| 3 | A review on the transformation of birnessite in the environment:Implication for the stabilization of heavy metals显示文摘Birnessite is ubiquitous in the natural environment where heavy metals are retained and easily transformed.The surface properties and structure of birnessite change with the changes in external environmental conditions,which also affects the fate of heavy metals.Clarifying the effect and mechanism of the birnessite phase transition process on heavy metals is the key to taking effective measures to prevent and control heavy metal pollution.Therefore,the four transformation pathways of birnessite are summarized first in this review.Second,the relationship between transformation pathways and environmental conditions is proposed.These relevant environmental conditions include abiotic(e.g.,co-existing ions,pH,oxygen pressure,temperature,electric field,light,aging,pressure)and biotic factors(e.g.,microorganisms,biomolecules).The phase transformation is achieved by the key intermediate of Mn(Ⅲ)through interlayer-condensation,folding,neutralizationdisproportionation,and dissolution-recrystallization mechanisms.The AOS(average oxidation state)of Mn and interlayer spacing are closely correlated with the phase transformation of birnessite.Last but not least,the mechanisms of heavy metals immobilization in the transformation process of birnessite are summed up.They involve isomorphous substitution,redox,complexation,hydration/dehydration,etc.The transformation of birnessite and its implication on heavy metals will be helpful for understanding and predicting the behavior of heavy metals and the crucial phase of manganese oxides/hydroxides in natural and engineered environments. | Miao Shi Qingzhu Li Qingwei Wang Xuelei Yan Bensheng Li Linhai Feng Chao Wu Rongrong Qiu Hongkai Zhang Zhihui Yang Weichun Yang Qi Liao Liyuan Chai | 2024 | Journal of Environmental Sciences2024，，5： | 0 |
| 4 | Highly selective growth of(6,5)single-walled carbon nanotubes from sigma phase alloy catalyst显示文摘The chirality structure of a single-walled carbon nanotube(SWNT)strongly depends on the composition of catalyst used in the chemical vapor deposition process.In this study,we develop a porous magnesia supported manganese-rhenium(MnRe/MgO)catalyst for chirality-selective synthesis of SWNTs.Detailed characterizations reveal that(6,5)tubes with a selectivity higher than 70%are grown from the Re-rich MnRe/MgO catalyst.By comparing the SWNT growth results with those of monometallic Mn or Re,the formation of sigma phase,an intermetallic compound occurring in transition-metal alloy systems,is revealed to be crucial for the dominant synthesis of(6,5)SWNTs.This work not only extends the application of sigma phase alloy for catalytic synthesis of SWNTs,but also sheds lights on the growth of SWNTs with a high chirality selectivity. | Liantao Xin Chen Ma Qianru Wu Shaokang Liu Linhai Li Xiuyun Zhang Liu Qian Maoshuai He Dong Li Fangqian Han Shulan Hao Lihu Feng Yahan Li Huaping Liu Lili Zhang Chang Liu Jin Zhang | 2024 | Nano Research2024，17，3： | 0 |
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