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Marek Kosmulski

Publications and source records attributed to Marek Kosmulski.

At least 19 recordsLinked to original sources
PubMed2006

High ionic strength electrokinetics of melamine-formaldehyde latex.

The electrokinetic potential of melamine-formaldehyde latex at high ionic strengths was measured by means of two different instruments. The present study confirms that the zeta potentials in 1 M 1-1 electrolyte solutions can be as high as +/-20 mV. The IEP of latex at low ionic strengths was at pH 11. The increase in the electrolyte concentration induced a shift in the IEP to low pH for all studied salts, and this indicates specific adsorption of the anions. The magnitude of the shift depends chiefly on the nature of the anion and increases in the series Cl < NO(3) = Br < I, and the nature of the cation (Li, Na, K, Cs) plays a rather insignificant role.

Journal Article↗
PubMed2006

Numerical values of the electrokinetic potentials of anatase at high concentration of NaI.

The electrokinetic potential of anatase (titanium dioxide) in 0.3, 0.5, and 1 mol dm(-3) NaI was studied by means of AcoustoSizer 1, AcoustoSizer 2 and DT-1200. Different stirring modes were studied for DT-1200. The increase in the electrolyte concentration produced a shift in the IEP of anatase to higher pH, and for 1 mol dm(-3) NaI there was no IEP at all, and the electrokinetic potential was positive over the entire pH range. The shifts in the IEP observed by means of different instruments were qualitatively consistent. On the other hand, the numerical values of the electrokinetic potentials of anatase at high concentration of NaI at low pH obtained by means of Acoustosizer 2 were substantially higher than those obtained by means of DT-1200. The discrepancies in the numerical values of the electrokinetic potentials obtained by means of different instruments increase as the ionic strength increases. The procedure of correction for the electroacoustic signal of the electrolyte is probably the main source of the discrepancies between DT-1200 and Acoustosizer at high ionic strengths. The difference in the efficiency of mixing in different stirring modes plays rather insignificant role in the observed discrepancies.

Journal Article↗
PubMed2006

pH-dependent surface charging and points of zero charge. III. Update.

The recently published points of zero charge (PZC) of various materials are compiled to update previous compilations [M. Kosmulski, Chemical Properties of Material Surfaces, Dekker, New York, 2001; M. Kosmulski, J. Colloid Interface Sci. 253 (2002) 77; M. Kosmulski, J. Colloid Interface Sci. 275 (2004) 214]. The recent results corroborate the previously found PZC with a few exceptions. The PZC of alumina obtained from the second-harmonic generation response is substantially lower than the PZC obtained by means of standard methods, while for titania the difference is less significant. PZC of Tl2O3 at pH 7.9 was reported for the first time. A surprisingly insignificant temperature effect on the IEP of rutile was found. Recent model studies aimed at explanation of the effect of the nature of 1-1 electrolytes on the course of charging curves and of discrepancies in the PZC of different materials having the same chemical formula are summarized.

Journal Article↗
PubMed2005

The surface charging at low density of protonatable surface sites.

The point of zero charge (PZC) of a sparingly soluble metal oxide depends on the density of protonatable surface oxygen atoms. The shift in the PZC is due to protonation/deprotonation of water in the regions free of protonatable surface oxygen atoms originating from the solid. The PZC of alumina increases when the density of protonatable surface oxygen atoms increases. In contrast, the PZC of titania is rather insensitive to the density of protonatable surface oxygen atoms. In surfaces of many materials the regions free of protonatable surface oxygen atoms dominate. These materials have a PZC at pH about 4.

Journal Article↗
PubMed2004

High ionic strength electrokinetics.

The electrokinetic potentials at high ionic strengths can be measured by means of electroacoustic method. The reported values are surprisingly high: up to 25 mV in 1 mol dm(-3) 1:1 electrolyte solution. The IEP of metal oxides in concentrated solutions of 1:1 electrolytes shifts to substantially higher pH values with respect to the pristine value, although these electrolytes are inert at low concentration. The shift in the IEP is salt-specific, and it is correlated with the hard-soft character of the anion and of the cation.

