矿物白度的影响因素与增白机理研究

Study on the influential factors and whitening mechanism of mineral whiteness

白度是矿物的重要光学性质之一。为了深化矿物的光学性质及白色矿物功能材料的研究与应用,根据测试分析结果和叶大年的结构光性矿物学理论,系统研究了影响矿物白度的主要因素,以及矿物增白效果的差异性及其产生机理。研究结果表明:(1)晶体化学是决定不同种类透明矿物白度的最主要因素,但对于某种透明矿物来说,影响其白度的主要因素是矿物中的碳质有机质、含铁钛矿物杂质、杂质元素的价态与晶体化学环境、介质环境、矿物中的水和粒度大小等。(2)证明了透明矿物白度大小与折射率呈正相关。白度相同的不同矿物的增白效果存在很大差异性,其根本原因是由矿物折射率所决定的反射率存在很大差别。(3)提出了真白度和假白度的概念,即主要由自色产生的白度称为真白度,主要由假色产生的白度称为假白度;真白度高的矿物具有增白作用,而真白度低的矿物,即使粉末白度高,也没有增白作用。(4)在影响矿物白度的主要因素中,矿物中的碳质有机质、含铁钛矿物杂质、杂质元素的价态等杂质成分对矿物白度和增白效果起负面作用。(5)矿物中与晶体结构相关的水所产生的颜色属于自色,脱去结晶水、层间水和结构水都有利于提高矿物的真白度或增白效果,但脱去沸石水的效果正好相反;由矿物粒度大小变化产生的颜色属于假色;通过降低粉体粒度大小所提高的白度属于假白度,由此增加的白度没有增白作用。另外,矿物粉体与使用介质之间的折射率大小差别越大,增白效果越明显。

Whiteness is one of the important optical properties of minerals. In order to deepen the research and application of the minerals’ optical properties and white mineral functional materials,based on the test results and Ye Danian’s theory of structural optical mineralogy,the main influential factors of mineral whiteness were systematically studied,as well as the differences in the whitening effects of minerals and its production mechanisms. The research showed that crystal chemistry is the most important factor in determining the whiteness of different transparent minerals,but for a certain kind of transparent minerals,carbonaceous organic matter,iron-titanium-containing mineral impurities,the valence states and the crystal-chemical environment of impurity elements,the medium used,the water in minerals,and the particle size of minerals are the main factors affecting the whiteness of the minerals. It is proved that the whiteness of transparent minerals is proportional to the refractive index. The whitening effect of different minerals with the same whiteness is very different. The fundamental reason is that the reflectivity determined by the refractive index of minerals is very different. And the concept of true whiteness and false whiteness is proposed. The whiteness mainly caused by idiochromatic color is called true whiteness,and the whiteness mainly caused by pseudochromatic color is called false whiteness. The white powder with high true whiteness has a whitening effect,while the mineral with low true whiteness has no whitening effect even if the whiteness of its powder is high. In the main factors that affect the whiteness of minerals,the carbonaceous organic matter,iron-titanium-containing mineral impurities and impurity element valence in minerals have the negative effects on the whiteness and whitening effect of minerals.The color caused by the water in mineral is idiochromatic,and the removal of crystal water,interlayer water and structural water in mineral is beneficial to increase the true whiteness and whitening effect of the mineral,but the effect of removing the zeolite water is just the opposite. The color produced by the variety of mineral particle size and the change of the particle size of the mineral belong to the pseudochromatic color. The whiteness increased by reducing the particle size of the powder is the false whiteness,and thus the increased whiteness has no whitening effect. In addition,the greater the differences exist in the refractive index between the mineral powder and the medium used,the more obvious the whitening effects will be.