Studies of the rate of gold sorption by the AM-2B anionite from cyanide-alkaline solutions

The paper presents the results of studies on the sorption leaching of gold-containing ore of the Vasilkovskoye deposit. Kinetic dependences of the sorption of gold and associated metals from cyanide-alkali solutions under different physical and chemical factors were obtained. It was found that gold on the AM-2B resin sorbed at a higher rate than, for example, copper and zinc. The solutions were analyzed using modern devices of a new generation: FT-IR spectrometer "Avatar 370". Laboratory studies were performed to determine the gold sorption rate by the AM-2B anionite from cyanide-alkaline solutions. It was found in the process of sorption of gold from multicomponent cyanide-alkali solutions on AM-2B anionite of mixed basicity, with the macroporous structure containing benzyl dimethylamine and dibenzyl dimethyl ammonium functional groups, that an important factor of qualitative and quantitative separation of gold and impurity metals is the concentration of cyanide and hydroxyl ions in solution. The temperature effect on the sorption rate of gold from cyanide-alkali solutions was studied with the temperature dependences F of t, Bt, of t, ln (l - F) of t, and D of t that show that the sorption process of dicyanoaurate ions is controlled by mixed diffusion.

Hygro-Thermal, Hydric, and Mechanical Properties of Fibre and Aggregate-Reinforced Earth Plasters

Earth plasters have been used as a protective coating for buildings but, due to their low strength and low resistance to weather conditions, they have been abandoned for more resistant materials which in return lack vapour permeability. Earth plasters have usually a high moisture sorption rate, and their water vapour permeability is high, allowing the transfer of humidity through the material. These properties make them an interesting material for controlling vapour movement in humid rooms. Improving their strength can be done by adding aggregates and/or fibres, but the real impact of using one type or another of fibres or aggregate is unknown. This research aims to understand the consequence of the choice of fibre or sand in the improvement of strength of plasters and the conservation of the plaster hygro-thermal properties. Properties of plasters using alternative fibres or aggregates such as wool, cow hair, pine needles, sand aimed for concrete mixes, or not properly graded sand have been compared to plasters made more traditionally with chaff fibres and mason sand.

Water vapor sorption behavior of bamboo pertaining to its hierarchical structure

Bamboo is an anisotropic, hierarchical, and hygroscopic material. Moisture transport in bamboo is one of the most fundamental properties affecting almost all other physical and mechanical properties of the material. This study investigated the water vapor sorption behaviors of bamboo at various structural levels: cell walls, cells (with pits) and bamboo blocks. The specimens with two sorption directions, longitudinal (L) and transverse (T), were measured by saturated salt solution method and dynamic vapor sorption. The parallel exponential kinetics model was used to analyze the sorption kinetics. The results showed that at the cell wall level, the sorption rate and equilibrium moisture content (EMC) of cell wall in the L specimens were larger than those in the T specimens. The differences were probably caused by the looser cell wall layers in the L specimens. At the cellular scale, pits in the cell wall resulted in an enhanced sorption rate and EMC of the T specimens compared with the L specimens where the pits in the parenchyma cells were only distributed in the lateral walls but not in end walls. At the macro scale, the sorption rate and moisture content of bamboo blocks were largely controlled by the vessel cells. As a hierarchically-structured plant, bamboo performs the biological function of moisture transport at all these scales. This work helps improve the understanding of water transport behavior in bamboo, which may lead to better bamboo drying and impregnation processes.

Evaluation of Porosity and Water Sorption in Conventionally Cured Modified Polymethyl Methacrylate Resin - An In Vitro Study

BACKGROUND Dimensional change and porosity in the polymethylmethacrylate based prosthesis affects its clinical performance. Hence, the present study aimed to evaluate the porosity and water sorption present in the modified polymethyl methacrylate polymer composite. METHODS Control group without fibre reinforcement and test groups with fibre reinforcement were prepared for the study. Three different fibres such as boron free-E glass fibre, untreated and plasma-treated polypropylene fibres in varying weight percentage and aspect ratio were considered for reinforcement. The porosity of the fractured surface was observed through a scanning electron microscope (scanning electron microscope) and sorption measured based on international standards organization (ISO) 1567:1999. RESULTS Control group exhibited porous structures, whereas all fibre-reinforced groups did not exhibit porous structure at the fracture surface. There was a significant difference in the sorption rate between control and test group (p < 0.001). Among fibrereinforced test groups, boron free E glass fibre reinforced polymethylmethacrylate exhibited maximum sorption followed by polypropylene fibre reinforced polymer test groups (p < 0.001). However, all samples showed sorption rate within the ISO specification. CONCLUSIONS Fiber reinforcement is an effective method to reduce porosity and water sorption in polymethylmethacrylate based polymer composite regardless of the fibre type. KEY WORDS Polymer Composite, Porosity, Water Sorption, Fiber Reinforcement, Polymethylmethacrylate

Kinetic Features of the Hydrogen Sulfide Sorption on the Ferro-Manganese Material

