Research On Preparation Of Micro-size Iron Oxide Red

Iron oxide red is an excellent pigment, which has fine qualities such as covering power, coloring power, heat resistance, resistance to solvent, acid fastness, innocuity and anti-rust. It is wildly used in the areas of coating, ink, plastic, spin, ceramic, art and cement. It can also be used in the fields of cosmetics, tape, food, adhesion agent, xerography and other fields.There has been more that thirty years since iron oxide red pigment is produced on industrial scales in china. However, compared with the same kind of product of abroad, its quality is obviously inferior. Aiming at solving the control of the particle distribution and media grain size in HNO₃-method industry, the paper has done some work as follows.The whole experiment process was divided into two parts: one is the preparation of crystal seed, the other is second oxidation process.The effect of reaction temperature, amount of acid, the flow of acid and reaction time on the yield of crystal seed has been studied. Raising temperature is favorable of the yield. We focus on reaction time, reaction temperature, ratio of V_acid/V_water on distribution of particle size and media grain size. The best process is that the reaction time is 4-6h, reaction temperature is 90-95 ℃ .The fine crystal seed, whose media grain size is about 50nm, is available.Second oxidation is the growth process of particles of a—Fe₂O₃, which grow up as the center of crystal seeds. The effect of reaction time, reaction temperature, flow of air, mole ratio of Fe(NO₃)₂/crystal seed on the distribution of particle size and media grain size has been studied. The mass transfer is reinforced between gas, liquid and solid according to enlargement of air flow. The concentration of crystal seed plays an important role on the cycle of the process. The lower is the concentration of crystal seed, the faster the particles grow up. The best process is that reaction temperature is 90-95℃, mole ratio of Fe(NO₃)₂/crystal seed is 12-16;pH is the token of second oxidation process. The reaction stops until pH reaches the end of point 4.2.The XRD, element-analysis and TG are applied in the study to explore the dark substance in the process. The substance is considered as cementile(Fe3C), which is not generated in this process.