mercury resting on a flat surface (iii) rise of liquids in capillary tubes and (iv) flotation of foils or powdery grains on liquid surfaces [10].
Figure 1: An assembly illustrating the phenomenon of surface tension by the forces acting on the molecules at the water surface “A” and within the bulk “B” in a beaker.
Surface tension may be considered as the tendency of a liquid to reduce its surface to a minimum surface energy in order to attain a stable surface equilibrium.
The surface tensions of liquid metals and molten salts are large in comparison with those of organic liquids.
Surface tension can be defined as the amount of energy required to expand the surface of a liquid by unit area, and which can be measured in Joules per square metre or Newton per metre .The assessment of surface tension of a liquid can be studied and evaluated by the following techniques; (1) Principle of Liquid Rise in a Capillary (2) Principle of Liquid Drop (3) Liquid Fall in a Capillary (4) Moving Boundary Film Assessment. In this work, the principle of liquid rise is the method of interest.
Principle of Liquid Rise
The principle of liquid rise can be achieved by using the Capillary Rise Method. The Latin word “capilla” means “hair”. The capillary rise phenomenon is not only the basis for an absolute and accurate means of measuring surface tension, but also one of the reliable and easy assessment of surface tension. The phenomenon accounts for the general tendency of wetting the pores and fine cracks. The absorption of vapour by porous solids to fill their capillary channels and the displacement of oil by gas or water in petroleum formations are specific examples of capillary effects. The water wetting of fabrics is a direct application of capillary effects. Fabrics are porous materials, the spaces between them amounting to small capillary pores [12,13].
The principle of the capillary rise involves the use of a clean glass tube which dips and stands vertically in a liquid which rises in the tube with a radius “r” to a level “h” much above the same liquid in a containing vessel as shown in Figure 2.
Capillarity is concerned with interfaces that are sufficiently mobile to assume an equilibrium shape, e.g. meniscuses and drops formed by liquids in air or in another liquid and thin films such as that forming a soap bubble. Capillarity occupies a place in the general framework of thermodynamics, since it deals with the macroscopic and statistical behaviour of interfaces rather than with the details of their molecular structure [15,16].
Figure 2: An Assembly for the study of liquid rise, h, in the capillary tube of water.
The liquid rise is due to the force of surface tension, Fs, against the downward force of gravity, Fg, such that at level “h”, the rise, these forces are at equilibrium by the expression:
Fs = Fg (1.1)
This upward force of surface tension acts along the periphery of the cylindrical bore with a contact angle, ϴ, between the liquid and the capillary glass wall [10]].
By considering the force of surface tension, γ, with ϴ as the contact angle, we have the expression:
Fs = 2nry cos ϴ (1.2)
Similarly, the force of gravity, Fg from the column of the liquid of height, h, is represented by:
Fg = nr2hpg (1.3)
where p and g are the density of the liquid and acceleration due to gravity, respectively. Since these forces are at equilibrium, then
2nry cos ϴ = nr2hpg (1.4)
On further simplification of equation (1.4) with γ as the subject of the formula, the expression becomes:
(1.5)
Also, by further consideration of equation (1.4), with the height “h” attained by the liquid rise as the subject of the expression:
(1.6)
Equation (1.6) provides the simple evaluation of γ by the plot h versus 1/r to obtain the slope of the profile as shown
(1.7)
In the case of water, the liquid rise wets the capillary tube and assuming that ϴ = 00, therefore,
cos ϴ = 1 as ϴ 00
Factors Affecting Surface Tension
The magnitude of surface tension is affected by many factors which either decrease its effects or in limited cases improve on its effects on liquid surfaces. These factors are: (i) Temperature (ii) Solute (iii) Contact angle (iv) Films (v) Miscelles formation.
Effects of Contact Angle, ϴ of a Liquid
The contact angle, ϴ , which liquids make with surfaces has greatest significance towards the preparation of the liquid on surfaces. Apart from its values, the influence of contact angle determines the degree of wetting of the said liquid on the surface and the extent of spreading.
The contact angle, ϴ, of a liquid is that angle that a liquid makes between the surface of a solid and the liquid. The liquid makes this contact angle with the tube and the value of that determines the extent of rise in the tube. The ultimate rise of a liquid means that the force of adhesion must be greater than the force of cohesion. By this phenomenon, the wetting of a liquid gives a tendency for the spreading of the liquid on the solid surface.
