Qin Wen-qing

Oxygen adsorption on pyrite (100) surface by density functional theory

Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2(100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2− have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.

Dynamics of electrodeposition of tetraethylthioram disulphide (TETD) on pyrite surface

The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiostatic and chronopotentiometry. Tetraethylthioram disulphide (TETD) was electrodeposited on pyrite electrode surface as the electrode potential is higher than 0.2 V. The relationship of the current density caused by diffusion and reaction time can be ascertained as i=1/(9.08×10−5+4.77×10−3t0.5), and the diffusion coefficient of DDTC on pyrite surface is about 3.72×10−6 cm2/s. At pH 11.4, the thickness of TETD adsorbed on pyrite surface is about 1.63 molecule layer. The electrochemical dynamics equation of the reduction of TETD on pyrite surface is given as η=0.116−0.064log[1−(t/τ)0.5]. The kinetic parameters were determined as follows: the exchange current density (i0) is 3.08 µA/cm2; the transmission coefficient(α) is 0.462.

Electrode process of diethyldithiocarbamate on surface of pyrrhotite

The electrode process of diethyldithiocarbamate on the surface of pyrrhotite was studied using systematic electrochemical analysis, including cyclic voltammetry, chronopotentiometry and galvanostatic. Experimental results show that tetraethylthioram disulphide (TETD) is electrodeposited on pyrrhotite electrode surface in the presence of 1.0×10−4 mol/L diethyldithiocarbamate when the electrode potential is higher than 0.25 V. The electrochemical kinetics parameters of the electrode process of diethyldithiocarbamate on surface of pyrrhotite are calculated as follows: the exchange current density is 2.48 µA/cm2, and the transmission coefficient is 0.46. The electrodeposition includes two steps electrochemical reaction. The first reaction is electrochemical adsorption of diethyldithiocarbamate ion, then the adsorbed ion associates with a diethyldithiocarbamate ion from the solution and forms tetraethylthioram disulphide on the surface of pyrrhotite.