Abstract: A system and method for removing heavy metals, such as hexavalent chromium from water. The system comprises at least two reactor containers for independently mixing chemicals with water. The system further comprises a flocculator and a clarifier whereby each container can separately treat water therein and separately transfer the treated water to the flocculator such that water treated in batches at the containers can be treated in a relatively independent manner with relatively constant results. The method of chemically treating the water in the containers includes decreasing the pH value, adding a reducing agent and then increasing the pH value in preparation for precipitating the heavy metals in the clarifier.

Abstract: A process for the removal of heavy metals such as lead, cadmium, zinc, chromium, arsenic and mercury from aqueous solutions containing one or more of said metals as well as competing ions such as calcium and/or magnesium by contacting said aqueous solution with a crystalline molecular sieve having the X-ray diffraction patterns of ETS-10 or ETAS-10.

Abstract: A method of separating a heavy metal ion from an aqueous solution containing the heavy metal ion, comprising the step of bringing a chitosan derived from a chitosan-producing microorganism into contact with said aqueous solution. The chitosan used, which can be produced by a simple process, has good heavy metal ion adsorptivity; this method can effectively separate heavy metal ion from a solution containing it.

Abstract: A useful method for the recovery of heavy metal sulfides and alkali or alkaline earth metal salts of N-substituted dithiocarbamic acids from material containing heavy metal salts of N-substituted dithiocarbamic acids.

Abstract: A method for removing and recovering toxic heavy metal contaminants from an iron-bearing sludge is provided. The method comprises one or more cycles of a two step, controlled chloride leach comprising a first non-acidic chloride leaching solution and a second acidic chloride leaching solution, wherein said toxic heavy metals are separated from said sludge and said iron-bearing sludge is a substantially non-hazardous material.

Abstract: A coal gasifier slag composition, and process utilizing a coal gasifier slag composition for the removal of a metal ion, or the ions of a plurality of metals, from an aqueous medium by contact of said coal gasifier slag composition with said aqueous medium. The coal gasifier slag, which is regenerable by contact with a dilute acid, is employed as a contact mass for the removal from an aqueous medium of a metal ion, or the ions of a plurality of metals, derived from Groups IB through VIIB, IIA through VA, and VIII of the Periodic Table of the Elements. The coal gasifier slag is useful for removing a metal ion, or the ions of a plurality of metals, from industrial waste water, groundwater, mine water and the like, or as a landfill, or as a protecting layer adjacent to or surrounding land fills, surface impoundments, tank farm beds and the like.

Abstract: Metal chelates in solution are decomposed more effectively and completely by ozonation when magnesium hydroxide is added to the chelate solution prior to ozonation. The process is particularly applicable to waste streams from which it is desired to recover metals to avoid contamination of the environment and/or reuse them.

Abstract: A process is disclosed for removing heavy metals, dissolved aluminum, sulfides and organic compounds from a caustic etch solution, thereby regenerating the etching power of the solution or facilitating its disposal into the environment. The process consists of forming a first filtrate from which heavy metals present in the solution have been removed, and a second filtrate obtained by precipitating and oxidizing residual chemicals remaining in the first filtrate. The latter is done over a selected pH and temperature range. The second filtrate is then either reclaimed back to the etching tank, or subjected to ozonization prior to disposing of it into the environment.

Abstract: A process for removing dichromates from chlorate-rich solutions containing hypochlorite and dichromate ions and produced by the electrolysis of brine. The dichromate is reduced in a two-stage process by the addition of ammonia under controlled conditions of pH and temperature to a mixed di- and trivalent chromium hydroxide which is precipitated from solution and removed. The process provides an economical method of recovering chromium from electrolytically produced chlorate solutions.

Abstract: A process is disclosed for recovering metals from chromium bearing material comprising one or more or the metals of cobalt, nickel, molybdenum, tungsten, iron, tin, aluminum. The process comprises atomizing the material to produce a flowable powder which is then fused in an oxidizing atmosphere with sufficient alkali metal hydroxide at a temperature sufficient to form a nonmagnetic fused material in which the chromium, tungsten and molybdenum are present as water soluble salts. The resulting fused material is then slurried with a sufficient amount of water to dissolve the water soluble compounds. The pH is adjusted to from about 9.2 to about 9.6 with an acid to allow insolubles to form which contain any cobalt, and nickel and the major portion of any iron, tin and aluminum followed by separating the insolubles from the resulting first liquor.

Abstract: An agent for adsorbing and preventing leakage of heavy metals in the industrial waste, etc. includes coral sand of 60 mesh or less. The coral sand can be heated in the atmosphere of reduced pressure, vacuum or argon or nitrogen gas, or air dried in order to accelerate activation of coral sand.

