用直接还原含钛炉渣制备水滑石/二氧化钛复合材料的基础研究

In this project, TiO2 pigment and its by-product of MgSO4 and Al2(SO4)3 can be produced from the titanium slag obtained by direct reduction-electric furnace smelting processes by aid of NaOH molten salt. In order to utilize the mixture of MgSO4 and Al2(SO4)3, the by-product will be synthesized into hydrotalcite intermediate, moreover, to obtain high-value of product, a chemical method will be chosen to bond the above intermediate with TiO2 pigment. The hydrotalcite / titanium dioxide composite as a kind of TiO2 substitute can be used both as pigment and flame retardant. Based on the two important processes, this project will focus on purification of by-product and synthesis of hydrotalcite with regular size. To obtain the mechanism of crystal growth of hydrotalcite, the periodic structure, charge distribution, band structure and density of states (DOS) of hydrotalcite would be investigated by using molecular simulation method. The process of salt hydrolyzed and filmed on hydrotalcite as the bonding layer would be researched. Furthermore, the possible structure of coated layers on particle (hydrotalcite or TiO2) would be investigated through computer simulation and experimental results (XPS or Zeta potential). According to the binding energy of this absorbed model, the activity of the surface will be estimated. It will reveal the chemical activation mechanism. Finally, the structure of TiO2 – bonding layer – hydrotalcite will be researched based on experimental results and theoretical calculations, the study on dehydration of bonding layer will reveal the particle - particle coating conformation and mechanism at molecular level, therefore, product quality will be improved. This work would not only help to design and prepare the TiO2 substitute pigment products, but also provide a new method to use the titanium slag.

本项目以直接还原含钛炉渣制备钛白粉的主、副产品的高值化利用为目的，将副产品镁–铝硫酸盐混合物制成水滑石中间体，并通过化学手段实现水滑石/二氧化钛的粒–粒包覆，制备具有阻燃及颜料性能的钛白代用品。围绕合成中的两个关键过程，通过研究副产物的纯化及水滑石的成核/晶化过程，深入解析水滑石晶粒尺寸的调控机制，实现水滑石基底的可控合成，并借助分子模拟手段，揭示水滑石晶体生长的机理；通过研究盐类物质在水滑石及二氧化钛表面吸附水解–聚合成膜–脱水键连的过程，建立分子膜层吸附模型，确定水解物质在二氧化钛及水滑石表面的赋存形态，进而调控水解物质对颗粒表面活化程度，经脱水实现水滑石、二氧化钛颗粒间的稳定粘结，从分子层面揭示粒–粒包覆的形成机理，进而从宏观上调控产品性能，制备功能化的复合产品。项目为钛白代用品的设计、生产和创新提供理论和技术支撑，也为有效利用含钛炉渣副产品提供新思路。

本项目以直接还原含钛炉渣为原料制备了具有小粒径的偏钛酸中间体、白度较高的水滑石中间体、以及具有较好颜料性能的钛白/水滑石复合材料。钛白/水滑石复合材料的最佳制备条件为：金红石型钛白与水滑石的复合比例为7：3，加入的连接层Si(OH)4占总质量的3%（以SiO2计），硅水解pH值为8.2，可以得到白度为96.4%、消色力TCS=1490的复合产品；在生产TiO2的过程中，副产的镁-铝硫酸盐混合物可以重结晶的方法实现纯化，并进一步制备得到了具有较高白度（>96.3%）的水滑石中间体；分别采用调控Mg、Al浓度及在硫酸-盐酸混合体系下控制钛的水解实现了小粒径偏钛酸（< 1μm）的制备，为获得超细TiO2提供了条件，这将有利于TiO2处于粒-粒包覆的外层，提高复合材料的颜料性能。在制备水滑石的环节上，得到了镁铝浓度、尿素、pH值、以TiO2为成核中心对镁铝水解的影响，实现了水滑石粒径及形貌的调控；借助分子模拟手段，得到Mg/Al=2的水滑石层板对吸附层的吸附能力，单体吸附能Si(OH)4> Ti(OH)4(H2O)2> Al(OH)3(H2O)3，对于周期性的结构，吸附能Mg3(OH)6@Mg2Al(OH)6NO3 (LDHs-N) > Si2O3(OH)2@LDHs-N > Al2(OH)6@LDHs-N > Ti2O2(OH)4@LDHs-N。