Selection and discussion of ilmenite flotation technology

As an important carrier of titanium resources, the optimisation of ilmenite flotation process is directly related to the extraction efficiency of titanium metal and resource utilisation. With the growth of industrial demand and the improvement of environmental protection requirements, ilmenite flotation technology has been constantly innovated, gradually evolving from the traditional single process to the combined process and green direction. This paper will systematically describe the current status and development of ilmenite flotation from the aspects of flotation process, key technologies, existing challenges and future trends.

The main component of ilmenite is FeTiO₃, often coexisting with quartz, wollastonite and other vein minerals, and titanium elements are embedded in the form of microfine grains, which makes flotation become the core process of its sorting. The traditional flotation process usually includes steps such as crushing, grinding, additive of chemicals, and flotation separation. However, it is difficult for a single flotation method to cope with the sorting needs of complex ores, so the combined process has gradually become the mainstream. For example, the combined magnetic separation-flotation process separates strong magnetic minerals in advance through magnetic separation, reduces the interference of subsequent flotation, and significantly improves the grade and recovery of ilmenite. The suspended vibration re-election-flotation combined process takes advantage of the difference in ore density to remove a large number of impurities in the re-election stage, creating a better slurry environment for flotation. These combined processes not only reduce the consumption of chemicals, but also improve the overall beneficiation efficiency.

Among the new flotation technologies, flocculation flotation and carrier flotation show unique advantages. By adding polymer flocculants, flocculation flotation promotes the aggregation of fine-grained ilmenite into clusters and enhances its ability to adhere to air bubbles, thus improving flotation recovery. Carrier flotation method selects hydrophilic minerals (such as quartz) as the carrier, so that ilmenite particles are attached to the surface of the carrier through physical adsorption or chemical bonding to form ‘composite particles’ that are easy to flotation. For example, at one mine, the recovery of fine-grained ilmenite was increased from less than 50 per cent to more than 75 per cent by using a carrier flotation process. The core of these technologies lies in changing the surface properties or aggregation state of minerals through physical or chemical means, breaking through the particle size limitation of traditional flotation.

The selection and optimisation of flotation agents is the key to the success of ilmenite flotation. Although the traditional capture agent such as oleic acid is low cost, it has poor selectivity and is easy to lead to the upward flotation of chalcopyrite minerals. In recent years, metal ion activation flotation technology through the introduction of copper, lead and other metal ions, and ilmenite surface to form complexes, enhance its hydrophobicity, significantly improve the selective adsorption of flotation agent. For example, after adding copper sulfate, the ζ-potential of ilmenite surface turns from negative to positive, the affinity with anionic collector is enhanced, and the flotation efficiency is increased by more than 20%. In addition, the surface chemical state adjustment technology changes the hydrophilic and hydrophobic differences on the mineral surface through the addition of surfactants (e.g. sodium dodecyl sulphate), further optimising the sorting effect. The application of these technologies makes it possible to industrially sort low-grade, complex symbiotic ilmenite.

Despite significant technological advances, ilmenite flotation still faces multiple challenges. Firstly, the proportion of ilmenite with fine particle size (<19μm) in the ore is as high as 30%, which is difficult to be effectively recovered by traditional flotation, resulting in a waste of resources. Secondly, the high energy consumption and environmental toxicity of chemicals in the flotation process need to be solved. For example, the residue of conventional collectors in wastewater may cause water pollution, while the excessive use of strong acid and alkali increases the difficulty of tailings treatment. In addition, complex mineral combinations (e.g. ilmenite coexisting with calcium and magnesium-bearing minerals) lead to a decrease in flotation selectivity and large fluctuations in concentrate grade. Take a mine in Inner Mongolia as an example, the titanium content of the original ore is only 3%, and after flotation, the grade of the concentrate is only 42%, which is far lower than the smelting requirements of more than 48%.

In view of the above problems, ilmenite flotation technology is moving towards the direction of greening and intelligence. The research and development of environmentally friendly flotation agent has become the focus, such as bio-based capture agent using microbial metabolites selective adsorption of ilmenite, not only to reduce toxicity, but also to enhance the efficiency of sorting.ZF-02 capture agent as a new type of environmentally friendly chemicals, has achieved a breakthrough in ilmenite sorting of micro-fine grains, its toxicity than the traditional agents to reduce 60%, recovery rate increased by 15%. In terms of comprehensive utilisation of resources, the tailings re-election technology extracts residual ilmenite from historical tailings through a combined magnetic separation-flotation process, increasing the resource utilisation rate to over 90%. The introduction of intelligent technology further optimises process parameters, such as the machine learning-based flotation process control system, which can adjust the dosage of chemicals and bubble size in real time to stabilise the flotation efficiency in the optimal zone.

In the future, ilmenite flotation will pay more attention to the synergistic innovation of the whole process. In the ore pretreatment stage, high-pressure roller milling and ultra-fine grinding technology can improve the dissociation degree of micro-fine-grained minerals; in the sorting stage, electromagnetic separation and bioleaching technology is expected to replace part of the chemical process, reducing the environmental load; in the tailings treatment stage, cement filling and ecological restoration technology can achieve the waste residue resourcefulness and ecological reconstruction of the mining area. For example, an enterprise adopts the integrated process of ‘high-pressure grinding-carrier flotation-tailings brick-making’, which not only raises the titanium recovery rate to 85%, but also realises zero discharge of tailings. The comprehensive application of these technologies marks the leap of ilmenite flotation from a single sorting to the whole life cycle management of resources.