Research of physical and chemical processes associated with corrosion of cements (“Caking”) in dampy wet air

Objective. The paper is aimed at clarifying the mechanism and kinetics of the processes leading to cement caking. Methods. To determine phase composition, the following modern physical and chemical methods were used: XRF, derivatography and electron microscopy. Results. The data obtained show that the “aging” of cements during their forced storage in humid air through the adsorption of water vapor, and then CO2, is associated with the processes of hydrolysis, hydration in surface layers of particles, is primarily relevant for the most reactive minerals of Portland cement clinker. The deepening of these processes also depends on the state of the corroded surface of minerals. Conclusion. The work carried out makes it is possible to preliminarily outline storage conditions for freshly ground Portland cements (according to the kinetics of sorption – the storage duration, according to isotherms – the permissible relative humidity), at which the LOI value of commercial cement remains stable for the required minimum time.

The utilization of okra leaves as an agricultural waste for the removal of As(III) and As(V)

<p>In the present study the sorption efficiency of okra leave sorbent for As(III) and As(V) is demonstrated. Sorption reaction is pH and time dependent. The sorbent shows maximum removal of As(III) and As(V) at pH 7 and pH 6 respectively and equilibrium was achieved at 180 minutes. In isotherm study experimental data were explained by Freundlich and Flory-Huggins models. Maximum sorption capacities calculated by Freundlich Isotherm were 5672.0 μg g-1 and 13160 μg g-1 for As(III) and As(V) respectively. Psuedo-second order rate equation and Morris-Weber equation explained the kinetics of sorption reaction. Due to the presence of heterogeneous active sites on the sorbent, surface sorption as well as intra-particle diffusion occurred. Thermodynamically, sorption reaction was endothermic in nature and proceeded spontaneously. Desorption study revealed that 89.82% of As(III) and 97.11% of As(V) were removed with 1M HCl.</p>

The participation of cyanobacteria in reducing the concentration of fusariotoxins and heavy metal ions in aqueous solutions (model experiments)

Aim. The goal was to establish the effect of soil cyanobacteria (CB) Fischerella muscicola, Nostoc paludosum and Nostoc linckia on change in the concentration of heavy metal ions (HM) and fusariotoxins in aqueous media.Material and Methods. In order to plot the kinetics of sorption by dry biomass of CB Fischerella muscicola and Nostoc paludosum of copper(II), lead(II) and cadmium ions from solutions with a concentration of 10‐4mol/L, the method of potentiometry with ion‐selective electrodes was used. The concentration of fusariotoxins in the filtrate of the contact medium of Fischerella muscicola CB and Nostoc linckia with F. culmorumwas determined by HPLC.Results. The kinetics of sorption of TM ions by dry biomass of the CB isbest described by a modified second‐order model. According to the model, the sorption process limits the ion exchange reaction. In the presence of CB Fischerella muscicola and Nostoc linckia with a titer of 1.8∙106 cells/mL (1:100 dilution), a decrease in toxin and lycomarasmin in T‐2 medium occurs. However, this increases the concentration of fusaric acid and deoxynivalenol. In the variant where the titer of CB is equal to 1.8∙107cells/mL, the concentration of lycomarasmin is significantly reduced, while there is no change in the concentration of other fusariotoxins.Conclusion. Dry biomass of CB, having a high bisorption potential, can act as a good biosorbent with respect to copper(II), lead(II) and cadmium ions. A decrease in the concentration of fusariotoxins indicates the possibility of isolating active CB substances that can inhibit the biosynthesis of certain toxins of micromycetes of the genus Fusarium, reducing both the phytotoxicity of plant growth media and increasing the safety of crop production.

Removal of Heavy Metals by Using Chitosan/ Poly (Acryl Amide-Acrylic Acid) Hydrogels: Characterization and Kinetic Study

In this Study, hydrogel P(CH/AA-co-AM) was prepared, identification and utilized as an efficient absorbent to eliminate Cr (III) and Cd (II) ions from the aqueous solution. The adsorption of these ions follows Freundlich isotherms. Due to greater activity surface of the hydrogel in adsorption of the contaminants, they can be utilized for elimination of the mentioned ions from water. Therefore, we characterized structural, surface and thermal properties of the prepared materials with technique: TGA, FE-SEM and FT-IR. Moreover, we implemented the kinetics of sorption with regard to the amounts of the metal sorbet at distinct time intervals and thus examined the modeling of the isotherm and kinetic curves. Finally, we computed the reaction order as well as rate constant.

Study of the kinetics of sorption of heavy metal ions by dry biomass of cyanobacteria

Sorption of copper (II), lead (II) and cadmium ions from a solution with a concentration of 1 ∙ 10-4 mol/L by dry biomass of cyanobacteria Fischerella muscicola occurred 1.4-1.9 times faster than Nostoc paludosum. The sorption rate of lead and copper ions was 1.9-2.6 times higher compared to cadmium ions.

METHODOLOGICAL PRINCIPALS OF THE INTEGRATED ECOLOGICAL EVALUATING ENVIRONMENTAL INFLUENCE OF COAL MINE DAMPS

It is shown that throughout all geo-technological periods of the existence of coal mines, there is a negative impact of waste dumps on the atmosphere, water resources and soil. Theoretical propositions have been formulated, in accordance with which the migration of liquid pollutants into the soil laver and underlving rocks in the zone of action of the waste dump is described by a one-dimensional equation of convective diffusion, taking into account the kinetics of sorption of pollutants. It is recommended to model the air movement when flowing around the waste dumps by the O. Reynolds system of equations for the turbulent motion of a viscous fluid, using the finite volume methodfor the numerical solution. The numerical solution of the equations of motion of O. Reynolds makes it possible to visualize the picture of air flow in special zones and predict the dust and gas transport in the surface layer of the atmosphere. It is expedient to simulate the dust and gas transfer by the equation of convective-turbulent diffusion, setting the convective transfer rate according to the results of calculating the velocity fieldformed when flowing around the dump.