Abstract: Highly purified ammonia for use in semiconductor manufacturing is prepared on-site by drawing ammonia vapor from a liquid ammonia reservoir, passing the vapor through a filter capable of filtering out particles of less than 0.005 micron in size, and scrubbing the filtered vapor in a high-pH aqueous scrubber.

Abstract: Process for the recovery of hydrogen fluoride (HF) from a mixture, preferably an azeotropic mixture, of HF with water and/or an organic compound such as 134a, 125 or 133a, which comprises contacting the mixture with lithium fluoride or an alkaline earth metal fluoride to form a metal fluoride-hydrogen fluoride compound (e.g. lithium bifluoride, LiHF.sub.2), separating the compound and decomposing it to liberate hydrogen fluoride therefrom. The process is useful for recovering HF from azeotropic or azeotropic-like mixtures.

Abstract: A system for purification and generation of hydrofluoric acid on-site at a semiconductor device fabrication facility. An evaporation stage (optionally with arsenic oxidation) is followed by a fractionating column to remove most other impurities, an Ionic Purifier column to suppress contaminants not removed by the fractionating column, and finally the HF Supplier (HFS).

Abstract: A method for separating hydrogen fluoride from a chemical mixture is provided. In the process of the invention, hydrogen fluoride is separated from a chemical mixture containing hydrogen fluoride by contacting the chemical mixture with a hydrogen fluoride binder. The separated hydrogen fluoride may be recovered from the hydrogen fluoride binder.

Abstract: Highly purified ammonia for use in processes for the production of high-precision electronic components is prepared on-site by drawing ammonia vapor from a liquid ammonia reservoir, passing the vapor through a filter capable of filtering out particles of less than 0.005 micron in size, and scrubbing the filtered vapor in a high-pH aqueous scrubber.

Abstract: A method of treating spent potliner material from aluminum reduction cells is disclosed. The spent potliner material is introduced into a sulfuric acid digester to produce a gas component including hydrogen fluoride and hydrogen cyanide and a slurry component including carbon, silica, alumina, sodium sulfate, iron, calcium and magnesium. The gas component is recovered and heated an effective amount to eliminate hydrogen cyanide and produce a remaining gas component including CO.sub.2, H.sub.2 O, nitrogen oxides and HF. The remaining gas component is directed through a water scrubber to form hydrofluoric acid, and the hydrofluoric acid is admixed with aluminum hydroxide to create aluminum fluoride. The slurry component is rinsed with water to separate a first solid fraction containing carbon, alumina and silica from a second liquid faction. The pH of the liquid fraction is adjusted to first create and separate aluminum hydroxide and then to separate sodium sulfate.

Abstract: The present invention provides a convenient method for separating hydrogen fluoride from a chemical mixture. More specifically, a method is provided in which hydrogen fluoride is separated from a chemical mixture containing at least one organic material by contacting the chemical mixture with a hydrogen fluoride binder. The hydrogen fluoride separated from the chemical mixture is readily recoverable from the hydrogen fluoride binder.

Abstract: HF can be recovered from aqueous streams, particularly those which are dilute and have a concentration of HF lower than the azeotrope between HF and water. Such aqueous streams are contacted with carbon molecular sieves, preferably those having an average pore size of about 3.5 Angstroms, which adsorb both HF and water. When regenerated by heating, more dilute aqueous streams are desorbed at lower temperatures, followed by desorption of HF which is free of water, making possible a separation of HF and water and avoiding formation of the azeotrope.

Abstract: A process for removing water and/or carbon compounds from hydrogen fluoride by contacting the hydrogen fluoride to be purified with elemental fluorine.

Abstract: The invention relates to a process for separating HF contained in liquid mixtures comprising HCFC 123 and/or 124. The mixtures, enriched in C.sub.2 Cl.sub.4 up to a content of such compound of 20-75% by weight, is subjected to a treatment for separating liquid phases, thereby obtaining an acid phase very rich in Hf and an organic phase impoverished in HF, which is subjected to a flash, so obtaining a liquid phase containing 123, 124 and C.sub.2 Cl.sub.4, having a very low HF content, and a gas phase enriched in HF. As an alternative to flash, a separation in a distillation column can be carried out.

