Environmental Fate of Gallium Arsenide Semiconductor Disposal

This article describes a methodology for the quantitative assessment of the environmental fate of gallium and arsenic from the disposal of mobile phones containing gallium arsenide (GaAs) semiconductors, using data from Japan. The product lifetime of mobile phones is short, and the recycling systems for such phones are currently underdeveloped. As a result, many mobile phones are disposed of via incineration and landfilling. The disposal of GaAs semiconductors could lead to some releases of gallium and arsenic to air and water. The methodology presented here begins with an estimation of the cumulative number of disposed mobile phones, using a logistic curve. Then, thermodynamic simulation and laboratory experiments are carried out to assess how much gallium and arsenic may be released into the environment. Using this method, the cumulative number of mobile phones disposed of in Japan is calculated to be 610 million by 2010. Distribution among air emissions, the leachate, and the insoluble residue (in landfilled incinerator ash) was determined to be 4.20 × 10‐2%, 1.58 × 10‐1%, and 99.8% for gallium, and 2.00 × 10‐1%, 19.5%, and 80.3% for arsenic, respectively. For phones that are disposed of directly in landfills, it is estimated that nearly 100% of the gallium and arsenic exists as the insoluble residue. We suggest that, in the conditions present in Japan, disposal of mobile phones directly into the landfill is preferable to the incineration with subsequent landfill of ash with respect to gallium and arsenic emissions into the environment. The proposed methodology may be adapted for the assessment of the environmental fate of problematic substances from the disposal of similar products.