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Recovery of tungsten and cobalt from tungsten carbide tool waste by hydrometallurgical method
Junji Shibata,Norihiro Murayama,Masakazu Niinae 한국자원공학회 2014 Geosystem engineering Vol.17 No.2
In a present process to treat the tungsten carbide (WC) tool waste, the wastes are roasted in air and then an alkali leaching is carried out in an autoclave. An environmentally friendly process is required to recover rare metals (Co and W) from the wastes. The effect of mechano-chemical (MC) treatment on leaching of rare metals was investigated in this study. The solvent extraction and crystallization-stripping methods were applied to separate and recover tungsten and cobalt in the leached solutions. The MC treatment for the rare metal leaching is effective to dissolve rare metals from the wastes due to the change in crystalline structure of WC and oxidation of WC with KMnO4. Cobalt ions are extracted with di-2-ethylhexyl phosphoric acid by a cation-exchange reaction. Tungsten in the leachate can be extracted by tri-octyl amine as an extractant, because tungsten species exist as anionic species in acidic solution. The rare metals in organic phase are recovered as insoluble salts such as oxalates and ammonium salts in the crystallization-stripping process.
( Yuichi Matsuno ),( Takehiro Torisu ),( Junji Umeno ),( Hiroki Shibata ),( Atsushi Hirano ),( Yuta Fuyuno ),( Yasuharu Okamoto ),( Shin Fujioka ),( Keisuke Kawasaki ),( Tomohiko Moriyama ),( Tomohiro 대한장연구학회 2022 Intestinal Research Vol.20 No.2
Background/Aims: Recent studies suggested a favorable effect of indigo naturalis (IN) in inducing remission for refractory ulcerative colitis (UC), however, the maintenance effect of IN for patients with UC remains unknown. Therefore, we conducted a prospective uncontrolled open-label study to analyze the efficacy and safety of IN for patients with UC. Methods: Patients with moderate to severe active UC (clinical activity index [CAI] ≥8) took 2 g/day of IN for 52 weeks. CAI at weeks 0, 4, 8, and 52 and Mayo endoscopic subscore (MES) and Geboes score (GS) at weeks 0, 4, and 52 were assessed. Clinical remission (CAI ≤4), mucosal healing (MES ≤1), and histological healing (GS ≤1) rates at each assessment were evaluated. Overall adverse events (AEs) during study period were also evaluated. The impact of IN on mucosal microbial composition was assessed using 16S ribosomal RNA gene sequences. Results: Thirty-three patients were enrolled. The rates of clinical remission at weeks 4, 8, and 52 were 67%, 76%, and 73%, respectively. The rates of mucosal healing at weeks 4 and 52 were 48% and 70%, respectively. AEs occurred in 17 patients (51.5%) during follow-up. Four patients (12.1%) showed severe AEs, among whom 3 manifested acute colitis. No significant alteration in the mucosal microbial composition was observed with IN treatment. Conclusions: One-year treatment of moderate to severe UC with IN was effective. IN might be a promising therapeutic option for maintaining remission in UC, although the relatively high rate of AEs should be considered. (Intest Res 2022;20:260-268)