The kinetics of hydrogen sulfide sorption by the surface of a ferromanganese material containing in its composition a mixture of iron (II) and (III) oxides FeO × Fe2O3, takanelite (Mn, Ca) Mn4O9 × 3H2O and quartz SiO2, and which is samples of unrefined ferromanganese ore, was studied in this work. Sorption rate constant and activation energy constant values were calculated. The catalytic effect of iron (III) oxide was established, the presence of which in natural material contributes to a decrease in the H2S sorption activation energy. Based on the results of X-ray phase and chromatographic analysis methods, a chemical (redox) reaction of the conversion of hydrogen sulfide into elemental sulfur and H2O was revealed. The overall process rate is expressed in terms of the physical sorption stage and chemical transformation of the components; the influence of the rate of the third stage—reaction products desorption—on the overall rate of the process is taken into account. The limiting stage of the process is determined—a chemical reaction. The relation between the heat and the activation energy of the chemical transformation is used according to the Bronsted—Polanyi rule for catalytic processes. It was found that with an increase in the chemisorption heat, the activation energy of the chemisorption stage decreases and, as a consequence, its rate increases. The sorption process parameters were calculated—the Fe2O3 coverage degree with the initial substances and reaction products providing the maximum sorption rate, which can be a criterion for evaluating the catalytically active sites of the catalyst surface for carrying out catalytic reactions.

Emission of gases from coal at low-temperature oxidation depending on the oxygen sorption rate

Coal oxidation by air oxygen can cause a process of spontaneous combustion with intense emission of carbon oxide and danger to initiate explosion of combustible gases. To detect the process of coal spontaneous combustion in mines, they use a gas analysis method providing control of concentrations of carbon oxide, hydrogen and hydrocarbons in the atmosphere. The conducted researches showed that at low-temperature oxidation of coal the intense emission of these gases without temperature increase is possible. Concentration of carbon oxide significantly increases with the growth of coal oxygen sorption rate. Ethylene and carbon dioxide show similar regularities. Acetylene is not found as a result of low-temperature oxidation of coal, and emission of hydrogen, methane, ethane, propane and propylene does not depend on the coal oxygen sorption rate.

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.

Susceptibility of the Cigarette Beetle Lasioderma serricorne (Fabricius) to Phosphine, Ethyl Formate and Their Combination, and the Sorption and Desorption of Fumigants on Cured Tobacco Leaves

The susceptibility of Lasioderma serricorne to phosphine (PH3), ethyl formate (EF) and their combination (PH3 + EF) was evaluated in this study. Eggs, larvae, pupae and adults were subjected to treatment with fumigants to determine the 90% lethal concentration time (LCt90) values. Treatment with PH3 for 20 h resulted in LCt90 values of 1.15, 1.39, 14.97 and 1.78 mg h/L while treatment with EF resulted in values of 157.96, 187.75, 126.06 and 83.10 mg h/L, respectively. By contrast, the combination of PH3 + EF resulted in LCt90 values of 36.05, 44.41, 187.17 and 35.12 mg h/L after 4 h. These results show that, through treatment with PH3 + EF, control can be achieved at lower concentrations than for treatment with EF alone and at lower exposure times than for treatment with PH3 alone. The sorption rates of the fumigants on cured tobacco leaves were determined for filling ratios of 2.5%, 5.0% and 10.0% (w/v). Cured tobacco leaves were treated with either 2 mg/L PH3, 114 mg/L EF or 0.5 mg/L PH3 + 109 mg/L EF. Treatment with PH3 showed sorption rates of 0.0%, 7.1% and 14.3%. EF, however, showed higher sorption rates of 64.9%, 68.5% and 75.5%, respectively, for the indicated filling ratios. When PH3 and EF were combined, the sorption rate of PH3 was 0.0%, while the sorption rates of EF were lower (9.1%, 12.0% and 23.2%) than treatment with only EF. EF required a ventilation time of longer than 22 h to desorb from cured tobacco leaves. Therefore, PH3 + EF can effectively control L. serricorne in cured tobacco leaves, with sufficient ventilation time required after treatment for the safety of workers.

Extended Rate Constants Distribution (RCD) Model for Sorption in Heterogeneous Systems: 2. Importance of Diffusion Limitations for Sorption Kinetics on Cryogels in Batch

Here we address the problem of what we can expect from investigations of sorption kinetics on cryogel beads in batch. Does macroporosity of beads indeed help eliminate diffusion limitations under static sorption conditions? Are sorption rate constants calculated using phenomenological kinetic models helpful for predicting sorption properties under dynamic conditions? Applying the rate constants distribution (RCD) model to kinetic curves of Cu(II) ions sorption on polyethyleneimine (PEI) cryogel and gel beads and fines, we have shown that diffusion limitations in highly swollen beads are very important and result in at least ten-fold underestimation of the sorption rate constants. To account for intraparticle diffusion, we have developed the RCD-diffusion model, which yields “intrinsic” kinetic parameters for the sorbents, even if diffusion limitations were important in kinetic experiments. We have shown that introduction of a new variable—characteristic diffusion time—to the RCD model significantly improved the reliability of sorption kinetic parameters and allowed prediction of the minimal residence time in column required for efficient uptake of the adsorbate under dynamic conditions. The minimal residence time determined from kinetic curves simulated using the RCD-diffusion model was in good agreement with experimental data on breakthrough curves of Cu(II) ion sorption on monolith PEI cryogel at different flow rates.