Departamento de Energía, Universidad Autónoma Metropolitana-Azcapotzalco, Av. San Pablo 180, Col. Reynosa Tamaulipas, Azcapotzalco, 02200 CDMX, Mexico.
CONACYT, Universidad Autónoma Metropolitana-Azcapotzalco, Av. San Pablo 180, Col. Reynosa Tamaulipas, Azcapotzalco, 02200 CDMX, Mexico.
Waste Manag. 2019 Aug 1;96:181-189. doi: 10.1016/j.wasman.2019.07.030. Epub 2019 Jul 24.
In this work, an environmentally-friendly leaching process for the recovery of indium (In) and tin (Sn) from LCD panel waste was investigated. Easily degradable citrates (CHO), i.e., sodium citrate and citric acid, were used as complexing agents. The morphology and composition of the species present in the LCD powder before and after the leaching processes were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The concentrations of In, Sn, and iron (Fe) present in the leachate were determined by atomic absorption spectrometry (AAS). The necessary thermodynamic conditions for achieving substantial In recovery were established by using MEDUSA software. The optimal process conditions were determined experimentally by varying the initial citrate concentration as well as by using reducing or oxidizing media, respectively hydrazine (NH) or hydrogen peroxide (HO). It was found that using NH in a citrate solution as a reducing agent enhances the leaching efficiency. However, high concentrations of Sn and Fe with respect to In were found in the LCD powder. Therefore, a pretreatment processes to first remove the excess of Sn and Fe, which compete with In for the citrate, was implemented. Leaching with 1 M citrate, 0.2 M NH, at pH = 5, using sodium hydroxide (NaOH) at solid:liquid (S:L) ratio of 20 g∙L, yielded a remarkably high In recovery of 98.9% after 16.6 h.
本工作研究了从液晶显示器（LCD）面板废物中回收铟（In）和锡（Sn）的环保浸出工艺。易降解的柠檬酸盐（CHO），即柠檬酸钠和柠檬酸，被用作络合剂。采用扫描电子显微镜（SEM）和能谱（EDS）对浸出前后 LCD 粉末中的物种形貌和组成进行了表征。采用原子吸收光谱（AAS）测定浸出液中 In、Sn 和铁（Fe）的浓度。通过使用 MEDUSA 软件确定了实现大量 In 回收所需的热力学条件。通过改变初始柠檬酸盐浓度以及分别使用肼（NH）或过氧化氢（HO）作为还原或氧化介质，实验确定了最佳的工艺条件。结果表明，在柠檬酸盐溶液中使用 NH 作为还原剂可提高浸出效率。然而，LCD 粉末中 Sn 和 Fe 的浓度相对于 In 较高。因此，实施了预处理过程以首先去除与 In 竞争柠檬酸的过量 Sn 和 Fe。在 1 M 柠檬酸盐、0.2 M NH、pH=5 的条件下，使用 20 g∙L 的氢氧化钠（NaOH）作为固液比（S:L），在 16.6 h 后可获得高达 98.9%的 In 回收率。
