1. Full name: Le Thu Thuy                                              2. Sex: Female

3. Date of birth: 08 March 1979                                       4. Place of birth: Bac Giang

5. Admission decision number: N0 4050/QD-DHKHTN-CTSV date on 19/9/2013 by the Rector of VNU University of Science.

6. Changes in academic process:

Decision to renew: N0 1033/ QD-DHKHTN date on 25/4/2017 by the Rector of VNU University of Science.

Decision to renew: N0 597/QD-DHKHTN date on 6/3/2018 by the Rector of VNU University of Science.

7. Official thesis title: “Research simulation on arsenic behavior, transfer and accumulate from pyrite and arsenopyrite in tailings ore dumps”

8. Major: Environmental Chemistry                                     9. Code: 62440120

10. Supervisors: Assoc.Pro.Dr. Tran Hong Con

                         Assoc.Pro.Dr. Nguyen Thi Cam Ha

11. Summary of the new findings of the thesis

The thesis has studied the weathering process and releasing arsenic from ore tails dump of typical pyrite and arsenopyrite-rich ores after sorting process by the simulation model of ores tail column under the conditions of water pulse and water submerged . The results found that the iron content in the ore considerably influences on the concentration of total arsenic as well as the ratio of As(III)/As(V) in the aqueous phase; in all cases, under the water pulse condition, As(V) is predominant; whereas  As(III) is prevailed under the submerged condition. However, the total arsenic concentration in the water pulse condition is always much higher than that in the submerged condition.

Research on behaviour of arsenic in the aqueous phase after weathering with the presence of accommpanied ions in two real conditions: (1) The anoxic condition, the  simulation process, where, after weathering, aqueous phase is moving along the cracks and soil holes under the ground and (2) The aerobic condition, the simulation of aqueous phase after weathering is moving on the ground. The results show that the concentration ratio of Fe/As and pH values are two decisive factors for the arsenic deposition and transportation.

The results have also shown that As(V) can exist in the condition of extremely decreased Eh and alkaline pH values without reducing into As(III).

The thesis has also demonstrated that the sulfur-reducing bacteria (Desulfovibrio. sp) have contribution to the arsenic speciation after weathering; they have the ability to reduce arsenate into arsenite and even into arsenide that is similar to the sulfate reduction process.

12. Practical applicability, if any:

The thesis’s results have contributed more knowledge to enhance the environmental protection in the sulfide ore mining and processing. The environmental pollution caused by weathering of pyrite or arsenopyrite - rich ores or other sulfide minerals could be prevented  if the sulfide containing wastes are discharged under water-submerged conditions, that will significantly decrease pollution in comparison with open-air conditions.

The thesis has contributed to explaining the mechanism of arsenic transformation, transport and accumulation after the weathering of pyrite and arsenopyrite ore. This currently is one of the most urgent issues in the study of geochemistry behavior of arsenic from sulfide ores dumps in mining areas.

13. Further research directions, if any

It is necessary to have further studies on other sulfide minerals, mixtures of sulfide minerals as well as the effects of other components on weathering, metabolism and transportation of arsenic and heavy metals.

14. Thesis-related publications:

[1] Le Thu Thuy, Tran Hong Con (2016), "Investigation of arsenic and heavy metals releasing from pyrite tailing using laboratory model", Jounral of Science on Natural Resources and Environment,  11, pp.60-63.

[2] Le Thu Thuy, Tran Hong Con (2016), “Investigation of arsenic and heavy metals releasing from arsenopyrite ore tailing”, Natural Resources and Environment magazine, 22(252) pp.29-31.

[3] Le Thu Thuy, Tran Hong Con, Nguyen Thi Cam Ha, Nguyen Thi Thuc Anh (2017), “Research on the speed of metalic release and arsenic behavior on water at the tailing dump”, General Department of Geology and Minerals of Vietnam, A, 364-365, pp.71-80.

[4] Le Thu Thuy, Tran Hong Con, Nguyen Thi Cam Ha, Nguyen Thi Thuc Anh (2018), "Study the release off arsenic and heavy metals and mobilization from pyrite tail", Jounral of Analytical Sciences, 23(2), pp.61-70.

[5] Le Thu Thuy, Tran Hong Con, Nguyen Thi Cam Ha, Nguyen Thi Thuc Anh (2018), “Arsenic behavior in water at the arsenopytite mine tailing”, 15th Regional Congress on Geology, Minerals and Energy of Southeast Asia (GEOSEA XV), Publishing House for Science and Tecnology, pp.212-213.

[6] Le Thu Thuy, Nguyen Thi Thuc Anh, Tran Hong Con, Nguyen Thi Cam Ha (2019), "Study the factors effecting to transfer of As(III) and As(V) after release from pyrite tail", Jounral of Analytical Sciences, 24(1), pp.78-84.