Abstract: A treatment composition and method is provided for removing a plurality of contaminants from a wastewater system in the form of a nonleachable sludge. The treatment composition comprises an alkali or alkaline carbonate; activated montmorrilonite; a catalyst, such as zirconium and polyelectrolyte; one or more flocculants, such as a metal salt and calcium oxide, lime, or calcium hydroxide; and bentonite. Additionally, the treatment composition may contain soda ash, lignite, and activated carbon. The treatment composition is introduced and mixed with the wastewater, which is then filtered to produce a sludge containing the contaminants in a nonleachable form.

Abstract: Alkaline earth silicate solids with a surface area in the range of about 0.1-1000 m.sup.2 /g are used to remove Ag, Pb, Zn, Ni, and Cr (III) metal ions from contaminated waste waters. The foregoing metal ions are removed from the contaminated waste waters by a process involving the steps of contacting the contaminated waste waters at a pH in the range of 4 to 6 with the alkaline earth silicate solid and thereafter filtering the alkaline earth silicate solid from the contaminated waste waters to remove the metal ions.

Abstract: The present invention relates to a cyclic continuous process and composition for the removal of metal ions, particularly transition metal ions, from aqueous solutions a fluid stream containing the metal ions is contacted with an aqueous solution of a water soluble organic polymeric chelant. The metal is chelated by the chelant: The separation of water and low molecular weight products (molecular weight less than 500) is accomplished usually by dialysis or ultrafiltration. The metal ion is then released using dilute mineral acid and collected. The water-soluble chelant is then recycled. The metal ions chelated removed included iron, cobalt, copper, vanadium, cadmium, nickel, zinc, lead, and aluminum. A preferred chelant is one having a pendant pyridine group in conjunction with alkyl amine groups, e.g., --N(R)--CH.sub.2 --C.sub.5 H.sub.4 N, where R is alkyl.

Abstract: A heavy metal can be removed from waste water, in which the metal is contained as ions, by adding to the waste water a metal scavenger together with at least one of sodium monosulfide, sodium polysulfides and sodium hydrogensulfide to form a metal ion containing floc. The resulting floc is then removed from the waste water by filtration. The metal scavenger contains at least one carbodithio group and/or at least one carbodithioate salt group as N-substituents per molecule.

Abstract: A system (10) is provided for treating wastewater discharged from airplane manufacturing operations. The system (10) includes a variety of sequential chemical adjustments to the waste stream which can remove substantially all toxic organics and heavy metals therefrom.

Abstract: The present invention involves a treatment technique for drastically reducing the volume of hazardous sludge generated by the chemical reduction of chromium contaminants and the precipitation of heavy metal contaminants from contaminated electroplating wastewater. The wastewater is first adjusted to a pH of from about 8 to 10 and then treated with sodium sulfide to provide sulfide ions to effect precipitation of heavy metal contaminants followed by treatment with ferrous sulfate or ferrous chloride to provide ferrous ions to chemically reduce the hexavalent chromium to its trivalent state. This method produces approximately one-fourth the sludge generated by the previously known acidic reaction treatment using only ferrous sulfide.

Abstract: A method of treating wastewater containing a contaminant selected from the group consisting of heavy metal cations, tars, oils and phenols or mixtures thereof, comprising mixing said wastewater with an effective amount of desulfurization slag, the composition of said slag including calcium oxide, calcium sulfide and iron oxides, causing deposition of said contaminant from the mixture, and separating the deposit from the supernatant liquid.

Abstract: In accordance with the present invention, the chromium content of an aqueous waste containing significant amounts of at least one soluble chromium compound, such as blowdown waters from cooling towers utilizing chromium-containing materials as corrosion inhibitors is reduced, by contacting the chromium-containing waste water with an aqueous waste containing sodium sulfides, particularly spent caustic utilized in a desulfurization of petroleum fractions, to precipitate a substantial amount of the chromium and, thereafter, separating the precipitated chromium from the mixture as a sludge, to produce a waste water which can be safely disposed of to the earth's surface in a sewer or the like.

Abstract: A method is disclosed for the elimination of hazardous metal wastewater and sludges by recovering the non-ferrous metals zinc, nickel, copper (II), cadmium or chromium (III) present in an aqueous sludge comprising mixed metal hydroxides by selectively precipitating the ferrous metal ions present while maintaining the non-ferrous metal ions in solution, isolating the precipitate and then precipitating the non-ferrous metal ions from solution.

