A developed method was designed for gold determination directly in organic medium in some sedimentary rocks (fine sandstone, carbonates), pyrite, serpentine and international standard gold sample (MA-1a) using flame atomic absorption spectroscopy (FAAS). Instrumental parameters; burner angle, fuel flow rate, band pass and burner height together with chemical parameters; different media, leaching and interference effect were optimized to improve gold determination. Selective leaching using a new mixture (5% KCN, 5% Na2S2O3 and hydrogen peroxide) offered maximum leaching percentage of gold (>99%) with minimal concentration of accompanying elements. Extraction parameters using methyl isobutyl ketone (MIBK) from 3 M HCl were optimized for more than 99% gold extraction, followed by scrubbing using 0.1 M HCl. Gold was determined directly in organic phase. Beer's law was obeyed from 0.01 μg/ml to 10 μg/ml. Standard deviation (from 0.017 to 1.05) and percentage error (from 1.5% to 2.5%) using the present developed AAS method were calculated.
A simple versatile developed spectrophotometric method for the determination of vanadium (V) in several geological matrices was suggested and studied in the present work, using alizarin red S as a chromogenic dye. Several factors were studied for optimum determination, namely; effect of pH, buffer solution, dye concentration, sequence of addition, duration time and molar ratio. The complex was stable for two hours. Beer ' s law was obeyed in the concentration range 0.05-6 µg ml-1 at λ max 483 nm with molar absorptivity (ε) value 0.72x10 4 L mol-1 cm-1 , percentage relative standard deviation (%RSD) (4.5%) and % error (1.97%). Tolerance limits of foreign cations and anions were studied. A precipitation method for separation of the concomitant interfering ions was applied to overcome the interference effect of these elements with vanadium, to ease its determination with accurate and precise values. The proposed method was successfully applied to analysis of vanadium in different rock types.
A simple and accurate spectrophotometric method for the determination of Yttrium using xylenol orange as a chromogenic dye in different rare earth concentrates of Egyptian monazite and xenotime by using direct and derivative spectrophotometric methods was described in the present work. The calibration curve was linear from 0.2 -6 μg ml -1 at a maximum wavelength value of 568 nm. The various parameters and reaction conditions, which influence the formation of the complex, were investigated where the complex were stable for one hour. The molar absorptivity (є) and Sandell ' s sensitivity were found to be 3.4x10 4 L mol -1 cm -1 and 2.7x10 -3 respectively. The % RSD and percentage error were 1.64% and 1.5% respectively. A high sensitivity and accuracy for the determination of yttrium in the rare earths Elements (REE) concentrates was observed when the first derivative spectrophotometric method was applied.
Uranium as a nuclear element with strategic importance and gold as one of the important economic precious metals made their selective leaching from the sedimentary lower carbonaceous sandstone rocks, Southwestern Sinai, Egypt with economic concentrations (5ppm gold and 160 ppm uranium), an important issue for facilitating either their accurate determination or highest percentage recovery. A sequential leaching of uranium followed by gold was proposed in this work after studying individually their optimized leaching conditions. From the latter; a lixiviant mixture of sample to sodium carbonate ratio 1:1, sample to sodium bicarbonate ratio 1:1 together with sodium thiosulphate, as oxidant, 0.5g was used for the selective leaching of uranium. On the other hand, a leaching reagent mixture of 5% (w/v) from each of potassium cyanide, sodium thiosulphate and 10 ml from 30% hydrogen peroxide was used for the selective leaching of gold where several factors were optimized; concentration of individual component in each lixiviant, agitation time, solid to liquid ratio, temperature and pH. A percentage leaching of 97% and 96% for uranium and gold respectively were reached. Uranium was selectively separated using Amberlite IRA 402 Cl resin ion exchange resin with 99.5 % percentage recovery. The recovery of gold needs a large bulk weight from the sample due to its relatively low concentration.
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