Abstract: A process for disposing of bromofluorocarbons, bromochlorofluorocarbons, or mixtures of any of bromofluorocarbons, bromochlorofluorocarbons, fluorocarbons, or chlorofluorocarbons. The process comprises thermally cleaving halons, halon-containing fluorocarbons, or halon containing chlorofluorocarbons, cooling the resulting gas stream, oxidizing the resulting hydrogen bromide to bromine by feeding excess elemental chlorine into the gas stream, absorbing the resulting HF or HCl from the gas stream with recovery of hydrofluoric acid or hydrochloric acid, and finally separating elemental bromine and chlorine from each other by distillation or reducing both to give the salts.

Abstract: The invention relates to a process for purifying industrial anhydrous hydrogen fluoride by means of oxygen difluoride.

Abstract: A process for preparing ultrapure hydrogen fluoride by contacting impure hydrogen fluoride with elemental fluorine in the presence of metal fluorides. The ultrapure hydrogen fluoride which can be obtained can be used in electronics or optics or for preparing fluorine-containing organic or inorganic compounds or ultrapure hydrofluoric acid.

Abstract: The invention relates to the removal of detrimental metal ions represented by Cu ion from a hydrofluoric acid solution for use in the manufacturing of semiconductor devices to clean silicon wafer surfaces. The acid solution is brought into contact with silicon granules which are used for the adsorption of the detrimental metal ions. To enhance the adsorption power and the rate of adsorption, the silicon granules are treated in advance to deposit a metal which is lower in ionization tendency than silicon on the surface of each silicon granule so as to partly cover the silicon granule surface by the deposited metal. Particularly Au or Ag is suitable as the metal deposited on the silicon granules.

Abstract: A method is provided for recovering an anhydrous hydrogen fluoride product from uranium hexafluoride gas by initially reacting the uranium hexafluoride in a primary reactor with steam to produce a uranyl fluoride intermediate and a gaseous mixture of hydrogen fluoride and water. The uranyl fluoride intermediate is fed to a secondary reactor and reacted with water to produce a triuranium octoxide product for disposal, and a gaseous mixture of water, hydrogen fluoride and oxygen. The two mixtures from the primary and secondary reactors are combined and subsequently separated in a distillation column to obtain an anhydrous hydrogen fluoride product stream and an aqueous azeotropic recycle stream containing water and hydrogen fluoride which is vaporized and returned to the primary reactor as the steam feed.

Abstract: A process is disclosed for regenerating a spent liquid acid catalyst comprising the steps of:(a) providing a spent liquid acid catalyst comprising HF, sulfolane, and conjunct polymeric byproducts formed during the HF-catalyzed reaction of isoparaffin and olefin to form isoparafinnic alkylate;(b) providing a finely divided solid sorbent, wherein said solid sorbent preferentially and reversibly sorbs said conjunct polymeric byproducts from a mixture containing HF, sulfolane;(c) mixing said spent liquid acid catalyst of step (a) with said solid sorbent of step (b) by charging said spent liquid acid catalyst to the driving fluid inlet of an eductor and drawing a stream containing said solid sorbent into said eductor;(d) holding said mixture of step (c) in contact for time sufficient for said solid sorbent to preferentially sorb at least a portion of said conjunct polymeric byproducts from said spent liquid acid catalyst to produce a conjunct polymer-enriched sorbent and to regenerate said liquid acid catalyst; an

Abstract: A method of treating a gas based on fluorine and containing hydrofluoric acid, and which may optionally contain condensable gaseous compounds, especially uranium compounds, and non-condensable gases. The gas is refrigerated to obtain a gaseous component containing fluorine and any non-condensable gases present, and a liquid phase containing liquid HF and condensable compounds in solution and/or suspension. The liquid phase is filtered to recover the compounds in suspension.

