Abstract: A method for selectively removing mercury from solutions, preferably solutions containing gold, such as gold cyanidation solutions, is provided comprising treating the solutions with dialkyldithiocarbamates, preferably potassium dimethyldithiocarbamate, to form stable mercury carbamate precipitates.

Abstract: The invention relates to a hydrometallurgical process for decontaminating soils 1 which are polluted with metallic elements, comprising a stage of basic leaching I so as to bring about the dissolution of the metallic elements to be removed, a cementation stage II bringing about the precipitation 6 of said elements in metal form, performed by electrochemical exchange with a zinc powder 5 produced by a stage of electrolysis III of the solution 7 originating from the cementation stage. In accordance with the invention a complementary addition of zinc is performed, preferably at the exit of the leaching stage in the form of a leachate 17 of waste from iron and steel manufacture, especially of dust 13 from electrical steel manufacture 15.

Abstract: A process is provided for the removal of fluoride from a metal sulphate solution, such as a zinc sulphate solution, which presents an option for the disposal of waste treatment sludge from the aluminum anodizing industry. The fluoride is removed from metal sulphate solution by mixing the sludge with the solution for a predetermined period of time and then performing a solid/liquid separation.

Abstract: A method for the recovery of zinc products, including zinc oxide and elemental zinc, and optionally iron-carbon feedstocks, from industrial waste streams containing zinc and iron, by treating the waste streams with carbon and an ammonium chloride solution, separating any undissolved components from the solution, displacing undesired metal ions from the solution using zinc metal, treating the solution to remove therefrom zinc compounds, and further treating the zinc compounds and the undissolved components, as necessary, resulting in the zinc products and the optional iron-carbon feedbacks.

Abstract: A process for extracting metal values especially zinc values from aqueous solutions of metal salts which comprises contacting the aqueous solution with an organic phase comprising a compound of the formula: ##STR1## wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4, independently, represents an optionally substituted hydrocarbyl or hydrocarbyloxy group or R.sup.1 and R.sup.2 together with the attached phosphorus atom and/or R.sup.3 and R.sup.4 together with the attached phosphorus atom form a 5- to 8-membered heterocyclic ring.

Abstract: A process for the recovery of a metal, in particular, cadmium contained in scrap, in a stable form. The process comprises the steps of mixing the cadmium-containing scrap with an ammonium carbonate solution, preferably at least a stoichiometric amount of ammonium carbonate, and/or free ammonia, and an oxidizing agent to form a first mixture so that the cadmium will react with the ammonium carbonate to form a water-soluble ammine complex; evaporating the first mixture so that ammine complex dissociates from the first mixture leaving carbonate ions to react with the cadmium and form a second mixture that includes cadmium carbonate; optionally adding water to the second mixture to form a third mixture; adjusting the pH of the third mixture to the acid range whereby the cadmium carbonate will dissolve; and adding at least a stoichiometric amount of sulfide, preferably in the form of hydrogen sulfide or an aqueous ammonium sulfide solution, to the third mixture to precipitate cadmium sulfide.

Abstract: A process for extracting metal values especially zinc values from aqueous solutions of metal salts which comprises contacting the aqueous solution with an organic phase comprising a compound of the formula: ##STR1## wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4, independently, represents a substituted hydrocarbyl or hydrocarbyloxy group or R.sup.1 and R.sup.2 together with the attached phosphorus atom and/or R.sup.3 and R.sup.4 together with the attached phosphorus atom form a 5- to 8-membered heterocyclic ring.

Abstract: A process of treating water to remove metal ion contaminants contained therein, said metal ion contaminants selected from the group consisting of metals in Groups 8, 1b, 2b, 4a, 5a, or 6a of the periodic table, lanthanide metals, and actinide metals including transuranic element metals, by adjusting the pH of a metal ion contaminant-containing water source to within the range of about 6.5 to about 14.0, admixing the water source with a mixture of an alkali or alkaline earth ferrate and a water soluble salt, e.g., a zirconium salt, in an amount sufficient to form a precipitate within the water source, the amount the mixture of ferrate and water soluble salt effective to reduce the metal ion contaminant concentration in the water source, permitting the precipitate in the admixture to separate and thereby yield a supernatant liquid having a reduced metal ion contaminant concentration, and separating the supernatant liquid having the reduced metal ion contaminant concentration from the admixture is provided.