Wetting of Liquid on Surface
Generally, wetting occurs when the mutual attraction between the molecules of the solid and the molecules of the liquid is stronger than the forces of cohesion within the molecules of the liquid. This principle is often described with the range of contact, ϴ0 < ϴ < 900. Therefore, within this range of ϴ the liquid wets the surface of either a solid/liquid or liquid/liquid surface.
Non-Wetting of Liquid on Surface
In the same token, non-wetting occurs when the mutual attraction between the molecules of the liquid is stronger than that between them and the molecules of the solid surface. Again, with respect to the values of contact angle, the range 900> ϴ<1800 indicates that the liquid will not wet the surface.
Surfactants
These are surface-active agents that act between two phases [5,6,11,18]. They can be grouped as either soaps or detergents which are active at the space between hydrocarbon (hydrophobic) and hydrophilic phases. A detergent acts at the interface, and modifies the surface tension by lowering it.
Some compounds while in an aqueous solution have the whole of them m inside the solution, i.e. both their hydrophilic and hydrophobic parts or ends are well within the aqueous solvent, e.g. strong electrolytes, sugar, glucose, sucrose, aminobenzoic acids. Some other compounds have their hydrophobic end – CH2 – CH2 – on the surface of the aqueous solvent, e.g. inorganic salts and organic acids of low molecular mass, their hydrophilic ends (-OH) are very much inside the solvent. These are the surfactants such as soaps and detergents. Also, an organic compound such as amphiphilic surfactant with two hydrophobic ends and hydrophilic middle atom e.g. 2-Aminoethan-1-o1 (NH2-CH2 CH2-OH) anchors on the liquid or solvent. These surface-active and surface-inactive substances produce varying effects on the surface tension of liquids as follows:
Case I increase the surface tension with an increase in the concentration of the solute such as sugar, glucose, etc in Figure 1.6. Case II decreases fairly the surface tension with an increase in the concentration of the solute, while Case III decreases the surface tension the more with an increase in the concentration of the solute such as soaps and detergents.
Figure 3 below is a graph that illustrates the three different cases I, II and III describes various behaviour of solutes.
Fig. 3: The variation of surface tension with types of solute concentrations, for surface-inactive, I, fairly active, II, and surfactants, III.
The surface tension of aqueous solutions is generally close to that of pure water if the solutes are salts such as NaCI or sucrose and other substances that do not preferentially collect at the air-water interface. On the other hand, a dramatic decrease in surface tension can result if the dissolved substance is a fatty acid or a lipid. These molecules consist of two regions: at one end, a polar group such as – COOH, which is hydrophilic (water-liking) at the other end, A long hydrocarbon chain that is non-polar and is therefore hydrophobic (water-hating). The non-polar groups tend to line up together along the surface of water with the polar group pointing towards the interior of the solution. Consequently, surface tension decreases. Any substance that causes a reduction in surface tension in this manner is called a “surfactant” [7,8,9,14].
The surface tension, or the surface free energy, is just (dG/dA)T.P; where A is the surface area. Substances that lower the surface tension also lower the free energy of the surface; they preferentially migrate to the surface. Thus, substances that lower the surface tension concentrate at the surface, and give large decreases in surface tension, but substances that raise the surface tension avoid surface and give only small increase in surface tension. The quantitative expression for this is called the Gibbs Adsorption Isotherm:
Γ = -1 dγ/RT dlna
R = -1 dγ/RT dInc (1.8)
where;
R = adsorption (excess concentration) of solute at the surface, mol m-2
Γ = Surface tension, Nm-1
R = gas constant = 8.314k-1 mil-1
a = activity of solute in bulk solution
c = concentration of solute in bulk solution (any unit can be used).
The sign of the excess surface concentration, Г, is opposite to the sign of the change of the surface tension with concentration (or activity) of solute in the solution.
Chemical and Reagents
Chemical
The only solid chemical used in this work was sodium hydroxide pellets which were sourced locally and used to prepare 2.5 molar solution with distilled water. This stock solution was stored in 5L Winchester bottle for use in the cleaning of the capillary tubes, rinsed in distilled water and dried in an oven at 105o prior to use.
Reagents
The underlisted organic reagents were commercially sourced from the local chemical vendors at Ogbete main market, Enugu; Ethane 1, 2-diol, 2-Aminoethan-1-1, Ethane – 1, 2 – diamine and
Distilled water (obtained from the laboratory).
