摘要：
The range between dietary deficient and toxic levels for selenium is quite narrow. In this study, the synergistic effects of electrokinetics (EK) and a permeable reactive barrier (PRB) on the reductive sequestration of Se(IV) oxyanions from spiked soils were investigated in detail. Activated charcoal (AC)-supported Fe(II) and nanoscale zero-valent iron (nZVI) were prepared as the PRB media for use in an electrolyzer. In aqueous equilibrium adsorption tests, the AC-supported nZVI medium had a higher adsorption capacity than that of the other adsorbents. The Se(IV) removal isotherms were well-fitted using the Langmuir model. The Se(IV) removal rates were accurately predicted by both pseudo-first- and pseudo-second-order kinetic models. For the coupled systems, a moderate increase in the number of PRBs and decrease in the PRB thickness in the electrolyzer enhanced the removal and catalytic recovery of Se(IV) from the spiked soil samples. A Se(VI) removal efficiency of approximately 95% and Se(VI) reduction efficiency of 90% were achieved in the optimized electrochemical system. The Se(IV) species were reduced to Se degrees and FeSe by the AC-supported nZVI regardless of the pH distribution. The experimental results provide guidance for the multichannel recovery of Se from abandoned ore tailings or solid wastes.
摘要：
A greenhouse pot experiment was performed to investigate the enhancement of repeated applications of citric acid (CA), ethylenediamine disuccinic acid (EDDS), and Oxalic acid (OA) on phytoremediation of uranium (U) contaminated soil by Macleaya Cordata. The chelates followed the order CA > EDDS > OA in terms of the enhancement on uranium uptake by M. cordata. The repeated applications of the chelates were found to be more effective than the one time application at the equal dose as the U concentration of soil solution increased significantly from the 8th to 14th day. The repeated applications of 10 mmol kg(-1) CA promoted the solubilization of U in the U-contaminated soil by significantly decreasing the pH of soil solution, achieved the maximum U concentration of soil solution (1463.6 microg L(-1)), bioconcentration factors (BCFs, 11.4), bioaccumulation factors (BAFs, 21.4) and transfer factors (TFs, 1.9), which were 215.2, 5.7, 30.6 and 16.3 times as compared with the control group, respectively. The three applied chelates significantly affected the activities of the antioxidant enzymes in the leaves. Repeated applications of CA further enhanced the activities of the antioxidant enzymes in the leaves of M. cordata as compared with the control, EDDS and OA, mitigated the oxidative stress induced by uranium and chelates, and maximized the enhancement on the uranium uptake, which will be beneficial for the enhancement on the phytoremediation of uranium contaminated soil by U hyperaccumulating plants. These results indicated that the phytoavailability of uranium in soil solution as well as the accumulation of U by M. cordata were both significantly increased after repeated applications of CA, and that the repeated applications of 10 mmol kg(-1) CA increased the activities of the antioxidant enzymes and promoted U accumulation by M. cordata. The study provided an environmentally friendly alternative for the enhancement on the phytoremediation of uranium contaminated soil using M. cordata.
作者机构：
[Li Feng; Zou Chao; Dai Zhong-ran; Ding De-xin; Li Guang-yue; Hu Nan; Wang Yong-dong; Cui Yue-ting; Sun Jing; Sha Yin-hua; Zhang Hui] Univ South China, Key Discipline Lab Natl Def Biotechnol Uranium Mi, Heng Yang 421001, Hunan, Peoples R China.
通讯机构：
[Wang Yong-dong] U;Univ South China, Key Discipline Lab Natl Def Biotechnol Uranium Mi, Heng Yang 421001, Hunan, Peoples R China.
作者：
Wen, Lei*;Luo, Zhou Quan;Yang, Shi Jiao;Qin, Ya Guang;Ma, Shao Wei;...
期刊：
ROYAL SOCIETY OPEN SCIENCE,2019年6(3):181591 ISSN：2054-5703
通讯作者：
Wen, Lei
作者机构：
[Wen, Lei; Luo, Zhou Quan; Ma, Shao Wei; Jiang, Hong; Qin, Ya Guang] Cent S Univ, Sch Resources & Safety Engn, Changsha 410083, Hunan, Peoples R China.;[Yang, Shi Jiao] Univ South China, Sch Nucl Resources Engn, Hengyang 421001, Peoples R China.
通讯机构：
[Wen, Lei] C;Cent S Univ, Sch Resources & Safety Engn, Changsha 410083, Hunan, Peoples R China.
关键词：
P-wave velocity;damage index;integrality coefficient;point load strength;rock mass
摘要：
The damage index is a crucial controlling parameter for rock mass strength and deformation in civil, geological and mining engineering projects. In this study, a new method was proposed for computing the damage index of a rock mass based on the field point load strength. This method provides a strength ratio whose numerator is the point load strength (PLS) of splitting along the pre-existing joint and whose denominator is the PLS of intact rock failure. To validate this method, the authors derived a relationship between the damage index and the integrality coefficient using an empirical relation. Moreover, numerous experimental tests were conducted, including P-wave testing and on-site point load testing. Finally, linear regression analysis was performed to analyse the correlation between the new damage index D R and the integrality coefficient K V . This study demonstrates that the presented new method is sensitive to both plasticity and damage in estimating the damage degree of rock masses in underground excavation and tunnel engineering.
