Gallium is widely used in electronic industry and its current price is about 500 US dollars pro kilogram. It has been found that its contents are very high in Permo-Carboniferous coal of China. In order to look for valuable associated gallium deposits in coal, gallium contents of 177 coal samples were determined by using inductively coupled plasma-mass spectrometry (ICP-MS) and the data of 873 coal samples from Chinese Permo-Carboniferous coalfields were collected. The results show that the average gallium concentration of Chinese Permo-Carboniferous coals is 15.49µg·g -1 . There are two concentration types of gallium in Chinese Permo-Carboniferous coals: One type is that gallium has enriched to an ore deposit, and another type is that gallium is locally enriched in coal seams, but has not formed a valuable associated gallium ore deposit. The gallium concentration in Chinese Permo-Carboniferous coal may have several different sources: concentration in sedimentation stage, magmatic hydrothermal inputs and low-temperature hydrothermal fluids.
Microbial induced carbonate precipitation (MICP) is a new geotechnical engineering technology used to strengthen soils and other materials. Although it is considered to be environmentally friendly, there is a lack of quantitative data and objective evaluation to support conclusions about its environmental impact. In this paper, the energy consumption and carbon emissions of MICP technology are quantitatively analyzed by using the life cycle assessment (LCA) method. The environmental effects of MICP technology are evaluated from the perspectives of resource consumption and environmental impact. The results show that for each tonne of calcium carbonate produced by MICP technology, 1.8 t standard coal is consumed and 3.4 t CO2 is produced, among which 80.4% of the carbon emissions and 96% of the energy consumption come from raw materials. Comparing using MICP with cement, lime, and sintered brick, the current MICP application process consumes less non-renewable resources but has a greater environmental impact. The major environmental impact that MICP has is the production of smoke and ash, with secondary impacts being global warming, photochemical ozone creation, acidification, and eutrophication. In five potential application scenarios of MICP, including concrete, sintered brick, lime mortar, mine cemented backfill, and foundation reinforcement, the carbon emissions of MICP are 3 to 7 times greater than the emissions of traditional technologies. The energy consumption is 15 to 23 times. Based on the energy consumption and carbon emissions characteristics of MICP technology at the current condition, suggestions are given for the future research of MICP.
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