Sorption of Arsenic(III) from wastewater using Prosopis spicigera L. wood (PsLw) carbon-polyaniline composite

Water contamination by toxic heavy metal ions causes a serious public health problem for humans. The present work reports the development of a new adsorbent of PsLw carbon-polyaniline composite by direct oxidation polymerisation of aniline with PsLw carbon for the removal of arsenic (As). The structure and morphologies of the adsorbent were characterised by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The ability of the adsorbent for the removal of As(III) was estimated by batch and kinetic studies. The optimum adsorption behaviour of the adsorbent was measured at pH=6.0. The equilibrium process was found to be in good agreement with Langmuir adsorption isotherm and the maximum adsorption capacity was 98.8 mg/g for an initial concentration of 60 mg/L at 30 °C. The kinetic study followed pseudo-second-order kinetics. Thermodynamic parameters predict the spontaneous, feasible and exothermic nature of adsorption. Column operation was carried out to remove As(III) bulk and column data obeys the Thomas model. The results indicated that PsLw carbon-polyaniline composite can be employed as an efficient adsorbent than polyaniline for removal of As(III) from wastewater.

Preparation of a Novel Activated Carbon from Cassava Sludge for the High-Efficiency Adsorption of Hexavalent Chromium in Potable Water: Adsorption Performance and Mechanism Insight

Particularly, because of the leakage risk of metal elements from sludge carbon, little attention has been focused on using sludge activated carbon as an adsorbent for the removal of Cr (VI) from contaminated water sources. Herein, a novel sludge carbon derived from dewatered cassava sludge was synthesized by pyrolysis using ZnCl2 as an activator at the optimal conditions. The prepared sludge activated carbon possessed a large BET surface (509.03 m2/g), demonstrating an efficient removal for Cr (VI). Although the time to reach equilibrium was extended by increasing the initial Cr (VI) concentration, the adsorption process was completed within 3 h. The kinetics of adsorption agreed with the Elovich model. The whole adsorption rate was controlled by both film and intra-particle diffusion. The Cr (VI) removal efficiency increased with elevating temperature, and the adsorption equilibrium process followed the Freundlich isotherm model. The adsorption occurred spontaneously with endothermic nature. The removal mechanism of Cr (VI) on the prepared sludge activated carbon depended highly on solution pH, involving pore filling, electrostatic attraction, reduction, and ion exchange. The trace leakage of metal elements after use was confirmed. Therefore, the prepared sludge activated carbon was considered to be a highly potential adsorbent for Cr (VI) removal from contaminated raw water.

The Study of Multilayer Graphene Membrane Performance in O2 Purification Process: Molecular Dynamics Simulation

We use molecular dynamics (MD) method to describe the atomic behavior of Graphene nanostructure for Oxygen molecules (O2) separation from Carbon dioxide (CO2) molecules. Technically, for the simulation of graphene-based membrane and O2-CO2 gas mixture, we used Tersoff and DREIDING force fields, respectively. The result of equilibrium process of these structures indicated the good stability of them. Physically, this behavior arises from the appropriate MD simulation settings. Furthermore, to describe the purification performance of graphene-based membrane, we report some physical parameters such as purification value, impurity rate, and permeability of membrane after atomic filtering process. Numerically, by defined membranes optimization, the purification value of them reach to 97.31%. Also, by using these atomic structures the CO2 impurity which passed from graphene-based membrane reach to zero value.

Non-equilibrium process of transfer of momentum in medium with relaxation microstructure

The non-equilibrium process of transfer of the momentum of polymer media with an evolving nonequilibrium relaxation microstructure is considered. For the basic conditions of deformation, the regularities for the structural and dynamic components of the stress tensor with conjugate forces are obtained and analyzed, which are consistent with experiment.

Constrain on Oil Recovery Stage during Oil Shale Subcritical Water Extraction Process Based on Carbon Isotope Fractionation Character

In this work, Huadian oil shale was extracted by subcritical water at 365 °C with a time series (2–100 h) to better investigate the carbon isotope fractionation characteristics and how to use its fractionation characteristics to constrain the oil recovery stage during oil shale in situ exploitation. The results revealed that the maximum generation of oil is 70–100 h, and the secondary cracking is limited. The carbon isotopes of the hydrocarbon gases show a normal sequence, with no “rollover” and “reversals” phenomena, and the existence of alkene gases and the CH4-CO2-CO diagram implied that neither chemical nor carbon isotopes achieve equilibrium in the C-H-O system. The carbon isotope (C1–C3) fractionation before oil generation is mainly related to kinetics of organic matter decomposition, and the thermodynamic equilibrium process is limited; when entering the oil generation area, the effect of the carbon isotope thermodynamic equilibrium process (CH4 + 2H2O ⇄ CO2 + 4H2) becomes more important than kinetics, and when it exceeds the maximum oil generation stage, the carbon isotope kinetics process becomes more important again. The δ13CCO2−CH4 is the result of the competition between kinetics and thermodynamic fractionation during the oil shale pyrolysis process. After oil begins to generate, δ13CCO2−CH4 goes from increasing to decreasing (first “turning”); in contrast, when exceeding the maximum oil generation area, it goes from decreasing to increasing (second “turning”). Thus, the second “turning” point can be used to indicate the maximum oil generation area, and it also can be used to help determine when to stop the heating process during oil shale exploitation and lower the production costs.