关键词：
Adsorption;Hexametaphosphate green rust;Hexavalent chromium removal;Intercalated anion;Layered double hydroxides
摘要：
Hexametaphosphate intercalated green rust (hexa-P GR) was fabricated by a coprecipitation process in an anaerobic environment to improve the adsorption of hexa-P GR for Cr(VI) and the total Cr under various aqueous conditions. Three kinetic models including the pseudo-first-order, intraparticle, and Elovich were appropriate in describing the adsorption of hexa-P GR towards Cr(VI) and the total Cr. The maximum mono-layer adsorption capacities (mg/g) of hexa-P GR for Cr(VI) at pH of 2 and 7 were 87.64 and 92.25, respectively, with the theoretical maximum capacity (mg/g) of 52.73 being obtained at pH of 7. Some competing cations existing in solutions such as Al(3+), Ca(2+), and Mg(2+) would consume more hexa-P GR to remove Cr species. The neutral and weak alkaline environment was conducive to the hexa-P GR reuse, while the strong alkaline environment was beneficial to the removal of the total Cr. The orthogonal variables including the initial pH, the flow rate, and the Cr(VI) concentration all significantly influenced Cr removal. The sequences of reaction pathways referring to the adsorption of hexa-P GR differently occurred in various pH conditions.
作者机构：
[Dai, Zhongran; Sun, Yusu; Zhang, Hui; Ding, Dexin; Li, Le] Univ South China, Key Discipline Lab Natl Def Biotechnol Uranium Mi, Hengyang 421001, Peoples R China
通讯机构：
[Ding, Dexin] U;Univ South China, Key Discipline Lab Natl Def Biotechnol Uranium Mi, Hengyang 421001, Peoples R China.
会议名称：
4th North American Symposium on Chemical Reaction Engineering (NASCRE)
会议时间：
MAR, 2019
会议地点：
Houston, TX
摘要：
Efficient removal of U(VT) from mine radioactive wastewater is important for environmental remediation and radiation protection. In this work, a new series of polyamidoxime/polydopamine-decorated graphene oxide (GO/PDA/PAO) composites were obtained by one-pot synthesis and used for the removal of U(VI) from mine radioactive wastewater. The as-synthesized GO/PDA/PAO composites (GO/PDA/PAO-0.2, GO/PDA/PAO-0.5, and GO/PDA/PAO-1) were examined by transmission electron microscopy, Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The effects of pH, ionic strength, contact time, initial U(VI) concentration, and temperature on the adsorption behavior of U(VI) by GO/PDA/PAO were investigated. The maximum adsorption capacity of GO/PDA/PAO-0.2 was 502.5 m g/g at pH 6.0 and 298 K. The adsorption kinetics and isotherms can be well illustrated by the pseudo-second-order kinetics model and Langmuir isotherm model. The thermodynamic study indicated that the removal of U(VI) by GO/PDA/PAO-0.2 was an endothermic and spontaneous process. The interactions between GO/PDA/PAO-0.2 and U(VI) were explained based on the FT-IR and XPS analyses. Furthermore, GO/PDA/PAO was applied for U(VI) removal from mine radioactive wastewater. The concentration of U(Vl) in the wastewater can be reduced to 7.28 /mu g/L, which is below the allowable uranium concentration for drinking water stipulated in the standard by the World Health Organization (30 mu g/L).
作者：
Wasantha, P. L. P.*;Ranjit, P. G.;Permata, G.;Bing, D.
期刊：
Measurement,2018年130:8-17 ISSN：0263-2241
通讯作者：
Wasantha, P. L. P.
作者机构：
[Wasantha, P. L. P.] Victoria Univ, Coll Engn & Sci, Melbourne, Vic, Australia.;[Ranjit, P. G.; Permata, G.] Monash Univ, Dept Civil Engn, Deep Earth Energy Lab, Clayton, Vic 3800, Australia.;[Bing, D.] Univ South China, Nucl Resources Engn Coll, Heng Yang 421001, Peoples R China.
通讯机构：
[Wasantha, P. L. P.] V;Victoria Univ, Coll Engn & Sci, Melbourne, Vic, Australia.
摘要：
Microscopic properties have a marked influence on the macroscopic mechanical response of sandstones. Improved understanding of the mechanical behaviour of these rocks caused by their microscopic properties is imperative for the successful design of rock structures. Here we experimentally investigate the damage evolution and deformation behaviour of three types of sandstones from Australia with contrasting petrographic properties under dry and saturated conditions with the aid of an optical strain and deformation measurement system (ARAMIS camera). More accurate and representative strain measurements are obtained using ARAMIS camera images compared to conventional strain measurement techniques. The results revealed that the quartz content of sandstone alone is not indicative of its strength, as the sandstone with the highest quartz content showed the lowest strength and this was attributed to the superior influence of other microscopic properties, such as grain size and porosity. However, the quartz content displayed a significant influence on the water-weakening behaviour of the sandstones, where the sandstone with the greatest quartz content was least affected by saturation and the sandstones with considerable clay mineral content showed greater weakening due to water. It was also found that some clay minerals are susceptible to swelling in the presence of water, and this can increase the initial crack volume and affect deformation characteristics. ARAMIS camera images clearly illustrated a more brittle behaviour by the sandstone with the greatest quartz content and notable early deformation by the sandstones with greater clay mineral content. Moreover, it was found that the overall deformation of sandstones was influenced by the swelling capacity of the constituent clay minerals, in addition to their composition by percentage.
