Experiment and Application of Iron Ore Flotation Reagents

Based on the increasingly difficult selection of iron ore in China, the important position of flotation skills in iron ore beneficiation is highlighted, and the current research status and application of iron ore flotation reagents are discussed. The main points introduced the role of Chinese scholars in the research and development of cationic collectors, anionic collectors, and regulators, and reviewed new types of iron ore flotation reagents. Secondly, the primary process used in the flotation process of iron ore was described, highlighting the importance of reverse flotation technology in iron ore flotation. After analyzing the advantages and disadvantages of various flotation reagents, it is pointed out that the selectivity and low temperature resistance of advanced iron ore collectors, as well as strengthening the research and development of new regulators, are the directions for further research in the future.
Keywords anionic collector cationic collector regulator flotation process
China is a major producer of iron ore, with an annual output value of over one billion tons in recent years, which continues to increase. Due to the relatively low average grade of domestic ductile cast iron ore, which is less than half of the grade of iron ore in countries such as Brazil and Australia, and the continuous decline in grade, the production cost of iron ore concentrate is relatively high [1], and the dependence on iron ore imports is high. Although imported iron ore has good sources and stable quality, there are also drawbacks such as high volatility in pricing and high levels of harmful elements such as sulfur, phosphorus, and lead. In order to provide an excellent development environment for China’s steel industry, it is necessary to accelerate the research and development of domestic iron ore beneficiation skills, especially to strengthen the research and development of disorderly and difficult to beneficiate iron ore beneficiation skills, in order to reduce costs. Not only can it improve the inductive utilization rate of China’s iron ore, but it is also of great significance for the construction of China’s iron ore resources to ensure talent.
The embedded particle size of iron ore in China is fine and requires fine grinding to achieve monomer dissociation, which is conducive to sorting. Flotation is a commonly used mineral processing method in China for treating fine-grained iron ore. Before the application of strong magnetic separation technology in industrial production, positive flotation is the primary method for iron ore beneficiation. The advantage of positive flotation is that the process flow is relatively simple, the reagents used have a wide range of sources, and the quotation is low; The flaw is that when multiple iron ore deposits coexist, the difference in floatability has a significant impact on the yield and quality. Various gangue, primary and secondary slimes in the ore not only increase the amount of flotation reagents, but also make it difficult to filter and dehydrate the flotation concentrate, severely affecting the flotation skill goals [4-5]. Ge Brangyong et al. used the chelating collector RN-665 with excellent selectivity and collectibility to conduct 1 coarse, 3 fine, and 1 sweep flotation experiments on a certain iron ore, and finally achieved the outstanding goal of 64.02% iron concentrate grade and 76.23% recovery rate [6-7].
The industrial application of strong magnetic separation skills in iron ore beneficiation in the 1970s greatly promoted the advancement of reverse flotation skills [8-9]. Anionic collector iron ore reverse flotation is mainly used for the separation of quartz type gangue deposits. First, calcium ions are used to activate quartz, and then fatty acid collectors are used to float the quartz in the gangue deposits. The product in the flotation tank is iron concentrate. Inhibitors such as sulfonated lignin, starch, or dextrin can be used alone or in combination with sodium carbonate to adjust the pH value of the slurry to above 11. The most commonly used activators on site are calcium oxide. Cationic collector iron ore reverse flotation is a direct method of reverse flotation of quartz, and the collector generally uses amine collectors such as ether amine or fatty amine. When the pH of the slurry is between 8-9, the flotation effect is best. This method has simple pharmaceutical guidelines and simple operation, and has a better separation effect when combined with the magnetic gravity separation process. It is primarily suitable for the flotation of high-grade and disordered iron containing ores [10]. In the early 1980s, the cationic collector iron ore reverse flotation was successfully put into production at Angang Sintering Plant after industrial transformation, which advanced the grade of iron concentrate from 61.5% to 65.5% [11]. In recent years, with the development of flotation processes and the development of various new and efficient flotation reagents [12-13], flotation has not only been able to treat fine-grained iron ore, but also played a certain role in the separation of ultra-poor iron ore and polymetallic co associated ore.
1 Collector
1.1 Cationic collectors
The cationic collector dodecylamine has poor selectivity, disordered dispensing, and high foam viscosity. Strengthening the research and development of new cationic collectors is of great significance in advancing the reverse flotation technology of cationic collectors in China. In recent years, Chinese scholars have made certain research efforts in this regard.
