Transformation from Organo-Cr (III) to Trivalent Chromium Mineral (Guyanaite/Grimaldiite) and its Environmental Implication |
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Authors: | Yangjian Cheng Xinya Xu Wenting Lin Ran Han Minghuai Liu |
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Affiliation: | 1. The College of Environment and Resources, Fuzhou University, Fuzhou, Fujian, Chinayjcheng@fzu.edu.cn;3. The College of Environment and Resources, Fuzhou University, Fuzhou, Fujian, China |
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Abstract: | Remediation of heavy-metal contamination by biomineralization has become an environmentally very important issue in the last two decades. Here we describe the transformation of amorphous organo-Cr(III) to chromium hydroxide oxide (guyanaite/grimaldiite) by hydrothermal treatment (HTT). First, glycine-Cr(III) was synthesized to serve as a simple model for exploring the conditions favoring HTT. Cell-bound Cr(III) was obtained by the reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] by Bacillus cereus. Then the reduced Cr(III) was chelated by ligands at the cell surface, forming cell-bound Cr(III). Subsequently, HTT was applied to treat cell-bound Cr(III) at different temperatures and for different lengths of time. The results showed that, by this treatment at 200°C for 7 days or at 250°C for 1 day, glycine-Cr(III) was converted to trivalent chromium mineral (guyanaite/grimaldiite), having the form of nanosheets with a length of 10~20 nm and a width of 3~5 nm under the described conditions. Cell-bound Cr(III) could also be converted to guyanaite/grimaldiite at 250°C for 9 days if it was bound by an organic compound more complex than glycine. Our finding showed that organo-Cr(III) could be transformed into minerals by an appropriate hydrothermal process, which is applicable to bioremediation of heavy-metal pollution. Our findings also suggest that organo-Cr(III) may play an important role in the biogeochemistry of chromium. |
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Keywords: | Biomineralization bioremediation guyanaite/grimaldiite nanosheets organo-Cr(III) |
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