砷黄铁矿的电化学氧化行为及表面相构成

Electrochemical Oxidation Behavior and Surface Phase Composition of Arsenopyrite

通过电化学循环伏安法(CV)研究了砷黄铁矿在弱碱性溶液中的氧化过程,在相应的氧化电位下,对砷黄铁矿进行恒电位极化1800 s,获得稳定的表面氧化相。并采用X射线光电子能谱(XPS)和电化学阻抗(EIS)研究了电位对表面氧化相构成的影响及相应的膜层特征。结果表明,砷黄铁矿在0.25 V(阳极峰A2范围内)氧化,主要发生Fe的初步氧化溶解,Fe氧化生成Fe(OH)_(3),As氧化生成As_(2)O_(3),S氧化生成多硫化物和少量的SO_(3)^(2-)。在0.45 V(阳极峰A2)氧化,砷黄铁矿表面Fe(OH)_(3)含量由0.25 V的2%变为3.02%,可能存在Fe(III)-SO(亚硫酸铁),As氧化产生As_(2)O_(5),多硫化物S_(n)^(2-)的含量由0.25 V的1.93%提高到2.45%,达到最大。在0.6 V(阳极峰A3范围内)氧化,砷黄铁矿表面的Fe(OH)_(3)含量达到5.79%,Fe(III)-SO的含量进一步增大;As仍然主要以As_(2)O_(3)和As_(2)O_(5)的形式存在,As_(2)O_(5)的含量进一步提升;多硫化物发生氧化溶解生成SO_(4)^(2-),Sn^(2-)的含量降低到1.51%。未氧化砷黄铁矿的膜内层反应电荷转移电阻R_(2)值为46478Ω·cm^(2),在0.25 V氧化后R_(2)值升高到83946Ω·cm^(2),反映膜内层厚度的1/C2值达到最大,之后随着电位的提升,砷黄铁矿表面的多硫化物被氧化溶解,同时生成大量Fe(OH)_(3),R_(2)值和1/C_(2)值不断减小,R_(2)值由0.25 V的83946Ω·cm^(2)降低到0.45 V的39313Ω·cm^(2),最后降低为0.6 V时的11068Ω·cm^(2)。

Arsenopyrite is often associated with stibnite as arsenic-bearing antimony gold ore,and because the two minerals have similar floatability,in the process of separating antimony and arsenic by traditional froth flotation,arsenopyrite is easily selected into the antimony concentrate,making the arsenic content in the antimony concentrate too high and difficult to meet the grade requirements,and there are problems such as large dosage of chemicals,low sorting efficiency,low recovery rate and complex process flow.Potentiometric flotation is a sorting technology that controls the surface potential of sulfide minerals,which in turn changes the surface of the minerals,affecting the hydrophilicity and hydrophobicity of the mineral surface,to achieve effective separation between different minerals,in order to achieve high selectivity and low chemical flotation reagents consumption of sulfide minerals.It can realize the flotation separation of arsenic and antimony with high selectivity and low chemical consumption,but there is no unified understanding of the oxidation behavior of arsenopyrite,the composition of the oxidation phase and the influence on the flotation behavior.The mineral working electrode was prepared by using the powder pressing method in the ratio of arsenopyrite powder∶analytically pure solid paraffin wax∶spectrally pure graphite powder=8∶1∶1(mass ratio).The platinum sheet was used as the auxiliary electrode and the saturated glycerol electrode(SCE)was used as the reference electrode.The oxidation process of arsenopyrite in weak alkaline solution was investigated by electrochemical cyclic voltammetry(CV),and the stable surface oxidation phase was obtained by constant potential polarization of arsenopyrite for 1800 s at the corresponding oxidation potential.X-ray photoelectron spectroscopy(XPS)and electrochemical impedance(EIS)were also used to study the effect of potential on the composition of the surface oxidation phase and the corresponding film layer characteristics.The results showed that:(1)Oxidation of arsenopyrite in weakly alkaline solution occurred in 3 anodic oxidation processes A1,A2 and A3.Among them,anodic peak A1 was the oxidation of reduction products;anodic peak A2 started at 0.25 V and reached a peak at 0.45 V;anodic peak A3 started at 0.5 V and reached a peak at 0.6 V.In the range of anodic peak A2(0.25 V).Fe was oxidized to produce Fe(OH)_(3),As was oxidized to produce As_(2)O_(3),and S was oxidized to produce polysulfide and a small amount of SO_(3)^(2-).And at this potential the arsenopyrite surface was mainly composed of hydrophobic phase polysulfide and a small amount of Fe(OH)_(3)hydrophilic phase.At 0.45 V,the content of Fe(OH)_(3)on the surface of arsenopyrite did not change much from 0.25 V,and a small amount of Fe(III)-SO might be present,except for the presence of As_(2)O_(3),As was oxidized to produce As_(2)O_(5),and the content of polysulfide Sn^(2-)on the surface of arsenopyrite increased slightly;at this potential the surface of arsenopyrite was mainly composed of hydrophobic phase polysulfides as well as a large amount of hydrophilic phase-Fe(OH)_(3).In the range of the anodic peak A3(0.6 V),Fe and polysulfides were oxidized and dissolved,with the content of Fe(OH)_(3)reaching a maximum of 5.79%and the content of Fe(III)-SO further increasing;polysulfides were oxidized to produce SO_(4)^(2-);As still existed mainly in the form of As_(2)O_(3)and As_(2)O_(5),and the content of As_(2)O_(5)was further increased.And at this potential,the surface of arsenopyrite was mainly dominated by a small amount of polysulfides and a large amount of hydrophilic phases-Fe(OH)_(3)and Fe(III)-SO.(2)The impedance results showed that reaction charge transfer resistance R_(2)value of the inner layer of unoxidized arsenopyrite was 46478Ω·cm^(2),and R_(2)value of the inner layer of arsenopyrite rose to 83946Ω·cm^(2)after oxidation at 0.25 V.1/C2 value reflecting the thickness of the inner layer of the film reached the maximum,and after that,as the potential rose,the polysulfide on the surface of arsenopyrite was oxidized and dissolved,while a large amount of Fe(OH)_(3)was generated,which constituted a loose and porous hydrophilic film,R_(2)value and 1/C_(2)value decreased continuously,and R_(2)value decreased from 83946Ω·cm^(2)at 0.25 V to 39313Ω·cm^(2)at 0.45 V and finally to 11068Ω·cm^(2)at 0.6 V.