Solidification performances of contaminants by red mud-based cementitious paste filling material and leaching behavior of contaminants in different pH and redox potential environments

Considering the urgent need for disposal of red mud and the comprehensive treatment of coal mined-out areas, this paper presented red mud-based cementitious paste filling material (RMFM) to achieve the purpose of green filling treatment. However, the solidification performance of alkaline RMFM for contaminants can be affected when in contact with acid goaf water in practice, which may in turn causes secondary pollution to the surroundings. The leaching tests of RMFM under different pH and redox potential (Eh) conditions were designed to investigate the effects of environmental elements on the solidification performance of RMFM, and primarily investigated the treatment effectiveness of RMFM on goaf water. The test results manifest that the acidic and oxidizing environments could damage the hydration products generated by alkali and sulfate activation, thus affecting the solidification performance, while the alkaline and reducing environments could effectively prevent the release of the contaminants by enhancing the degree of alkali activation and inhibiting oxidation acid forming process. In the possible exposure environment, RMFM could effectively stabilize its own pollutants without secondary pollution. In addition, the powder RMFM samples had significant removal effects on heavy metals, the values of Cu, Pb, and As removal efficiency all reached more than 96.15%.

Detecting Redox Potentials Using Porous Boron Nitride/ATP-DNA Aptamer/Methylene Blue Biosensor to Monitor Microbial Activities

Microbial activity has gained attention because of its impact on the environment and the quality of people’s lives. Most of today’s methods, which include genome sequencing and electrochemistry, are costly and difficult to manage. Our group proposed a method using the redox potential change to detect microbial activity, which is rooted in the concept that metabolic activity can change the redox potential of a microbial community. The redox potential change was captured by a biosensor consisting of porous boron nitride, ATP-DNA aptamer, and methylene blue as the fluorophore. This assembly can switch on or off when there is a redox potential change, and this change leads to a fluorescence change that can be examined using a multipurpose microplate reader. The results show that this biosensor can detect microbial community changes when its composition is changed or toxic metals are ingested.

Tuning the Photocatalytic Activity of Tin Oxide Through Mechanical Surface Activation

Tin oxide (SnO2) nanoparticles were synthesized by the co-precipitation method and mechanically modified by high-energy ball milling. The experimental results demonstrate that the collision with zirconia balls produces slight changes in the crystalline, electronic, morphological, and surface properties of SnO2, which lead to an increase in the redox potential of the energy level and the formation of the hydroxyl group on the SnO2 surface. Moreover, these changes are intensified over the milling up to 90 min, directly affecting the photocatalytic performance, which was monitored by the rate of rhodamine B (RhB) degradation driven by ultraviolet (UV) irradiation. As a result, all ground samples showed better photocatalytic activity than pristine SnO2 (Sn-cop). The maximum degradation of rhodamine B was ca. 75%, achieved with 90 min-milled SnO2 nanoparticles (Sn-M90), compared to the Sn-cop sample induced a 1.67 times higher degradation rate. The reaction mechanism suggests that its better photocatalytic activity may be associated with the higher increased redox potential of the valence and conduction bands and the formation of hydroxyl active sites on the catalyst surface principal oxidizing agent generated. Therefore, we conclude that the ball milling process is an efficient way to induce stable activation of oxide metal for photocatalytic applications.

High Performance Lithium Ion Electrolyte Based on a Three-dimensional Holey Graphene Frameworks Cross-linked with Polymer

Metallic lithium based batteries hold great promise for next generation high-performance lithium ion batteries mainly due to its with extremely high theoretical capacity of 3860 mAh g-1 and low redox potential...

Tungsten and Molybdenum Heteropolyanions with Different Central Ions—Correlation between Theory and Experiment

Density functional theory calculations were carried out to investigate the electronic structures of Keggin-typed [XMo12O40]n− and [XW12O40]n− anions with different heteroatoms (X = Zn2+, B3+, Al3+, Ga3+, Si4+, Ge4+, P5+, As5+, and S6+). The influence of solvent on redox properties of heteropolyanions was discussed. For [XW12O40]n− systems two linear correlation: first, between the experimental redox potential and energies of LUMO orbital; and second, between the experimental redox potential and total energy interaction (calculated between internal tetrahedron (XO4n−), and rest of Kegging anion skeleton, (W12O36)) were designated. Taking into account the similarity of XW12O40n− and XMo12O40n− systems (in geometry and electronic structure), the estimated redox potential of molybdenum heteropolyanions (with X being p block elements) in different solvent were proposed.