| In view of the micro disseminated primary gold ore,the quartz coated gold is as high as66.92%,sulfide coated gold is 15.94%,and silicate coated gold is 1.44%,the project team adopted advanced oxidation pretreatment alkali leaching pretreatment non cyanide leaching process in the early stage of the study,and achieved good gold leaching effect,but the dissolution mechanism of quartz was not explored,especially the influence of ions on quartz dissolution.In this paper,pure quartz minerals and actual ores are taken as the research objects to investigate the influence of unavoidable ions produced by alkaline materials dissolving quartz and advanced oxidation pretreatment on alkali dissolving quartz;the reaction mechanism of quartz solution interface is explored by using kinetics and quantum chemistry.The significant effect of alkaline substances on the dissolution of quartz minerals is Na OH>Na2CO3>Na HCO3>Ca O.In Na OH system,the influence of quartz particle size and dissolution temperature on the dissolution of quartz is particularly significant.NH4+and Fe2+in the solution can promote the dissolution of quartz by Na OH,and the concentration of unavoidable ions is between 0.01 mol/L and 0.06 mol/L.with the increase of dissolution time,the influence of unavoidable ions NH4+is obviously better than that of unavoidable ions Fe2+;the promotion effect of high concentration of unavoidable ions NH4+on the dissolution of quartz by Na OH is not obvious as that of low concentration.The（NH4）2SO4-Na OH system is used to dissolve gold bearing quartz in micro disseminated gold ore,and the dissolution behavior is consistent with that of pure quartz.In the（NH4）2SO4-Na OH system,the effect of quartz size and dissolution temperature on the dissolution of quartz conforms to the kinetic equation of chemically controlled shrinking nucleus 1-（1-α）1/3=kt,but the apparent activation energy calculated by Arrhenius formula is 12.02 k J/mol.This shows that the quartz has the particularity of Na OH dissolved quartz under the influence of unavoidable ions.It is speculated that the system is not a simple Na OH dissolution because it is a complex multi-phase and multi-phase system.The unavoidable ions lead to the particularity of Na OH-dissolved quartz.According to quantum chemistry calculation,the dissolution reaction path of Na OH,NH4+-Na OH and Fe2+-Na OH with quartz is"RC–TS1–IC–TS2–PC",in which the first transition state is the key to restrict the dissolution of quartz.The bond length of"RC–TS1–IC–TS2–PC"decreases in the three systems,but the change of bond angle has no obvious rule.In the process of Na OH dissolving quartz,the old bond breaks and new bond forms.In the three systems,the dissolution of quartz is nucleophilic addition elimination reaction.The chemical reaction formulas are as follows:-O（OH）2Si-O-Si（OSi（OH）3）3+H2O→（OH）3Si-OH+-O-Si（OSi（OH）3）3-O（OH）2Si-O-Si（OSi（OH）3）3+NH3·H2O→（OH）3Si-OH+-O-Si（OSi（OH）3）3+NH4+-O（OH）2Si-O-Si（OSi（OH）3）3+Fe2++3H2O→Si（OH）3Si-OH+-O-Si（OSi（OH）3）3+Fe2++2H2OThe calculated activation energies are 14.7 k J/mol,10.1 k J/mol and 13.7 k J/mol,respectively.The apparent activation energy（12.02 k J/mol）and the activation energy calculated by quantum chemistry are in the range from 10 k J/mol to 15 k J/mol,which proves that the calculation results of quantum chemistry have reference value for guiding experiments. |
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