Hamaura Jin, Hori Hisao, Fujishima Ayane, Mukae Hirofumi
Faculty of Science, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan.
Technology Innovation Center, Daikin Industries, Ltd., 1-1 Nishi-Hitotsuya, Settsu 566-8585, Japan.
Molecules. 2023 Oct 12;28(20):7057. doi: 10.3390/molecules28207057.
The mineralization of fluoroelastomers (FKMs) in superheated water in the presence of potassium hydroxide (KOH) was investigated with the aim of developing a methodology for recycling the fluorine element. Two FKMs-an "uncrosslinked FKM", representing a poly(vinylidene fluoride--hexafluoropropylene) (poly(VDF--HFP)) copolymer with a VDF/HFP molar ratio of 78/22 and a "crosslinked FKM" consisting of this copolymer (cured by peroxide) and carbon black-were treated. The fluorine content of these FKMs was efficiently transformed into F ions in the reaction solution using low KOH concentrations (0.10-0.50 M) at 200-250 °C. When the uncrosslinked or crosslinked FKMs reacted with aqueous KOH (0.20 M) at a rather low temperature (200 °C) for 18 h, the fluorine content of these FKMs was completely mineralized (both F yields were 100%). Although the crosslinked FKM contained carbon black, the fluorine mineralization of the FKM was not inhibited. The addition of Ca(OH) to the reaction solutions after the superheated water treatment at 250 °C for 6 h with aqueous KOH (0.50 M) led to the production of pure CaF, identified using X-ray spectroscopy, with 100% and 93% yields for the uncrosslinked and crosslinked FKMs, respectively.
为了开发一种回收氟元素的方法，研究了在氢氧化钾（KOH）存在下，氟弹性体（FKM）在过热水中的矿化作用。处理了两种FKM：一种是“未交联FKM”，它是一种偏二氟乙烯-六氟丙烯（poly（VDF-HFP））共聚物，VDF/HFP摩尔比为78/22；另一种是“交联FKM”，由该共聚物（用过氧化物固化）和炭黑组成。在200-250°C下使用低KOH浓度（0.10-0.50 M），这些FKM中的氟含量在反应溶液中有效地转化为F离子。当未交联或交联的FKM在相当低的温度（200°C）下与KOH水溶液（0.20 M）反应18小时时，这些FKM中的氟含量完全矿化（F产率均为100%）。尽管交联FKM含有炭黑，但FKM的氟矿化并未受到抑制。在250°C下用KOH水溶液（0.50 M）进行6小时的过热水处理后，向反应溶液中添加Ca(OH)2，分别以100%和93%的产率得到了经X射线光谱鉴定的纯CaF2，未交联和交联FKM的产率分别为100%和93%。