Zou Wenbo et al. selected Gemini type cationic surfactants as collectors to conduct floatability experiments on three single mineral deposits of hematite, magnetite, and quartz. The results showed that the separation goals of Gemini type collectors in the quartz hematite system were hematite recovery rate of 99.0% and quartz recovery rate of 0.3%; The separation targets in the quartz magnetite system are magnetite recovery rate of 93.4% and quartz recovery rate of 8.3%. Clarify that Gemini type collectors have outstanding selectivity due to their high surface activity, which involves adsorption on the surface of mineral particles and then advancing their hydrophobicity.
Cao Yuchuan [15] and others formed a new cationic collector DHPA-3 after mixing DDA and HOB at the mass ratio of 1:1.4 for 6 hours at 60 ℃. It has the advantages of strong collection ability, good selectivity and high brittleness of foam. In the reverse flotation experiment of a certain beneficiation plant’s iron concentrate, DHPA-3 was used as a collector to obtain an iron concentrate with an iron grade of 62.60% and a recovery rate of 53.87% in one flotation. Compared with dodecylamine, DHPA-3 has slightly weaker collection function, but compared to tailings yield, DHPA-3 shows better selectivity than dodecylamine.
Zhu Yimin et al. [16] developed a new low-temperature resistant cationic collector DBA-2, which overcame the energy consumption problem of heating the slurry during the iron ore reverse flotation process. The research results of DBA-2 on the collection of quartz indicate that the outstanding goal of 98.0% recovery can be achieved by flotation of -0.038 mm pure quartz at a dosage of 197.5 mg/L. Zhu Yimin et al. [17] also developed a new cationic collector DBA-1, and compared it with DBA-2, DBA-1 collector has a better recovery effect on pure quartz deposits with particle sizes ranging from 0.038 to 0.074 mm. When the dosage of DBA-1 is 75 mg/L, the flotation recovery rate of pure quartz ore is 97.3%. The new room temperature cationic collector DYP developed by Zhu Yimin et al. [18] has advantages such as fast defoaming, high selectivity, low component cost, and relatively simple reagent criteria. In manual mixed ore flotation, the recovery rate of quartz reaches over 97.0%, while magnetite and hematite do not float. After analyzing the mechanism of DYP’s collection of quartz, it was found that DYP’s collection of quartz mainly relies on the adsorption of hydrogen bonds, supplemented by electrostatic adsorption. On this basis, Yang Yanping [19] conducted reverse flotation experiments on the mixed magnetic separation concentrate of Donganshan Sintering Plant using DYP. The results showed that under the conditions of slurry temperature of 25 ℃ and DYP dosage of 180 g/t, the outstanding goal of achieving an iron concentrate grade of 60.52% and a recovery rate of 73.17% could ultimately be achieved.
Xu Baihui [20] proposed a reverse flotation process for iron pit limonite from Jiangxi Xinyu Iron and Steel Company using coconut oil amine as a cationic collector. Under the optimal reagent criteria, the outstanding goals of iron concentrate yield of 39.56%, iron grade of 57.05%, and recovery rate of 60.78% were achieved, and the beneficiation difficulties caused by fine particle size, high mud and water content, and poor washability of limonite in the area were successfully addressed. Coconut oil amine is an excellent cationic collector in the flotation of limonite.
Lei Zhe [21] and others formed a new type of cationic collector M-201 with sodium silicate, epoxy chloride and trimethylamine salt as materials. In the comparison experiment with dodecylamine and ether amine, it was found that M-201 flotation target was slightly higher than dodecylamine and ether amine, with high collection ability, excellent low-temperature resistance, and high brittleness and fast defoaming of foam. It has great advantages for subsequent foam product treatment, and has solved the problem of high viscosity of traditional cationic flotation agent foam. The reverse flotation experiment was conducted on a certain iron ore in Jiugang using M-201 as a collector. The results showed that under the condition of M-201 dosage of 700 g/t, an outstanding target of 56.58% iron concentrate grade and 70.26% recovery rate was achieved.
The dodecylamine polyoxyethylene ether composed of Liu An and Fan Minqiang [22] has a stronger ability to capture quartz than dodecylamine and dodecyl ether amine, and the amount used is relatively small, resulting in better sorting objectives. Wang Yuhua et al. [23] explored the application of quaternary ammonium salt combination collectors in reverse flotation desilication of iron ore deposits. Dodecyldimethylbenzylammonium chloride and dodecyldimethylammonium chloride were mixed in a mass ratio of 2:1 (CS-22) as combination collectors. The results indicate that quaternary ammonium salt collectors have better collection performance and selectivity than dodecylamine salts.