Abstract: A thermal image transfer recording medium comprising a support, and a thermofusible ink layer formed thereon, which comprises a resin matrix and a thermofusible ink, with the above resin matrix and the thermofusible ink having a property of repelling each other.

Abstract: A process for preparing hydrogen fluoride, which comprises (i) reacting calcium fluoride with sulfuric acid to produce a gypsum and a gas containing hydrogen fluoride, (ii) separating hydrogen fluoride from said gas containing hydrogen fluoride, (iii) absorbing said hydrogen fluoride-separated gas with water to obtain an aqueous solution containing hydrogen fluoride and silicofluoric acid, (iv) reacting calcium carbonate with said aqueous solution to obtain a suspension containing silicic acid and calcium fluoride, (v) adding an alkaline substance to said suspension to make pH at least 8, thereby stabilizing the silicic acid as a colloidal solution, (vi) separating a calcium fluoride solid and the colloidal solution of silicic acid from said suspension, and (vii) recycling the separated calcium fluoride as a starting calcium fluoride.

Abstract: A method is disclosed for detoxification of aluminum spent potliner by thermal treatment in a rotary kiln while blended with limestone and metal silicates to destroy cyanides and convert the soluble fluoride salts to relatively insoluble calcium fluoride and fluoride-bearing minerals, quenching the hot kiln discharge with an aqueous lime slurry to convert residual soluble fluoride salts on the particle surfaces to an insoluble form, and treating aqueous landfill runoff and capture with lime or limestone and recycling the treated water to the process. The treated material is suitable for landfilling in a non-hazardous waste landfill or marketing as a raw material. Air emissions are innocuous and there is no aqueous discharge.

Abstract: During the pickling, etching, chemical shaping etc. of steels, stainless steels, special alloys and special metals and the dissolution of those metals, metalliferous solutions of the acids employed arise in the course of such processes which must either be disposed of by neutralization or be used for the recovery of the acids and metals by expensive processes. According to the invention the production or recovery of nitric acid or a mixture of nitric acid and hydrofluoric acid takes place by spray-roasting the solutions at temperatures of 200.degree. to 500.degree. in a reactor (1) and subsequent absorptions or condensation of the gases generated in column means (7, 8) at temperatures of 0.degree. to 70.degree. C.

Abstract: A process for manufacturing high purity anhydrous hydrogen fluoride (HF) having low levels of oxidizable impurities by electrolytically oxidizing the impurities. Specifically, trivalent arsenic impurity in the anhydrous hydrogen fluoride is oxidized to a non-volatile pentavalent arsenic compound. The resultant solution is distilled to recover high purity anhydrous hydrogen fluoride with low levels of arsenic impurity.

Abstract: A process for manufacturing high purity anhydrous hydrogen fluoride (HF) having low levels of oxidizable impurities by electrolytically oxidizing the impurities. Specifically, trivalent arsenic impurity in the anhydrous hydrogen fluoride is oxidized to a non-volatile pentavalent arsenic compound. The resultant mixture is distilled to recover high purity anhydrous hydrogen fluoride with low levels of arsenic impurity.

Abstract: The present invention provides a process for the conversion of hazardous hexafluoroarsenic acid or any salt thereof to arsenic acid or salt thereof which can be rendered nonhazardous. In particular, the hexafluoroarsenic acid or salt is converted to arsenic acid or salt which can be converted to a water insoluble salt. Known insolubilization and stabilization technology then renders the material nonhazardous.The present process involves converting hexafluoroarsenic acid or salt thereof contained in an aqueous mixture to arsenic acid or salt thereof.

