Research On The Surface Character Of The Solid Powder With The Contact Angle Method

The surface modification of powder has the key action for changing the capability of the material, and it is also a hot field in the modern material science. In the research on the surface modification, an important aspect is the estimation method of the effect of the surface modification. Many estimation methods have been applied, and the powder contact angle method was more intuitional and convenient. But we have a few reports on this way, and many problems will be still solved. The magnesia powder has the broad use in the material industry. The magnesia surface was modified with the sodium stearate, and then the wet degree on the powder surface was changed. Based on the mentioned investigations, the powder contact angle method has been studied in estimating the modified effect, the surface character on the powder and the surface character on the sediment of Chang Jiang River in this article. The research work could be divided into the following six parts.1. The preparation of the modified magnesia powder. We chose the sodium stearate to modify the magnesia powder, and then in the fixed condition of the definite solid/liquor ratio, reviewed the modified time, the pH value of solution and temperature for the influence of the modified effect. Finally we found the optimum condition. In this condition, we used different concentration of the sodium stearate to modify the magnesia powder, and then got a series of modified magnesia powder.2. The adsorption capability of the magnesia powder. Throngh the relation of Γ~ ce, we knew that the adsorption type was LS, and the sodium stearate brought the adsorption of two phases on the powder surface. We calculated the adsorption enthalpy of the stearate sodium on the powder surface with three different isotherms, and then knew that the adsorption was exothermic reaction and the high temperature was not helpful for the adsorption.3. The action of the adsorption kinetics. Through the adsorption kinetics curve of the sodium stearate, we knew that the adsorption was the first order reaction. Based on the experiment data and the kinetics theory, the adsorption of the stearate group ion on the powder surface had three phases: the movement of the stearate group ion from the noumenon solution to the solid-liquid interface, the stearate group ion through the solid-liquid interface, the adsorption of the stearate group ion on the powder surface. And in the experiment, the stirring speed was higher, so the adsorption process was dominated by the phase of the adsorption of the stearate group ion on the powder surface, and that was that the adsorption process was dominated by the particle diffusion.4. The character token of the magnesia and the modified magnesia powder. In the IR spectrum of the magnesia and the modified magnesia, we found the absorbability apexes of the magnesia and the sodium stearate. They showed that the sodium stearate was on the magnesia surface and the intensity of the absorbability increased with the sodium stearate concentration increases. In addition, The IEP of the magnesia powder was determined with the JS94G+ electrophoresis meter. The result was that the IEP of the magnesia was 12.2 and the IEP of the modified magnesia was 10.9. When we compared the data of two kinds of magnesia, we found that the IEP of the magnesia moved with the tendency of the acidity. It approved that the sodium stearate was on the magnesia surface.5. The estimation of the effect of the modified magnesia. We had used JF99A contact angle meter to measure the contact angle of the magnesia and the modified magnesia powder. And then we got the relation of the contact angle of the modified magnesia powder with the balance concentration of the sodium stearate. This also reflected the relation of the modified effect of the magnesia with the balance concentration of the sodium stearate. Based on the relation and the schedule modifiable demand, we can confirm the condition of the concentration of the modification reagent. So the contact angle method judging the modified effect of thepowder is more intuitional and convenient and it may be widely used in the modified effect of the powder.6. Measuring the surface free enthalpy change of the sediment of with contact angle method. The relative contact angles of various liquids such as deionized water, sodium chloride solution of mass fraction 0.05, ethanol and ethanol-water solution of volume fraction 0.15 on the sediment surface of Chang Jiang River were measured by the JF99A contact angle meter. The surface free enthalpy change was received from the relative contact angle of the sediment. The data of the contact angle showed that the sequence of the contact angle was sodium chloride solution of mass fraction 0.05, deionized water, ethanol-water solution of volume fraction 0.15, ethanol, but the wetness capability of the sediment in the liquids was opposite. The data of the surface enthalpy change showed that in these liquids the wetness capability of the sediment without the contaminant was better than with the contaminant. The experiment showed that the surface free enthalpy change of the sediment was measured by the powder contact angle method could estimate the organic pollution degree on the sediment, and this method was quick and easy, so it was a kind of more perfect method.