The research on iron ore reverse flotation collectors abroad mainly focuses on cationic collectors such as ether amines, while there is less research in this area in China. Brazil’s R.M.F. Lima et al. [24-25] systematically studied the infrared spectra of decylamine molecules and their acetate or salts to distinguish the spectra of amine cations and acetate anions. Yugoslavia Ζ. Sekulic et al. [26] explored the collection functions of various collectors on a quartz ore sample containing impurities. The results showed that the collector Aero 3030c had better flotation performance than the combination of R-825 and Armac C collectors, and the recovery rate of concentrate quartz could increase by 0.25 percentage points. In the process of reverse flotation of iron ore using amine collectors, the cost of these reagents is the primary cost of flotation.
1.2 Anionic collectors
Due to the difference in density between iron ore deposits and quartz, it is difficult for anionic collectors to achieve the desired flotation target for iron ore. The advantages of anionic collector reverse flotation quartz process are strong synergistic effect of reagents, good selectivity, high recovery rate, and strong habit of modifying ore properties. It plays an important role in advancing iron recovery rate and reducing tailings grade, but there are also disadvantages such as high energy consumption and high dosage of activator.
Xiao Guoguang [27] conducted a reverse flotation study on Yuanjiacun iron ore using anionic collector RFe-561. The outstanding goal of achieving a grade of 66.25% and a recovery rate of 96.45% for iron concentrate can be achieved through the closed circuit experiment of 1 coarse, 1 fine, and 3 sweeps. Comparing RFe-561 with the on-site application of reagents in Qidong Iron Mine, it was found that RFe-561 can increase the concentrate yield by 1.32 percentage points, the recovery rate by 1.2 percentage points, and the iron content in tailings by 1.12 percentage points.
Zhu Yimin et al. [28] used the anionic collector DL-1 newly developed by Northeastern University to conduct a closed circuit reverse flotation experiment on the mixed magnetic concentrate of Dashan Iron Mine beneficiation plant in a sequence of 1 coarse, 1 sweep, and intermediate ore return. The study showed that quartz was first activated by a small amount of Ca2+at room temperature, and then participated in an appropriate amount of DL-1 for reverse flotation, achieving an outstanding goal of 65.38% iron concentrate grade and 89.56% iron recovery rate. Under the conditions of pH=11.50 and no Ca2+activation, DL-1 exhibits various forms of adsorption with quartz, including physical adsorption, hydrogen bonding adsorption, and chemical adsorption. The application of DL-1 can reduce the amount of activator used and then reduce the cost of beneficiation. Zhu Yimin et al. [29] developed a new anionic collector DZN-1 for reverse flotation of mixed magnetic concentrate from Dashan beneficiation plant. The results showed that under the conditions of slurry temperature of 25 ℃ and DZN-1 dosage of 800 g/t, the flotation target of 65.38% iron concentrate grade and 89.56% recovery rate can be achieved, demonstrating the excellent low-temperature resistance of DZN-1.
Tang Xuefeng et al. conducted temperature habit experiments on the new low-temperature resistant anionic collector CY-12 #, and the results showed that under the conditions of slurry temperature of 15 ℃ and optimal reagent criteria, outstanding goals of iron concentrate grade of 69.86%, iron recovery rate of 98.62%, and SiO2 content of only 2.87% can be achieved. Compared to the flotation target achieved at 30 ℃, the grade of iron concentrate decreased by 0.27 percentage points, but the iron recovery rate increased by 0.44 percentage points, advancing the resource utilization rate.
Luo Huihua et al. [31] developed a new type of anionic collector YRA-5 using cottonseed oil oleic acid as the material. During the composition process, an appropriate amount of surfactant was added to enhance the activity of the collector. The reverse flotation experiment was conducted on the strong magnetic tailings of the second section of Lilou Iron Mine at a slurry temperature of 17 ℃ using a 1 coarse, 1 fine, and 2 sweep closed circuit process. The outstanding goal of achieving an iron grade of 65.91% and a recovery rate of 91.61% was achieved, demonstrating the outstanding selectivity and low temperature resistance of YRA-5.
