The Surface Modification Of Brucite And The Determination Of Surface Free Energy

In the article it was summarized the methods and principles of the surface modification technology, so that the methods that suited brucite (main ingredient was magnesium hydroxide) surface treatment could be concluded for industry application. Furthermore, the surface modification effect of anion surfactant on brucite was also investigated. Based on the result above, the technology operation conditions were optimized, and the surface free energy determination methods were studied to evaluate the modification effect at the same time.Anion surfactant, which was one kind of surface active agents, was widely used in surface modification process for its cheap price and broad source. Anion surfactant was the ideal surface modification agent for brucite because the treatment process was quite convenient and the effect was outstanding. It can be devided into different categories according to the hydrophilic group such as carboxylic acid sort, phosphoric acid sort, sulfoacid sort, sulphuric acid sort. There were immense differences in modification effect among the four categories: the former two showed good effect on surface modified brucite while the latter two did not show visible effect. On the other side, it was found that the length of hydrophobic hydrocarbon chain in anion surfactant could affect the hydrophobic property of the final product: the more the number of carbon, the more hydrophobic property of the product. The agglomeration in the treatment could be avoided in some extent because of the adsorption by the surface modification agents.The technology operation conditions of the brucite surface modification were optimized: the optimum dosage of surface modifier was 0.3% mol percentage of the whole brucite amount; the optimum temperature was around 60-70 centigrade; the modificaition time was about 20 minutes; after surface treatment it was the filtration and drying process, the optimum drying temperature was 80 centigrade and the time was 60 minutes. Results showed that there existed physical and chemical adsorption effects of the surface modifier on brucite. Based on the technology optimization result the principle of the modification process could be further speculated.As the surface free energy could express the solid surface properties, it had practical meaning in the research. However, it had many difficulties in the determination of powder surface energy because the powder had no smooth and continuous surface. It was still on its primary phase to use contact angle method to determine the surface energy. In this article, contact angle method was used to measure the energy. After surface modification, the solid surface free energy was changed evidently for the anion surfactant adsorbbing on the brucite. This kind of change could be reflected by the concrete numerical value: anion surfactants with bad modification effect changed the surface energy little while carboxylic acid sort and phosphoric acid sort modifiers could change the surface energy of brucite a lot; with the increase of carbon number in anion surfactants, the surface energy of modified brucite powder was gradually declined. All of the conclusions were according to the existed results. Washburn equation could be probably used to calculate the powder contact angle, and the contact angle could be used to determine the solid surface free energy.