Abstract: There is disclosed a process wherein impurities are removed from hydrofluoric acid by converting the highly volatile arsenic compounds into a compound with a very high boiling point. The process comprises the following steps: input of distilled hydrofluoric acid, which contains arsenic, into a reactor and cooling down to a temperature below room temperature; oxidation of the arsenic contained in the hydrofluoric acid in the form of arsenic trifluoride with an oxidizing agent in the presence of a surplus of potassium ions coming from potassium bifluoride in order to obtain an arsenic complex which is both stable and of high boiling point; halting the cooling of the reaction mixture and continuation of the stirring for a period of from 1-24 hours, permitting the mixture to remain quiescent to permit deposition; and finally distilling of the hydrofluoric acid at a temperature below reflux conditions, whereupon the arsenic complex formed during the oxidation reaction is removed from the hydrofluoric acid.

Abstract: A continuous process for the recovery of anhydrous hydrogen fluoride gas by contacting an aqueous solution of an alkali metal fluoride in hydrofluoric acid with a sulfur-containing dehydrating stream. The dehydrating stream preferably consists of sulfur trioxide dissolved in sulfuric acid. The desired product is obtained in high yield and purity.

Abstract: A process for preparing hydrogen fluoride that involves treating anhydrous hydrogen fluoride containing primarily trivalent arsenic impurities with an iodine compound capable of providing iodide ions (e.g., HI) so as to precipitate the arsenic (i.e., as AsI.sub.3) following by separation and recovery (e.g., by distillation or filtration) or purified anhydrous hydrogen fluoride.

Abstract: A process for producing hydrofluoric acid from SiF.sub.6.sup.2- in a wastewater is disclosed. The process is carried out by(i) combining (NH.sub.4).sub.2 SO.sub.4, at a pH high enough such that the sulfate is in its divalent state, with SiF.sub.6.sup.2- from said wastewater in an amount in excess of that stoichiometrically required to form (NH.sub.4).sub.2 SiF.sub.6 as follows:(NH.sub.4).sub.2 SO.sub.4 +SiF.sub.6.sup.2- .fwdarw.(NH.sub.4).sub.2 SiF.sub.6 +SO.sub.4.sup.2-(ii) concentrating a solution including (NH.sub.4).sub.2 SiF.sub.6 and excess (NH.sub.4).sub.2 SO.sub.4 to precipitate and separate (NH.sub.4).sub.2 SiF.sub.6 of high purity therefrom;(iii) re-solubilizing the (NH.sub.4).sub.2 SiF.sub.6 for reaction with NH.sub.4 OH to form NH.sub.4 F liquor and precipitated Si(OH).sub.4 ;(iv) separating the NH.sub.4 F liquor from the precipitated Si(OH).sub.4 ;(v) reacting the NH.sub.4 F with water to form precipitated NH.sub.4 F.multidot.HF and ammonia gas;(vi) reacting NH.sub.4 F.multidot.

Abstract: A process for preparing hydrogen fluoride that involves treating anhydrous hydrogen fluoride containing primarily trivalent arsenic impurities with a sulfur compound capable of providing sulfide ions (e.g., H.sub.2 S) so as to precipitate the arsenic (i.e., as As.sub.2 S.sub.3) followed by separation and recovery (e.g., by distillation or filtration) of purified anhydrous hydrogen fluoride.

Abstract: A process for preparing hydrogen fluoride involving treating anhydrous hydrogen fluoride containing primarily trivalent arsenic impurities with an effective amount of chromium (VI) oxide (i.e., CrO.sub.3) and oxygen such as to oxidize substantially all of the trivalent arsenic to pentavalent arsenic (i.e., As.sup.+3 .fwdarw.As.sup.+5) followed by separation and recovery (e.g., by distillation) of purified anhydrous hydrogen fluoride.