Abstract: A process for recycling a zinc phosphating system sludge comprising forming a mixture of the sludge with water and phosphoric acid. The mixture is formed at an elevated temperature and a pH of between 1.5 and 2.4. The sludge substantially dissolves in the mixture and iron phosphate precipitates out. The resultant liquid comprises a substantially zinc ion and phosphate ion solution suitable for use as a make-up feed in zinc phosphating system.

Abstract: A process is disclosed for recovering zinc, lead, copper and precious metals from zinc plant residue, said process comprising leaching the residue with return zinc spent electrolyte, neutralizing residual acid and reducing ferric iron in the solution by addition of zinc sulphide concentrate in the presence of a limited quantity of oxygen, flotation of the resulting slurry to separate unreacted zinc sulphide, treatment of flotation tailings with sulphur dioxide and elemental sulphur to further leach iron, zinc and impurity elements and precipitate copper, flotation of the resulting slurry to separate a copper sulphide concentrate, thickening, filtering and washing of the flotation tailings followed by addition of lime and sodium sulphide to activate lead sulphate and flotation of a lead concentrate from the residue.

Abstract: A method for the recovery of copper from copper-containing materials, for example, scrap, ores or dust. An aqueous cupric tetrammine sulfate lixiviant is contacted with the copper-containing material to produce a leachate containing cuprous, nickel, and zinc ions, ammonium sulfate and free ammonia. Copper can be recovered from the leachate by electrolysis. Nickel and zinc can be precipitated from the resulting spent electrolyte by oxidizing substantially all of the cuprous ions in the copper ammine sulfate solution to cupric ions and lowering the pH of the solution to a range from about pH 7.5 to about pH 8.0 in order to form a precipitate. Alternatively, copper sulfate can be added to the cupric ammine sulfate-containing solution in order to form nickel and/or zinc containing precipitate.

Abstract: A process for selectively recovering dissolved heavy metals from a solution is disclosed that involves selectively reacting a xanthate with such dissolved heavy metals. Selective reaction of a xanthate with selected dissolved heavy metals is accomplished by conducting the reaction under conditions such that only some of the heavy metals react with the xanthate, to the exclusion of reaction with other dissolved heavy metals. Selectivity of the reaction is particularly influenced by the pH at which the reaction occurs. Typically, the reaction should occur at a pH below about 4.0. Xanthates, once reacted, can be separated from the heavy metal xanthate reaction product and recycled for use within the process. Purified heavy metal product can be produced if desired.

Abstract: A process for the removal of mercury from industrial waste streams is disclosed wherein the waste stream is a nitrate based solution that has been decomposed by the addition of hypochlorite. The method involves adding a reducing agent to reduce the hypochlorite and/or adjusting the pH by the use of a strong acid to less than about 2.0, converting any residual chlorine to a soluble unreactive salt, adding a soluble precipitating agent, such as sodium sulfide, to the solution in a ratio to the mercury present of greater than 1:1 to about 2:1 to precipitate out the mercury as a mercury compound. The solution is then filtered to remove the precipitated mercury compound.

Abstract: Methods are disclosed for treating smelter flue dust and other smelter by-products so as to recover non-ferrous metals therefrom and convert arsenic and sulfur in the flue dust into non-leachable compounds. The methods allow the flue dust and other smelter by-products such as smelter sludges to be disposed of in a natural environment without subsequent leaching of heavy metals, sulfur, and arsenic. The smelter by-products are mixed with hydrated lie, formed into agglomerates, and roasted at an optimal temperature of about 650.degree. C. to form oxidized arsenic and sulfur which react with the lime in the agglomerates to form non-leachable compounds. The roasted agglomerates are contacted with a basic lixiviant comprising dissolved ammonia and an ammonium salt to dissolve non-ferrous metals such as copper from the roasted agglomerates. Used lixiviant can be boiled to precipitate the non-ferrous metals dissolved therein and vaporize the ammonia, thereby regenerating the lixiviant.

Abstract: The present invention describes a method of making metal stannates by reacting a solid metal oxide, hydroxide or carbonate with an aqueous stannate solution and recovering the precipitated metal stannate, the solid component being added in an amount which is stoichiometrically not substantially more then the amount of tin.

