Study On Mechanism Of Activation On Malachite Flotation By Octyl Hydroxamic Acid

Copper oxide ore is an important part of copper resources.With the continuous increase of copper demand,the development and utilization of copper oxide ore become inevitable.In view of the prominent effect of organic chelating agents on the activated flotation of copper oxide,it is necessary to conduct an in-depth study on the activation mechanism in order to provide a theoretical basis for the development of cheap and efficient activators.The study consists of three parts:Firstly,the flotation characteristics and interaction mechanismof the representative copper oxide mineral malachite and the commonly used organic chelating agent octyldihydroxamic acid were studied by solution chemistry theory and density functional theory.And then,the activated flotation of malachite was studied by flotation test,Zeta potential test,XPS test and determination of the amount of adsorption.Finally,molecular dynamics tools were used to simulate the activation of malachite flotation.The thesis draws the following main conclusions:Through the chemical analysis of the solution of malachite,it is found that the concentrations of the components dissolved by malachite are different under different pH values.At acidic pH,the surface of malachite is dominated by positive ions Cu2+;At alkaline pH,the surface of malachite is dominated by negative ions Cu(OH)42-.Density functional theory calculations of malachite crystals show that the malachite crystals exhibit metallic properties with good electrical conductivity.Cu and O atoms have higher reactivity in the malachite crystal.The dominant cleavage plane of malachite is(201).The calculation of the adsorption of isoamyl xanthate and octyl hydroxamic acid on malachite(201)shows that,octyl hydroxamic acid mainly interacts with Cu on the surface of malachite in the form of O,O five-membered chelate rings,while isopentyl xanthate is mainly adsorbed between the single bond S atom and the Cu atom on the surface of malachite.The adsorption energy calculation shows that the adsorption capacity of octyl hydroxamic acid on the malachite surface is much greater than that of the isoamyl xanthate.Analysis of the density of states shows that,when octyl hydroxamic acid is adsorbed on malachite(201),the 2p orbital electrons of O,C and S atoms in octyl hydroxamic acid all strongly interact with the 3d orbital electrons of Cu atom near the Fermi level.In the structure of octyl hydroxamic acid,a conjugate consisting of a pair of unsymmetrical electrons of C,O and a pair of N,0 atoms may be the main reason for the strong interaction.Flotation experiments show that the use of tantalum reagents,octyl hydroxamic acid and other copper-chelating agents as activators,can effectively activate the flotation of malachite.Under the condition of low chelating agent dosage,the dosage of isopentyl xanthine can be greatly reduced.The optimum pH for activated flotation is generally between 7 and 9.And the better the activator effect,the wider the effective pH range for activated flotation.Zeta-potential test showed that,The negative Zeta-potential of malachite increased greatly with the combination of hydroxamic acid and xanthate,which was significantly higher than that of octyl hydroxamic acid or xanthate adsorbed on malachite surface.This shows that the strengthening of the adsorption is not because of a simple combination of the two agents.XPS test showed that isopentyl xanthate and octyl hydroxamate can chemically react with copper ions on malachite surface and formed octyl hydroxamic acid-Cu and isopentyl xanthate-Cu adsorption membranes.Octyl hydroxamate and isopentyl xanthate do not interact with O on the malachite surface.The results of adsorption capacity show that there is a significant"synergistic-competitive" effect between isopentyl xanthate and octyl hydroxamic acid,but the synergistic effect is mainly manifested as the competition effect only occurs.when the concentration of one is too high.Their relationship between the amount and concentration of octyl hydroxamic acid and isopentyl xanthate adsorbed on the surface of malachite accords with the Freundlich equation.Octylhydroxamic acid and isopentyl xanthate adsorbed unevenly on the surface of malachite minerals,and their adsorption forms were mainly laminar.Octyl hydroxamic acid adsorbed on the inner layer of activation.Molecular dynamics studies on the malachite(201)hydrated membrane confirmed the presence of a water film on the malachite surface,and the malachite(201)surface belongs to the hydrophilic surface.Molecular dynamics simulations of the surface interaction with single-agent in aqueous environment found that the presence of hydration membrane on malachite(201)hinders the adsorption of the agent on the malachite surface.The molecular dynamics simulations under multivariate system showed that the existence of octyl hydroxamic acid and Cu2+ could significantly increase the adsorption capacity of isopentyl xanthate on malachite surface.And after the adsorption occurs,the agent tends to aggregate into a micellar structure,which effectively destroys the hydration membrane on the malachite surface and greatly improves the flotation performance of malachite.Further structural and kinetic analysis showed that when Cu2+ was present in the solution,a ternary blend was formed with octyl hydroxamic acid and isopentyl xanthate molecules,thus promoting the aggregation of xanthate to hydrophobic groups and accelerating the hydrophobization of malachite surface,thereby improving malachite floatability.At last,the mechanism model of octanoyl hydroxamic acid-activated flotation malachite was proposed based on the above research.