Solid-phase extraction of silver in geological samples and its determination by FAAS

A macroporous and a nonionic resin, Amberlite XAD-16 as a solid sorbent and N,N-diethyl-N'-benzoylthiourea (DEBT) as a chelating agent have been used for the selective separation and preconcentration of silver. Sorption of silver was studied in three ways: sorption on DEBT impregnated Amberlite XAD-16 by batch and column processes and sorption of Ag-DEBT complex on Amberlite XAD-16 by column process. Factors affecting the sorption and desorption of silver ion were investigated. The stripping of silver was achieved by using either sodium thiourea or sodium thiosulfate solution. The silver ion capacity of impregnated resin was found to be 11.22mg Ag+/g resin and 870 mu g Ag+/g resin for batch and column processes, respectively. It was 370 mu g Ag+/g resin for Ag-DEBT complex. The interference effects of possible co-existing metal ions and some electrolytes were investigated. The applicability of the proposed method was shown by analyzing the geological copper ore samples

Formation and characterization of humic acids from low rank anatolian coals by air oxidation

The results of this study are aimed at evaluating the effects of air oxidation time, temperature and demineralization on humic acid production from two low-rank Anatolian coals. Two Anatolian low rank coals were studied at 120 and 200degreesC up to 10 days with and without demineralization. The best results for humic acid formation were obtained at a high temperature for longer times. Demineralization effect is negligible for studied coals. The rate of humic acid formation increased at first with increase in oxidation time, reached a maximum, and then decreased at high oxidation time. Also, a detailed study of the elemental composition, the characterization by FTIR, and the acidity of humic acids are reported

Extraction of some transition metals with N,N-dibutyl-N '-benzoylthiourea into molten paraffin at 65 degrees C

The solid-liquid extraction behaviour of some transition metals (Cu(II), Co(II), Ni(II), Cd(II) and Pb(II)) by the use of N,N-dibutyl-N'-benzoylthiourea as an extractant in paraffin (58-60 degrees C) has been investigated at 65.0 +/- 0.5 degrees C. The effect of equilibration time, pH of the aqueous phase, concentration of extractant and solid solvent used on the extraction efficiency of these metals have been discussed. The interferences of various ions are examined. The method has been applied to the determination of these metals in synthetic samples, mushrooms and sediment

Polymer supported humic acid for separation and preconcentration of thorium(IV)

The resin impregnating humic acid (HA) onto XAD-4 has been prepared to investigate adsorption behaviour of Th(IV). The characterization of the resulting resin has been carried out by infrared spectral data and sorption capacity. Maximum adsorption capacity of Th(IV) on the resin is found to be 1.51 X 10(-4) mol g(-1) at pH 4. The sorbent was found to possess a high selectivity for Th(IV) with an optimum extraction pH around 3-7. Recoveries for Th(IV) determined prior to breakthrough were found to be quantitative (96-99%). The resin exhibits good chemical stability, reuseability, and a faster rate of equilibration for Th(IV) determination. The influence of several ions as interferents is discussed. The method has been successfully applied for the separation of Th(IV) in synthetic mixtures

Effect of molten caustic leaching on demineralization and desulfurization of asphaltite

Molten caustic leaching process is effective in reducing significant amounts of ash-forming minerals, pyritic sulfur, and organic sulfur from solid fossil fuels. The effect of leaching asphaltite samples from Seguruk and Harbul collieries of Sirnak and Silopi asphaltite fields (situated in the Southeast Anatolia region of Turkey) with molten sodium hydroxide and followed by mild acid on demineralization and desulfurization was investigated. The effects of alkali/asphaltite ratio, time, and temperature on the leaching efficiency were detailed, and the experimental results are presented here. Chemical demineralization and desulfurization of asphaltite samples using molten sodium hydroxide were investigated in the temperature range of 200 degrees C-400 degrees C. The percentage of demineralization and desulfurization increased with the increase in alkali/asphaltite ratio. The removal of total sulfur and ash increased with increasing leaching temperature and time. Most of the inorganic sulfur and a significant portion of the organic sulfur were removed