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Reverse Flotation with Flotigam 2835-2 reduces silica content to improve magnetite quality and increase its commercial value

The Bottom Line

Using Clariant’s Ether Diamine collector, reverse flotation helps customers to obtain financing for development of a low-grade iron ore mine in Australia’s Midwest Region. By partnering with the customer, Clariant designs a reverse flotation process to: 

  • Cost-effectively reduce silica content from 7% to below required specifications
  • Optimize the process to decrease collector concentration and/or improve ore capture rates


Australia’s mining industry faces many challenges by processing low-grade iron ore in the country’s Midwest Region. With unacceptably high silica content characteristics, magnetite mined from the deposits require a reverse flotation process using a proprietary collector developed by Clariant Mining Services to produce a commercially attractive product.

Preliminary lab studies confirm that Clariant’s Flotigam 2835-2 collector effectively lowers the ore’s silica content, improving final product quality and increasing the sale price. This is done while working with the customer to meet target production goals.

Once full-scale production commences at the mine, Clariant continues to partner with the customer by conducting optimization procedures at the reverse flotation stage to reduce collector dosing and/or improve product recoveries.


Flotation of iron ore is a new concept for the Australian mining industry. The high-Fe-grade hematite deposit in Australia’s largest mining region, the Pilbara, requires only crushing, sizing and washing prior to being sold as directly shipping ore.

A new, low-Fe-grade magnetite deposit containing higher silica content is under development in Western Australia’s Midwest Region. With its negative impact on the steel production process, silica content in the magnetite must be reduced as low as possible to improve the grade and increase the selling price.

A partnership between an Australian mining company and Chinese steel mills is developing the mining of Australia’s Midwest Region to diversify the iron ore supply chain and replace the low-grade ore found in China. Clariant is partnering with the joint venture to provide the necessary chemistry to improve the magnetite’s grade extracted from the mine.

Clariant offers decades of experience in helping customers optimize the process in which impurities are removed from low-grade iron-ore deposits like those found in Australia’s Midwest Region. In the Brazilian market, Clariant’s flotation processes removes silica content as high as 50% found in iron ores.

Based on preliminary lab tests of core samples taken from the deposit, Clariant recommended its proprietary Ether Diamine, Flotigam 2835-2, collector to efficiently remove the silica. With the chemistry and financing in place, development of the mine began in 2010.


Initial core testing confirmed that the deposit’s magnetite contains greater than 30% silica, which reduced by magnetic separation to 6.5 to 7%. The customer’s goal is to produce a commercially viable iron ore product containing the least possible silica content.

Clariant’s reverse flotation featuring Flotigam 2835-2 removes the silica that cannot be removed by magnetic separation. In this process, the ore slurry navigates through a series of large flotation cells, where air is introduced to create the bubbles for float separation.

Flotigam 2835-2 collects and floats the silica. Once completing the circuit, only the high-grade iron ore slurry remains, which is filtered and dried.

Since silica is often removed at the natural pH of the water and the arid Midwest Region’s water supply is frequently of poor quality, Clariant continually analyzes the water’s effects on production during full-scale processing. Dosage adjustments are made along with potential additions of frothers and depressants to cost-effectively remove the silica.


At the flow-sheet/lab testing stage, Clariant’s reverse flotation with Flotigam 2835-2 collector…

  • Proves successful in lowering silica content from 7% to below target specification
  • Helps the customer to obtain financing for mine development

As full-scale low-grade magnetite mining begins in 2012, Clariant will work to ensure…

  • An uninterrupted supply chain of Flotigam 2835-2 using optimized ourcing from multiple Clariant sites regionally and globally
  • Staged increases in ore throughput, ranging from 8 million TPY at commissioning to 30 million tons per year in 2014
  • Process optimization to increase iron recovery and reduce silica grade, while significantly decreasing collector concentration
  • Water quality does not negatively impact the production process and make adjustments as required
  • Suitable frothers are introduced as required to modify the stability of the produced froth and improve selectivity and recovery
  • Investigation of depressants to prevent magnetite losses by separation of iron and silica particles


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