Electrochemical Research Based On Polysiloxane Inhibiting Oxidation Of Pyrite Powders

Pyrite, one common sulfide in metallic ores and coal mine, is easy to be oxidised withthe help of water and oxygen. The mining and mineral industry has been adversely affected bythe oxidation of pyrite which lead to acid mine drainage (AMD) formation. From theprespecitive of enviroumental stafety, controling AMD radically is necessary. A protectivefilm comprised of polysiloxane formed on the pyrite surface, which prevents it fromcontacting water and oxygen, will greatly restrain the pyrite oxidation.Firstly, the efficiency of polysiloxane coating to suppress the pyrite oxidation underenvironmentally relevant conditions was investigated with electrochemical techniques. Theincreased proportion of polysiloxane in the modifying agent would enhance the protectiveeffect of the coating. The modifying agent with the least proportion of polysiloxane was usedin subsequent experiments to illustrate the excellent passivation of polysiloxane. Secondly, atpH2and pH4, all the experiment results, such as the anode peak area, current and thehysteresis obtained from the cyclic voltammograms, showed the uncoated pyrite was moreseriously oxidized than the coated one. The further information about charge transferresistance and electric double layer capacitance was obtained by Nyquist plot, and simulatedby the corresponding equivalent circuit. Thirdly, pH values was showed no significant effecton the coated pyrite oxidation current in cyclic voltammograms, that is to say, the passivationeffect arised from the coating was scarcely relative to pH value. With the increase of Fe3+concentration increase, the coating on the pyrite still showed good effect to retard the pyriteoxidation based on the Nyquist plot. No distinctive difference of Nyquist plots of coatedpyrite was obsvered after water impacting with different volumes, which identified theexcellent washing durability of the coating.The second part tried to interpret the inhibition of pyrite oxidation from surfacechemistry point of view. Active Si-H may crosslink with-OH on the pyrite surface thuspolysiloxane was adhered with pyrite via Si-O bond, which is the basic principle for theapplication of polysiloxane agent in this experiment. Contact angles of coated and uncoatedpyrite with time were tested and the results showed the pyrite with polysioxane film tended to be more hydrophobic than the uncoated pyrite. Accordingly, the efficiency of coating, withdifferent proportion of polysiloxane, to improve the pyrite hydrophobicity underenvironmentally relevant conditions was investigated. We confirmed the hydrophobicity ofcoated pyrite was scarcely crippled by pH values, Fe3+concentrations and the coating on thepyrite possessed good washing durability. All these results have explained the preventiveeffect of polysiloxane agent proved in the electrochemical part.Overall, this paper theoretically demonstrates the polysiloxane of pyrite oxidationinhibition, and provides the potential application forAMD treatment.