Dissolution behaviour of freibergite-tetrahedrite concentrate in acidic dichromate solution

Asgat ore sample with estimated content of 431g/t silver was concentrated by using floatation method and obtained freibergite-tetrahedrite concentrate with 9050g/t Ag, 35.75% Cu, 28.5% Sb and 10.6% Fe, respectively. The dissolution of concentrate in acidic potassium dichromate solution has been investigated with respect to the sulfuric acid and potassium dichromate concentrations and by changing leaching temperature and time. Leaching freibergitetetrahedrite concentrate in dichromate acidic solution (K2Cr2O7-0.1M, H2SO4-0.4M leaching time 4h, leaching temperature 95°С) resulted total amount of leaching of 95.65 % silver, 93.85% copper, 99.86 % antimony and 30.18% iron. DOI: http://dx.doi.org/10.5564/mjc.v14i0.196 Mongolian Journal of Chemistry 14 (40), 2013, p36-4

The Precious metals (Au, Ag, Pt, Pd, Rh) adsorption on the Silicon – organic sorbents

Sorption activity of two types of Silicon-organic sorbents for the previous metals has been studied. A polymer – poly (3- silsesquioxanilpropylthiocarbamate) - 3- silsesquioxanilpropylammonium which was obtained by the hydrolytic poly-condensation reaction and has been determined its physical, chemical characteristics and its sorption activity for the Ag(I), Au(III), Pt(IV), Pd(II), Rh(III). It has been found out that the sorbent shows high static sorption of Gold (III), Mercury (II) at acidic condition. The second a net structured silicon-organic copolymer {SiO2*2[O1.5Si(CH2)3NHC5H4N}n was synthesized by hydrolytic co-poly-condensation reaction. It likely to react as an anionit that adsorbs chloro-complex anion of the Au (III), Pt(IV), Pd(II), Rh(III).DOI: http://dx.doi.org/10.5564/mjc.v12i0.167 Mongolian Journal of Chemistry Vol.12 2011: 29-3

Dissolution behavior of copper concentrate in acidic media using nitrate ions

This study was conducted to investigate the dissolution process of copper concentrate using sodium nitrate (NaNO3) in a sulfuric acid (H2SO4) medium under various controlling parameters, including dissolution temperature, time, particle size, solid/liquid (S/L) ratio and concentration of NaNO3 and H2SO4. The thermodynamic probability of mineral dissolution (CuFeS2, Cu2S, CuS, FeS2) reaction in the concentrate was estimated by standard Gibbs energy. The activation energy (Ea) for the dissolution of copper concentrate was calculated as 15.96kJ/mol. Batch experimental results show that about 89.9% of copper in the intact concentrate have been leached and it increased to 96.5% at the fraction with <25.4mm particle size. Copper leaching rate has direct correlation with increase in time, temperature, solid/liquid (S/L) ratio and H2SO4 concentration. The XRD and XRF analyses of the solid residue after leaching revealed the presence of elemental sulfur.DOI: http://doi.dx.org/10.5564/mjc.v15i0.328 Mongolian Journal of Chemistry 15 (41), 2014, p79-8

Arsenic occurrence in water bodies in Kharaa river basin

Distribution of arsenic (As) and its compound and related toxicology are serious concerns nowadays. Gold mining activity is one of the anthropogenic sources of environmental contamination regarding As and other heavy metals. In Mongolia, the most productive gold mining sites are placed in the Kharaa river basin. A hundred water samples were collected from river, spring and deep wells in this river basin. Along with total As and its species-As(III) and As(V), examination of concentration levels of other key parameters, 21 heavy metals with pH, total hardness, electric conductivity, anion and cations, was also carried out. In respect to the permissible limit formulated by the Mongolian National Drinking water quality standard (MNS 0900:2005, As10 µg/l), the present study showed that most of samples were found no contamination. In Kharaa river basin, an average concentration of total As in surface water was 4.04 µg/l with wide range in 0.07−30.30 µg/l whereas it was 2.24 µg/l in groundwater. As analysis in surface water in licensed area of Gatsuurt gold mining showed a mean concentration with 24.90 µg/l presenting higher value than that of value in river basin by 6 orders of magnitude and it was 2 times higher than permissible level as well. In Boroo river nearby Boroo gold mining area, As concentration in water was ranged in 6.05−6.25 µg/l. Ammonia pollution may have present at estuary of Zuunmod river in Mandal sum with above the permissible level described in national water quality standard. Geological formation of the rocks and minerals affected to change of heavy metal concentration, especially As and uranium (U) at spring water nearby Gatsuurt-Boroo improved road