Determination of the Physical Properties of the Reagents
The physical properties of the reagents (i) Refractive index (ii) Specific gravity (iii) appearance (iv) viscosity (v) Boiling point were determined.
Preparation of Solutions of the Reagents
The solutions used in this work were prepared from the reagents listed as follows:
Preparation of Various Concentrations of Ethane -1,2-diol
The various concentrations of Ethane-1-2-diol were prepared by pipetting volumes of 0.10,0.25, 0.45, 0.65 and 0.85ml into 25ml of distilled water in 50ml flat-bottom volumetric flask which was later made up to 1000ml to obtain the various concentrations of 7.20, 17.96, 32.32, 46.80, and 61.20 x 10-2 mole/litre respectively.
Preparation of Solutions of 2-Aminoethan -1-o1
Similarly, various concentrations of the reagent 2-Aminoethan-1-ol were prepared by pipetting the volumes (0.10, 0.25, 0.45, 0.65, and 0.85ml) of the reagent into 25ml of distilled water in a flat-bottom flask made to 100ml to obtain the concentrations: 6.64, 16.59, 29.86, 43.12 and 58.40 x 10-2 mole/litre respectively.
Preparation of Solutions of Ethane-1,2-diamine
The various volumes of Ethane -1, 3-diamien were pipette (0.10, 0.25, 0.45, 0.65 and 0.85 ml) into 25ml of distilled water and topped up to 1000 ml in a flat-bottom volumetric flask to obtain the varied concentrations: 6.00, 15.00, 26.16, 38.96 and 50.80 mole/litre respectively.
Determination of Liquid Rise in Capillary
The experimental measurements of various liquid rises in the various capillary tubes of specific radii (2.22, 2.86, 3.33, 4.00 and 5.30mm) were achieved using the capillary rise method assembly in Figure 3.1 for:
Distilled water as the blank
Various concentrations of ethane-1, 2-diol in distilled water
Various concentrations of 2-Aminoethan-1-ol in distilled water.
Various concentrations of Ethane -1, 2-diamine in distilled water.
These methods are described in details as follows:
Measurement of the Rise of Distilled Water in the Capillary
After pouring 25ml of distilled water into the petri-dish with a capillary tube of 2.22mm radius, the rise “h” up of the water in the capillary tube was allowed to attain the maximum height, h which was recorded from the bottom of the meniscus. The same process was repeated separately using capillary tubes of 2.86, 3.33, 4.00 and 5.30mm radii, and the liquid rise, h recorded for each radius of the capillary tube.
Measurement of the Rise of Various Concentration of Ethane-1, 2-diol, 2-Aminoethan-1-ol, and Ethane-1,2-diamine in Distilled Water, respectively.
After pouring an aqueous solution of 0.10ml ethane-1,2-diol dissolved in25ml of distilled water into the petri-dish with a capillary tube of 2.22mm radius, the rise “h” up to 0.10ml of Ethane-1,2-diol in 35ml of distilled water in the capillary tube was allowed to attain the maximum height h which was recorded at the bottom of the meniscus. The same process was repeated using capillary tubes of 2.86, 3.33, 4.00 and 5.30mm, liquid rise, h was recorded for each radius of the capillary tube.
The entire procedure was repeated using aqueous solutions of 0.25, 0.45, 0.65 and 0.85ml of ethane-1,2-diol, respectively, and the readings were recorded for each concentration.
Evaluation of the Values of Surface excess Concentrations, Гi
The values of the surface excess concentrations for the various organic reagents were obtained from the various experimental data on the surface tension variation with the concentrations of the organic reagents from the relation in equation (2.60) in section 2.9 as restated herein.
dγ = ГRTd In Ci
Evaluation of the Surface Pressure, ∏ of the Solutions
The effects of the concentrations of the organic reagents on the surface pressure of the solvent distilled water were also evaluated by obtaining the differences in the changes of the surface tension of the pure solvent (distilled water) and the distilled water/organic reagents of equation (2.34) of section 2.6 as restated herein:
שּ = γ solvent – γ solution.
Results of Variations of Water Rise as Blank
The variations of water rise as blank, h(mm) for the various radii, r x 10-1mm of the varied capillary tubes are shown in Table 4.4.
