Novel treatment process to inhibit toxic metal dissolution from low-grade hydrothermal ore during seafloor mining

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K19991
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 64020:Environmental load reduction and remediation-related
• Research Institution: Tokyo University of Marine Science and Technology (2022-2023); Waseda University (2020-2021)
• Principal Investigator: Fuchida Shigeshi 東京海洋大学, 学術研究院, 准教授 (50762126)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 海底熱水鉱床開発 / ガルバニック腐食反応 / 不溶化処理 / 有害元素溶出 / 硫化鉱物

Outline of Final Research Achievements

Seafloor massive sulfide (SMS) mining has been attracted to obtain base metal resources during these decades. This study conducted an SMS-seawater reaction experiment to determine the metal dissolution rate and its mechanisms using natural SMS samples collected in Okinawa Trough. My result showed that direct contact with different sulfide minerals is estimated to accelerate greatly the zinc dissolution from SMS. In addition, I tried that SMS was reacted in carbonate solution to inhibit Zn dissolution by passivation of secondary minerals. I found that PbCO3 was formed by the reaction with Pb2+ released from soluble PbSO4 and it covered an SMS particle, resulting in that it can inhibit ZnS dissolution by the galvanic reaction in seawater.

Free Research Field

環境化学工学，地球化学

Academic Significance and Societal Importance of the Research Achievements

本研究で取り扱った硫化鉱物は資源開発に際して汚染源となりうることから，その地球化学的特徴や汚染発生メカニズム，汚染抑制方法について長年研究されてきた。今回の研究では知見の少ない海底熱水鉱床の硫化鉱物を対象として，硫化鉱物の分解が単なる酸化溶解反応のみならず，ガルバニック腐食反応によって速度が大きく向上することを定量的に明らかにした。また，海底熱水鉱床開発を見据え，炭酸塩を用いた不溶化処理が可能であることも明らかにした。これらの知見は今後進められる海底熱水鉱床開発への技術転用のみならず，現在進行中の陸上鉱山の様々な問題解決にも寄与することが期待される。