Abstract: A method for purifying hydrofluoric acid, comprising the steps of filtering the hydrofluoric acid to remove particulates, passing the filtered acid through a cation exchange material and an anion exchange material to remove ions therefrom, at least periodically automatically monitoring the acid that has passed through at least a predetermined portion of the cation exchange material for a predetermined level of cationic impurity representative of actual or impending ionic breakthrough in the cation exchange material, at least periodically automatically monitoring the acid that has passed through at least a predetermined portion of the anion exchange material for a predetermined level of anionic impurity representative of ionic breakthrough in the anion exchange material, automatically interrupting flow of acid through the anionic or cationic exchange material at or prior to the time the breakthrough in such material occurs, while the flow is interrupted, regenerating the anionic or cationic exchange material,

Abstract: A two-step distillation process provides semiconductor purity, concentrated hydrofluoric acid. Further, the distillation process, occurring under reduced pressures eliminates essentially pure water after the first distillation step. The product output of the second distillation process provides an acid of weight percent greater than 27 weight percent. The product acid is carefully diluted to the required concentrations during the dilution step.

Abstract: A process for manufacturing high purity anhydrous hydrogen fluoride (HF) having low levels of arsenic impurity by contacting anhydrous hydrogen fluoride product, or an intermediate product obtained during the manufacture of HF, with hydrogen peroxide to oxidize the arsenic impurity in the presence of a catalyst which comprises a catalytic amount of a component selected from the group consisting of molybdenum, a molybdenum compound, vanadium, and a vanadium compound, and a phosphate compound. The volatile trivalent arsenic impurity in the anhydrous hydrogen fluoride is oxidized to a non-volatile pentavalent arsenic compound and the resultant mixture is distilled to recover high purity anhydrous hydrogen fluoride with reduced levels of arsenic impurity. In one embodiment, an oxidizing agent such as nitric acid or a nitrate salt is added to the reaction mixture to oxidize organic compounds.

Abstract: A process for the treatment of waste materials such as spent cathode liners involving combustion of the contained carbonaceous material, decomposition of the contained cyanides, sulphides and nitrides, and recovery of fluoride values by a sulpholysis reaction, is characterized in that the sulpholysis reaction is carried out in a separate stage. The process enables a recovgery of fluoride values from smelter wastes which is especially favourable environmentally. A further advantage of the invention is that recovery of the contained fluoride values, initially in the form of gaseous fluoride species, may subsequently be treated with alumina to produce aluminium trifluoride, which is of significant economic importance.

Abstract: A distillable liquid containing non-volatile impurities is freed of those impurities by boiling the liquid to form vapors of the liquid, passing the vapors through a packed column heated to a temperature such that liquid entrained in the vapors is completely vaporized and the non-volatile impurities remain in the packed column, and condensing the vapors from the column.

Abstract: A method of recovering HF from an aqueous solution containing NH.sub.4 F and HF is provided. The solution is contacted with a water-immiscible, amine-containing extractant which extracts HF in preference to NH.sub.4 F. The HF:NH.sub.4 F molar ratio of the solution, the amine, the concentration of the amine in the extractant and the contact temperature are selected so as to form an HF-loaded organic liquid phase having an HF:amine molar ratio of at least about 1.2. The extractant is preferably selected from amines, amine-HF complexes, quaternary amine fluorides and mixtures thereof with inert organic diluents. After equilibration, the HF-loaded amine is separated from the solution and HF is stripped therefrom in an amount sufficient to lower the HF:amine molar ratio by at least about 0.2.

Abstract: A process for manufacturing high purity anhydrous hydrogen fluoride (HF) having low levels of arsenic impurity by contacting anhydrous hydrogen fluoride product, or an intermediate product obtained during the manufacture of HF, with hydrogen peroxide in the presence of a catalyst which comprises effective amounts of molybdenum or an inorganic molybdenum compound and a phosphate compound. The volatile trivalent arsenic impurity in the anhydrous hydrogen fluoride is oxidized to a non-volatile pentavalent arsenic compound and the resultant mixture is distilled to recover high purity anhydrous hydrogen fluoride with reduced levels of arsenic impurity. In one embodiment, an oxidizing agent such as nitric acid or a nitrate salt is added to the reaction mixture to oxidize organic contaminants.