Table 4.4: The values of water (blank) rise in radii of capillary tubes
R
3.33
Results of Surface Tension of Water
A plot of the values of water rise, h, with the reciprocal of the radii of the capillary tube (1/r mm-1) is shown in Figure 4.1. The value of the slope indicates that surface tension of water (distilled water as blank) is obtained with the value 72.40Nm-1.
Figure 4.1: A plot of the capillary rise, h (mm) of distilled water for different capillary tubes of radii of range 2.22 – 5.30 x 10-1mm).
Figure 4.1 shows that the capillary rise, h (mm) of distilled water for different capillary tubes has a direct relationship with the reciprocal of the radii of capillary tube and is inversely proportional to the radii of capillary tubes.
Capillary Rise of Solutions of ethane – 1, 2-diol
The values of the capillary rise, h (mm) of aqueous solutions of Ethane – 1, 2-diol of various concentrations in capillary tubes of varying radii are shown in Table 4.5.
Table 4.5: The values of capillary rise, h (mm) of solutions of varied concentrations in mole/dm3 for the various radii of capillary tubes in aqueous solutions of Ethane-1, 2-diol at 30oC.
Conc. Of Solutions (mole/dm3)x 10-2
The plots of the capillary rise, h (mm) of various concentrations of Ethane – 1 , 2-diol for various radii are shown in Figure 4.2.
Figure 4.2: The profiles of the plots of the capillary rise, h (mm) of various concentrations in moles/dm3 of Ethane-1, 2-diol in aqueous solutions at 30oC for various radii of the capillary tubes.
Figure 4.2 shows that the capillary rise, h (mm) of ethane – 1, 2-diol at different concentrations for different capillary tubes has a direct relationship with the reciprocal of the radii of the capillary tubes and is inversely proportional to the radii of capillary tubes.
The plots of the capillary rise, h (mm) with varying concentrations of Ethane-1,2-diol at constant radius (0.33mm) are shown in Figure 4.3.
Figure 4.3: The plots of the variation of the capillary rise with concentration (C) in mole/dm3 of the solutions Ethane -1, 2-diol at 30oC at constant radius (0.33mm).
Figure 4.3 shows that the capillary rise has an inverse relationship with the various concentrations of Ethane-1, 2-diol at 30oC at constant radius (0.33mm).
4.5 Capillary Rise of Solutions of 2-Aminoethan -1-ol
The values of the capillary rise, h (mm) of aqueous solutions of 2-Aminoethan -1-ol of various concentrations in capillary tubes of varying radii are shown in Table 4.6.
Table 4.6: The values of capillary rise, h (mm) for various radii of the capillary tubes in concentrations (C) in mole/dm3 of 2-Amonoethan – 1-ol in aqueous solutions at 30oC.
Conc. Of solutions (mole/dm3) X 10-2
The plots of the capillary rise, h (mm) of various concentrations fo 2-Aminoethan-1-o; for various radii are shown in figure 4.4
Figure 4.4: The profiles of the plots of the capillary rise, h (mm) of various concentrations (C) in mole/dm3 of 2-Aminoethan-1-ol in aqueous solutions at 30oC for various radii of the capillary tubes.
Figure 4.4 shows that the concentrations for different capillary rise, h (mm) of 2-Aminoethan-1-ol at different concentrations for different capillary tubes has a direct relationship with the reciprocal of the radii of the capillary tubes and is inversely proportional to the radii of capillary tubes.
The plots of the capillary rise, h (mm) with varying concentrations of 2-Aminoethan-1-ol at constant radius (0.33mm) is shown in figure 4.5.
Figure 4.5: The plots of the variation of the capillary rise, h (mm) versus concentrations (C) in mole/dm3 of the solutions 2-Aminoethan-1-olin aqueous solution at 30oC at constant radius (0.33 mm).
Figure 4.5 shows that the capillary rise has an inverse relationship with the various concentrations of 2-Aminoethan-1-ol at 30oC at constant radius (0.33 mm).
Capillary Rise of Solutions of Ethane – 1, 2-diamine
The values of the capillary rise, h (mm) of aqueous solutions of Ethane – 1, 2-diamine of various concentrations in capillary tubes of varying radii are shown in Table 4.7.
Table 4.7: The values of capillary rise, h (mm) of varied concentrations (C) in mole/dm3 of Ethane-1, 2-diamine for different radii of the capillary tubes in aqueous solutions at 30oC.
