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| Number | Title | Issue Date |
| 8034312 | Purification of phosphoric acid rich streams The invention relates to a method for the purification or recovery of orthophosphoric acid rich streams by suspension-based melt crystallization. The orthophosphoric acid is crystallized as the hemi-hydrate form and subsequent separation of such crystals in a wash-c... | 10/11/2011 |
| 7473409 | Process for recycling waste acid A recycling process is presented to treat spent waste acid solutions whereby useful products are produced. Spent waste acid containing inorganic and organic contaminants is mixed with a magnesium compound containing aluminum and iron compounds that form oxyhydroxide... | 01/06/2009 |
| 7396474 | Dual injection of two polymeric filtration aids for gypsum removal from phosphoric acid/gypsum slurry A process to improve the polymeric filtration aid performance used in removal of gypsum from phosphoric acid/gypsum slurry. A synergistic effect has been observed by using a Dual Injection method. This method more specifically involves using two polymers (A & B) of ... | 07/08/2008 |
| 7273555 | Process for continuous ion exchange A process for continuous countercurrent ion exchange comprises piping a contaminated feed stream into a closed loop ion exchange contactor. The contactor is an ion exchange bed that has three or more reaction segments. The segments are comprised of at least an adsor... | 09/25/2007 |
| 7166264 | Processes for purifying phosphoric acid and for preparing phosphoric acid A process for purifying phosphoric acid includes removing volatile components from phosphoric acid rich in impurities to form a crude phosphoric acid liquid substantially free of volatile components; heating the crude phosphoric acid liquid to a temperature above 25... | 01/23/2007 |
| 7119047 | Modified activated carbon for capacitor electrodes and method of fabrication thereof A novel electrode and method of making the same. The electrode includes activated carbon that has been modified by treatment with an alkali solution and an acid, such as nitric acid, and then washed and dried. The carbon may then be annealed. The method of modifying... | 10/10/2006 |
| 7083768 | Processes for purifying phosphoric acid and for preparing phosphoric acid A process for purifying phosphoric acid includes removing volatile components from phosphoric acid rich in impurities to form a crude phosphoric acid liquid substantially free of volatile components; heating the crude phosphoric acid liquid to a temperature above 25... | 08/01/2006 |
| 7022242 | Reduction of wastewater in phosphate manufacturing Use and reduction of wastewater or “pond water” created by the wet-process phosphoric acid manufacturing there is created a large amount of wastewater or “pond water” to substantially reduce or eliminate the discharge of pond water with contaminants to the e... | 04/04/2006 |
| 6911191 | One-step oxidation of wet-process phosphoric acid A one-step method for production of green-colored, stabilized wet-process phosphoric acid in which black-colored, wet-process phosphoric acid containing incidental metallic impurities and a carbonaceous content of less than 1000 ppm is oxidized to produce a green-co... | 06/28/2005 |
| 6861039 | Method for purification of phosphoric acid high purity polyphosphoric acid The present invention provides a purification method of phosphoric acid, which includes bringing phosphoric acid containing arsenic into contact with hydrogen halide, thereby to remove the arsenic from the phosphoric acid, and a purification method of phosphoric aci... | 03/01/2005 |
| 6758976 | Simplified purification of phosphoric acid plant pond water A simplified process for the partial purification of contaminated phosphoric acid plant pond water having a molar calcium plus magnesium to fluorine ratio greater than or equal to about 0.60, is described, in which the pond water is treated with a basic compound, cl... | 07/06/2004 |
| 6758977 | Purification of phosphoric acid plant pond water A process for the partial purification of contaminated phosphoric acid plant pond water is described, in which the pond water is treated sequentially, with two basic compounds, clarified, aged, clarified again and re-acidified. The thus treated pond water, still con... | 07/06/2004 |
| 6666973 | Method for fixing fluorine and phosphorus in waste water containing fluorophosphoric acid-derived compound to remove them A method is provided for fixing and eliminating fluorine and phosphorus in waste water wherein the waste water includes a fluorophosphate compound in which hydrochloric acid is added to the waste water including the fluorophosphate compound. The waste wat... | 12/23/2003 |