Abstract: A process for recovery of metal from a feedstock comprising copper is provided. The process comprises the steps of:(a) contacting the feedstock with an aqueous mixture comprising ammonium nitrate having a concentration greater than about 1.5M and sulphuric acid having a concentration greater than about 6M at a temperature of from about 105.degree. C. to about 130.degree. C., to produce a first residue comprising a cuprous salt and a leachate comprising copper;(b) separating the residue from the leachate; and(c) electrowinning copper from the leachate.The process may also be used advantageously to recover iron present in the feedstock in a form other than jarosite.

Abstract: Concentrations of cobalt and copper of electrolysis solution for electrowinning of zinc can be measured any time during electrowinning operation by continuously sampling the solution, diluting it, adding coloring reagent to the flow of the solution and spectrophotometrically analyzing the solution.The cobalt and copper as deleterious impurities can be removed continuously and automatically by measuring their concentrations by the above method and adding precipitation reagents for them in an amount calculated by a microcomputer on the basis of said analysis.

Abstract: A white colored deodorizer comprising titanium oxide and zinc oxide and a method for its preparation are disclosed.

Abstract: Needle-like electrically conductive zinc oxide filler having low specific volume resistance and excellent electrical conductivity-imparting effect per unit weight thereof is provided, including a method for its preparation.

Abstract: Dipicolylamine (DPA) is chemically bound to the surface of a silicate, forming a solid phase particle without substantially decreasing the affinity constant of the DPA for certain ions. Then, the solid phase particle is contacted with the solution, thereby binding an ion to the particle. Subsequently the ion can be stripped from the ligand by treatment with a complexing agent or acid.

Abstract: A method of precipitating metals from a spent geothermal brine containing the same comprises admixing the geothermal brine with a condensate of steam, derived from the brine, in a volume ratio of brine to condensate of 1:2 to 1:10. The invention is particularly applicable to geothermal brine processes for the production of electric power, such as are practiced at the Salton Sea.

Abstract: Flaky fine particles of zinc oxide have an average particle diameter of 0.1 to 1 micron, an average particle thickness of 0.01 to 0.2 micron and a mean platy ratio (aspect ratio) of at least 3. They are useful as an ingredient for an external composition containing a medicine or cosmetic.

Abstract: A process for treatment of incinerator ash typically including heavy metals and both water soluble and insoluble fractions. The insoluble fraction is first removed from the fly ash. The soluble fraction is treated to precipitate heavy metal compounds. Preferably, the heavy metal precipitates are incorporated in a vitrifiable batch. In a separate vitrifiable batch, the insoluble fly ash portions may also be incorporated. Most preferably, bottom ash from the incinerator is also incorporated in a glass batch. The bottom ash glass batch may also incorporate the insoluble fraction from the fly ash.Precipitation of the heavy metal constituents in the soluble portion of the fly ash is preferably accomplished by raising the pH of the solution, most preferably above 10 by addition of alkali metal or alkaline earth metal hydroxides.

Abstract: Natural gas, particularly gas to be processed in liquefied natural gas plants, is treated to remove residual mercury by scrubbing with an aqueous solution containing alkali metal polysulfide and sufficient pH adjusting compound to maintain the pH above 8.4.

Abstract: A process of refining zinc oxide from roasted zinc sulphide bearing concentrates comprises leaching the concentrate in an aqueous sulphur dioxide solution under controlled conditions providing selective separation of zinc from other elements contained in the concentrate. The zinc bisulphite solution so obtained is separated from the remaining solids and is heat treated, preferably with steam, to precipitate zinc monosulphite crystals, possibly after first adding zinc dust to the solution to cement out residual copper and cadmium. The zinc monosulphite is then separated from the solution, possibly washed with water, and calcined to yield purified zinc oxide.

Abstract: A process for the removal of mercury from natural gas condensate wherein hydrogen sulfide is mixed into the natural gas condensate and the mixture is fed along with a stripping gas through a reactor containing a catalyst, e.g. a cobalt/molybdenum catalyst.

Abstract: Heavy metals can be precipitated from waste water or aqueous reaction solutions containing inorganic and/or organic complexing agents with substituted thiorureas of the general formula R.sub.1 R.sub.2 N-CS-NH-COR.sub.3. N,N-dialkyl-N'-benzoyl thioureas are used with preference, whereby methyl, ethyl, n-propyl or isobutyl groups are used as alkyl substituents.

