Wyniki wyszukiwania - BazTech

1

Thermoelastic surface properties of seawater in coastal areas of the Baltic Sea

Boniewicz-Szmyt K., Pogorzelski S. J.

Oceanologia

|

2016

|

No. 58 (1)

25--38

EN

Correlations and data for the thermoelastic surface properties of seawater were determined by means of surface tension-temperature and surface pressure-area isotherm measurements performed in Baltic Sea coastal waters (Gulf of Gdańsk, Poland). Thermodynamic surface parameters examined include: surface free energy-γ, entropy, enthalpy, surface specific heat of air-seawater (AW), air-crude oil (AO) and crude oil-seawater (OW) interfaces, and the surface elasticity was quantified in terms of complex viscoelasticity modules with relaxation times of the transition processes. The spatial and temporal evolution of the parameters differed significantly from the literature data for seawater since the effect of surface active substances of natural and municipal origin was likely to be present in these coastal waters. The seawater surface turned out to have the viscoelastic 2D character as well as other interfacial systems AO and OW where three crude oils in contact with the seawater were studied for comparison. The dilational elasticity modules were found to follow the sequence EAW > EOW > EAO. Composite oil lens-covered seawater exhibited a significant drop of E from EAW (crude oil free surface) even for low oil coverage fraction F0. The obtained surface and interfacial tension-temperature dependences allowed to correct the spreading coefficient (S = γAW − γAO − γOW) to the desired temperature range, for example. The latter parameter with the sea surface elasticity data allows one to test the modified model of crude oil spreading proposed by the authors (Boniewicz-Szmyt and Pogorzelski, 2008), for spreading kinetics phenomenon at the surface-tension regime.

2

Adsorption of natural surfactants present in sea waters at surfaces of minerals: contact angle measurements

Mazurek A., Pogorzelski S.J., Boniewicz-Szmyt K.

Oceanologia

|

2009

|

No. 51 (3)

377-403

EN

The wetting properties of solid mineral samples (by contact angles) in original surfactant-containing sea water (Gulf of Gdańsk, Baltic) were characterised under laboratory conditions on a large set (31 samples) of well-classified stones of diverse hydrophobicity using the sessile drop (ADSA-P approach), captive bubble and inclined plate methods. An experimental relation between the static contact angle θ_eq and stone density ρ was obtained in the form θ_eq = B-ρ+ C, where B = 12.23 š 0.92, C = - (19.17 š 0.77), and r2 = 0.92. The histogram of ?eq distribution for polished stone plates exhibited a multimodal feature indicating that the most abundant solid materials (hydrophilic in nature) have contact angles θ_eq = 7.2, 10.7, 15.7 and 19.2^(o), which appear to be applicable to unspecified field stones as well. The contact angle, a pH-dependent quantity, appears to be a sensitive measure of stone grain size, e.g. granite. The captive bubble method gives reproducible results in studies of porous and highly hydrophilic surfaces such as stones and wood. The authors consider the adsorption of natural sea water surfactants on stone surfaces to be the process responsible for contact angle hysteresis. In the model, an equation was derived for determining the solid surface free energy from the liquid's surface tension γ_LV it also enabled the advancing θ_A and receding θ_R contact angles of this liquid to be calculated. Measurements of contact angle hysteresis Δθ(=θ_A - θ_R) with surfactant-containing sea water and distilled water (reference) on the same stone surfaces allowed the film pressure ΔΠ (1.22 to 8.80 mJ m-2), solid surface free energy ??S (-17.03 to -23.61 mJ m-2) and work done by spreading ΔWS (-1.23 to -11.52 mJ m-2) to be determined. The variability in these parameters is attributed to autophobing, an effect operative on a solid surface covered with an adsorptive layer of surfactants. The wetting behaviour of solid particles is of great importance in numerous technological processes including froth flotation, demulgation, anti-foaming procedures and the coal industries. It is believed that the approach presented here and the examples of its application to common sea water/solid mineral systems could be successfully adapted to optimise several surfactant-mediated adsorption processes (see below) of practical value in natural water ecology.

3

Adsorptive properties of natural water surfactant films. Dead Vistula catchment water studies

Pogorzelski S. J., Kogut A. D.

