Research On The Sulfidation Of Malachite Flotation And Its Ammonium Salt Strengthening Mechanism

With the exhausting of sulphide ores,the development and utilization of oxidized copper ores have been received increasing attention in recent years.Sulfidization flotation is an extensively used method to recover copper oxide minerals,and sulfidization is a key part of this methodology.Researchers have done a large amount of work in studying the sulfidization flotation of oxidized copper ores for many years.In the sulfidization flotation of malachite,however,the investigation of sulfidization mechanism was landed in the argument regarding whether the generation of sulfidization product was due to sulfide ions adsorbed on metal sites of the mineral surface or ion exchange between the sulfidizing agent and the mineral particles.On the other hand,at present the crystal phase of sulfidization products has not yet been determined.Therefore,the sulfidization mechanism of malachite is still unclear.Certainly,the enhancing mechanism of ammonium salt or ethylenediamine for the sulfidization of malachite is also still unclear.It seriously hinders the development of theory and practice of sulfidization flotation of copper oxide.The flotation experiment results indicate that sulfide agents with a proper concentration can activate cerussite flotation,while excessive sodium sulfide can depress the flotation.The depression mechanism of excess sulfide ions on malachite flotation is not only linked to the liquid phase,but also to the mineral surfaces.After ultrasonic treatment,yellowish-brown colloidal substances detached from the sulfidized malachite surfaces,and the flotation experiment results show that the yellowish-brown colloidal substances are responsibility to the activation of malachite flotation.FESEM-EDS studies indicated that floccules grown on malachite surfaces are the sulfidization products.The distribution of sulfidization products on malachite surfaces was obviously regional,mainly in the crystal corrugates,crystal angles and slits of malachite,which was also confirmed by EPMA surface scan results.These results show that new phases have been formed when malachite were treated with the optimum flotation concentration of sodium sulfide solution.However,there is no diffraction peak of sulfidization products in the XRD spectra of sulfidized malachite samples,because the amount of sulfidized products is much lower than the detection limit of XRD.XPS results of sulfidized malachite show that the valence of copper in sulfidization products is+1.By means of the difference of solubility between Cu₂?OH?₂CO₃ and Cu_xS_y in dilute sulfuric acid solution,the sulfidization products of malachite was purified.XRD results show that the main sulfidization products of malachite are Cu₃₁S₁₆?Djurlerite?and Cu₇S₄?Anilite?,both are sulfides of cuprous,which are consistent with their XPS results.Based on the above,a reasonable sulfidization mechanism of malachite,a heterogeneous nucleation mechanism,is proposed.The sulfidization reaction in malachite flotation is a heterogeneous solid-liquid reaction.The adherence of solid products(Cu_xS_y)to the surface of malachite is responsibility for malachite flotation.The driving force of sulfidization reaction is the great difference in solubility between sulfidization products and malachite.The sulfidization process is a crystallization process,Because nuclei are formed in heterogeneous phase,sulfide products are formed via heterogeneous nucleation mechanism.And the sulfidization reaction of malachite is a redox reaction.On the basis of the above,the enhancing mechanism of ammonium salt on sulfidization was studied.Under neutral pH conditions,the concentration of free ammonia in ammonium salt solution is very low,and the addition of ammonium salt cannot significantly affect the concentration of copper ion in malachite pulp.that is to say,it is difficult for ammonium salt solution to react with malachite particles to form copper-ammonia complex.EDS,XPS and ammonium nitrogen concentration measurements show that ammonium nitrogen mainly exists in liquid phase in the interaction system of“malachite+ammonium salt”and“malachite+ammonium salt+sodium sulfide”.Ammonium ion cannot be adsorbed on malachite surfaces,nor can it"co-adsorb"with sulfur ion on malachite surfaces.N element does not participate in the formation of sulfide products.The addition of ammonium salts can reduce the formation of sulfide colloids in liquid phase.FESEM results show that the sulfide products of ammonium salt system have obvious geometrical shape at the same magnification,while the malachite sulfide products without ammonium salt cover the surface of Malachite like"sludge"and are aggregates of more microscopic crystals.XRD results showed that the proportion of Cu₃₁S₁₆ in sulfidization products increased significantly in the presence of ammonium salt.The results show that ammonium salts can reduce nucleation rate,promote the growth of sulfide products,make sulfide products have larger particle size,and thus have stronger mechanical strength,which makes it difficult to fall off and form sulfide colloids in liquid phase.Therefore,under the action of ammonium salts,the surface of Malachite has more sulfide coverage and higher flotation recovery.Therefore,the academic viewpoint of“enhanced sulfidization of ammonium salts based on the crystal phase control of sulfidization products”is preliminarily put forward.