(1) Collector
The research and application of flotation reagents for rare earth minerals can be divided into three stages.
The research and application of oleic acid collector is the first stage. Because the selectivity of oleic acid is not high, it can only be applied to ores with relatively simple mineral composition, and is mainly used for the flotation of fluorocarbon cerium ore.
The research and application of chelating agent hydroxamic acid collector is the second stage. It is a good collector for copper oxide minerals (malachite and silicon malachite), wolframite, perovskite, cassiterite, iron oxide, apatite, pyrochlore and rare earth minerals.
The third stage is the research and application of efficient and new collectors. One of the most important reasons is that it is difficult to separate these two minerals from the mixed rare earth concentrate of fluorocarbon cerite and monazite, because their density, specific magnetization coefficient, dielectric constant and floatability are very close. This is the case at the beginning of Bayan Obo rare earth ore in China.
At present, the collectors of rare earth minerals are mainly oleate, phosphonic acid or phosphonate, alkyl sulfonic acid, hydroxamic acid, 802, 804 and H894.
(2) Adjusting agent
Adjusting agents include activators for rare earth minerals, inhibitors for non-rare earth minerals (and pH adjusting agents).
Activator rare earth mineral activator is mainly sodium fluorosilicate, its main role has three: cleaning rare earth mineral surface oxidation pollution film and adhesion of slime, restore its pure surface, inhibit silicate minerals, enhance the rare earth mineral surface and collector activity.
Since the optimal flotation pH value of rare earth minerals is 8.5~9.5, the dissociation and hydrolysis of sodium fluosilicate at this time are carried out according to the following formula:
Many ions and molecules produced by the above reactions have inhibitory effects on quartz, feldspar and other silicate minerals.
Silicate minerals are the main minerals associated with rare earth minerals, and water glass is an effective inhibitor. It not only inhibits silicate minerals. And also inhibit rare earth minerals and iron minerals. However, in medium alkaline medium (pH = 8.0~9.5), the floatability of rare earth minerals is the highest, while the floatability of other minerals is poor, which can achieve effective inhibition. The main application indicators of water glass in the flotation of rare earth minerals are:
A. the content of active ingredients, that is, the total content of xNa2O and ySiO2, is generally 40% to 50%;
B. modulus, that is, m = SiO2/Na20 (rare earth flotation, m = 2.0~3.0.
(3) Foaming agent
When oleic acids and alkyl hydroxamic acids are used as collectors for rare earth minerals, they do not need to be added as foaming agents due to their strong foaming properties. With the application of new collectors H205 and H894, new, efficient, non-ionic surface active foaming agents, such as 210, J102, H103, etc., have emerged.
(1) Using NaCl to extract rare earths from ion-adsorbed ores is one of the main chemical beneficiation methods for treating this type of ore. The ore transported from the stope is sent to a rectangular cement pool for immersion. The leachate is discharged from the outlet through the filter layer at the bottom of the pool. The leachate is manually removed. The leachate is precipitated in saturated oxalic acid solution. After filtration, the filtrate is neutralized by lime and added with salt for reuse. The filter cake is rare earth oxalate, which is burned, washed and then burned to obtain mixed rare earth oxides. At present, the main problem of this process is that the leaching residue contains high NaCl, which causes soil salinization.
(2) Ammonium sulfate method with (NH4) 2SO4 from the ion adsorption of rare earth ore, is a successful method in recent years. The difference with NaCl method is that the ore is soaked with 1% ~ 2% (NH4)2 S04 solution, then precipitated with oxalic acid to obtain rare earth oxalate, and then the mixed rare earth oxide containing REO>90% can be obtained by burning again, and the filtrate is returned for reuse by adding ammonium sulfate. Compared with the NaCl method, the leaching residue does not cause soil salinization problems.