Journal Article↗
PubMed2004

Electroacoustics in low-temperature ionic liquids.

Titanium dioxide was used as a model colloid to demonstrate the possibility of obtaining reliable values of the electrophoretic mobility in low-temperature ionic liquids. Mobilities as low as -0.98 +/- 0.16 x 10(-10) and -1.25 +/- 0.33 x 10(-10) m2 V(-1) s(-1) were found in dry and wet 1-butyl-3-methylimidazolium triflate, respectively. These values are lower by two orders of magnitude than typical mobilities in stable aqueous dispersions due to a high viscosity of the ionic liquids.

Journal Article↗
PubMed2004

pH-dependent surface charging and points of zero charge II. Update.

Recently published PZC (points of zero charge) of metal oxides and related materials are compiled to update the previous compilations (M. Kosmulski, Chemical Properties of Material Surfaces, Dekker, New York, 2001; J. Colloid Interface Sci. 253 (2002) 77). The electroacoustic method has been widely used; it has become a standard tool, and it has proved to produce IEP (isoelectric points) comparable with those obtained by means of classical electrokinetic methods. The recently published numerical values of PZC/IEP of various materials corroborate the old results, with one exception: the PZC of magnetite found at pH 8 is substantially higher than the values reported in the old literature. New approaches to the electrokinetics of sparingly soluble salts have recently been proposed; e.g., the hysteresis in electrokinetic curves of (nominally) BaTiO3 has been interpreted in terms of changes in the surface stoichiometry caused by leaching.

Journal Article↗
PubMed2004

Dilatometric study of the adsorption of heavy-metal cations on goethite.

The specific volumes of adsorption of Cd, Co, Cu, Ni, Pb, and Zn on goethite determined by means of the dilatometric method are 21, 32, 32, 31, 31, and 42 cm3/mol, respectively, and are independent of pH. The effect of NaCl (up to 0.5 mol dm(-3)) on the specific volume of adsorption is rather insignificant. The specific volume of precipitation of corresponding hydroxides (determined experimentally and calculated) is about 60 cm3/mol. Apparently, the adsorbed heavy-metal cations lose half of their hydration water. The adsorption constant decreases as the pressure increases, and the effect becomes significant at pressures of > 10(7) Pa, i.e., more than 1 km of water column.

Journal Article↗
PubMed2004

Morphology of synthetic goethite particles.

The specific surface area of synthetic goethite depends on the preparation: the Fe(III):OH ratio, the rate of base titration of Fe salt, and the temperature and time of crystallization. The crystals also have different morphologies as determined by SEM or TEM. Carbon coating is used to improve the quality of SEM images of nonconducting specimens. We show here that needle-like goethite particles become substantially thicker in the course of standard carbon coating, and the length-to-width ratio obtained for carbon-coated particles is lower than that for the original goethite particles. The morphology of the goethite particles was also studied by tapping mode AFM.

Journal Article↗
PubMed2003

Multilaboratory study of the shifts in the IEP of anatase at high ionic strengths.

The zeta-potentials of anatase at pH 2-11 in 0.1, 0.3, 0.5, and 1 moldm(-3) NaI were studied using the DT 1200 in three laboratories. At [NaI]=1 moldm(-3) the zeta-potentials were positive over the entire pH range. The previously observed tendency of the isoelectric point of anatase to shift to high pH at high ionic strength (M. Kosmulski, J.B. Rosenholm, J. Phys. Chem. 100 (1996) 11681) and the salt specificity of this effect were confirmed. The zeta-potentials obtained in different laboratories using DT 1200 are consistent within 3 mV.

Electrochemistry↗
PubMed2003

Synthesis and characterization of goethite and goethite-hematite composite: experimental study and literature survey.