| 6620395 | Treatment of phospho gypsum A process is provided for recovering phosphoric acid from phospho gypsum produced as a by-product in a phosphoric acid production process and having water soluble P2 O5 bound in the crystal lattice thereof. The process includes a) fo... | 09/16/2003 |
| 6391149 | Method and apparatus for concentrating a solute in solution with a solvent The present invention provides a method, and an apparatus, for forming a prescribed concentration of a substance in a mixture with a fluid, from a comparatively dilute mixture. The mixture is most preferably a solution of a solute in a solvent. The follow... | 05/21/2002 |
| 5989508 | Liquid medium extraction purification method Method of purification by extraction of at least one substance to be isolated from a liquid medium, comprising an addition to the latter of an organic compound, entrainable by a vapor, which has a molecule with an acidic-basic character in the Lewis sense... | 11/23/1999 |
| 5945000 | Methods of purifying phosphoric acid In one aspect, the invention includes a method of purifying phosphoric acid comprising filtering a feed solution of phosphoric acid through a membrane, wherein the feed solution is maintained at a temperature of from about 30° F. to about 90° F. during ... | 08/31/1999 |
| 5910257 | Process for producing a semiconductor device using purified phosphoric acid A process for the preparation of an analytical sample characterized by depositing and separating solely the impurity to be analyzed from phosphoric acid; a process for analysis of the impurity characterized by depositing and separating solely the impurity... | 06/08/1999 |
| 5824132 | Method of phosphoric acid concentration The wet process phosphoric acid evaporation, its clarifying, fertilizer production and fertilizer efficiency is improved in the presence of multi-component mixture of anionic surfactants and ammonium compound.... | 10/20/1998 |
| 5449819 | Process for removing waste pox, alendronate and its by products Disclosed is a process for removing by-product phosphorus-containing (POx) materials, alendronate and alendronate byproducts from crude mother liquors in an omega amino-1-hydroxy-C2 -C6 alkylidene-1,1-bisphosphonic acid sy... | 09/12/1995 |
| 5431895 | Process for the removal of lead and cadmium from phosphoric acid To remove lead and cadmium from phosphoric acid, alkali solution and aqueous sulfide solution are simultaneously introduced with thorough mixing into a phosphoric acid having a P2 O5 content of up to 32% by weight, an iron content of... | 07/11/1995 |
| 5318707 | Method of clarifying phosphoric acid A method for clarifying phosphoric acid by flocculation or coagulation of solids wherein an effective amount of a carboxylic-type polymer having a portion of sulfonic functionality is used as the clarification aid. Preferred polymers are high molecular we... | 06/07/1994 |
| 5312610 | Defluorination of phosphoric acid Fluorine in the form of fluoride is removed from phosphoric acid having an initial phosphate concentration of less than about 50 percent by determining the concentration of fluoride to be removed from the acid and the concentration of silicon in the acid.... | 05/17/1994 |
| 5279806 | Process for eliminating heavy metals from phosphoric acid Process for treating phosphoric acid for removing heavy metal cations, in particular cadmium, and sludges contained in the acid, characterized in that concentrated phosphoric acid having a low solids content is used and in that the calcium sulfate supersa... | 01/18/1994 |
| 5246681 | Process for the removal of cadmium from solutions of phosphoric acid Process for the removal of cadmium from solutions of phosphoric acid derived by the sulphuric and nitric digestion of phosphatic rocks, including the following steps: adding to the phosphoric acid solution bromide ions, such as hydrogen bromide or the bro... | 09/21/1993 |
| 5230876 | Removal of vanadium from phosphoric acid An apparatus for removing vanadium from phosphoric acid includes a precipitator that receives vanadium-containing process-feed phosphoric acid and adds an oxidant to the process-feed phosphoric acid, whereupon precipitates containing phosphorus and vanadi... | 07/27/1993 |
| 5211928 | Method of improving gypsum slurry filtration in the production of phosphoric acid A method for improving gypsum slurry filtration in the production of wet process phosphoric acid wherein an effective amount of carboxylic-type polymer having a portion of sulfonic functionality is used as the filtration aid. Preferred polymers are high m... | 05/18/1993 |
