Obtaining artificial carnallites from magnesium chloride brines

The excess of magnesium chloride brines is formed during the polymineral ores processing in order to obtain potassium sulfate. One way to regenerate such brines is to produce artificial carnallite. It is necessary to purify these brines from sulfates for their further use as raw materials for the artificial carnallite production. In this work, the process of desulfurization of magnesium chloride brines with a solution of calcium chloride is studied. The temperature and the processing time, the magnesium chloride solutions concentration and the consumption of desulfurizing agent (calcium chloride) influence on the degree of magnesium chloride solutions purification from sulfate ions was determined. It has been established that almost all sulfate ions interact with calcium ion in 15 minutes and the desulfurization degree reaches 98,08 %. The increase in duration of the suspension mixing is necessary in order to establish equilibrium in the system and relieve the supersaturation in the solution. It has been shown that with increasing solutions saturation with MgCl2, the degree of the magnesium chloride brines purification from SO4 2– ion increases. Complete precipitation of calcium sulfate requires a certain excess concentration of calcium chloride.

PRECIPITATION OF CHROMIUM-CONTAINING TANNING SOLUTION OF SUSPENSION MAGNESIUM HYDROXIDE

Comparative studies of the deposition of tanning chromium compounds from waste tanning solutions of tannery production containing from 3 to 5 g/l chromium oxide were carried out, using as a chemical reagents a suspension of magnesium hydroxide and sodium carbonate solution. It is shown that the main factors influencing the precipitation process are the pH value and the consumption of the precipitant. The costs of reagents contributing to complete precipitation of chromium compounds in the form of a hydroxide are established. The high efficiency of the use of a suspension of magnesium hydroxide as a precipitator is shown, due to the higher deposition rate and the absence of chromium compounds in the supernatant. The rate of precipitation of chromium using a slurry of magnesium hydroxide is 4.9 cm3/min, and using sodium carbonate 2.5 cm3/min. In the supernatant, after precipitation with sodium carbonate, traces of chromium oxide are found - less than 2.53 g/l. It is shown that when using a suspension of magnesium hydroxide for the precipitation of chromium, periodic mixing of the liquid is necessary to more completely dissolve the precipitator, which in the first stage after dosing drops out of the solution as a precipitate. When sodium carbonate is used, the formation of hydroxyl ions occurs much faster than in the case of a suspension of magnesium hydroxide. However, the formed sediment has a rather loose structure and is characterized by a high moisture content. The precipitate of chromium hydroxide obtained by using a suspension of magnesium hydroxide is characterized by a higher density and better filtration ability. A gradual increase in pH during the precipitation of a tanning solution with a suspension of magnesium hydroxide results in a precipitate with a large particle size and lower humidity.

Direct Conversion of CO2 into Dimethyl Ether over Al2O3/Cu/ZnO Catalysts Prepared by Sequential Precipitation

Bifunctional Al2O3/Cu/ZnO catalysts with Al composition of between 30 mol% and 80 mol% were prepared by sequential precipitation (SP) for the conversion of CO2 into dimethyl ether (DME). In the SP synthesis, the concentration of a precipitation agent managed to be high enough to induce the complete precipitation of Al3+. The prepared precipitates were composed of zincian malachite and amorphous AlO(OH). Furthermore, the calcined mixed metal oxide materials of 60% and 80% Al exhibited a higher acidity than commercial Al2O3 and the H2-reduced catalysts showed the similar Cu dispersion of 6%–7% at all Cu loadings. In the activity test at 573 K and 50 bar, the SP-derived catalyst of 80% Al (SP-80) displayed the best performance corresponding to CO2 conversion of 25% and DME selectivity of 75% that are close to equilibrium values. In order to overcome the thermodynamic limitation, a dual-bed catalyst system was made up of SP-80 in the first layer and zeolite ferrierite in the next. This approach enabled DME selectivity to be enhanced to 90% while CO2 conversion increased a little. Consequently, the studied catalyst system based on the SP-derived catalysts can contribute greatly to selective DME production from CO2.

Development of the homogenized monthly precipitation series during 1910–2014 and its changes in Hunan Province, China

Based on the statistical method and the historical evolution of meteorological stations, the precipitation time series for each station in Hunan Province of China during 1910–2014 are tested for their homogeneity and then adjusted. The missing data caused by war and other reasons at the eight meteorological stations which had records before 1950 is filled by interpolation using adjacent observations, and complete precipitation time series since the establishment of stations are constructed. After that, according to the representative analysis of each station in different time periods, the precipitation series of Hunan Province during 1910–2014 are built and changes are analyzed. The results indicate that the annual precipitation has no significant linear trend but has obvious inter-decadal fluctuation during 1910–2014 and a periodic oscillation of 20 years is the most significant. Precipitation in winter (DJF) and summer (JJA) shows a slight wetter trend, and a slight dryer trend in spring (MAM) and autumn (SON). Abrupt change test suggests that annual and seasonal precipitations except for MAM and SON have abrupt ascending changes in the recent 100 years.

Chemical guidance of Onchocerca lienalis microfilariae to the thorax of Simulium vittatum

SUMMARYThe behavioural responses of Onchocerca lienalis microfilariae (mf) to tissue factors of the surrogate black fly host, Simulium vittatum, were studied using a novel in vitro bioassay. Mf accumulated towards thoracic tissues to a density 4 times higher than towards abdominal tissues, despite the larger surface area and volume of abdominal tissues. Mf migrated toward thoracic tissues regardless of whether or not contact with thoracic tissues was possible. Therefore, mf directed themselves toward the thorax rather than arresting their movement after they make contact with thoracic tissues. Chemical cue(s) provided a principal guidance for mf to locate thoracic tissues. Mf lost their ability to differentiate thoracic and abdominal tissues following addition of thoracic attractant(s) to excised abdomens and reversed their differential response when excised thoraces were depleted of chemical cue(s). Mf did not respond to salivary gland product, but to other thoracic factor(s). Intact thorax that was connected to 1–2 abdominal segments attracted considerably less mf than excised thorax. However, intact thorax attracted more mf than excised abdomen. Abdominal tissue size did not affect thorax attractiveness. Involvement of a large molecular weight protein(s) was suggested by the high attractiveness of the 100 kDa Centricon concentrator retentate and complete precipitation of attractant(s) by ethanol.

Polyfunctional Carboxylic Acids as Coprecipitating Agents For Barium, Yttrium, and Copper

ABSTRACTThe suitability of several polyfunctional carboxylic acids as coprecipitating agents for Ba, Y, and Cu was investigated. Essentially complete precipitation from alcoholic solutions was achieved for all three metals when tartaric acid was employed as the precipitating agent. The amorphous precipitate formed under these conditions was composed of uniform particles about 50 nm in diameter, and was converted readily to high purity Ba2YCu3O7−x.

Effects of Nitrogen Ion Implantation in 304 Stainless Steel at High Temperatures

ABSTRACTWe studied the effect of varying the target temperature (by changing the beam power) on the structure and properties of nitrogen ion implanted 304 stainless steel. With a beam power of 0.1 W/ cm2 the target temperature is restricted to 150°C. After a dose of 3. 5x1017N2+/cm2 the microhardness measured at 10g increases by 15%. With a beam power of 1.1 W/cm2 the target temperature is 500°C. After the same dose as before, the irdcrohardness increase is 40%. Glancing Angle X-ray Diffraction and Auger depth profiling results suggest that the increased hardness is due to the presence of nitrogen in solution as opposed to complete precipitation. A sample deformed by compression formed an enhanced oxide layer during implantation. This oxide layer appears to have a capping action against the out-diffusion of nitrogen.