Oceanologia

|

2003

|

No. 45 (3)

373-394

EN

The paper contains the results of natural film experiments carried out on inland waters in the Dead Vistula (Martwa Wisła) catchment area during 1999-2002 using the integrated Langmuir trough-Wilhelmy plate system, which "cuts out" an undisturbed film-covered area without any physicochemical sample processing. The static film parameters result from the generalized scaling procedures applied to the surface pressure-area isotherms. They appear to correspond well to observations of the film composition Alim, MW, Eisoth, film solubility and the miscibility of its components (via R, ΔSc and y factors), and surface concentration Πeq, Γeq. A novel approach is presented for the adsorption dynamics on the basis of the mixed kinetic-diffusion model and analyses of the dynamic surface pressure plots, which leads to the determination of the effective relative diffusion coefficient Deff / D and activation energy barrier Ea / RT. There is reason to believe that certain classes of film-forming components or "end-members" may dominate the static and dynamic surface properties. Some of these substances can be used as source-specific surface-active biomarkers to trace temporal and spatial changes due to environmental factors or the production of biological matter. The concept was tested for the Dead Vistula river and its tributaries. The results demonstrate that natural films are a complex mixture of biopolymeric molecules covering a wide range of solubilities, surface activities and molecular masses with an apparent structural film architecture. Such studies could lead to the development of film structure parameters - indicators of ecosystem quality and the state of the environment.

4

Static and dynamic properties of surfactant films on natural waters

Pogorzelski S.J., Kogut A. D.

Oceanologia

|

2001

|

No. 43 (2)

223-246

EN

The paper contains the results of natural surface film surface pressure - area experiments carried out in inland waters and shallow offshore regions of the Baltic and Mediterranean Seas during 1990-99 under calm water conditions using the Langmuir trough - Wilhelmy filter paper plate system, which "cuts out" an undisturbed film-covered sea area without any initial physico-chemical sample processing. The limiting specific area Alim (268–3157 A2/molecule-1) and mean molecular mass (0.65-9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Film structure signatures were derived from π– A isotherm hysteresis and application of the 2D polymer scaling theory. The stress-relaxation measurements revealed a two-step relaxation process at the interface with characteristic times τ1 (1.1–2.8) and τ2 (5.6-25.6) seconds suggesting the presence of diffusion-controlled and structural organization relaxation phenomena. The results demonstrate that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular mass with an apparent structural organization exhibiting a spatial and temporal variability.

5

Kinetics of marine surfactant adsorption at an air water interface. Baltic Sea studies

Pogorzelski S.J., Kogut A. D.

Oceanologia

|

2001

|

No. 43 (4)

389-404

EN

The paper contains the results of studies of natural surface film adsorption kinetics carried out in inland waters and in shallow offshore regions of the Baltic Sea during 2000-01 under calm sea conditions. The novel approach presented here for the adsorption dynamics is based on the mixed kinetic-diffusion model and analyses of the surface pressure-time plots at short (t →0) and long( t →∞) adsorption time intervals. Values of the effective relative diffusion coefficient Deff / D (= 0.008-0.607) and energy barrier for adsorption Ea / RT (= 0.49-7.10) agree well with the data reported for model non-ionic surfactant solutions of pre-cmc concentrations. Wind speed is one of the factors affecting the adsorption barrier via the increased surface pressure of the natural film exposed to wind shear stress (~ U102), and enters the relation Ea / RT = 1.70 U101/3.

6

Detection of micellar structures in oil-water-surfactant systems with a photoacoustic method

Pogorzelski S. J., Szurkowski J., Śliwiński A.

Archives of Acoustics

|

1999

|

Vol. 24, no. 3

319-330

EN

Model studies were performed with a layered system consisting of thin olive oil layers (25-250žm in thickness) spread over the water surface using a photoacoustic method. Significant variations in the signal phase and amplitude found out at the interfaces (air/oil and oil/water) as well as at a depth of 9-13žm beneath the oil surface point to the formation of organized clathrate molecular structures under the film-covered surfaces and micellar structures of surfactants if present in a bulk oil phase at an appropriate concentration (above CMC) and temperature (Krafft point). Such organized structures have different thermodynamic properties (like specific heat or thermal diffusivity, discussed in terms of classical thermodynamics of thin surface layers) that is supposed to affect the photoacoustic effect used for depth profiling.

7

The surface film effect on underwater noise of rain

Pogorzelski S. J.

Hydroacoustics

|

1997

|

Vol. 1

181--184

EN

The spectrum of rain noise shows a peak at 13.5 - 15kHz, stronger winds smear the peak. The spectral level (SL) at 15 kHz shows a linear dependence on the log of the rain rate with wind speed as a parameter. The presence of a monomolecular film on the sea surface results in a pronounced reduction of SL beneath the film by 10 log K. The damping ratio K is related to the viscoelastic properties, surface activity, concentration and diffusional coefficient of the surface-active substances composing the film.