Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, United States.
Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, United States.
Waste Manag. 2018 Jul;77:1-9. doi: 10.1016/j.wasman.2018.04.027. Epub 2018 May 26.
Gallium arsenide (GaAs) is a material widely used in electronic devices. Disposal of electronic waste containing GaAs in municipal solid waste landfills raises concerns about the public health and ecological risks associated with the potential release of toxic arsenic (As) species. In this study, different tests were performed to investigate the leaching behavior of particulate GaAs in aqueous solutions. In the U.S. Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET), the concentrations of As released from the GaAs particles were about 2.6-2.8-fold higher than the regulatory limit (5 mg/L). A much higher As concentration (72 mg/L), accounting for as much as 15.4% of the initial As in GaAs, was solubilized in a pH-7.6 synthetic landfill leachate under ambient atmosphere after 120 days. Additional tests performed to evaluate the dissolution of GaAs under a range of redox conditions, pH levels, ionic strength, and presence of organic constituents commonly found in landfills revealed that oxic environments and mildly alkaline conditions (pH 8.1-8.5) promote release of As (chiefly arsenite) and gallium species to the surrounding aqueous environment. The rate of As release in long-term exposure experiments was initially constant but later progressively diminished, likely due to the formation of a passivating layer on the surface of GaAs consisting of corrosion products rich in poorly soluble gallium oxides (GaO and Ga(OH)). This hypothesis was confirmed by surface analysis of GaAs particles subjected to leaching using X-ray photoelectron spectroscopy (XPS). These findings suggest that further research is needed to assess the potential release of toxic As from electronic waste in municipal landfills.
砷化镓（GaAs）是一种广泛应用于电子设备的材料。将含有 GaAs 的电子废物处置在城市固体废物填埋场中，引起了人们对潜在释放有毒砷（As）物种对公共健康和生态风险的关注。在这项研究中，进行了不同的测试来研究颗粒状 GaAs 在水溶液中的浸出行为。在美国毒性特征浸出程序（TCLP）和加利福尼亚废物提取测试（WET）中，从 GaAs 颗粒中释放的 As 浓度比法规限制（5mg/L）高约 2.6-2.8 倍。在环境气氛下，在 pH-7.6 的合成垃圾渗滤液中，120 天后溶解的 As 浓度（72mg/L）要高得多，占 GaAs 中初始 As 的 15.4%。在一系列氧化还原条件、pH 值、离子强度和填埋场中常见的有机成分存在下进行的额外测试表明，有氧环境和弱碱性条件（pH8.1-8.5）促进了 As（主要是亚砷酸盐）和镓物种向周围水相环境的释放。在长期暴露实验中，As 的释放速率最初是恒定的，但后来逐渐减少，可能是由于在 GaAs 表面形成了一层由富含难溶氧化镓（GaO 和 Ga(OH)）的腐蚀产物组成的钝化层。这一假设通过使用 X 射线光电子能谱（XPS）对浸出后的 GaAs 颗粒进行表面分析得到了证实。这些发现表明，需要进一步研究来评估电子废物在城市垃圾填埋场中释放有毒 As 的潜力。