The plots of the capillary rise, h (mm) of various concentrations of Ethane-1, 2-diamine for various radii are shown in figure 4.6.
Figure 4:6: The profiles of the plots of the capillary rise, h (mm) of various concentrations (C) in mole/dm3 of Ethane-1-2-diamine in aqueous solutions at 30oC.
Figure 4.6: shows that the capillary rise, h (mm) of Ethane-1, 2-diamine at different concentrations for different tubes has a direct relationship with the reciprocal of the radii of the capillary tubes and is inversely proportional to the radii of capillary tubes.
The plots of the capillary rise, h (mm) with varying concentrations of Ethane-1, 2-diamine at constant radii (0.33mm) are shown in figure 4.7.
Figure 4.7: The plots of the variations of the capillary rise, h (mm) versus concentrations (C) in mole/dm3 of Ethane-1, 2-diamine in an aqueous solution at 30oC at constant radius (0.33 mm).
Figure 4.7 shows that the capillary rise has an inverse relationship with the various concentrations of Ethane -1, 2-diamine at 30oC at constant radius (0.33 mm).
The comparative profiles of the capillary rise, h (mm) of varying concentrations of the surfactants ethane – 1, 2-diol, 2-Aminoethan -1-ol and ethane-1, 2-diamine at constant radius.
Figure 4.8: The comparative profiles of the variation of capillary rise, h (mm) with various concentrations of the surfactants, namely; ∆ Ethane – 1, 2 – diol, 2 – Aminoethan-1-ol and Ethane-1, 2-diamine in aqueous solution at 30oC at constant radius (0.33 mm).
The comparative profile shows that Ethane -1, 2-diol has the lowest rise, while Ethane -1, 2-diamine has the highest rise.
Changes in Surface Tension with Changes in Concentration of Ethane-1, 2-diol, 2-Aminoethan-1-ol and Ethane-1,2-diaminee.
The values of the surface tension, changes in surface tension, concentrations and changes in concentration for Ethane-1, 2-diol, 2-Aminoethan-1, 2-diamine, respectively.
The values of the surface tension and its changes as well as the concentrations and their changes for Ethane-1, 2-diol are shown in Table 4.8.
Table 4.8: The values of γ, dγ, (C) and d In C for Ethane -1, 2-diol.
Calculation
γH20 = 72.40 Nm
The values of the surface tension and its changes as well as the concentrations and their changes for 2-Aminoethan-1-ol are shown in table 4.9.
Table 4.0: The values of Y, dY, (C) and d ln C for 2-Aminoethan-1-ol.
-0.5727
The values of the surface tension and its changes as well as the concentrations and their changes for Ethane-1,2-diamine are shown in table 4.10.
Table 4.10: The values of Y, dy, (C) and dlnC for Ethane-1, 2-diamine
The comparative profiles of the changes in concentrations of the surfactants Ethane -1, 2-diol, 2-Aminoethan-1-o1 and Ethane-1, 2-diamine are shown in figure 4.9.
Figure: 4:9: The comparative profiles of the differences in surface tensions against the changes in concentrations of the surfactants, namely: Ethane – 1, 2-diol, 2-Aminoethan -1-o1 and Ethane -1, 2-diamin, in aqueous solutions.
The comparative profile of the changes in surface tension with changes in concentration of the surfactants show that Ethane -1, 2-diol has the highest while Ethane -1, 2-diamine has the lowest surface excess concentrations.
Calculation of the Surface Excess Concentration
The surface excess concentration, was calculated using the formula:
dy = ГRT dlnC
= ГRT
– r = -slope / RT
r = -slope / -RT
R = 8.314 Joules/mol/K
T = 25oC = 298k
RT = (8.314) (298k) – 207.85.
Ethane-1,2-diol
N/m
= 10.75
-0.32
= -33.59N/m
= 0.1616 mol/m2
= 16.20 x 10-2 mol/m2
2-Aminoethan-1-ol
=
= -25.65N/m
r = -25.63 / -207.85
= 0.1233 mol/m2
= 12.33 x 10-2 mol/m2
Ethane -1, 2-diamine
= 5.51
– 0.32
= -17.22N/m
r = – (17.22)
207.85
= 0.0828 mol/m2
= 8.28 x 10-2 mol/m2
The values of the surface excess concentration obtained for Ethane – 1,2 – diol, 2 – Aminoethan -1-o1 and Ethane -1, 2-diamine are shown in table 4.11.
