the Disadvantages of Adding Too Much or
Too Little Phosphoric Acid to Titanium Dioxide
During salt treatment, adding an appropriate amount of phosphoric acid or other salts can improve the whiteness and weather resistance of titanium dioxide, and make the particles soft and easy to crush, which can promote its transformation into anatase crystal form when producing anatase titanium dioxide And prevent the formation of rutile crystal form.
However, if too much phosphoric acid is added, the acidity of metatitanic acid in the kiln will increase, and desulfurization will be difficult, so that the calcination temperature for maximum decolorization power will be moved to a higher temperature, and the calcination temperature will be increased, so that the material will be processed at a higher temperature. Lower calcining sometimes produces sintering phenomenon, which not only wastes fuel, but also makes the calcined particles hard and difficult to crush, the whiteness and decolorizing power of titanium dioxide decrease, and the oil absorption increases.
If too little phosphoric acid is added, relatively increase the amount of potassium carbonate to reduce the acidity, which is beneficial to the desulfurization of the material at a lower temperature, so that the calcined particles are soft, the color is white, the decolorizing power is improved, and the oil absorption is reduced. Even due to the relative increase of potassium carbonate, even if it is calcined at a higher temperature, it will not lose its excellent pigment performance, because when calcined at a higher temperature, the particles of titanium dioxide are dense, which is conducive to improving the weather resistance of the product and reducing oil absorption. However, the amount of phosphoric acid is too small to convert all the iron into light yellow iron phosphate, and the unconverted iron will eventually appear as reddish-brown iron oxide, which cannot achieve the purpose of improving the whiteness of titanium dioxide.
