Investigation On New Process For Preparation Of Natural Iron Oxide Red Pigment By Deep Purification Of Specularite

Iron oxide pigments are colored inorganic pigments,and their use ranges across multiple industries.Iron oxide red is one of the commonly used ones.The commercially available iron red has the largest dosage and is mostly chemically synthesized.It has the advantages of high purity and good color,but it has a long production process,serious pollution and high cost.The natural iron oxide red has the advantages of simple production process,stable physical,chemical properties and low price.It is an ideal substitute for synthetic iron oxide red.The specularite has a simple ore structure and the same crystal structure as iron oxide red,so it is a high-quality raw material for preparing natural iron oxide red.This subject aims to develop a new process for preparing natural iron oxide red from specularite.The research contents of beneficiation and purification of specularite,ultra-fine grinding of concentrate,and surface modification of iron oxide red were mainly carried out.It provides a new way for the high value utilization of specularite and the performance optimization of iron red pigment.Main tasks as follows:(1)The rule of impurity removal and purification of specularite was systematically studied.The effects of grinding size and magnetic field intensity on the grade and recovery rate of concentrates were investigated.The effects of the dosage of reagents,pH and other conditions on the reverse floatation of specularite were analyzed.The feasibility of specularite selection,focusing on the influence of conditions such as feed concentration and speed.The results show that at a grinding size of-0.038 mm,which accounts for 93wt%,the feed concentration is 5wt%,the drum speed is 600 r/min,the amount of rinsing water is 2.15 L/min,and the rinsing time is 3 min.The double centrifugation can realize the deep purification of the specularite,and obtain a high-purity iron concentrate with an iron oxide purity of 99.11wt%and a recovery rate of 54.40%.(2)The effects of different grinding conditions on the particle size distribution of specularite were systematically studied,including ball milling time,mill speed,grinding concentration,and volume ratio of ball milling tanks.The results show that increasing the time and rotational speed,maintaining an appropriate concentration and volume ratio are beneficial to reduce the particle size.After comparison with the international standard of iron red and commercially available iron red,the physical and chemical indicators have reached the requirements,and the oil absorption value,matter soluble in water,and residue on sieve are better than those on the market.(3)The hue adjustment mechanism of iron oxide red products was investigated.Scanning electron microscopy,XRD,and UV-visible spectrophotometric analysis revealed that calcination for a certain period of time caused Fe2(SO4)3 to be converted to Fe2O3;Different calcination temperatures and sulfuric acid mass fractions change the reflection,refraction and absorption of light by affecting the particle size,thereby adjusting the hue;After calcination,the sample changed from irregular flake to oval structure.