Table 4.11: The values of the surface excess concentration for Ethane – 1, 2-diol, 2-Aminoethan -1-o1 and Ethane – 1, 2-diamine.
16.20 x 10-2
Surface coverage or occlusion is in the order: NH2-CH2-NH2<OH-CH2-CH2-NH2<OH-CH2-CH2-OH
Or
OH-CH2-CH2-OH>OH-CH2-CH2-NH2>NH2-CH2-CH2-NH
The purity of the reagents used in this research has been certified by the results in Tables 4.1, 4.2 and 4.3 which are in concordance with the commercial grade.
The results in table 4.4 show that the rise of water, h (mm), in the capillary tubes increases with a decrease in the radii of the capillary tubes. A plot of the values of h (mm) with the reciprocals of the radii, 1 (mm-1) of the capillary tubes is a straight line (Figure 4.1), the slope of which was utilized in equation (1.5) to obtain the surface tension, Y (Nm -1) of distilled water as blank with the value of 72.40Nm-1
The results in Tables 4,5, 4,6, and 4.7 show that the values of the capillary rise, h (mm) of varying concentrations, (C) in mole/dm3 of the surfactants: Ethane-1, 2-diol, 2-Aminoethan-1-ol and Ethane-1, 2-diamine in aqueous solutions are consistent with the characteristics of water, but this time with lower values of h (mm). The plots of the values of the capillary rise, h (mm) of various concentrations (C) in mole/dm3 of aqueous solutions of the surfactants with the reciprocals of the radius, 1 (mm-1) of the capillary tubes are straight lines (Figures 4.2, 4.4 and 4.6 respectively, the slopes of which were utilized in equation (1.5) to obtain the values of the surface tensions of Ethane-1, 2-diol (52.60,48.70, 43.10, 37.05 and 32.35 Nm-1), 2-Aminoethan-1-ol (59.50, 55,15, 52.60, 48.50 and 44.40Nm-1) and Ethane-1, 2-diamine (66.40, 62.25, 59.91, 57.76 and 54.31 Nm-1) respectively. The trend of the values of surface tension, Y (Nm-1) is observed from the results to be as follows: Ethane -1, 2-diol < 2-Aminoethan-1-ol < ethane-1, 3-diamine. The lower the surface tension seems to indicate that the surface coverage of ethane-1, 2-diol > 2-Aminoethan—1-ol > Ethane-1, 2-diamine.
Figures 4.3, 4.5 and 4.7 which depict the plots of the variations of h(mm) with the concentrations (C) in mole/dm3) of the solutions of Ethane-1, 2-diol, 2-Aminoethan-1-ol and Ethane-1, 2-diamine, respectively, at a constant radii (0.33 mm) confirm the effectiveness of these surfactants in the lowering of surface tension due to surface coverage. This is shown in Figure 4.8 which illustrates the comparative profiles of the variation of capillary rises, h, with various concentrations of the surfactants. The trend is as follows: Ethane-1, 3-diol < 2-Aminoethan-1-ol < Ethane-1, 2-diamine.
Using Tables 4.8, 4.9 and 4.10, the plots of the differences in the surface tensions (dṿ) with the differences in the logarithms of the concentrations (dlnC) were achieved, as illustrated in figure 4.9, for each of the three surfactants, with the trend Ethane-1, 2-diol > 2-Aminoethan-1-ol > Ethane- 1, 2-diamine. The slopes obtained were used to determine the values of the surface excess concentration, Г (mole/m2) of the surfactants according to equation (2.60). By their values, 16.20 x 10-2, 12.33 x 10-2, and 8.28 x 10-2 mole/m2 for Ethane-1, 2-diol, 2-Aminoethan-1-ol and Ethane-1, 2-diamine respectively, Г for Ethane-1, 2-diol > 2-Aminoethan-1-ol > Ethane 1, 2-diamine. This trend of the surface excess concentrations, Г (mole/m2) suggests a drastic lowering of surface tension of water by the same order of activity. Also, the efficacy of Ethane-1, 2-diol in a commanding lead as an effective amphiphilic surfactant among the groups such by its configuration remains longer at cis-configuration, while 2-Aminoethan-1-ol and ethane 1, 2-diamine remain much longer at trans-configuration. These preferences of geometric configuration stability of trans – and cis – suggest the effectiveness of surface coverage have been used herein to explain the effective surface coverage, and, in consequence, the lowering of surface tension by the large values of surface excess concentration of these amphiphilic surfactants.
