Te-coprecipitation

The blend is molten in a fireproof crucible at temperatures up to 1100°C. The fusion leads to the production of a NiS-button containing the precious metals, while most matrix elements react with the flux components to form slag, which is discarded. The NiS-button is cut up and dissolved with HCl, while Pd and other insoluble noble metal sulphides remain in the residue to be filtered off and dissolved with diluted HNO3 or HCl and H2O2. PGE-recovery is reported to improve if Te-coprecipitation is used after the digestion of the NiS-button with HCl (Shazali et al. 1987). 

Often Te-coprecipitation is used to reduee analyte losses occurring during the dissolution of the NiS-button in fire assays (Sun et al. 1998 de Vos et al. 2002). For environmental samples like APM however, Te-eoprecipitation is often employed as sole preconeentration proeedure (Sehafer et al. 1999 Gomez et al. 2003). 

Whenever Fe oxides, especially ferrihydrite, are formed in nature, a range of toxic or unwanted elements is coprecipitated. A case of natural detoxification of arsenic by Fe oxides was observed on the Coral Reef of Amberlite Island, Papua New Guinea. Upon reaching the aerobic surface waters, hydrothermal fluids rich in dissolved As and Fe, lose their As (and Fe) almost completely by adsorption on and/or coprecipitation of 2-line ferrihydrite. The precipitate contained (besides tens of mg of Cu, Pb, Zn) 55g/ kg As, and, thus, it prevented any damage to the biota (Pichler Veizer, 1999). Arsenic peaks (0.1-0.6 xM) at a depth of 2-6 cm in surficial sediments in 16 Canadian lakes were closely correlated with hydroxylamine reducible Fe (0.2-1 mM), suggesting again a close association between As and poorly ordered Fe oxides (Belzile Tes-sier, 1990). 

After neutron irradiation bismuth (canned in aluminum jackets) is dissolved in a mixture of hydrochloric and nitric acids and excess NO3 is removed by adding a reducing agent, such as, urea or formic acid. If bismuth is used as an anode, the reducing agent is dissolved in HCl. Various methods are applied for concentration of polonium in the acid mixture and its subsequent separation from bismuth. Such processes include spontaneous deposition of polonium over a less electropositive metal and coprecipitation with tellurium. In the latter method, a Te + or Te + salt is added to the extract, followed by addition of stannous chloride, which reduces both the tellurium and polonium to their metallic state, coprecipitating them from bismuth in the extract mixture. 

The NiO/NiAl30< catalyst was prepared in our laboratory by coprecipitation of nickel nitrate hexahy drate and aluminium nitrate nonahydr te following a method described elsewhere [3]. The samples were calcined in an oxidant atmosphere at 1023 K for a period of time of 3 hours. 

May contain Au, Mo, Se, and Te as chlorides or acids. Concentrate to remove ammonia, boil with several millilitres saturated oxalic acid solution, dilute, boil and filter. Extract ppt. with HQ to remove coprecipitated tellurous acid. 

The Sherritt-Cominco process was developed as an alternative to smelting of sulfide concentrates. The key feature of the Sherritt-Cominco process is the removal of iron before the leaching of copper. The concentrate is thermally activated and leached with sulfuric acid to dissolve iron. Iron is precipitated as jarosite. The leach residue is pressure leached with oxygen in acid solution to convert copper sulfides to copper sulfates. The solution is purified by the coprecipitation of Te, As, Bi, Sb, Pb, and Se with Fe2C>3. The electrolyte contains 30 g L 1 Cu and 140 g L 1 sulfuric... 

It has been recommended that one should co-precipitate traces of Te with Fe(OH)3 as collector (pH 6-9) [3]. Traces of Te(IV) have been separated from sea-water by coprecipitation with Fe(OH)3 and flotation [4]. The tellurium compounds with trifluoroethyl xanthate [5], methylpiperazine dithiocarbamate [6], and 2-mercapto-4-methyl-5-phenyl-azopyrimidine [7] can be co-precipitated with microcrystalline naphthalene. 

Scientists have fabricated scaffolds in a two-step approach that combines an in situ coprecipitation synthesis route with the electrospinning process to prepare a novel type of biomimetic nanocomposite nanofibres of HA/CHT. The electrospun composite nanofibres of HA/CHT, with compositional and structural features close to the natural mineralised nanofibril counterparts, are of potential interest for bone TE. The results of HA/CHT indicate that although an initial inhibition occurs, the nanofibrous scaffolds which contained HA, as compared to scaffolds of CHT alone, appeared to have significantly stimulated the bone forming ability as shown by the cell proliferation, mineral deposition, and morphological observations, due to the excellent osteoconductivity of HA [19, 34, 56, 70]. 

If it is used for quantitative precipitation of tin, care must be taken that all complexing and interfering ions are absent, or precipitation will not be complete. If its precipitation is intended as a separation step, Sb, Te. Nb, and the other acid-insoluble elements must be expected to coprecipitate with the tin. If it is once precipitated, it is di icult to wash because of its marked tendency to peptize. And if it is washed effectively without peptizing, it is difficult to redissolve. It is possible to dissolve metastannic acid by boiling... 

Pd can also be precipitated with other organic reagents [139], however only two of them were used for radiochemical separations, namely salicylaldoxime [163] and a-furildiox-ime [190]. Other reagents used to precipitate Pd are S [109, 200], CN [139], and i [110]. The reduction of Pd was accomplished with Zn [99, 162], Mg [127], Cu [77, 91, 109], and by electroplating [81, 119]. The decontamination factor achieved by precipitation with Cu from fission product mixtures is quite high. Elemental Pd can also be coprecipitated with Te [158] or Se [139]. These precipitations can be used to recover small quantities of Pd from very dilute solutions. For this purpose the precipitation of PdS can also be used [139]. 

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