The effect of nanoparticles on viscosity solution near the critical point

The effect of nanoparticles on viscosity solution near the critical point

B.Zh.Abdikarimov, A.Zh.Kurmangali

Currently, studies of the influence of external factors on the state of matter near a critical point remains an urgent task in the physics of the condensed state of matter. These studies are important for new areas of research in the field of energy, ecology and medicine, are intensively developing in connection with the unique properties of systems with the addition of charged particles, nanoparticles, which include systems with laponites.

The industrial use of nanocomposite membrane materials containing nanoclay as nanoscale components covers a wide range of tasks of rational nature management, the development of environmentally friendly, resource and energy-saving technologies, such as desalination of sea and salt water, ultrapure water, industrial waste processing, biotechnology, food industry separation of gas mixtures. The introduction of 2% to 5% of the nanocomponents during the formation of the nanocomposite material enhances the transport properties of the membranes, while also improving the mechanical properties, shape stability, increasing fire resistance, electrical conductivity, and stabilizing emulsions.

The relevance of experimental studies of the equilibrium and kinetic properties of condensed systems in the near-critical state is associated with their anomalously high susceptibility to the action of various factors and fields. The special extreme properties of the substance near the critical point is the reason for their successful practical use in the latest technologies.

In this work, we studied the effect of adding laponite nanoparticles to the kinetic characteristic — viscosity near the critical temperature of the separation of the isobutyric acid – water + KCl solution [ⁱ].

The critical viscosity equation was used in the calculations, taking into account the finiteness of the viscosity at the critical point. Theoretically, the final value of the critical viscosity, based on the classical theory of critical phenomena [ⁱⁱ], was first obtained in the work of M. Fixman [ⁱⁱⁱ], in which the author takes into account the spatial dispersion of the system near the CT ( ). Based on this approach, the critical viscosity equation was proposed in [^iv,^v], which also takes into account the spatial dispersion of the system. In these works, the fluctuation part of the viscosity in the vicinity of the critical point is represented as:

Here - is the amplitude of the singular part of the viscosity. Formula (1), which is in qualitative agreement with the Fixman calculations [3], provides the final shear viscosity in the CT. As can be seen, with t and an unlimited increase in the correlation radius ( ), the viscosity of the system at the critical point assumes the final value:.

Then, based on (10) - (11), we write the equation of full viscosity in the form:

This viscosity equation was previously tested in [5, ⁱ] when analyzing the viscosity behavior of a wide class of binary solutions and metal melts near the critical stratification temperature.

Earlier, the temperature dependences of the viscosity (Т) of an isobutyric acid-water solution (critical mass concentration of isobutyric acid in water , critical temperature  К ) and an isobutyric acid-water + KCl solution for 3 mass ion concentrations (х=0,07%; х=0,14%; х=0,3%) were studied using a capillary viscometer in the vicinity of the critical stratification temperature.

In these works, it was concluded that with an increase in the concentration of ions, the fluctuation part of the viscosity _f increases. This leads to an increase in the temperature region (T_f  =Т_к - Т_f (_f = 0)) of the manifestation of the fluctuation part of the viscosity.

The aim of this work was to establish the nature of the effect of the addition of laponite nanoparticles to the solution of isobutyric acid - water + KCl near the critical stratification temperature. For this, laponite nanoparticles with a mass concentration of 0.025% and 0.15% were alternately added to the investigated solution.

In this work, for the first time, experimental studies of the temperature dependence of the viscosity of a solution with the addition of laponitive nanoparticles near the critical temperature of separation are carried out. The experimental technique using the capillary viscometer method was similar to the experimental study of the temperature dependence of the solution viscosity [1] without the addition of laponites. The experimental results are shown in fig.1

Figure 1 - Temperature dependences of the viscosity of a solution of isobutyric acid-water + KCl (1), and a solution of isobutyric acid-water + KCl with the addition of laponite nanoparticles with a mass concentration of 0.025% (2) and 0.15% (3). Inclined dashed lines show regular parts of the viscosity. The vertical dashed lines show the increase in the temperature of the phase transition upon the addition of laponites.

When processing the obtained data, (T), fig. 1, the critical viscosity equation (1) was used. The value of the regular part of viscosity was initially calculated at temperatures far from the critical temperature (T  10 К), fig.2 In this temperature range, the parameters A and B of the regular part of the viscosity were found.

Figure 2 - Dependences of the logarithm of the viscosity of the solution isobutyric acid-water + KCl (1) and the solution of isobutyric acid-water + KCl with the addition of laponite nanoparticles with a mass concentration of 0.025% (2) and 0.15% (3) on the inverse temperature. The dashed straight line shows the regular parts of the viscosity.

Using these values of the regular part of the viscosity, according to formula (2), the fluctuation parts of the viscosity were calculated: _f =  – _r. The results are shown in Fig. 3.

Figure 3 - Temperature dependences of the fluctuation part of the viscosity of a solution of isobutyric acid-water + KCl (1) and a solution of isobutyric acid-water + KCl with the addition of laponite nanoparticles with a mass concentration of 0.025% (2) and 0.15% (3). The vertical dashed lines show the increase in the temperature of the phase transition upon the addition of laponites.

An analysis of the obtained temperature and concentration dependences of the fluctuation part of the viscosity allowed us to conclude that with an increase in the concentration of laponites, the fluctuation part of the viscosity _f increases. Based on the relationship between the fluctuation part of the shear viscosity and the correlation radius of the system, it can be concluded that the addition of laponites to the solution leads to an increase in the correlation radius of the solution.

Another manifestation of the effect of the addition of laponite nanoparticles is an insignificant (0.5 K and 1 K at concentrations of 0.025% and 0.15%, respectively) shift of the extrema of the fluctuation part of the viscosity towards higher temperatures. This indicates an increase in the phase transition temperature, and therefore, an increase in the forces of intermolecular interaction as a result of the addition of laponite nanoparticles.

The studies conducted in this work (Fig. 1. - 3.) of a solution with the addition of laponites are consistent with our earlier studies of the temperature dependence of the viscosity of solutions of isobutyric acid - water, isobutyric acid - water + KCl, methanol - hexane and methanol - hexane + KCl [1]. It also follows from these data that the addition of KCl ions to isobutyric acid – water and methanol – hexane solutions leads to an increase in the fluctuation part of the solution viscosity and phase transition temperature.

An analysis of the above experimental results (Figs. 1–3) of the effect of laponite nanoparticles on the behavior of the solution viscosity near the critical stratification temperature allows us to draw a number of conclusions:

1. The effect of the addition of laponite nanoparticles on the kinetic characteristic of solutions — the viscosity of the substance — has been experimentally studied. It was shown for the first time that the addition of laponite nanoparticles to a solution near the critical temperature of delamination leads to an increase in its viscosity.

2. The addition of laponite nanoparticles leads to an increase in the phase transition temperature and an increase in the forces of intermolecular interaction in solution.

3. The conclusions reached are consistent with the results of experimental studies of the viscosity of methanol-hexane, isobutyric acid-water solutions and with the addition of KCl ions to them near the critical stratification temperature.

Based on the direct relationship between the viscosity and the correlation radius of the system, it was concluded that the addition of laponites to the solution leads to an increase in the radius of correlation of the solution.

Literature

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