Abstract: Effluent acid from a non-evaporating chlorine dioxide-generating process is subjected to diffusion-dialysis across an anion-exchange membrane to preferentially transfer sulphuric acid from the effluent acid stream to a recipient aqueous medium while sodium sulphate remains in a waste stream. The sulphuric acid extracted from the effluent acid stream on this way may be recycled to the chlorine dioxide generator, after concentration, if desired.

Abstract: A method for treating a heavy metal-containing liquid, such as a wastewater stream, oil for recycling, or other metal-bearing liquid, with a trithiocarbonate, particularly an alkali metal trithiocarbonate, such as sodium trithiocarbonate, to precipitate the metals as insoluble sulfides. The precipitated metal sulfides are recovered as a low volume sludge, which can be processed through standard metallurgical techniques to yield the metals in economically useful forms. Among the most unexpected results produced by this method is the lowering of the selenium content in a naturally occurring body of water from 1.0 ppm to 0.0015 ppm.

Abstract: A process for producing a non-hazardous sludge from an aqueous solution which contains heavy metals comprising the steps of: (a) adding phosphoric acid or an acid phosphate salt to the aqueous solution to precipitate the heavy metals; (b) lowering the pH of the solution to less than about 5.0; (c) adding a coagulant to the solution; (d) raising the pH of the solution to above about 7.0 by the addition of a calcium source; and (e) dewatering the resulting non-hazardous sludge.

Abstract: An improved process for treating aqueous effluents and purge streams to selectively remove polluting elements such as iron, copper, lead and mercury therefrom is described. The procedure comprises contacting the effluent with a poly(dithiocarbamate) chelating agent whereby the polluting elements are absorbed. The resin is extracted with an acidic aqueous solution having a pH of from about 4 to about 6; and removing the resin. When this is done, the residual content of these polluting elements in the effluent is reduced to a level below EPA required levels so that the effluent can safely be discharged into the surrounding ecosystem. The poly(dithiocarbamate) resin containing the polluting elements can be disposed of, for example, by being deposited in an unsecured landfill.

Abstract: A chromium hydroxide precipitate obtained by a continuous process is described, wherein chromium containing waste waters are subjected to continuous hot treatment with acetic acid or with alkaline acetates and alkaline hydroxides at a temperature from 40.degree. C. to boiling point and at atmospheric pressure, at a pH higher than 6.5, preferably between 7 and 10, particularly about 7.5. Thus, a "sandy" type of chromium hydroxide is obtained, having a titer in Cr.sub.2 O.sub.3 of 20 to 40% by weight, which quickly filters, is easily soluble in acids, and thereby affords an easy valorization both as a tanning agent and as a raw material for preparing other chromium compound.

Abstract: A method for treating waste fluids to remove selected chemicals such as minerals and metals wherein a bacterial culture that will attach to a selected chemical is transferred to a nutrient medium for a time period sufficient to produce satisfactory bacterial cell growth. The bacterial cells are then attached to a porous fiber webbing supported in a suitable container and the nutrient medium is then withdrawn from the container and waste fluid introduced into the container for a period of time sufficient to attach the chemical to the bacterial cells. The waste fluid is then removed from the container and the chemical separated from the fiber webbing.

Abstract: A new strain of Pseudomonas fluorescens is disclosed for use in the removal of chromate from waste water.

Abstract: A method for removing heavy metals from brines used as well servicing fluids in which the heavy metal is oxidized to a higher, stable oxidation state of +3 or greater, the oxide or variants thereof of the oxidized metal is formed resulting in a generally water insoluble precipitate which is then removed by filtration leaving the brine free of deleterious amounts of the heavy metal.

Abstract: This invention provides a process for detoxifying or decontaminating liquid effluents and/or waste gas containing poisonous chromium (VI) NOx by reacting these with each other with formation of chromium (III) and higher oxide(s) of N. Optionally in addition another suitable reducing agent may be used.The process is particularly useful, for example, in a plant such as a stainless steel pickling plant where both these chemical components are available. Preferably liquid-liquid extraction may be used to extract and recover nitric acid formed as an oxidation product and preferably if additional chromium (VI) is required, this may be provided by electrolytic oxidation of chromium (III) to chromium (VI) in a suitable chemical circuit.

Abstract: A water treatment process for removing turbidity-causing impurities from water which involves contacting water containing such impurities with a relatively small amount of filter aid material, e.g., diatomaceous earth, for a time sufficient for impurities in the water to become adsorbed on said filter aid material, passing the water containing the filter aid material with impurities adsorbed thereon through a pre-filter having a flow rate of two liters/min./sq. m., or greater, and thereafter through a filter medium in the form of a porous, non-woven matrix consisting essentially of randomly arranged, irregularly intersecting and overlapping cellulose fibers intermixed with micro-bits of an expanded thermoplastic styrene-polymer or lower polyolefin, or of a flexible foamed polyurethane.