Abstract: A method for removing iron(III), copper(II), zinc(I) and nickel(II) from an effluent containing chelant (EDTA, DEPA, HOEDTA) comprising treating the effluent with a soluble calcium compound (e.g., Ca(OH).sub.2) CaCl.sub.2, Ca(NO.sub.3).sub.2) in a molar equivalent to the chelant in combination with a monovalent hydroxide to a pH greater than 12.4 and then adding an effective amount of a dialkyldithiocarbamate (e.g.; sodium-N,N-diethyldithiocarbamate) to precipitate the metal hydroxides and nickel dialkyldithiocarbamate. Heating the solution to about 180 F. further speeds up the removal of the nickel(II). The nickel concentration of spent chelant cleaning solution can be reduced to less than 1 ppm.

Abstract: A process for the removal of mercury from natural gas condensate wherein the natural gas condensate is passed over a catalyst, while also passing a stream of methane containing hydrogen sulfide over the catalyst.

Abstract: A process for the removal of mercury from natural gas condensate wherein elemental sulfur is mixed into the natural gas condensate and the mixture, along with a stream of hydrogen, is fed through a reactor containing a hydrodesulfurization catalyst.

Abstract: A process is provided for working up dusts which have been precipitated electrostatically from the gas mixture composed essentially of carbon monoxide and phosphorus vapor produced in the electrothermal production of yellow phosphorus, which process comprises converting the dusts into a calcinate at 300.degree. to 800.degree. C. under oxidizing conditions in a first step, leaching the calcinate with phosphoric acid in a second step, adjusting the pH of the solution in phosphoric acid to 0 to 1.5 with sodium hydroxide solution in a third step, precipitating the sulfides of lead, copper and cadmium from the partially neutralized solution in phosphoric acid by adding sulfide and filtering them off in a fourth step, adjusting the pH of the filtered, partially neutralized solution in phosphoric acid to about 1.5 to 5.

Abstract: According to the subject method of refining a ferrous ion-containing acid solution, a metal selected from a group including Al, Cr, V, B, and Zn or an acid solution of that metal is added to a ferrous ion-containing acid solution, such as an acid solution which remains after steel is washed with an acid. The pH value of the acid solution is controlled to be within the range of 3.5 to 6 by adding an alkali liquid to the acid solution, whereby a hydroxide salt of the added metal is produced in the acid solution and the impurities in the acid solution are captured by the produced hydroxide salt. As a result, the impurities can be eliminated from the acid solution such that the Si component (e.g., SiO.sub.2) content in the acid solution is within the range of 2 to 3 ppm or less. Since the content of the other impurities such as Al, Ti, and Cr can also be reduced, a high-purity iron oxide can be obtained from the resultant acid solution.

Abstract: An elastic bar member is coupled to an orbiting mass oscillator and the entire assembly is suspended from a cable or the like such that the bar member has freedom of lateral motion and is nakedly immersed in a slurry having particulate material contained therein such as a mineral ore reject from which metal has been extracted. The rotor of the orbiting mass oscillator is driven at a speed such as to generate cycloidal sonic energy in the bar preferably at a frequency such as to set up resonant standing wave vibration of the bar in a cycloidal quadrature pattern. The cycloidal vibrational energy tends to set the surrounding fluid material into a whirling rotation or rotary traveling wave which facilitates the agglomeration or coagulation of the particles in the material and enhances the settling operation to make for more complete separation of the particles from the liquid.

Abstract: An elastic bar member is clamped to an orbiting mass oscillator and the entire assembly is suspended from a cable or the like such that the bar member has freedom of lateral motion and is nakedly immersed in a leachant having a material contained therein such as a mineral ore from which metal is to be extracted. The rotor of the orbiting mass oscillator is driven at a speed such as to generate cycloidal sonic energy in the bar preferably at a frequency such as to set up resonant standing wave vibration of the bar in a cycloidal nutating pattern. The cycloidal vibrational energy tends to set the surrounding fluid material into a whirling rotation or rotary traveling wave which facilitates the mixing of the ore and leachant and enhances the leaching operation to make for more complete separation of the mineral from the ore.

Abstract: This invention can treat a uranium-containing solution of high or low concentration and/or the waste generated from uranium conversion processes, etc. It is characterized by the use of acorns, nuts of oak tree, which can be easily obtained in our botanical system. By coprecipitating the uranium or other heavy metal elements with the extract of acorns, this invention can not only recover the uranium of other heavy metal elements but also can reduce them before being discharged to the environmental radioactivity level.