Keith Quest [32] conducted flotation experiments on magnetite using C6~C18 saturated fatty acids. The results showed that as the carbon chains in the saturated fatty acids increased, the collection effect became more and more significant. However, an increase in the length of the carbon chains in the fatty acids would lead to a decrease in solubility, which in turn led to a decrease in flotation power. Therefore, choosing tetramine as the flotation agent for hematite is the most ambitious choice.
2 Adjusting agents
2.1 Huan San Ji
For the flotation of some disorderly and difficult to select iron ores, the primary role of dispersants is to avoid the aggregation of ore particles and reduce the interactive effects between different ore deposits, and then advance the flotation goal.
The structure of carbonate containing iron ore is disordered, and the interactive impact of mineral deposits is severe, resulting in low beneficiation power. Lu Jiwei et al. conducted a 1 coarse 1 fine flotation experiment on Donganshan carbonate containing intermediate ore using organic dispersant NM-3 (which can maintain stable and uniform dispersion of mineral particles). The results showed that under the condition of NM-3 dosage of 200 g/t, an iron concentrate with an iron grade of 62.32% and a recovery rate of 42.57% was obtained. Compared with the previous closed circuit flotation process using YJ as the dispersant, the application of NM-3 simplifies the beneficiation process and improves the utilization rate of intermediate ore.
Luo Ximei et al. [34] investigated the effect of inorganic dispersant water glass on the reverse flotation of a refractory iron ore magnetic separation concentrate in Anshan. They found that water glass can adsorb on the surface of iron ore particles, enhance the electrostatic repulsion between particles, and cause fine particles to disperse. After a closed circuit process of 1 coarse, 2 fine, and 2 sweeps, and the return of China Mining, an outstanding goal of 66.26% iron concentrate grade and 70.23% recovery rate has been achieved.
2.2 Flocculants
The flocculant flocculates fine mineral particles into clusters through bridging action, improving its settling effect. When the embedded particle size of iron ore is fine, it is necessary to grind it carefully before it can be effectively sorted. Fine ore particles often have problems such as slow settling and long filtration time during concentration and dehydration. By adding flocculants to the slurry, it can accelerate the concentration of fine concentrate and avoid its loss.
In recent years, flocculation flotation has gradually been applied to the flotation of fine-grained lean hematite. Firstly, a dispersant is added to the slurry to keep the ore particles in a highly dispersed state. Then, a polymer flocculant is used to selectively flocculate the iron ore deposit, flocculate into clusters, settle, and then remove the suspended slime. Ultimately, reverse flotation separates the flocculated iron ore deposit [35].
With the development of industry and the demand for environmental protection, the position of polymer flocculants in flocculation and flotation is becoming increasingly prominent. The commonly used flocculants mainly include starch, polyamide, and humic acid salts. Chen Wanqi et al. [36] studied the effects of various flocculants on the settling behavior of a Brazilian hematite concentrate. Through experiments on the effect of pH on the settling behavior of flocculants, it was found that under alkaline conditions, the settling effect of polyamide flocculants M216 and M110 was significant, and the settling speed was the fastest at pH=10; The settling speed of sodium polyacrylate flocculants is the fastest at pH=4. Through experiments on the influence of temperature on the settling effect of flocculants, it was found that the settling effect of M110, M216, and S20 was more significant at a temperature of 25 ℃; When the temperature is 15 ℃, the sedimentation effect of Y2 is more significant; The temperature change has little effect on the sedimentation of M213;
2.3 Activator
The activator is activated by adsorption and covering on the surface of the mineral deposit, and then enhances the adsorption of the collector on the surface of the mineral deposit, which is beneficial for the collector to function. In the reverse flotation of iron ore deposits using anionic collectors, quartz is difficult to use sulfonic acid and fatty acids for flotation. However, after adsorbing metal ions such as Ca2+, Mg2+, Pb2+on the surface of quartz, these ions can be used to adsorb and activate the collector, making it easy to collect.
