Abstract: Qidashan Concentrator uses anionic collector LKY to purify the mixed magnetic iron concentrate by reverse flotation. The obtained concentrate of iron grade is 67.77% and the recovery rate is 78.86%. The slurry with collector LKY requires heating not only increases the energy consumption in the beneficiation. And the process is complexity， and will reduce the stability of the process. In order to solve these problems， the relevant research group conducted flotation test on the on-site mixed magnetic iron concentrate sample with the newly developed desiliconization collector DJW-II at room temperature （21 ℃）， and XRD and SEM analysis of closed-circuit test concentrate and tailings were performed. The results show that the -0.037 mm fraction yield is 68.21%， the main minerals are iron minerals and silica， the iron is obviously enriched in the fine fraction， and the pH adjuster NaOH is 500 g/t （ pH=9.0）， the inhibitor carboxymethyl starch dosage is 150 g/t， and the collector DJW-II dosage is 175 g/t. The sample is treated with single-stage roughing， single-stage cleaning and three-stage scavenging， to obtain iron concentrate with iron grade 67.60% and iron recovery rate of 86.05%. The test results is obviously superior to the on-site concentrate index. Therefore， the reverse mixed magnetic iron concentrate in the Qidashan Iron Ore Concentrator will use DJW-II as the collector， which will not only reduce the complexity of production process， but also reduce the production energy consumption， improve the production index and improve the economic benefit. XRD pattern analysis proved the high efficiency of DJW-II in the desiliconization separation of iron concentrates. The SEM images showed that the fine particles in the samples were mainly iron mineral particles.

Key words: Reverse flotation, Mixed magnetic iron concentrate, DJW-II Collector, Flotation temperature