Abstract: The zinc and ammonia values in solutions containing zinc chloride or zinc monoammine chloride and ammonium chloride can be recovered by adding ammonia to a pH of about 5.5 to about 8.5 and separating the precipitated zinc diammine chloride from the residual aqueous solution of ammonium chloride. The zinc diammine chloride can be used as is or further converted to anhydrous zinc chloride and ammonia and the aqueous solution of ammonium chloride can be used as is or basified to recover the ammonia.

Abstract: There is disclosed a process and an apparatus for beneficiating a mineral ore, such as phosphate-containing ore, in a substantially vertical column. The feed subjected to the benefication preferably has a particle size of less than 20 mesh. The feed is introduced into the column, containing at least one baffle, into which there is also introduced a gas at the bottom portion thereof and a liquid through at least one column inlet at the top of the column. The baffle and the rates of introduction of the feed, the gas, and the liquid are such as to create relatively high turbulence conditions within the column. The enriched, beneficiated product is removed at the top of the column, while the waste products, such as silica-containing material, in the case of a phosphate ore, are recovered at the bottom of the column.

Abstract: A process is described for the controlled oxidation roasting of zinc bearing sulphidic ores and concentrates by adjusting the furnace temperature and residence time together with the oxygen availability to the sulphide retention requirements in the calcine. The obtained calcine is subsequently subjected to various physical and chemical process steps to separate the unreacted sulphides which are then dead roasted and treated for zinc recovery, according to one embodiment of the process. In another embodiment the separated, unreacted sulphides are returned to the controlled oxidation roasting step.The chemical separation process steps include sulphur dioxide leaching. In one embodiment zinc is preferentially dissolved as sulphite and the solution obtained is further treated for zinc recovery. In other embodiments sulphuric acid, or ammonical ammonium carbonate or similar leaching reagents are used for the preferential dissolution of the zinc oxide present in the calcine.

Abstract: A process comprises leaching zinc oxide either separately or in conjunction with iron oxides from a partially desulfurized zinc bearing sulfide ore of concentrate. The ore is pretreated to eliminate in a controlled manner sulfur-sulfur-sulfide in the ore yet leaving sufficient residual sulfur-sulfide in the material such that iron values are maintained substantially wholly in the ferrous state, while converting zinc sulfide to zinc oxide without formation of FeO-ZnO complexes. The partially desulfurized material may be selectively leached with a sulfuric acid containing solution under neutral leach conditions to dissolve thereby preferentially the zinc oxide over the iron oxide. Alternatively the material may be leached with a higher concentration of sulfuric acid containing solution to dissolve preferentially zinc oxide and iron oxide simultaneously. The leach liquor may be subsequently treated to electrolytically remove zinc.

Abstract: Disclosed is a process for the precipitation and separation of cadmium sulphide from the raffinates derived from phosphoric acid purification by treating the cadmium containing streams of the raffinates with a H.sub.2 S containing solvent phase in a mixing-settling apparatus, by separating the raffinate phase from the cadmium sulphide containing solvent phase and by separating the precipitated cadmium sulphide from the solvent phase. By operating this process it is possible to remove cadmium in a simple manner from the raffinates since their inherent properties don't influence the precipitation and separation of cadmium sulphide.

Abstract: Solid residues arising from the burning of solid wastes have lead and cadmium sufficiently insolubilized to pass the EPA toxicity test only where the pH in the EPA test is between 7.5 and 12.0. Addition of water soluble phosphate, especially phosphoric acid, increases the immobilization of lead and cadmium so as to make such residues in compliance with the toxicity tests over a substantially broader pH range.

Abstract: This invention is a process for removing mercury from the desorption or cyanide liquor of a precious metal recovery, cyanide leach system. A sulfide ion-producing compound and a flocculating agent are added to the desorption liquor to form and flocculate mercuric sulfide. The desorption liquor typically has a cyanide concentration of between about 0.5 percent and about 2.0 percent by weight. The flocculated mercuric sulfide is separated from a substantially mercury-free precious metal-containing, cyanide solution.

