Study On The Mechanism Of Cassiterite Flotation By Ricinoleic Acid Enhanced By Copper And Lead Ion

Tin is widely used in high-tech fields,such as aerospace,national defense,biomedicine and high-tech product manufacturing,and cassiterite is the most important raw material for the extracting metallic tin.Gravity separation method is generally used to recover coarse-grained cassiterite,while the beneficiation of fine-grained cassiterite is less efficient than flotation.The commonly collectors for cassiterite flotation include fatty acids,arsenic acids,hydroxamic acids,alkyl sulfosuccinic acids,etc.Among them,hydroxamic acid is a widely used collector,but the dosage of hydroxamic acid is large and the price of this collector is high.Due to its high toxicity and effect on environment,plants still need environmentally friendly collectors with higher flotation efficiency.While,fatty acid collectors come from a wide range of sources and have high flotation efficiency,but disadvantages of fatty acids are their poor selectivity.In recent years,with the development of various carbonate inhibitors,the selectivity of fatty acids has been improved,and the application of fatty acids in cassiterite flotation has received widely attention again.In this paper,sodium ricinoleate（NaRA）,a fatty acid collector,was used for the flotation of cassiterite.Pb（NO₃）₂and Cu Cl₂are used as activators.HRA has a OH group in the molecule.Using flotation experiment,contact angle experiment,Zeta potential test,X-ray photoelectron spectroscopy（XPS）,secondary ion time-of-flight mass spectrometer（TOF-SIMS）and FTIR,the flotation behavior of RA for cassiterite was investigated.The activation mechanism of copper and lead species and the effect of intermolecular hydrogen bonds of HRA on cassiterite flotation were studied.The flotation results show that NaRA is an extremely effective collector for cassiterite flotation,canefficiently float cassiterite under alkaline conditions,and the flotation efficiency is higher than that of oleic acid（HOI）.Pb（NO₃）₂has the best activation effect on cassiterite at p H=8.When the NaRA concentration was5×10^-5mol/L and the Pb（NO₃）₂concentration is 1×10^-4mol/L,the flotation recovery of cassiterite reached 73%.Cu Cl₂showed the best activation effect on the cassiterite flotation at p H=7.When the concentration of NaRA was 5×10^-5mol/L and the concentration of Cu Cl₂was 1×10^-4mol/L,the recovery of cassiterite activated by NaRA was close to 70%.Although the optimum p H of the two activators is different,the activation response is similar.The Zeta potential analysis and ion distribution calculation show that Pb（OH）⁺is the main lead component in the Pb（NO₃）₂solution at p H=8,and the effect of Pb（NO₃）₂indeed promoted the adsorption of RA^-anions on the cassiterite surface;Cu²⁺and Cu（OH）⁺is the main copper component in the Cu Cl₂solution at p H=7.Copper activation introduced a large amount of copper ion species on the cassiterite surface,which effectively enhanced the adsorption of RA^-anions on the mineral surface.The activation of Cu Cl₂promoted the adsorption of RA^-anions on the cassiterite surface,improving the adsorption density of the collector on the cassiterite surface,which was beneficial to the flotation of cassiterite.The binding energies of the electrons in the inner layers of various atoms on the surface of cassiterite were further analyzed by XPS,and the surface activation products on cassiterite surface were determined.For the surface of lead-activated cassiterite,at p H=8,the main lead component（Pb（OH）⁺）in the solution reacted with the cassiterite surface,producing≡Pb（OH）₂and≡Pb-O.For copper-activated cassiterite surface,the main components of copper ions in Cu Cl₂solution at p H=7 are Cu²⁺and Cu（OH）⁺.These two copper components interacted with the cassiterite surface,producing≡O-Cu⁺and≡O-Cu-OH.The TOF-SIMS analysis results show that a large amount of lead species was adsorbed on the lead-activated cassiterite surface,forming a lead-rich cassiterite surface,which promotes the adsorption of HRA.The copper-activated cassiterite surface adsorbed a large amount of copper ions.HRA can adsorbed on the surface Cu sites,thus increasing the adsorption amount of HRA on the cassiterite surface.The FTIR results confirmed that Pb（RA）₂and Cu（RA）₂precipitates occurred on the lead-activated and copper-activated cassiterite surfaces.Thereby,the adsorption amount of the HRA on the mineral surface was increased,and the cassiterite flotation is promoted.According to the results of various surface detections above,the adsorption mechanism of NaRA in the activation of lead and copper is at p H=8,in Pb（NO₃）₂solution,Pb（OH）⁺is adsorbed on the surface of cassiterite,generating≡Pb（OH）₂and≡Pb-O forms a lead-rich surface,and the collector continues to adsorb on the Pb site,resulting in the formation of Pb（RA）₂precipitation.At p H=7,there are Cu²⁺and Cu（OH）⁺in Cu Cl₂solution,Cu²⁺can be directly adsorbed on the O site of cassiterite surface,or can interact with≡Sn-OH to generate≡Sn-O-Cu⁺.Cu（OH）⁺interacts with cassiterite≡Sn-OH to form≡O-Cu⁺.On the copper-activated surface,the agent can react with the surface Cu atoms to form Cu（RA）₂precipitation.