Application Foundament Research On High Efficient Activation Of Complex Low Activaty Pyrites

Sulfuric acid is widely applied in many national economy departments as an important chemical product. Main resources of its raw material involve pyrite, sulfur and smelting off-gas. Soaring development of national economy results in boosting demand of sulfuric acid, and requires us to expand sulfuric acid resources and increase the flotation recovery of pyrite ore. It is very important to exploit low-cost and high performance activators to effectively recover for low activation refractory pyrites. This thesis focuses on application foundament research on high efficient activation of complex low activaty pyrites. Pyrites and pyrrhotite were chosen as samples to investigate their activation and depress regularity in flotation process.In order to investigate pyrite and pyrrhotite flotation behavior under different system and electric potential, single mineral flotation tests was completed.The tests result indicate that butyl xanthate is a highly efficient collector. Pyrites have good floatability in acidic condition; while in alkaline medium especially strong alkaline system (pH>11), pyrite and pyrrhotite were depressed since the oxidizing potential of changing their surfaces to generate hydrophilic produce was low, which made the surface hydrophilic easily. Lime has good deppression performance on pyrites flotation, especially in strong alkaline condition. With increasing dosage of lime, the value of pulp potential of pyrites and pyrrhotite were reduced evidently. Inorganic acid and salt and organic acid can increase the value of pulp potential of pyrites and pyrrhotite and improve performance of flotation pyrites under strong alkaline and calcium system. Flotation results with single activators demonstrated the order of activating ability as follows:oxalic acid> sulfuric acid> cupric sulfate> ferrous sulfate> ammonium hydrocarbonate; However, compound activators had better activation, especially compound of oxalic acid and ferrous sulfate had obvious depression performance on pyrite and pyrrhotite. The surface wetting performance of pyrites and change of surface electron transfer of pyrites in the strong alkaline and calcium condition have been studied based on contact angle tests, and electro-chemical measurements including AC impedance technology and cyclic voltammetry. It is shown that both high alkaline systems with NaOH and lime can reduce oxidizing potential on surfaces of pyrite and pyrrhotite, resulting in easily oxidation on pyrite ore surfaces with hydrophilic products involving Fe(OH)3?S2O32- and SO42-, consequently conducing to flotation suppression. In the system of high alkaline with lime, Ca(OH)2?CaCO3 and CaSO4 were further produced on the surface, which leads to further decline of flotability.The mechanisms of activation of pyrites ore with presence of activtors were investigated using contact angle tests, and electro-chemical measurements including AC impedance technology and cyclic voltammetry to study the surface wetting performance of pyrites and change of surface electron transfer of pyrites.The result showd that flotation activator reduce the pH value of solution and increases the self oxidizing potential, which impedes oxidation progress on the surface of pyrite ore and concequently prevents the form of the hydrophilic products. On the other side, part of the hydrophilic products dissolve in the solution, accordingly fresh surfaces of pyrite and pyrrhotite are refurled. Oxalic acid has better activating performance than sulfuric acid, for it can not only reduce the pH value of pulp, increase pyrite self oxidizing potential, and dissolve part of the hydrophilic products, but also interact with the cation on the surfaces of pyrite which produces soluble complex.Eh-pH graphs based on thermodynamic calculation and analyse, infrared spectrometry, X-ray diffraction analysis and X-ray Photoelectron Spectroscopy (xps), were used to study the change of mineral surface effection and reaction from flotation depressor and activator. It reveals that pyrite and pyrrhotite have wide range of oxidizing potential of generating hydrophobic produce in acidic condition. It indicate that reduce pulp potential was be propitious to formming hydrophobic produce and improving floatability. In strong alkaline system (pH> 10),it is easy to oxidate so as to generate hydrophilic produce at lower potential. The velocity oxidizing of pyrites using lime as depressor is great than using sodium hydroxide as depressor at the same pH value. In the system of high alkaline with lime, electrochemistry reaction take place on the surface of minerals and Ca(OH)2?CaCO3 and CaSO4 were further produced on the surface. When oxalic acid used as activator to deal with drpressed pyrites, The characteristic peaks of Ca(2p), Ca(2s) and Fe3+ will disappear. The oxidating and generating hydrophilic produce on surface were stoped, at the same time, because oxalic acid can dissolve the Ca(OH)2, Fe(OH)3 and other cation hydroxid adsorbing on surface, so the fresh surface is exposed renewedly and minrals have good floatability.Results of quantum chemistry calculation and simulation verify that the Ca2+ and Ca(OH)+ were able to adsorb on the disaggregation (100) surface of pyrites in the strong alkaline and with lime condition, but the adsorption of Ca(OH)+can take precedence of adsorption of Ca2+, so hydrophilic calcic compounds were further produced on the surface, which leads to depress pyrites'flotation. The molecular dynamics simulation of system with oxalate ion, Ca2+ and OH- show that complexation combines oxalate ion with Ca2+. Oxalate ion can chelate with Ca2+ in the solution, which leads to decline of Ca2+ concentration and concequently results in dissolution of the Ca film on the surface of pyrite. Results of calculation of binding energy between oxalate ion and OH-, oxalate ion and Ca2+ indicate that the interaction between the latter was stronger comparatively, which leads to dissolution of Ca film.According results of on-site tests, including laboratory test, expanding test, and industrial test, it was proved that compound activator with oxalic acid and ferrous sulfate had satisfactory performances in all kinds of scale tests. Tests in Dongguashan concentration plant revealed that this method optimized reagent system of sulphur flotation, remarkably increased sulphur flotation efficiency. Even concentration was maintained at 34%, recovery at 85%, which successfully validated the effectiveness of this high efficiency novel cleaning technology.Though applying these newly-developed high efficiency reagents to sulphur and ferrum flotation in Dongguashan concentration plant, favorable results were obtained. Recovery of sulphur products increased from 20%to 70%. Recovery of ferrum soared from 0 to 30%. With all this reform technology, good economic effect was yielded, among which 87.7 million RMB was achieved per year in sulphur flotation department. Huangshaping concentration plant was the second plot to apply this technology, and positive indexes were obtained, evincing the efficiency of these novel activators.