Research On Preparation Of Chromium-based Pigment From Precursors And Influence Of Iron Contents

Chromium belongs to strategic metal,has important applications in many aspects.Chromium oxide is the main products in the salt industry.And pigment grade chromium oxide has good heat resistance,thermal stability and weather resistance,used for ceramics,pigments,military and other industries.In this study,a new approach was proposed which was the preparation of chromium oxide pigment from chromite.Including the precursor preparation of chromium oxide,clean separation of chromium and iron,controlling the content of metal heterozygotes in solution by selective adsorbent(SA).Meanwhile,the method of “combination membrane and hydrothermal approach” was used to prepare hydrated chromium oxide first time.And the mechanism in the experiment are analyzed,the specific contents are as follows:In the preparation of chromium hydroxide precursor,sodium chromate was used as raw material and synthesized by the combination of membrane and hydrothermal method.The influence of the presence of CO2 on the current efficiency,desalination efficiency and energy consumption in the pretreatment of sodium chromate solution by membrane method was investigated.The results show that CO2 can improve current efficiency,desalination efficiency,and reduce energy consumption.Combined with data analysis,the possible causes of this situation are analyzed.In the hydrothermal preparation of hydroxyl chromium oxide,combined with Thermogravimetric-Differential Thermal Analysis(TG-DTA),Scanning Electron Microscopy(SEM),Transmission Electron Microscopy(TEM)to characterize the morphology of hydroxyl chromium oxide,and puts forward the possible mechanism in the process of the formation of hydroxyl chromium oxide;X-ray diffraction(XRD)characterization shows hydroxy chromium oxide did not form obvious crystal structure;Fourier Transform Infrared Spectroscopy(FTIR)characterization of the surface active groups.The rich iron liquid used in this study for sulfuric acid leaching of chromite,and using the method of partial oxidation of low temperature hydrothermal fluid rich iron,chromium pretreatment,reached the preliminary separation of chromium and iron to.Then,SA was used as adsorbent to control the impurities such as iron ion in the solution.Study on the adsorption of iron ion by SA,the adsorption capacity could reach 15 mg/g.The removal rate could reach 98.7%.And the mechanism of SA adsorption of metal ions was analyzed,through the adsorption reaction kinetics,adsorption model of iron ion by SA.More in line with the two level dynamic model.The chromium oxide crystal can be formed by the process of complete dehydration and crystallization by using chromium hydroxide as precursor and calcination at high temperature.The combination of TG-DTA decomposition temperature analysis about 425 °C,and then through the different calcination temperature,XRD characterized,found higher calcination temperature had no effect on the crystal type of chromium oxide;chromium oxide of SEM,TEM,UV visible near infrared(UV-Vis-NIR)characterization results show that.The chromium oxide has good crystal nano size and good crystallinity,and has optical properties,the near-infrared absorption ability of different elements;when the content of iron containing chromium oxide in the characterization of XRD,SEM,UV-Vis-NIR,and that of iron are isomorphous replacement phenomenon in chromium oxide crystals,product and contains a certain amount of iron in the near infrared reflectance relative to the pure chrome oxide change.