| 5185135 | Method of dewatering a wet process phosphoric acid slurry A digested slurry from a wet process phosphoric acid production process is dewatered by gravity-assisted vacuum filtration using as a filtration aid an aqueous solution of a polymeric filtraton aid that has been subjected to high shear mixing to enhance t... | 02/09/1993 |
| 5173280 | Method of clarifying phosphoric acid using high charge sulfonic-type polymers A method for clarifying phosphoric acid by flocculation or coagulation of solids wherein an effective amount of a polymer having a predominantly sulfonic functionality is used as the clarification aid. Preferred polymers are high molecular weight acrylami... | 12/22/1992 |
| 5171548 | Process for the removal of vanadium from wet process phosphoric acid A process for removal of vanadium from wet process phosphoric acid comprising the steps of; (i) adsorbing an anionic pentavalent complex of vanadium, derived from the wet process phosphoric acid, onto an anion exchange resin or into an organic layer; and ... | 12/15/1992 |
| 5171452 | Phosphoric acid wastewater treatment Phosphoric acid wastewater treatment to substantially eliminate discharge of contaminants to the environment. Acid pond water from conventional wet-phosphoric acid manufacturing is replaced by gypsum pond water having a pH closely matching that of the sur... | 12/15/1992 |
| 5124137 | Process for the preparation of alkali metal phosphate solutions Alkali metal phosphate solutions having a fluorine content of less than 20 ppm, based on P2 O5, are prepared by first digesting crude phosphate using sulfuric acid, and separating the calcium sulfate from the crude phosphoric acid. A... | 06/23/1992 |
| 5120519 | Scale control in phosphoric acid manufacture High molecular weight copolymers of acrylamide which contain between 5-100 mole % of acrylic acid and have a molecular weight of at least 1,000,000 prevent scale adhering to surfaces in contact with digested phosphate rock and/or phosphoric acid produced ... | 06/09/1992 |
| 5084261 | Recovery and utilization of gypstack leachate in hemihydrate phosphoric acid process Disclosed is a process for treating a waste stream containing calcium sulfate by depositing said waste stream on a gypstack, collecting the leachate from the gypstack, and recovering the P2 O5 values therefrom. Also disclosed is appa... | 01/28/1992 |
| 5066471 | Lowering post-precipitation in merchant acid The present process stabilizes merchant acid from bottoms solutions against post-precipitation by heating the acid to a temperature of at least about 180° F. for about 12 to about 48 hours. The stabilized acid product exhibits less than about 1 wt % soli... | 11/19/1991 |
| 5002744 | Method for defluorinating wet process phosphoric acid A method for defluorinating wet process phosphoric acid. Phosphatic waste clay from phosphate rock beneficiation is mixed with the wet process phosphoric acid. The mixture is heated for a time sufficient to remove fluorine from the acid as gaseous silicon... | 03/26/1991 |
| 4994248 | P2 O5 recovery and phosphoric acid purification Disclosed is an improved process for purifying phosphoric acid where a calcium sulfate hemihydrate slurry is first filtered to produce a first filtrate and a filter cake which comprises calcium sulfate hemihydrate, the calcium sulfate hemihydrate filter c... | 02/19/1991 |
| 4988489 | Recovery of phosphorus values from waste phosphoric acid liquors The phosphorus values from waste phosphoric acid containing organic contaminents such as wastes obtained in the manufacture of quinacridone pigments can be recovered in purified form by hydrolyzing phosphate esters, removing any formed alcohol, dissociati... | 01/29/1991 |
| 4986970 | Method for removal of heavy metals, especially cadmium, from phosphoric acid containing solutions The present invention relates to a method for removal of heavy metals, especially cadmium, from phosphoric acid containing solutions, primarily such solutions made by digestion of rock phosphate by nitric acid and subsequent removal of the main part of ca... | 01/22/1991 |
| 4978511 | Methods for selectively recovering vanadium from phosphoric acid and vanadium sources Vanadium is selectively recovered from vanadium-containing phosphoric acid solutions also containing metals other than vanadium by selectively converting the dissolved vanadium to a vanadate compound insoluble in the phosphoric acid solution and separatin... | 12/18/1990 |
