The 3rd LP-SAM* was held on June 22, 2018 (Friday). Three LP students made presentations, as stated below: The first presenter, who is the last member of this spring semester’s newly enrolled students**, introduced himself, his previous works and future research plans in the field of mining technology. The other two presenters gave progress reports on their current researches in the field mineral processing and economic geology, respectively.
Presenter 1: Hajime Ikeda (M1)
Traditional methods of collecting underground mine properties and qualities take up a lot of time and effort, not to mention that they usually interrupt operations and potentially expose human personnel to various hazards. A near-autonomous, wireless network of sensors and data loggers can greatly improve the way underground mines are monitored. The primary objective of my research is to develop a comprehensive communications system using Wi-Fi technologies (Wi-Fi Ad Hoc and Wi-Fi Direct) that will allow for this data collection and transmission to be possible, and ensure a safe and efficient mining operation. The key features of these Wi-Fi technologies is their ability to directly establish a peer-to-peer (P2P) connection between devices without the need for an access point or router, and as such can harness the movement of equipment and personnel (equipped with smartphones) as a form of data transmission. As various sensors underground monitor properties and qualities, data is sent and accumulated in data loggers found throughout the mine network. This data can then be sent through the network to a remote data center on the surface for analysis and visualization by trained staff. It is also possible to send the analyzed and/or visualized data to miners underground. Specifically, the process is developed by combining MANET (Mobile Ad hoc Network) and DTN (Delay Tolerant Network). We conducted preliminary experiments at the Osarizawa underground mining site in Akita prefecture and the results reveal that Wi-Fi Ad Hoc wireless communication has adequate communication performance suitable for underground mine monitoring system compared with other wireless sensor networks (WSNs).
Presenter 2: Enkhzul Bayarmagnai (M2)
This research is focusing on improving the flotation methods used to separate arsenic-bearing copper minerals from other sulphide minerals. The effects of using various flotation conditions such as pulp density, slurry pH and modifier reagents have been studied to build on the previous work done and improve the efficiency of flotation processing.
The ore studied consists of 0.9 mass% Cu, 0.3 mass% As and a small amount of other elements such as iron (Fe), zinc (Zn) and a high content of quartz (SiO2) which makes up 82 mass% of the ore. The main arsenic-bearing copper minerals is enargite (Cu3AsS4), with small amounts of tennantite (Cu12As4S13). The complex sulphide ore was crushed to below 125 μm using laboratory hammer crusher and a ball mill, and particle sizes of 80% passing 51 μm and 50% passing 21 μm were obtained using a particle size analyzer.
A sieve analysis was conducted with different particles size and the results indicated that approximately 37% of ore total mass was distributed in the finest fraction of <15 μm of the ore, with the distribution of Cu and As higher than 50% compared to other elements.The slurry pH during the flotation test was adjusted between 4 and 12 using 1M sulfuric acid (H2SO4) and 1M calcium oxide (CaO) solutions as required. After regulation of the pH, sodium silicate (Na2SiO3), Potassium Amyl Xanthate (PAX) and methyl isobutyl carboxymethyl (MIBC) were added into the slurry and stirring continued for five more minutes. After conditioning, the froth was scratched for ten minutes after each flotation.
The results confirm that a high pH of the slurry was progressively effective on Cu separation with a depression effect on pyrite (FeS2). The addition of other organic reagents such as dextrin, tannin and guar gum did not affect the recovery of the main elements. However, inorganic depressants (e.g. Na2SiO3 and Na2CO3) showed a significant change in the content of SiO2 in the concentrate.
In summary, the content of SiO2 reduced from 41% to 10%, and the grade of Cu and As reached to 17 mass% and 6.5 mass%, respectively. Recovery of Cu and As in the concentrate reached 65% and 55%, respectively, and the enrichment ratio of both Cu and As was 20. Finally, about 40% of Cu and As could not be recovered using conventional flotation processes. In the further work planned, I am going to control both the bubble size and pulp potential to increase the copper recovery in the concentrate.
Presenter 3: Carmela-Alen Jayme Tupaz (D1)
One of the objectives of my PhD study is to elucidate the mineral and chemical variations in Ni-laterite deposits and hence, I presented preliminary results on the mineralogical characteristics of a Ni-laterite profile in Palawan, Philippines. Petrographical observations reveal that the dominant primary mineral of the bedrock is serpentine, whereas olivine (forsterite) and pyroxene (enstatite) are minor. Both of the latter minerals are highly fractured and crosscut by serpentine veins. Accessory chromian spinel is dark-red and euhedrally-to-subhedrally-shaped. The main mineral in the saprolite horizon is serpentine with trace amounts of goethite and Fe-oxide mineral (magnetite). Overlying the saprolite horizon is the limonite horizon, which is characterized by the occurrence of goethite, hematite and gibbsite, and minor amounts of residual silica and chromian spinel. Based on X-ray diffraction analysis, goethite appears to be the dominant mineral near the transition boundary between the saprolite and limonite horizons. Hydration of olivine and pyroxene is considered to have resulted in the formation of serpentine and magnetite. High magnetic susceptibility values in the upper part of the limonite horizon corresponded with the relative enrichment of fine-grained magnetite at profile depths of 6 m and 9 m. The profile generally shows a mineral evolution from a silicate dominant (serpentine) horizon to a Fe-oxyhydroxide dominant (goethite, hematite) horizon.
*LP-SAM: Leading Program Student Activity Meeting
LP-SAM provides a platform for students of different research backgrounds and professors to interact. It is aimed at developing and sharpening students’ organization and communication skills in a global environment. At such meetings, students share the activities that they are/were engaged in during the course of the academic year. These activities include reports on research progress, field survey, conferences and field trips etc.
Assistant Professors Dr. Altansukh Batnasan and Dr. Kofi Adomako-Ansah manage the LP-SAM course.
**Three LP students were newly enrolled in this April