Preparation and formation mechanism of nano-iron oxide black pigment from blast furnace flue dust

摘要

A mixed solution of ferrous and ferric sulfate leached from blast furnace (BF) flue dust was used to prepare nanometer-sized iron oxide black pigment (Fe_3O_4, magnetite) by the co-precipitation method. The pH value played a very important role in affecting the color and particle size of Fe_3O_4 and the evolution of green rust in to Fe_3O_4 or FeOOH. The experimental conditions including the solution pH, the way of adding precipitant, volume of air and reaction time for the formation of nano-iron oxide black pigment were investigated carefully in order to determine the optimal ones. The color, morphology and particle size of as-prepared Fe_3O_4 pigment were characterized by means of a color measurement instrument, X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. The results showed that the obtained pigment had low average spectral reflectance (<4%), good oil absorption (～23%), high black intensity and narrow size distribution of 60-70 nm. Furthermore, the formation mechanism of Fe_3O_4 from the mixed solution of ferrous and ferric sulfate was discussed.