Mechanism Of The Wing-shield Effect Of Iron-ammonium Chloride In The Separation Of Copper And Arsenic

Copper is a strategic resource which plays an important role in the development of the national economy.However,with the large-scale mining of copper resources for decades,high-grade and easy-to-process copper resources have been depleted.The development of refractory copper ore with low grade,fine disseminated grain size and high impurity content has become the focus of current research,and high-arsenic copper ore is a typical representative among them.Chalcopyrite is the main copper mineral and arsenopyrite is the main arsenic mineral in most high-arsenic copper deposits in China.The separation of chalcopyrite and arsenopyrite by flotation is always a difficult problem in mineral processing research.In this thesis,chalcopyrite and arsenopyrite were taken as research objects,and the chemical bond structure and surface relaxation of chalcopyrite and arsenopyrite crystalloid were studied by quantum chemical calculation.The effect of common ions on chalcopyrite and arsenopyrite flotation was determined by single mineral flotation test.It was found that Fe Cl₃-NH₄Cl can ensure better floatability of chalcopyrite while inhibiting arsenopyrite.Based on this,the"Shielding Effect"of the reagent was proposed,that is,when two kinds of minerals are being separated by flotation,modifier A（Fe Cl₃）is being added to inhibit the non-target mineral（arsenopyrite）while modifier B（NH₄Cl）is being added to shield to protect the target mineral（chalcopyrite）and reduce the inhibitory effect of modifier A on the target mineral.And then the selective separation of minerals is realized.In this paper,XPS,To F-SIMS surface analysis,Micro-area electrochemical analysis,Zeta potential test,and quantum chemical calculation are used to analyze the action mechanism of Fe Cl₃-NH₄Cl on chalcopyrite and arsenopyrite.The inhibition mechanism of Fe Cl₃ on arsenopyrite,chalcopyrite and the activation mechanism of NH₄Cl on chalcopyrite were analyzed and explained.Finally,the results of mechanism research were applied to the actual ore flotation through the flotation test for a high-arsenic copper ore in Yunnan Province.The mineral crystalloid and minera surface calculation showed that the S-Fe bond properties of chalcopyrite and arsenopyrite are similar.The surface relaxation of chalcopyrite is more obvious than that of arsenopyrite.After relaxation,the surface of chalcopyrite is in the state of"High Sulfur",and the Fe atoms on the surface of chalcopyrite and arsenopyrite are more active than the S and Cu atoms.The results of thermodynamic calculations showed that arsenopyrite is more easily oxidized in the solution than chalcopyrite.Under alkaline conditions,the two will be more easily oxidized due to the lower oxidation-reduction potential as they required.The results of single mineral flotation test showed that Fe³⁺,Mg²⁺,Ca²⁺and Pb²⁺have a certain inhibitory effect on the flotation of arsenopyrite,and Fe³⁺has the strongest inhibitory effect among them.The activation behavior of Cu²⁺in the flotation process of arsenopyrite is obvious,while NH₄⁺and Al³⁺have weak effects on the flotation of arsenopyrite.Under alkaline conditions,Fe³⁺,Mg²⁺,and Ca²⁺also have a certain inhibitory effect on chalcopyrite,and Cu²⁺and NH₄⁺can activate chalcopyrite.However,the effective separation between chalcopyrite and arsenopyrite cannot be completed by using only a single ion.Through the ion mixing flotation test,it can be found that the mixing behavior of Fe Cl₃-NH₄Cl can inhibit arsenopyrite while it protect chalcopyrite better to float up,so as to achieve better separation effect of copper and arsenic.The mechanism study showed that the Zeta potential of mineral surface increases and the oxidation degree of mineral surface deepens when Fe Cl₃ is added.More hydrophilic substances（ferric hydroxide,arsenate,arsenite,sulphate and sulfites）are produced on the mineral surface,leading to the decrease of the floatability of arsenopyrite.Under high p H conditions,the oxidation of S is hindered to some extent due to the existence of As and Fe oxide residues on the surface of arsenopyrite.Quantum chemical calculation showed that Fe³⁺can replace As atoms but cannot replace S atoms on the surface of arsenopyrite.Both Fe³⁺and Fe（OH）₃ can be adsorbed on the surface of arsenopyrite,and the optimal adsorption site for Fe³⁺on the surface of arsenopyrite is the central site;the optimal adsorption mode of Fe（OH）₃ on the surface of arsenopyrite is side adsorption.The two hydroxyl groups near the mineral surface of Fe（OH）₃ are also moving away from the mineral surface,showing that it is difficult for the hydroxyl group in Fe（OH）₃ to interact with the mineral surface,and the main participants in the reaction are Fe atoms in the molecule.The effect of Fe Cl₃ on the surface of chalcopyrite leads to the deeper oxidation of Fe sites on the mineral surface,but it has no obvious effect on Cu and S sites,and more hydrophilic compound Fe（OH）₃ is found on the mineral surface.The adsorption energy of Fe（OH）₃ on the surface of chalcopyrite is negative,and the optimal adsorption mode of that is normotopia adsorption.Therefore,the action of FeCl₃ on the surface of mineral results in the decrease of the adsorption capacity of xanthate and the decrease of the floatability of mineral.The hydrophilic oxide on the chalcopyrite surface did not decrease after the addition of NH₄Cl,but the adsorption amount of xanthate increased significantly.The results of quantum chemical calculations showed that the effective composition NH₃ in NH₄Cl reacts with Cu sites on the chalcopyrite surface,resulting in weakening of the electronic interaction between Cu and S atoms,increasing the activity and positive charge of Cu sites,strengthening the effect of xanthate acid radical on mineral surface,and finally making chalcopyrite activated.The raw ore flotation test results showed that the raw ore of a high-arsenic copper ore in Yunnan contains 0.76%copper and 1.03%arsenic.By using the Fe Cl₃-NH₄Cl mixed reagent based on the"Shielding Effect"as the modifier,the copper concentrate Cu grade of 23.88%,recovery rate of 88.45%,and the arsenic content of 0.43%could be obtained.Consequently,the effective recovery of copper resources could be achieved.