Abstract: Iron is recovered from an iron-containing dust obtained in processing iron or steel by dissolving iron and bivalent metals present in the dust in an acid. Subsequently the iron is precipitated as iron hyroxide by adding an alkaline substance or ammonia to adjust the pH to 5 to 8. Before or during precipitation of any iron the bivalent metal ions present, such as zinc, cadmium and lead, are converted into a soluble complex by the addition of a complexing agent, preferred complexing agents being polyamines, particularly triethylene tetramine. The process may be conducted more than once in the same solution, thereby providing a final solution containing considerable amounts of zinc, cadmium, or other bivalent metals, which may be separated by boiling or precipitation.

Abstract: The invention relates to a process for the recovery of gold from an alkaline aqueous liquid solution containing gold-cyanide ion, and possibly silver and/or copper and/or mercury, which comprises adding a quantity of thiourea to the solution so as to allow formation of a gold complex with thiourea which gold complex is soluble and stable in dilute acid solution, then adjusting the pH of the solution to make the solution mildly acidic, whereby gold and mercury remain in solution in the liquid and silver and/or copper is incorporated in a precipitate containing silver and/or copper cyanide compounds, and then separating the precipitate from the liquid to leave a solution of dissolved gold complex and subsequently recovering the gold from the solution.

Abstract: This is a method for the complete leaching of the valuable metals in a metal sulphide material which contains copper, zinc, lead, silver and iron by the use of a solution which essentially contains cupric chloride/sulphates. After the valuable metals have been recovered, the solution is regenerated whereby ferrous chloride and cuprous chloride/sulphate is oxidized to a ferric hydroxide solid and a cupric chloride solution respectively. The regenerated solution is split into two part-solutions and returned to the process.One part-solution goes to a metathesis stage where the fresh metal sulphide material is added in large excess with respect to the part-solutions's content of copper. The result is that only the valuable metals like zinc, lead and silver are leached while copper and iron remain in the residue.The other part-solution goes to a leach stage where the residue from the metathesis stage is added.

Abstract: A process for purifying aqueous solutions of zinc sulphate removed from leaching processes and containing metals such as Cu, Cd, Ti, Ni, Co, Ge, As, Sb which consists in cementing said metals with zinc dust and with a couple of activators chosen between Cu-As and Cu-Sb in one or more reaction vessels having a bottom portion of cylindrical shape, an intermediate portion of cone frustum shape, and a top portion having an enlarged section thereof.

Abstract: A process for the removal of cadmium contained in wet-process phosphoric acid by flotation by means of a cadmium-collector anionic surface active agent and an injected gas in the presence of other impurities including iron and possibly uranium which is characterized in that, in order to improve the removal of cadmium, the iron contained in the phosphoric acid in the trivalent state is reduced to the divalent state before the cadmium collector is introduced into the medium to be purified by flotation.The collector agent is selected from the group of dithiophosphoric acid esters and the alkali metal salts thereof.

Abstract: A process for the recovery of anhydrous zinc chloride from aqueous solutions containing zinc chloride and typical impurities, comprising: extracting zinc chloride onto a suitable organic extractant such as TBP; stripping the organic extractant with an organic reagent immiscible in the extractant, such as ethylene glycol; adding ammonia or other ammine donor to the loaded organic strip to precipitate a zinc chloride-ammine composition which may be decomposed to anhydrous zinc chloride by heating. The anhydrous zinc chloride is of high purity suitable for fused salt electrolysis to produce elemental zinc.

Abstract: Process for the recovery of heavy metals from aqueous solution by reaction with soluble, functionally-substituted polymer upon which the heavy metal loads, and optionally crosslinks by interaction with the heavy metals present in solution. Metals including those having atomic numbers of 39-51, 57-84 and 89-117, inclusive, can be recovered by the practice of the present invention.

Abstract: The present invention relates to a process for purifying flue gases developed during the combustion of waste materials and containing solids of various compositions as well as pollutant gases and heavy metals in gaseous form, wherein the primarily solid components are removed from the flue gas in a separating system and are collected as flue ashes and wherein the flue gas is washed for the purpose of binding the pollutant gases of the residual solids components, particularly in the slag.It is the object of the present invention to provide a process wherein, during flue gas purification, the gaseous heavy metal contaminants as well as the heavy metal contaminants which are present in the flue ash and in the slag in soluble form, can be removed from the flue gas purification process in the most compact form, with simultaneously achieving good, or even improved, initial purification of HCl, SO.sub.2. NO.sub.x. All other residues should be returnable for further use.