Aging of synthetic goethite at 140 degrees C overnight leads to a composite material in which hematite is detectable by Mössbauer spectroscopy, but X-ray diffraction does not reveal any hematite peaks. The pristine point of zero charge (PZC) of synthetic goethite was found at pH 9.4 as the common intersection point of potentiometric titration curves at different ionic strengths and the isoelectric point (IEP). For the goethite-hematite composite, the common intersection point (pH 9.4), and the IEP (pH 8.8) do not match. The electrokinetic potential of goethite at ionic strengths up to 1 mol dm(-3) was determined. Unlike metal oxides, for which the electrokinetic potential is reversed to positive over the entire pH range at sufficiently high ionic strength, the IEP of goethite is rather insensitive to the ionic strength. A literature survey of published PZC/IEP values of iron oxides and hydroxides indicated that the average PZC/IEP does not depend on the degree of hydration (oxide or hydroxide). Our material showed a higher PZC and IEP than most published results. The present results confirm the allegation that electroacoustic measurements produce a higher IEP than the average IEP obtained by means of classical electrokinetic methods.

Journal Article↗
PubMed2003

Electrokinetic potentials of mineral oxides and calcium carbonate in artificial seawater.

Electroacoustic method was used to measure the zeta potentials of mineral oxides and calcium carbonate in artificial sea water (pH 8), and the following values were obtained: synthetic hematite: 0.87 mV; goethite: 1.01 mV; fumed silica: -3.56 mV; quartz: -1.38 mV; calcium carbonate: 1.91 mV. The absolute values of the zeta potentials obtained in the present study are substantially lower than the zeta potentials in seawater reported by other authors. Our results indicate that the effect of electrostatic repulsion in the interactions between the particles of these materials in seawater is negligible.

Acoustics↗
PubMed2002

The significance of the difference in the point of zero charge between rutile and anatase.

The points of zero charge (PZC) of titanium dioxide reported in the literature range from 2 to 8.9. A set of 138 PZC of titanium dioxide was used to explore the effect of the crystalline structure on the PZC. The average and median PZC at pH 5.6 and 5.8, respectively, was found when the entire data set was taken into account. The PZC of anatase (31 entries, average and median 5.9 and 6, respectively) is slightly higher than that of rutile (49 entries, average and median 5.4 and 5.5, respectively), and the difference between the polymorphs corresponds to half of a standard deviation in each set of PZC.

Journal Article↗
PubMed2002

The pH-dependent surface charging and the points of zero charge.

The recently published points of zero charge of metal oxides and related materials are compiled to update the previous compilation. The purity of materials is the most important factor responsible for discrepancies in the literature data. In contrast to the success of new spectroscopic methods in the studies of specific adsorption, the progress in studies of primary surface charging of oxides over recent years is less spectacular.

Journal Article↗
PubMed2002

Multiinstrument study of the electrophoretic mobility of quartz.

The electrophoretic mobility of quartz in 0.01 mol dm(-3) NaCl and NaNO3 over the pH range 2-8 was studied using five different commercial instruments. The mobilities over the pH range 4-8 were relatively consistent, but the mobilities over the pH range 2-4 and the position of the isoelectric point IEP varied from one instrument to another. This result suggests that the discrepancies in the apparent IEP of quartz (and other silicas) reported in the literature are due to the instrument artifacts.

Journal Article↗
PubMed2002

The specific adsorption of sodium cations on less common metal oxides at high ionic strengths.

Sodium cations adsorb specifically on metal oxides at high ionic strengths. This results in a shift in the isoelectric point (IEP) to higher pH values. When the critical concentration of electrolyte is exceeded there is no IEP at all and the electrokinetic potential is positive even at very high pH values. The critical NaI concentration is rather insensitive to the nature of the metal oxide (but silica behaves differently), and this suggests that the specific adsorption is chiefly due to ion-ion and ion-solvent interaction in solution. The experimental results obtained with indium and niobium oxides (critical concentrations of about 0.35 mol dm(-3)) confirmed this trend.

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