The use of activators is relatively common in the separation of pyrite in China. Pyrite often coexists with sulfide mineral deposits such as lead, copper, and zinc, and the flotation of pyrite is suppressed when separating from other useful mineral deposits [38], bringing certain difficulties to the sorting operation. After discussing the activation flotation of pyrite, Huang Chijun has developed a new type of pyrite recovery technique using ferrous sulfate and oxalic acid as activators. This combination activator can reduce the pH of the slurry, hinder the generation of hydrophilic substances on the surface of pyrite, react with Ca2+in the slurry, and improve the floatability of pyrite. This skill has been industrially applied in the Dongguashan Copper Mine beneficiation plant. The industrial experimental results show that after applying this skill, the sulfur concentrate recovery rate has increased by 50%, and the iron concentrate recovery rate has increased by 30%, bringing huge economic benefits to the beneficiation plant.
A certain beneficiation plant in Xuzhou ultimately exceeded the sulfur content of the iron concentrate due to the presence of pyrrhotite in the purchased high sulfur iron powder. Liao Ruihu et al. used the new activator MHH-1 developed by the Ma’anshan Mining Research Institute to activate pyrrhotite and conducted flotation experiments. They successfully reduced the sulfur content in the iron concentrate to 0.29%, ultimately achieving the outstanding goal of 68% iron concentrate grade and 85.98% iron recovery rate [40-41].
2.4 Inhibitors
Inhibitors can advance the wetness of a certain mineral deposit, making it outstanding in contact with aqueous solutions, and then reducing the probability of touching bubbles during the mineral flotation process. Using cationic collectors, starch, amylose, branched starch, maltose, and glucose as inhibitors, hematite can be suppressed during quartz flotation. Maltose and glucose have a good inhibitory effect on hematite at high concentrations (above 1000 mg/L), while starch inhibitors can also suppress hematite at low concentrations without affecting the floatability of quartz. The inhibitory effect of starch and its derivatives on magnetite is related to the relative molecular weight of the compound, and the greater the relative molecular weight, the more significant the inhibitory effect [42-43].
The Angang Mining Research Institute [44] uses modified carboxymethyl corn starch as a substitute for corn starch as a depressant for iron ore deposits in the continuous grinding weak magnetic separation strong magnetic separation anionic reverse flotation processes at the Diaojuntai beneficiation plant. Under the same conditions of mineral processing objectives, using modified starch as a depressant can reduce the amount of starch by half compared to directly using natural starch. Liu Ruohua [45] explored the inhibitory effect of different modified starch on hematite, and the results showed that at pH=10-12.5, the inhibitory effect of caustic corn starch on hematite was better than that of ordinary starch, and the inhibitory effect on quartz was not significant, which was more conducive to the reverse flotation of hematite.
When flotation of oolitic hematite, starch depressants often have problems such as disordered dosing, high energy consumption, and poor inhibition of fine particles. Ouyang Guangzun [46] used dextrin as an iron ore depressant to conduct reverse flotation experiments on magnetic roasting magnetic separation iron concentrate, achieving outstanding goals of 64.12% iron concentrate grade and 89.15% iron recovery rate. When the pH of the slurry is 6-9, dextrin neutralizes and reacts with the exposed Fe2+or Fe3+on the surface of the ore deposit, or forms iron chelates, causing significant changes in the concentration of charged ions on the surface, and then increasing the inhibitory effect on the iron ore deposit.
3 Conclusion
(1) Cationic reverse flotation process is rarely used in the production of domestic iron mine concentrators. The primary reason is that the cationic reagent flotation product foam is sticky, which is not conducive to continuous industrial production. At present, the anionic reverse flotation process is still the primary method adopted in the flotation of iron ore in China. Its advantage is that the obtained concentrate has a high grade, but its disadvantage is that it requires heating the slurry and a large amount of activator.
(2) Further strengthen the research on the selectivity and low temperature resistance of iron ore collectors. Develop specialized reagents based on the characteristics of different ore deposits, strengthen selective research while ensuring the collection capacity of the reagents, complete one ore, one drug or multiple drugs, and then significantly improve the quality and recovery rate of iron concentrate; Together, developing low-temperature collectors is beneficial for overcoming the energy consumption problem caused by heating the slurry, reducing industrial costs, and achieving energy conservation and emission reduction.
(3) The efficient use of fine-grained iron ore, ultra-poor iron ore, and multi metal co associated ore has become a new challenge for China’s iron ore dressing. This requires strengthening the development of new reagents such as dispersants, flocculants, and slime resistant reagents. On this basis, it is necessary to continue to strengthen the research on the flotation skills of disorderly and difficult to select iron ore, advance the beneficiation power of China’s iron ore, and work together to formulate a reasonable beneficiation process flow, This is of great significance in guiding the practice of mineral processing industry.