The electronic structure and properties of FeS2 with the space groups of Pa3 and P1 were studied by the density functional theory. The generalized-gradient approximation exchange-correlation functional was used in con...The electronic structure and properties of FeS2 with the space groups of Pa3 and P1 were studied by the density functional theory. The generalized-gradient approximation exchange-correlation functional was used in conjunction with a plane wave-ultrasoft pseudopotential representation. Calculation results show that differences are observed in electronic structures and properties between Pa3 and P1 crystals. The band gap and energy loss of P1 are smaller than those of Pa3 crystal, while the dielectric constant, conductivity, refractive index, extinction coefficient, and intensity of optical absorption of P1 are larger than those of Pa3. These behaviors are attributed to the differences in symmetry, atomic arrangement, and Mulliken bond population of each unit for Pa3 and P1 crystals.展开更多
The thermal decomposition of pyrite, arsenopyrite and auriferous concentrates in the presence of sodium hydroxide was studied by using TG DTA and XRD methods. For the arsenopyrite mineral the reaction takes place at ...The thermal decomposition of pyrite, arsenopyrite and auriferous concentrates in the presence of sodium hydroxide was studied by using TG DTA and XRD methods. For the arsenopyrite mineral the reaction takes place at 200～350℃ with the formation of Na 2SO 4, Na 3AsO 4, FeSO 4, Fe 8As 10 O 23 and FeAs, and a large amount of FeAsS do not decompose at this temperature. When the temperature arrives at 800℃, the exothermic reaction takes place with the formation of Na 3AsO 4, Na 2SO 4, Fe 2O 3 and a little amount of As 4S 3. For the pyrite mineral the reaction takes place between 200～350℃ with the formation of Fe 2(SO 4) 3, Fe 3S 4, FeS, Na 2Fe(SO 4) 2 in addition to unreacted FeS 2 and NaOH. When the temperature arrives at 800℃, almost all the pyrite decomposes and the Fe 2O 3, Na 2SO 4, Fe(SO 4) 3 and a minor amount of Fe 1- x S are produced. The decomposition temperatures of arsenopyrite and pyrite get lower as their particle sizes are small. The results also indicated that with the addition of an appropriate amount of NaOH, nearly complete containment of arsenic and sulphur during the decomposition of auriferous concentrate may be possible.展开更多
Anodic dissolution of arsenopyrite in ammoniacal solution has been investigated by electrochemical methods. The process is an irreversible reaction with formation of a ferric oxidized film and is retarded by the film....Anodic dissolution of arsenopyrite in ammoniacal solution has been investigated by electrochemical methods. The process is an irreversible reaction with formation of a ferric oxidized film and is retarded by the film. The process rate is controlled by the electrochemical reaction on the electrode surface in the lower temperature range, or alternatively by the diffusion through the film in the higher temperature range. The overall reaction has 14 electron transferred and can be expressed by FeAsS + 11H2O = Fe(OH)3 + SO42- + HAsO42- + 18H+ + 14e-, and the reaction involves two steps: (1) FeAsS + 7H2O = Fe(OH)3 + HAsO42- + S0 + 10H+ + 8e- , (2) S0 + 4H2O = SO42- + 8H+ + 6e- .展开更多
基金financially supported by the Program for New Century Excellent Talents in Universities of China (No. NCET-11-0925)the National Natural Science Foundation of China (No. 51164001)the Scientific Research Foundation of Guangxi University (No.XBZ100498)
文摘The electronic structure and properties of FeS2 with the space groups of Pa3 and P1 were studied by the density functional theory. The generalized-gradient approximation exchange-correlation functional was used in conjunction with a plane wave-ultrasoft pseudopotential representation. Calculation results show that differences are observed in electronic structures and properties between Pa3 and P1 crystals. The band gap and energy loss of P1 are smaller than those of Pa3 crystal, while the dielectric constant, conductivity, refractive index, extinction coefficient, and intensity of optical absorption of P1 are larger than those of Pa3. These behaviors are attributed to the differences in symmetry, atomic arrangement, and Mulliken bond population of each unit for Pa3 and P1 crystals.
文摘The thermal decomposition of pyrite, arsenopyrite and auriferous concentrates in the presence of sodium hydroxide was studied by using TG DTA and XRD methods. For the arsenopyrite mineral the reaction takes place at 200～350℃ with the formation of Na 2SO 4, Na 3AsO 4, FeSO 4, Fe 8As 10 O 23 and FeAs, and a large amount of FeAsS do not decompose at this temperature. When the temperature arrives at 800℃, the exothermic reaction takes place with the formation of Na 3AsO 4, Na 2SO 4, Fe 2O 3 and a little amount of As 4S 3. For the pyrite mineral the reaction takes place between 200～350℃ with the formation of Fe 2(SO 4) 3, Fe 3S 4, FeS, Na 2Fe(SO 4) 2 in addition to unreacted FeS 2 and NaOH. When the temperature arrives at 800℃, almost all the pyrite decomposes and the Fe 2O 3, Na 2SO 4, Fe(SO 4) 3 and a minor amount of Fe 1- x S are produced. The decomposition temperatures of arsenopyrite and pyrite get lower as their particle sizes are small. The results also indicated that with the addition of an appropriate amount of NaOH, nearly complete containment of arsenic and sulphur during the decomposition of auriferous concentrate may be possible.
基金Supported by the National Natural Science Foundation of China (No.: 59674023)
文摘Anodic dissolution of arsenopyrite in ammoniacal solution has been investigated by electrochemical methods. The process is an irreversible reaction with formation of a ferric oxidized film and is retarded by the film. The process rate is controlled by the electrochemical reaction on the electrode surface in the lower temperature range, or alternatively by the diffusion through the film in the higher temperature range. The overall reaction has 14 electron transferred and can be expressed by FeAsS + 11H2O = Fe(OH)3 + SO42- + HAsO42- + 18H+ + 14e-, and the reaction involves two steps: (1) FeAsS + 7H2O = Fe(OH)3 + HAsO42- + S0 + 10H+ + 8e- , (2) S0 + 4H2O = SO42- + 8H+ + 6e- .