In considering these surfactants, one can conclude that they are good where they can be used for minimizing the volatility of the perfume by anchoring on the surface of the solvent. In the case of detergents, they can be used to lower the surface tension of water to bring about the union between water and fabric. The surfactants ethane-1, 2-diol, 2-Aminoethan-1-ol and ethane-1, 2-diamine derived from organic compounds are found in this work to lower the surface tension of water by having their hydrophobic ends on water surface, thereby imparting a film which acts as a masking agent. Therefore, the findings of this work show that these surfactants have proven to be effective surface suppressants of volatile solutes in aqueous solution. These suppressants are used in perfume industry as well as agro-allied industries in their application as masking agents for insecticides, fungicides and other aerosols.
Atkins P.W, (2001), Elements of Physical Chemistry, Oxford University Press, 3rd edition, New York : 405-407.
Chang, R. (2002), Physical Chemistry, with Applications to Biological Systems, 3rd ed., Macmillan Publishing Company. Incorporation NY : 59-62.
Chataraj, D.K. Birdi, K.S., Kalder, K., Das, K.P. and Mitra, A. (2006). Surface activity coefficients of spread monolayaers of behenic acid salts at air-water interface. Adv. Colloid Interface Sci. 151: 123-126.
Engel, T. and Reid, P. (2005), Physical Chemistry, 3rd ed, Pearson NY U.S.A; pp. 182-184.
Holmberg. K., Jonsson, B., Kornberg. B. and Lindman, B. (2003), “Surfactants and Polymers in aqueous solution”, 2nd edition. John Wiley & Sons, Inc. New York.. 121-124.
Jean-Louis, S. (2002), “Surfactants types and uses, teaching aid in surfactant science and engineering in English, Version II, Merida-Venezuela.
Lu, J.R. Thomas, R.K. and Penfold, J. (2000). Adv. Colloid Interface sci. 84: 143-304.
Moroi, Y. Rusdi, M. and Kubo, I. (2004). J.Physic. Chem. B., 108: 6351-6358.
Moroi, Y. Yamabe, T. Shibata, O. and Abe, Y. (2000), Langmuir, 16: 9697-9698.
Onuchukwu, A. I. (2006), chemistry of surface and Colloid, Ambix Printers Nigeria, pp. 1-17.
Rosen, J.M. (2004), Surfactants and Interfacial Phenomena. 3 New York: Wiley.
Sharma, K.K. and Sharma L.K. (2004), A Textbook of Physical Chemistry, 4th Ed, Vikas Publishing House PVT Ltd New Delhi: 78-85.
Sharma, K.K. and Sharma L.K. (2004), A Textbook of Physical Chemistry, 4th Ed, Vikas Publishing House PVT Ltd : 605-606.
Silbey, R.J., Alberty, R.A, and Bawendi, M/G. (2006), Physical Chemistry, 4th ed. Wiley and sons Inc, India (New Delhi): 843.
Tharwat, F., F. Th, (2009). “Colloids in Agrochemicals”, Journal of Colloids and Interface Science. 5: 14.
Tincoco, I. (Jr.), Saver,K., Wang, J. And Puglisi, J.D. (2002). Physical Chemistry Principles and Applications in Biological Sciences, 3rd Ed; Pearson Education International New Jersey:.218-224.
Yamabe, T. Moroi, Y. Abe, Y. And Takahashi, T. (2000), Langmuir 16: 9754-9758.
Zdziennicka, A. and Janczuk. B. (2010). Behaviour of cationic surfactants and short chain alcohols in mixed surface layers at water-air and polymer-water interfaces with regard to polymer wettability. I. Adsorption at water-air interface. J. Colloid Interface sc. 349: 374-383.
Okonkwo, NA; Onuchukwu, AI; Ikeh, OA; Anarado, IL; Ejidike, LC (2024). A Study of the Surface Excess Concentrations of Some Surfactants in an Aqueous Medium. Greener Journal of Physical Sciences, 10(1): 1-16.
PDF VIEWER
Download [730.51 KB]
Your email address will not be published. Required fields are marked *
Comment *
Name *
Email *
Website
Save my name, email, and website in this browser for the next time I comment.
Post Comment