Abstract: This invention discloses processes for the treatment of coal and coal derivatives in order to remove contaminates to produce a high purity coal product. The processes generally comprise a sequential acid leaching in which a hydrofluoric acid leach is followed by a hydrochloric acid leach. The pyrite and other heavy metals from the coal are removed by physical separation, either gravity or magnetic separation. The leached coal is then treated either by a washing and drying step or by a heat treatment to remove volatile halides. The HF acid and the HCl acid leachates are recovered for regeneration of the respective leachates and are recycled for use in the leaching steps. In additional processing, the coal may be pre-treated by a mild HCl acid leach and by pre-drying or physical beneficiation of the coal feedstock.

Abstract: A process for treating solid substantially non-volatile wastes contaminated with a heat sensitive contaminant is disclosed. The wastes are heated to form a liquid slag. The liquid slag is held at elevated temperature until at least a portion of the contaminating components have either decomposed or evolved from the melt as a gas. The slag is subjected to cooling and the contaminating compounds are bound or encapsulated into a solid glassy slag. The process is particularly suitable for handling fluoride and cyanide contaminated aluminum smelting wastes such as spent potliner material. It is advantageous to add silica to such wastes. The residue from the slagging reaction is a glassy solid sodium metal silicate matrix such that the fluoride residues remaining in the wastes are encapsulated. The amount of silicate blended with the feed material is selected to substantially tie up all of the sodium remaining in the residue after slag melting and is typically 7.5 to 50 weight percent of the feed.

Abstract: The purpose of the method is to remove chlorides and fluorides from a valuable metal raw material by leaching the raw material into sulphuric acid solution and by crystallizing the valuable metal sulphate selectively out of the solution. The valuable metal sulphate crystals are washed in sulphuric acid solution, and the recovered dechlorinated and defluorinated crystals are leached into water and conducted into electrolysis. The sulphuric acid solution employed in the raw material leaching and in the crystal washing is preferably the same as the return acid of the electrolysis. Chlorides and fluorides are removed from the mother liquor of crystallization in the bleed.

Abstract: A process for purifying hydrogen fluroide characterized by adding fluorine to hydrogen fluoride containing at least one element selected from the group consisting of boron, silicon, phosphorus, sulfur, chlorine and arsenic, and/or at least one compound of these elements, reacting the fluorine with said element and/or said compound and distilling the resulting mixture.

Abstract: A process is provided for the distillation of a composition containing 4-hydroxyacetophenone and hydrogen fluoride in the presence of an alkane assisting solvent having from 4 to 16 carbon atoms e.g. n-hexane or n-octane. The process is carried out to obtain an overhead vapor containing alkane solvent and most of the hydrogen fluoride in the feed, and a liquid residue containing most of the 4-hydroxyacetophenone in the feed. The overhead vapor is condensed to form two immiscible phases, one containing a preponderance of hydrogen fluoride and the other a preponderance of alkane solvent, with the latter phase being returned to the distillation as reflux. The liquid residue also separates into two immiscible layers, one containing most of the 4-hydroxyacetophenone in the feed which is recovered and the other a preponderance of alkane solvent.

Abstract: Alkali metal phosphates and HF can be produced from a substantially calcium-free fluoroaluminum phosphate precipitate (which also contains iron) made by the aging of wet process phosphoric acid containing iron, fluorine and aluminum, preferably phosphoric acid analyzing in the range of about 15%-45 weight percent P.sub.2 O.sub.5, 2-4% Al.sub.2 O.sub.3 and 1-2% fluorine. One process involves digestion of phosphate ore matrix in recycled phosphoric acid, filtration to remove the insoluble residue, precipitation and filtration to remove gypsum, and aging of the product acid to precipitate the aluminum impurity as a fluoroaluminum phosphate compound. The fluoroaluminum phosphate can be decomposed (as by heating at above 195.degree. C.) to produce HF and aluminum phosphate. The aluminum phosphate can be contacted with alkali metal hydroxide under conditions which produce an alkali metal phosphate.

