Investigation of Sludge Volume from Abandoned Mine Wastewater Treatment by Layered Double Hydroxides: A Case Study Targe
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Investigation of Sludge Volume from Abandoned Mine Wastewater Treatment by Layered Double Hydroxides: A Case Study Targeting As and Fe Xinyi Yang1 · Mir Tamzid Rahman2 · Tomohito Kameda1 · Yusei Masaki3 · Yuko Saito1 · Shogo Kumagai1 · Toshiaki Yoshioka1 Received: 9 April 2019 / Accepted: 8 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We treated three samples of wastewater from an abandoned mine using NO3-type Mg–Al layered double hydroxides with different Mg/Al ratios (denoted LDH-2 and LDH-4) and the conventional neutralizer Ca(OH)2. We determined the optimal condition for each treatment before confirming the residual As and Fe concentrations, pH, and the amount of suspended solids (SS) in the supernatant after treatment under optimal conditions. We then estimated and compared the volume of sludge generated over 8 h in each treatment. We found that when treated under optimal conditions, both As and Fe were removed in compliance with Japan’s Uniform National Effluent Standards and that pH and SS met the standard in all cases. The final sludge volume at 8 h was 70 mL when Ca(OH)2 was used; this was twice as much when LDH-2 was used (30 mL) and four times that when LDH-4 was used (15 mL). These results strongly suggest that LDH has a high potential for treating wastewater from mines. Keywords Mg–Al LDH · Ca(OH)2 · Metal · Water treatment · Optimization
Introduction Japan used to be a leading mining country; production peaked around World War II. However, the depletion of mineral resources and massive imports of high-quality, low-cost foreign resources led to the closure of nearly 5000 mines in Japan; ≈ 450 of these abandoned mines are still pollution sources (JOGMEC 2018). Since Japan mined mostly Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10230-020-00697-4) contains supplementary material, which is available to authorized users. * Tomohito Kameda [email protected] 1
Graduate School of Environmental Studies, Tohoku University, 6‑6‑07 Aoba, Aramaki‑aza, Aoba‑ku, Sendai, Miyagi 980‑8579, Japan
2
Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
3
Metals Environment Management Department, Japan Oil, Gas and Metals National Corporation (JOGMEC), 10‑1 Toranomon 2‑chome, Minato‑ku, Tokyo 105‑000, Japan
sulfide minerals, the minerals remaining after the mines were closed include pyrite ( FeS2), chalcopyrite ( CuFeS2), and galena (ZnS); these are exposed to oxygen in the air and groundwater, generating acid mine wastewater containing various harmful metals (JOGMEC 2006). The proper treatment of abandoned mine wastewater is vitally important for the safety of humans and the environment. Chemical precipitation is widely used to treat mine wastewater. Lime (Ca(OH)2) or caustic soda (NaOH) are often used to precipitate metal hydroxides, which are generally stable and insoluble in alkaline solutions. The process is relatively simple and effective and
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