Abstract: The invention relates to a process and a solvent for extraction of the chromates present in an aqueous solution. According to the invention, the aqueous phase is brought into contact with an organic phase comprising 2 to 10% by volume of a solvent selected from the group of tertiary or quaternary amines and 15 to 40% of a solvent selected from the group of esters of phosphoric acid in a diluent based on petroleum hydrocarbons. The invention is applicable to the production of concentrated solutions of chromates easily recyclable from an extraction of the chromates contained in an industrial solution.

Abstract: Novel compositions containing fluoride are provided for the removal of organic and heavy metal pollutants from waste waters and methods of utilizing same. The compositions comprise components selected from ion exchange absorbent gels, cements, water soluble fluoride containing salts and optionally alkali metal ortho phosphates. The procedures of the present invention yield not only clarified waters but provided a sludge which can be disposed of under environmentally acceptable conditions.

Abstract: Process for the irreversible treatment of toxic waste by means of a silicate, in the presence of water, in such a way as to form a solid aggregate includes treatment of the silicate in an acid medium, for the purpose of obtaining silicic acid of low molecular weight; mixing the silicic acid with the waste to be treated, in the presence of water and controlling the pH between 0 and 4 in a sufficiently acid medium to cause the waste to undergo at least partial solution; precipitation of a gel of high molecular weight from the resultant aqueous mixture; addition thereto of a mixture which reacts with the gel of high molecular weight to form a silicate, possibly in the presence of a cementation agent, in such a way as to produce a sludge, and the hardening of the sludge into a solid aggregate which can not be changed physically so as to release again the harmful or toxic waste into the environment.

Abstract: A continuous process is described, wherein chromium-containing waste waters are subjected to continuous hot treatment with acetic acid or with alkaline acetates and alkaline hydroxides at a temperature from 40.degree. C. to boiling point and at atmospheric pressure, at a pH higher than 6.5, preferably between 7 and 10, particularly about 7.5. Thus, a "sandy" type of chromium hydroxide is obtained, having a titer in Cr.sub.2 O.sub.3 of 20 to 40% by weight, which quickly filters, is easily soluble in acids, and thereby affords an easy valorization both as a tanning agent and as a raw material for preparing other chromium compound.

Abstract: A powder of a slag formed at the time of manufacturing steel is used to remove heavy metals contained in waste water. After the use the slag may be heated to recover the heavy metals adsorbed thereby or the used slag may be formed into solid blocks, ballast or aggregate by admixing with Portland cement or alumina cement.

Abstract: From a chlorate cell liquor containing an alkali metal chlorate, an alkali metal chloride and Cr(VI) ions, Cr(VI) ions are recovered by means of a combination of simple chemical procedures and re-used in an electrolysis step for manufacturing an alkali metal chlorate.

Abstract: An apparatus and a process are provided which are particularly suited for treatment of sludge eminating from a metal finishing solution regeneration process, especially aluminum finishing solution. The sludge is washed on a horizontal belt vacuum filter from which a majority of the washing fluid is returned to the regeneration process. A portion of the washing water is wasted. After washing, the sludge is reslurried. Thereafter, the reslurried sludge is pumped to a reaction vessel in the presence of carbon dioxide under pressure. Sufficient carbon dioxide is provided to react with excess lime in the sludge to produce calcium carbonate and a substantially neutral pH. The sludge after carbonation is dewatered in a rotary drum vacuum filter and thereafter is suitable for placement in a landfill.

Abstract: A process for recovery of reusable chromic acid from waste chromic acid solution containing impurities, which process comprises a first step in which the solution containing chromic acid is introduced into the cathode compartment in an electro-dialysis process and free chromic acid or chromate ions in the above solution are transferred to the anode compartment, a second step in which H.sub.2 SO.sub.4 is added in at least equivalent amounts to the heavy metallic ion contained in the outlet solution, in which chromic acid ion concentration is reduced, in order to convert chemical species of the contained metallic ion and increase the H.sup.+ ion concentration and then chromate ions in the resultant solution are extracted into an organic phase with contact of an organic solvent (A), and a third step in which residual amounts of chromic acid ion remaining in the aqueous raffinate from the second step are extracted into an organic phase with contact of an organic solvent (B).