Abstract: Hydrogen fluoride is produced by the electrodialysis of an alkali metal fluoride salt solution or an ammonium fluoride solution in an electrodialysis cell having an anode compartment and a cathode compartment spaced from one another by an inner electrodialysis compartment bounded by spaced cation exchange membranes.

Abstract: A method for separating and recovering substantially pure aluminum, iron and silica from fly ash, a by-product of coal combustion, includes reacting the fly ash with aqueous fluosilicic acid and aqueous hydrogen fluoride at temperatures sufficiently high to form aqueous silicon fluoride vapor and fluorides and fluosilicate of aluminum and iron, separating the aluminum and iron fluorides and fluorosilicates from the aqueous silicon fluoride vapor, hydrolizing the silicon fluoride vapor to form silicon dioxide in substantially pure form and hydrogen fluoride, recovering and recycling the hydrogen fluoride for reuse in the process, and separating the aluminum and iron fluorides and fluosilicates from one another, and recovering substantially pure aluminum fluoride, substantially pure iron and other substantially pure metals, by electroplating or otherwise.

Abstract: Substantially calcium-free fluoroaluminum phosphate precipitate (which also contains iron) can be produced by the aging of wet process phosphoric acid containing iron, fluorine and aluminum, preferably phosphoric acid analyzing in the range of about 15%-45 weight percent P.sub.2 O.sub.5, 2-4% Al.sub.2 O.sub.3 and 1-2% fluorine. One process involves digestion of phosphate ore matrix in recycled phosphoric acid, filtration to remove the insoluble residue, precipitation and filtration to remove gypsum, and aging of the product acid to precipitate the aluminum impurity as a fluoroaluminum phosphate compound. The fluoroaluminum phosphate can be decomposed (as by heating at about 195.degree. C.) to produce HF and aluminum phosphate.

Abstract: Arsenic impurities are removed from anhydrous hydrogen fluoride by treating the hydrogen fluoride with elemental chlorine and anhydrous hydrogen chloride or a fluoride salt or both and then separating the purified anhydrous hydrogen fluoride, preferably by distillation, from the nonvolatile arsenic compounds.

Abstract: A method for treating a waste stream from an alkylation process is disclosed, where the waste stream comprises a fluoride, sulfuric acid, and an acid soluble oil. The method comprises combusting the waste stream, scrubbing the combustion products to remove, fluorine, and recovering sulfur from the combustion products.

Abstract: A novel method is provided for the production of anhydrous hydrofluoric acid from low-grade metallic fluorides using an intermediate aluminum fluoride compound. The method involves the reaction of low-grade metallic fluorides such as fluorspar with sulfuric acid to produce weak hydrofluoric acid. The weak acid is then reacted with a metallic salt (such as aluminum chloride) to form precipitated aluminum fluoride (AlF.sub.3.3H.sub.2 O). After dewatering, the aluminum fluoride is reacted with strong sulfuric acid to form aluminum sulfate and strong hydrofluoric acid.

Abstract: A method for recovery of fluoride values from spent potlining and fluoride containing insulating materials associated with the potlining is disclosed. Spent potlining and the insulating materials are reduced to a fine particle size and incinerated. The ash residue is leached with a dilute caustic and the leachate is treated with a calcium compound to precipitate calcium fluoride. The calcium fluoride is dried to a moisture content of less than 0.1 percent and is treated with about 93 to 99 percent concentration of sulfuric acid to produce hydrogen fluoride gas and a metal sulfate. The hydrogen fluoride gas is fed into an alumina dry scrubber to produce alumina with absorbed fluorides to be used as feed material to reduction cells used in the manufacture of aluminum by electrolytic reduction. The metal sulfate residue is treated with lime and constitutes an environmentally safe product which can be disposed of as landfill material.