A First-principles Study Of The Mechanism Of Interaction Between Acidic And Oxidizing Media And Chalcopyrite

Chalcopyrite as the main source of minerals in copp er smelting was widely studied.Although the oxidative leaching of chalcopyrite in traditional acid med ium has made a great progress,there are still some problems,such as large acid consumption,low recovery rate of copper,the difficulty of the waste acid circulation and the leaching residue recycling and so on.In order to develop an efficient and clean hydrometallurgical technology.In this paper,the structure and properties of chalcopyrite bulk and sulfur terminated chalcopyrite(001)surface[labeled as(001)-S surface],the adsorption and interaction mechanism between chalcopyrite(001)-S surface and traditional leaching agent hydrochloric acid,sulfuric acid and commonly used oxidant Na Cl O₃,H₂O₂ as well as the changes of the electronic structure and properties before and after adsorption were studied with First-principles calculation in detail.The chemical reaction s between all materials and chalcopyrite surfac e are discussed during the adsorption process.The research work can provide a theoretical basis and guidance for related research.The adsorption of hydrochloric acid in dissoci ated form on chalcopyrite(001)-S surface was studied by First-principles method.The calculated results show that the reconstructed chalcopyrite(001)-S surface leads to the formation of disulphide S ₂^2-.In the process of leaching,the adsorption of H⁺on the chalcopyrite(001)-S surface will destroy the S₂^2-formed on the surface and the adsorption energy for the most favorable adsorption site is calculated to be-20.9 kcal/mol.The surface structure of chalcopyrite(001)-S surface is destroyed by adsorption of chlorid ion Cl^-.During the adsorption process,the chemical reactions between H⁺and Cl^-with the surface of chalcopyrite produce the Fe Cl₂ and H₂S,which are both beneficial to the leaching of chalcopyrite.Similarly,the process of sulfuric acid adsorbed on chalcopyrite(001)-S surface in the form of dissociation was studied with First-principles calculation.The study find that the adsorption of H⁺on most of S sites on the chalcopyrite(001)-S surface will destroy the S₂^2-formed on the surface,which increases the reactivity of the chalcopyrite surface.Simultaneously,the adsorption of SO₄^2-,HSO₄^-on chalcopyrite(001)-S surface results in a degree of damage to the surface.However,HSO₄^-has a stronger binding ability with an adsorption energy of-29.5 kcal/mol and a larger damage to the surface,which indicates that the adsorption of sulfuric acid in the dissociation form of HSO₄^-is more beneficial to chalcopyrite leaching.In addition,sulfuric acid dissociate and adsorb in the form of H⁺and SO₄^2-will occur chemical reaction with the surface of chalcopyrite,and the reaction will result in the formation of H₂S and Fe SO₄reduction products.The adsorption of Cl^-,ClO₃^-on chalcopyrite(001)-S surface were studied by First-principles study.It is found that Cl^-,Cl O₃^-can produce a chemical adsorption with chalcopyrite surface,and the adsorption will also cause a certain degree of damage to the surface structure,but Cl O₃^-plays a major role in the proces s of chalcopyrite leaching.In addition,Cl O₃^-is more likely to adsorb at Fe site on chalcopyrite surface with an adsorption energy of-45.0 kcal/mol but further reaction will generate sodium jarosite precipitation,while the adsorption of Cl O ₃^-at the Cu site destroys the Cu-S bond directly and can not further reaction to produce precipitation.This also can explains why the concentration of Cu in the leaching solution is much higher than that of Fe during the process of Na Cl O₃ oxidative leaching chalcopyrite.The adsorption of H₂O₂ on different sites of chalcopyrite(001)-S surface was studied by First-principles method.The results indicate that t he oxidant H₂O₂is more likely to adsorb on the Fe sites of chalcopyrite(001)-S surface and the adsorption energy for the most favorable ads orption mode is calculated to be-62.1 kcal/mol.Only when H₂O₂ adsorbed on the Fe sites,it can dissociate.The calculated results show that it dissociates into hydroxyl anion and hydroxyl radical,and there will be the formation of SO₄^2-and elemental S in the reacti on under acidic medium,which are consistent with the experimental results.