About Some Properties Of Highly Dispersive Oxide Of A Titanium (iv) And Adsorption On It
About some properties of highly dispersive oxide of a titanium (IV) and adsorption on it
A. M. Ukrainets, M. M. Soltys, V. D. Havryliv, M. M. Jatsyshyn,
I. E. Opaynych, R. Ja. Il\’chyna
Ivan Franko National University
Kyryla and Mefodija si. 8, 79005, L`viv, Ukraine
In this work the outcomes of research of an oxide surface of titanium of rutile modification and adsorption of Atlas G - 3300 (C12H25C6H4SO3Na) on it are submitted. For this purpose have been used TiO2 RCL-2 (corporation Du Pont, USA) with mean radius of fragments 0,23 microns.
Depending on pH of the medium change of a charge of a TiO2 surface can be presented by following equations:
The change of heats of watering TiO2 by aqueous solutions with different pH (1,5-11,5) has allowed to define area of a zero charge of a surface. The general enthalpy of watering in pH boundaries from 5,0 up to 5,6 is maximum and constant value. ΔH of formation of a double electrical sphere in this pH interval comes nearer to zero value.
The interesting outcomes are obtained at pH analysis and electrical conductivity (א) solutions of a water extract of TiO2, located in a contact to solutions of a different ion concentration of Hydrogenium. These data and values of a (ζ-potential at different pH of initial solution are indicated in the table. The minimum value of electrical conductivity is watched at pH=5,2. It corresponds to a zero charge of a surface TiO2. Near this pH point the value of an electrokinetic potential also passes through zero value, that is the inverse it from positive in negative area. The conducted researches uniquely determinate area of pH in which the recharge of a surface of titanium oxide implements (point of a zero charge).
pH of initial solution
pH of a water extract
א·103,Sm/m
ζ,mV
1,49
1,56
1331,0
+16,4
1,92
1,94
410,5
+45,5
2,54
2,68
86,3
+95,7
3,18
4,09
8,6
+145,5
3,39
4,25
7,2
+150,8
4,04
5,31
1,2
+117,4
4,62
6,30
0,7
+25,4
5,11
6,49
0,6
+17,5
5,61
6,75
0,9
-52,4
7,52
7,30
2,1
-121,7
9,56
7,48
3,0
-134,4
10,95
8,36
22,3
-80,1
11,49
8,97
29,2
-49,5
The isotherm of an adsorption of Atlas on TiO2 reflects composite ambiguous relation and consists of three segments:
– Up to CMC1=l,4 mmol/dm3, where the adsorption of separate molecules implements;
– Up to CMC2=6,2 mmol/dm3, where supermolecular formation (micelle) are adsorbed;
– After CMC2, where the adsorptive layer is reshaped by formations of more composite constitution.
At equilibrium concentrations of the Atlas, larger than 9 mmol/dm3, the isotherm leaves on a horizontal part, which corresponds to completion of formation of an adsorptive layer.
The area on a surface TiO2, applicable to one adsorbed molecule of the Atlas in before micellar area makes Sm=0,52 nm2. This value is greater, than average value of the area So=0,42 nm2, which responds one molecule at its different orientations on a surface.
The value S`M (area, which corresponds to one molecule of the Atlas located in an adsorbed micelle) after CMC1 is almost five times less, than SM. After CMC2 S`M decreases more essential.
The thermochemical researches of process of an adsorption of the Atlas are conducted also. Measured heats of adsorption demonstrate that at concentration of a surfactant 0,1÷0,5 g/dm3 the exothermal process is watched. At increase of Atlas concentration quantity of disengaged heat decreases sharply.
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