Filtration acid digestion

Water Filtration acid digestion add matrix modifier FAAS (Method D3920 7780) No data No data ASTM 1999 OSW1992... 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

Wbter, extracts or digests of waste Filtration or digestion as appropriate (depends on matrix, dissolved or total, acid leachable, etc.) ICP/MS (EPA Method 6020) No data 71-137% (11-23% RSD) for aqueous solutions 90-104% (6-28% RSD) for solid samples EPA 1994e... 

Soil, wastes, and groundwater Acid digestion of sample, dilution with water, and filtration AAS (EPA method 7420) GFAAS (EPA method 7421) 0.1 mg/L 1 pg/L No data No data EPA 1986e... 

In one acid digestion process, monazite sand is heated with 93% sulfuric acid at 210°C. The solution is diluted with water and filtered. Filtrate containing thorium and rare earths is treated with ammonia and pH is adjusted to 1.0. Thorium is precipitated as sulfate and phosphate along with a small fraction of rare earths. The precipitate is washed and dissolved in nitric acid. The solution is treated with sodium oxalate. Thorium and rare earths are precipitated from this nitric acid solution as oxalates. The oxalates are filtered, washed, and calcined to form oxides. The oxides are redissolved in nitric acid and the acid solution is extracted with aqueous tributyl phosphate. Thorium and cerium (IV) separate into the organic phase from which cerium (IV) is reduced to metalhc cerium and removed by filtration. Thorium then is recovered from solution. 

Insoluble silica residues are removed by filtration. The solution now contains beryllium, iron, yttrium, and the rare earths. The solution is treated with oxalic acid to precipitate yttrium and the rare earths. The precipitate is calcined at 800°C to form rare earth oxides. The oxide mixture is dissolved in an acid from which yttrium and the rare earths are separated by the ion-exchange as above. Caustic fusion may be carried out instead of acid digestion to open the ore. Under this condition sihca converts to sodium sihcate and is leached with water. The insoluble residue containing rare earths and yttrium is dissolved in an acid. The acid solution is fed to an ion exchange system for separating thuhum from other rare earths. 

CDFs) to sample filtration, homogenization, acid digestion (Modification of for TCDD ( 20%) 1996... 

Water and wastes Acid digestion filtration (dissolved) acid digestion (total recoverable) ICP-MS (total uranium) 0.1 pg/L 105-110% Long and Martin 1991 (EPA Method 200.8)... 

The ICP-MS method was developed for measuring total uranium in water and wastes. The sample preparation is minimal—filtration for dissolved uranium, acid digestion for total recoverable uranium. Recovery is quantitative (near 100%) for a variety of aqueous and solid matrices and detection limits are low, 0.1 pg/L for aqueous samples and 0.05 mg/kg for solid samples (Long and Martin 1991). 

David (D9) determined iron in plants and gives detailed instructions for the treatment of plant samples, entailing acid digestion and filtration before aspiration. The determination of iron in protein solutions is briefly mentioned (M2a). 

Sediments, sludges, soils Acid digestion, oxidation, filtration/centrifugation AAS, ICP/AES Variable, depending on matrix 93+6% EPA 1986a, 1986b... 

It should be pointed out that the performance of the packed-bed methane digester is more dependent perhaps on the influent volatile acids concentration than the overall VS loading rate. Thus, filter performance with acid-digester filtrate might be expected to be better than that obtained with methane-digester effluents having comparable volatile acids content. 

The packed-bed digester had a gross volume of 18.5 t The bed had a void ratio of 0.63. Filtrate from a slurry-phase acid digester effluent having a volatile acid content of 1550-2000 mg/J as acetic acid and a solids content of about 0.5 wt % was used as feed. No pH control was used. 

Place an intimate mixture of 125 g. of powdered, anhydrous zinc chloride and 26-5 g. of acetophenonephenylhydrazone in a tall 500 ml. beaker in an oil bath at 170°. Stir the mixture vigorously by hand. After 3-4 minutes the mass becomes hquid and evolution of white fumes commences. Remove the beaker from the bath and stir the mixture for 5 minutes. Then stir in 100 g. of clean, white sand in order to prevent solidification to a hard mass. Digest the mixture for 12-16 hours on a water bath with 400 ml. of water and 12 ml. of concentrated hydrochloric acid in order to dissolve the zinc chloride. Filter off the sand and the crude 2-phenylindole, and boil the solids with 300 ml. of rectified spirit. Treat the hot mixture with a little decolourising carbon and filter through a pre-heated Buchner funnel wash the residue with 40 ml. of hot rectified spirit. Cool the combined filtrates to room temperature, filter off the 2-phenylindole and wash it three times with 10 ml. portions of cold alcohol. Dry in a vacuum desiccator over anhydrous calcium chloride. The yield of pure 2-phenylindole, m.p. 188-189°, is 16 g. 

Place 27 g. of o-phenylenediamine (Section IV,92) in a 250 ml. round-bottomed flask and add 17 -5 g. (16 ml.) of 90 per cent, formic acid (1). Heat the mixture on a water bath at 100° for 2 hours. Cool, add 10 per cent sodium hydroxide solution slowly, with constant rotation of the flask, until the mixture is just alkaline to litmus. Filter off the crude benzimidazole at the pump, wash with ice-cold water, drain well and wash again with 25 ml. of cold water. Dissolve the crude product in 400 ml. of boiling water, add 2 g. of decolourising carbon, and digest for 16 minutes. Filter rapidly at the pump through a pre heated Buchner funnel and flask. Cool the filtrate to about 10°, filter off the benzimidazole, wash with 25 ml. of cold water, and dry at 100°. The yield of pure benzimidazole, m.p. 171-172°, is 26 g. 

Turmeric paper (gives a rose-brown coloration with boric acid) wash tbe ground root of turmeric with water and discard tbe washings. Digest with alcohol and filter, using the clear filtrate to impregnate white, unsized paper, which is then dried. 

Wet-process acid is manufactured by the digestion of phosphate rock (calcium phosphate) with sulfuric acid. Depending on availabiHty, other acids such as hydrochloric may be used, but the sulfuric-based processes are by far the most prevalent. Phosphoric acid is separated from the resultant calcium sulfate slurry by filtration. To generate a filterable slurry and to enhance the P2O5 content of the acid, much of the acid filtrate is recycled to the reactor. 

Cesium isotopes can be recovered from fission products by digestion in nitric acid, and after filtration of waste the radioactive cesium phosphotungstate is precipitated using phosphotungstic acid. This technique can be used to prepare radioactive cesium metal or compounds. Various processes for removal of Cs isotopes from radioactive waste have been developed including solvent extraction using macrocycHc polyethers (62) or crown ethers (63) and coprecipitation with sodium tetraphenylboron (64). 

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