Adsorption kinetics for the removal of copper(II) from aqueous solution by adsorbent PSTM-3T

The batch removal of copper (II) from aqueous solution under different experimental conditions using silicon-organic sorbent poly[N,N’-bis(3-silseskquioxanilpropyl)thiocarbamide] (PSTM-3T) was investigated in this study. This sorbent was produced from the hydrolytic poly-condensation reaction. The removal was favoured at pH = 5 for PSTM-3T. The effects of concentration and temperature have been reported. PSTM-3T was found to efficiently remove Cu(II) from solution. The batch sorption kinetics have been tested for a first-order reaction. The rate constants of adsorption have been calculated. The thermodynamic parameters (ΔG0, Kc) obtained to indicate the endothermic nature of Cu(II) adsorption on PSTM-3T.DOI: http://dx.doi.org/10.5564/mjc.v12i0.162 Mongolian Journal of Chemistry Vol.12 2011: 1-

The comparison between novel reagent H-142, H-143, H-145 and xanthate for flotation behaviour of molybdenum-containing ores

DOI: http://dx.doi.org/10.5564/mjc.v13i0.160 Mongolian Journal of Chemistry Vol.13 2012: 46-4

Preparation of rare earth oxides from Synchysite oxidized ore by acid leaching

Mixed rare earth oxides have been prepared from synchysite ore from the Lugiin gol rare earth deposit (Mongolia) which contains about 6% of cerium light rare earth elements. Ore powders were leached for up to 60 min using 80-120 g/l sulfuric acids at an acid to powder ratio of 20, agitation was performed by magnetic stirring followed by precipitation and calcination at 700°C for 1h. The highest leaching of REEs equal to 85% of the total REE was observed in the acid solution of 80 g/l. Obtained mixed rare earth oxides represent a layered type structure

Study on synthesizing Mg/Al layered double hydroxides at different pHs

Mg/Al layered double hydroxide (LDH) was successfully synthesized at different pHs values. The Mg/AL LDH was well characterized by X-Ray diffraction and Fourier transform infrared analysis. The morphology of the LDH was observed using Scanning electron microscopy with energy dispersive X-ray spectroscopy. The influence of pH values on the morphology of the Mg/Al LDHs were studied. The result showed that the well-synthesized Mg/Al LDHs could be obtained when the pH value was about 10.0 at room temperature.DOI: http://doi.dx.org/10.5564/mjc.v15i0.319 Mongolian Journal of Chemistry 15 (41), 2014, p36-3

Persistent organic pollutants (PCBs and OCP) in air and soil from Ulaanbaatar and the Lake Hovsgol region, Mongolia

The investigations of POPs in soil and air in three urban and rural sites of the Mongolia are presented. The POPs distribution in air repeats the POPs distribution in soil on the area investigated. The POPs levels in soil and air are lower than maximum permissible concentrations (MPC) and preliminary permissible concentrations (PPC) of PCBs and OCP accepted in Russia. POPs levels in Mongolian soil obtained in the investigation are comparable with those from background areas of the world. POPs levels in Mongolian air are in the frame of concentrations found in the world. The PCB homological pattern in soil near electric power station in Ulaanbaatar is close to homological pattern in PCB technical mixture (Sovol or Arochlor 1254). The homological patterns in soil from other sites changed due to the redistribution of PCB congeners in the environment. The ratio of DDT and its metabolites indicates fresh entrance of DDT in the environment of Mongolia due to the atmospheric transboundary transport from countries using DDT (China, India) or from local agricultural sources. Hazard indexes in result from human exposure with POPs in soil and air are lower by 2-4 orders than 1 that denotes the possible default of disturbances in target organ and system. CR under the same scenario corresponds to the first diapason that is taken by population as negligible risk, not differ from usual everyday risks. Such risks don’t require additional measures for the reducing of risks and their levels are a subject of periodical control. The necessity of additional investigation of POPs distribution and the fate in Mongolian environment is indicated.DOI: http://dx.doi.org/10.5564/mjc.v12i0.176 Mongolian Journal of Chemistry Vol.12 2011: 69-7

Effect of pretreatment on synchysite-Ce (CaCe(CO3)2F) leaching

Synchysite is a rare mineral which has potential as a new source of rare earth elements. The influence of roasting temperature and time on the solubility of rare earth elements from a synchysite concentrate is examined. The maximum solubility of rare earth oxides in 57% HNO3 was 97% in a sample roasted at 700 °C for 120 min. Increasing the roasting temperature decreased solubility due to formation of cerium (IV) and calcium oxides