The Study Of Properties And Technological Improvement Of Chromium Oxide Green

Chromium oxide green is a kind of important inorganic pigment. Chromium oxide green with corundum crystal structure has such characteristics as high thermal stability, high painted capacity, chemical corrosion-resisting capacity, etc. At present, in China, the produce of chromium oxide green has reached a certain scale, but there are still some disparities in the producing technology and product quality between home and abroad chromium oxide green. However, the essential factors which result in the disparities are reported scarcely. MinFeng Agricultural and Chemical Factory is one of the main manufacturers producing chromium oxide greens. How to improve the quality of chromium oxide greens and increase economic and environmental benefits as quickly as possible are the keys to our factory's development and prospect. So the researches have some apparent application values and theoretical significance.The pigmental properties of chromium oxide green have much relationship with its particles' structures, especially the crystal structures and cation-anion coordination structures, in which trivalent chrome(Cr3+) and the O2- ligands bonded to Cr3+ play main roles. Considering the structural properties of this basic unit and the electron distributing states is helpful to deeply identify the relation between it's structure and it's effect, and we can get beneficial information on how to improve the pigments' properties from it. To get full information about chromium oxide green we analyzed the properties, state and structure of standard chromium oxide green and several representative chromium oxide green samples from MFACF co. ltd. with several apparatus analysis such as X-ray diffraction analysis, IR spectrum analysis, UV-analysis, Atomic Absorption, EDS(energy dispersive spectroscope), Electron Microscope, TG and DTA analysis,laser partial size analysis, chroma and chromatism analysis, Liquid Chromatography and BET analysis, etc. At the same time, we calculated theoretically with ab initio calculation and compared some related results. It shows that the color property difference between the MFACF and Bayer samples mainly comes from the difference of its structures, especially the subtle changes of the parameter a direction , which will change the intensity of ligand field around chromium ion and lead to apparent changes of quantum transition around Fermi energy level consequently affects the hue-showing function of chromic ion. In addition, the impurities(such as Cr6+), granularity and the surface properties will also affect theproperties of chromium oxide green .On the basis of previous analysis, some advices are given to improve producing technics about chromium oxide green. For example, the crystal shape can be controlled and stabilized by controlling baked temperature scope and stabilizing heating-up program, adding plastic reagent, improving smashed method etc. We can also reduce the content of some bad impurities (such as Cr6+), adopt some after-processing working procedure, etc. At the same time we discussed the recycling of solid scrap produced by chromic acid anhydride workshop. From our experiments, we put forward a procedure that can reclaim chromium oxide green from the scrap. This procedure includes alkaline neutralization, filtration, water-washing, baking, smashing, etc. The procedure not only can improve the whole application of chrome resource but also can greatly alleviate environment pollutions and bring certain economic benefits.