Preparation of Gemini Type Ester−containing Guanidine Salt Cationic Collector and Study on Its Flotation Performance for Magnetite

Traditional collectors often suffer from limited functionality, rendering them inadequate for meeting the flotation requirements of polymetallic or complex ores. Moreover, they frequently causes sencondary polution to the environment during the flotation process. Bromododecane, 1, 1, 3, 3−tetramethylguanidine, succinic acid and epichlorohydrin were used as raw materials to synthesize a new type of Gemini dodecanidine salt cationic collector (C₁₂−2−C₁₂) featuring an ester bond linkage. At 25 ℃, C₁₂−2−C₁₂ exhibits a surface tension of 25.10 mN/m. Notably, its critical micelle concentration (0.01 mmol/L) is significantly lower than that of single−chain dodecyl guanidine (5.01 mmol/L). The foam stability of C₁₂−2−C₁₂ reaches 74.79% with a water separation time of 313 seconds for 10 mL of water, exhibiting outstanding emulsification performance. The collection performance of C₁₂−2−C₁₂ as a magnetite reverse flotation collector was systematically evaluated during the experiment. The results show that the single mineral simulated flotation tests reveal that C₁₂−2−C₁₂ show excellent selectivity towards quartz at pH=7 and a collector concentration of 0.3 mmol/L. Under these conditions, the quartz recovery rate achieved with C₁₂−2−C₁₂ is 87.6%, which is significantly higher than the 69.46% recovery rate obtained with dodecylguanidine. In the reverse flotation of actual magnetite ore samples at pH=7, with a collector dosage of 320 g/t and an inhibitor (caustic starch) dosage of 250 g/t, the concentrate grade reaches 67.58%, with a recovery rate of 76.35%. In the biodegradation experiment, the biodegradability of C₁₂−2−C₁₂ was investigated using the shaking culture method. After 40 days, the final degradation rates of C₁₂−2−C₁₂ and dodecylguanidine are 52.12% and 44.56%, respectively. In comparison to traditional single−chain collectors (with a biodegradability of approximately 30%) and Gemini quaternary ammonium salt collectors (with a biodegradability of around 26%), C₁₂−2−C₁₂ demonstrates superior environmental friendliness. Finally, the collection mechanism of the C₁₂−2−C₁₂ collector synthesized in this study was analyzed. Results from infrared spectroscopy and Zeta−potential tests indicate that the adsorption of the collector on the surfaces of quartz is mainly eiectrostatic adsorption and and it has almost no effect on the surface of magnetite. Quantum chemical calculations further reveal that C₁₂−2−C₁₂ carries a strong positive charge and interact with the quartz surface by donating electrons to the lowest molecular orbital of C₁₂−2−C₁₂ through quartz. In conclusion, C₁₂−2−C₁₂ proved to be an excellent reverse flotation collector for magnetite, exhibiting favorable biodegradability.