Abstract: Heavy Metals contained in industrial waste streams are removed therefrom by flocculation using a source of ferric ions and an alkaline material at a basic pH. Both the flocculated heavy metals and the coagulant chemicals are recovered by acidifying the floc to a pH of between 3.2 and 3.7. This liberates the heavy metals back into solution but does not destroy the floc particles. After separation and removal of the concentrated heavy metal solution, the floc is further acidified to completely dissolve it. This dissolved ferric ion containing solution may then be reused to treat succeeding portions of heavy metal containing waste streams. The concentrated heavy metals solution may also be recycled or the metals contained therein recovered for reuse or disposed of in an acceptable manner.

Abstract: The invention relates to a process for the removal of heavy metal ions, particularly chromium, lead and/or zinc ions, from aqueous liquids by precipitation wherein the aqueous liquid containing the heavy metal ions and an aqueous liquid containing a base which precipitates the heavy metal ions in the form of their hydroxide or basic salt are added simultaneously to an amount of water at a pH between 5 and 10 and a temperature between 60.degree. and 100.degree. C. and the pH and the temperature are maintained in the specified ranges during the precipitation.

Abstract: According to the present invention we provide a method of controlling the heavy metal content of the water in an aqueous system which comprises incorporating in the system an amount of gamma dicalcium silicate to insolubilize heavy metals present.

Abstract: The multivalent metals of iron and chromium are removed by reducing the metal values to their lowest valence state by acidifying to a pH of below about 6 and adding an excess of hydrogen peroxide. The reduction is conducted at the foregoing pH value and in the presence of a sufficient amount of an organic compound which is a stronger reducing agent than the metal in its lowest valence state. Thereafter, a sufficient amount of a reactive metal hydroxide source is added to raise the pH above about 7 and to form a metal hydroxide with the metal in its lowest valence state. The resulting metal hydroxide is then easily removed from the aqueous effluent.

Abstract: In a liquid membrane process for removing ions from solution which comprises contacting a feed solution containing a first ion with an emulsion, said emulsion comprising an external phase which is immiscible with said solution and contains a complexing agent, said complexing agent being capable of forming a first complex with said first ion, which is soluble in said external phase, and an internal phase, the improvement which comprises providing a second ion, in the internal phase, of the emulsion, said second ion being capable of converting said first complex to a second complex by replacing said first ion in said first complex, said second complex being also soluble in said external phase, whereby the first ion diffuses from said solution into said internal phase, and said second ion diffuses from said internal phase into said solution.

Abstract: In a process for pretreating hazardous waste prior to solidification the waste is received in containers (10). The containers are deposited in a large vessel containing a chemical pretreatment media (9) and subjected to an agitating process in the vessel whereby the containers are ruptured and their contents deposited in the media. Neutralization, precipitation and chemical modification processes are envisaged in the container. After pretreatment the liquid is removed for ultimate solidification.

Abstract: A process is disclosed for the removal of chrome from waste water containing chrome in addition to at least one chelating agent for trivalent chromium. The chrome-containing waste water is treated at low pH with both a reducing agent suitable for converting hexavalent chrome to trivalent chrome and with a ferric or aluminum sulfate or chloride salt. Following the reduction step, the pH of the now acidic solution is raised, using an inorganic base, to a pH sufficient to cause the formation of chromic hydroxide. The process of this invention is particularly suitable where rapid sedimentation processes, such as are achievable by the use of the lamella separator, are contemplated.

Abstract: A method has been devised for removing hexavalent chromium from concentrated aqueous alkali metal chlorate solution by reacting the solution with an inorganic sulfur containing compound and separating divalent and trivalent chromium compounds from the solution. Alkali metal hypohalites may be simultaneously removed from the chlorate solution by reaction with excess inorganic sulfur containing compound.

Abstract: Almost complete elimination of metal ions in aqueous effluents can be effected by treating said effluent with a base and then adding amorphous, hydrated magnesium silicate. This sequential process allows metal ion concentration to be reduced to less than 0.1 part per million while using a fairly small amount of amorphous hydrated magnesium silicate.

Abstract: Solid and/or dissolved contaminants are separated from a polar liquid such as water by providing in the contaminated liquid medium a galvanically charged particulate dispersion of defined size, concentration, density and free surface energy, and then flowing such loaded medium through successive treatment zones of an electrically insulated apparatus at a rate defined by dimensionless parameters such as Reynolds Numbers so as to prevent phase separation. Gaseous oxygen adheres to particle surfaces and oxidation is further promoted by bringing medium to pH 2.0 to 2.5 as with sulfur dioxide gas, plus exposure to action of heavy-metal ions such as ferrous/ferric. After air blowing, medium is neutralized and brought to pH 10-11 with continuous aeration of suspended flocculant, then treated with soda ash and optionally additional particulate (recycled sludge), and the contaminant matter then allowed to precipitate with concurrant galvanic grounding of the medium.