SiSn mediated formation of polycrystalline SiGeSn

Si1-xSnx and Si1-x-yGexSny polycrystalline thin layers were grown using Sn nanodots as crystal nuclei. Si1-xSnx crystallization occurred around Sn nanodots, and the substitutional Sn content was estimated as high as 1.5%. In the case of the poly-Si1-x-yGexSny, Ge and Si were deposited simultaneously on the Sn nanodots, however, Ge was preferentially incorporated into the Sn nanodots, resulting in the formation of the poly-Si1-x-yGexSny with amorphous Si residue. It was found that the poly-Si1-xSnx formed by the Sn nanodots mediated formation can be used as the new virtual substrate to be alloyed with Ge, namely the 2step formation process consisting of poly-Si1-xSnx crystallization and Ge alloying with the Si1-xSnx is the effective formation process for the poly-Si1-x-yGexSny formation. This non-equilibrium process with achieving crystallization resulted in the substitutional Si and Sn content in the as-grown poly-Si1-x-yGexSny as high as 19.4% and 3.4%, respectively.

Steric interactions and out-of-equilibrium processes control the internal organization of bacteria

Despite the absence of a membrane-enclosed nucleus, the bacterial DNA is typically condensed into a compact body—the nucleoid. This compaction influences the localization and dynamics of many cellular processes including transcription, translation, and cell division. Here, we develop a model that takes into account steric interactions among the components of the Escherichia coli transcriptional–translational machinery (TTM) and out-of-equilibrium effects of messenger RNA (mRNA) transcription, translation, and degradation, to explain many observed features of the nucleoid. We show that steric effects, due to the different molecular shapes of the TTM components, are sufficient to drive equilibrium phase separation of the DNA, explaining the formation and size of the nucleoid. In addition, we show that the observed positioning of the nucleoid at midcell is due to the out-of-equilibrium process of mRNA synthesis and degradation: mRNAs apply a pressure on both sides of the nucleoid, localizing it to midcell. We demonstrate that, as the cell grows, the production of these mRNAs is responsible for the nucleoid splitting into two lobes and for their well-known positioning to 1/4 and 3/4 positions on the long cell axis. Finally, our model quantitatively accounts for the observed expansion of the nucleoid when the pool of cytoplasmic mRNAs is depleted. Overall, our study suggests that steric interactions and out-of-equilibrium effects of the TTM are key drivers of the internal spatial organization of bacterial cells.

Solution Chemistry

Solution Chemistry discusses the solution process, properties of solutions, saturated solutions and solubility, and factors affecting the solubility of solutes. Several quantitative measures of concentration are explained: percent by mass, parts per million, molarity, molality, normality and mole fraction. A systematic method of solving solubility problems is reviewed and several illustrative examples provided. Solubility is described as an equilibrium process with emphasis on the effect of temperature and pressure on the solubility of solute. The relationship between solubility and temperature for ionic compounds is illustrated by solubility curves. Henry’s law, which expresses the relationship between the pressure of a gas and its solubility, is discussed.

Universal and Programmable Thinning and Thickening of Topologically-Active DNA Fluids

Understanding and controlling the rheology of polymeric fluids that are out-of-equilibrium is a fundamental problem in biology and industry. For example, to package, repair, and replicate DNA, cells use enzymes to constantly manipulate DNA topology, length, and structure. Inspired by this impressive feat, we combine experiments with theory and simulations to show that complex fluids of entangled DNA display a rich range of non-equilibrium material properties when undergoing enzymatic reactions that alter their topology and size. We reveal that while enzymatically-active fluids of linear DNA display universal viscous thinning, circular DNA fluids - undergoing the same non-equilibrium process - display thickening with a rate and degree that can be tuned by the DNA and enzyme concentrations. Our results open the way for the topological functionalization of DNA-based materials via naturally occurring enzymes to create a new class of "topologically-active" materials that can autonomously alter their rheological properties in a programmable manner.

The Study of Boron-Nitride Nanotube Behavior as an Atomic Nano-Pump for Biomedicine Applications

In this study we use molecular dynamics (MD) simulations to describe the nanopumping process of Boron Nitride Nanotube (BNNT) with fullerene molecule displacement for the first time. Technically, for the simulation of BNNT and fullerene structures, we used Tersoff force-field. The result of the equilibrium process of these structures shows the excellent stability of them which this atomic behavior arises from the appropriate settings in our MD simulations. Further, to describe the BNNT nanopumping process, we calculate the velocity and translational/rotational kinetic energy of fullerene molecule. Numerically, by increasing of simulated structures temperature from 275 K to 350 K, the nanopumping time varies from 9.31 ps to 8.55 ps, respectively. Further, the atomic wave producing in BNNT is an important parameter for nanopumping process and we decrease the nanopumpint time to 7.79 ps by this atomic parameter optimization.