USRE36915E - Process for sodium sulfide/ferrous sulfate treatment of hexavalent chromium and other heavy metals - Google Patents
Process for sodium sulfide/ferrous sulfate treatment of hexavalent chromium and other heavy metals Download PDFInfo
- Publication number
- USRE36915E USRE36915E US08/032,581 US3258193A USRE36915E US RE36915 E USRE36915 E US RE36915E US 3258193 A US3258193 A US 3258193A US RE36915 E USRE36915 E US RE36915E
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- United States
- Prior art keywords
- stream
- ferrous
- sulfide
- ion
- chromium
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- 238000000034 method Methods 0.000 title claims abstract description 70
- 230000008569 process Effects 0.000 title claims abstract description 56
- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 31
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 title claims abstract description 28
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 title claims description 15
- 229910000359 iron(II) sulfate Inorganic materials 0.000 title claims description 15
- 239000011790 ferrous sulphate Substances 0.000 title claims description 14
- 235000003891 ferrous sulphate Nutrition 0.000 title claims description 14
- 229910052979 sodium sulfide Inorganic materials 0.000 title description 12
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 title description 12
- 239000010802 sludge Substances 0.000 claims abstract description 61
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims abstract description 57
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000011651 chromium Substances 0.000 claims abstract description 47
- 230000009467 reduction Effects 0.000 claims abstract description 39
- 229910001448 ferrous ion Inorganic materials 0.000 claims abstract description 33
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 32
- 229920000642 polymer Polymers 0.000 claims abstract description 9
- 238000005352 clarification Methods 0.000 claims abstract description 5
- 239000002351 wastewater Substances 0.000 claims description 18
- 238000001914 filtration Methods 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 230000015572 biosynthetic process Effects 0.000 claims description 5
- 230000001376 precipitating effect Effects 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims 3
- 230000003311 flocculating effect Effects 0.000 claims 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims 3
- 239000000463 material Substances 0.000 claims 3
- 230000003134 recirculating effect Effects 0.000 claims 3
- 239000002699 waste material Substances 0.000 abstract description 36
- 238000001556 precipitation Methods 0.000 abstract description 15
- 238000004519 manufacturing process Methods 0.000 abstract description 9
- 239000010842 industrial wastewater Substances 0.000 abstract description 4
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- 239000002184 metal Substances 0.000 description 19
- 238000009713 electroplating Methods 0.000 description 17
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- 238000012360 testing method Methods 0.000 description 11
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- 238000003756 stirring Methods 0.000 description 10
- 230000036961 partial effect Effects 0.000 description 8
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- 150000002739 metals Chemical class 0.000 description 7
- 238000002156 mixing Methods 0.000 description 7
- 239000012153 distilled water Substances 0.000 description 6
- 239000002440 industrial waste Substances 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000010949 copper Substances 0.000 description 5
- 239000011701 zinc Substances 0.000 description 5
- 229920000742 Cotton Polymers 0.000 description 4
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- 239000002920 hazardous waste Substances 0.000 description 4
- 239000011133 lead Substances 0.000 description 4
- 230000007935 neutral effect Effects 0.000 description 4
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 4
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 3
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229920006318 anionic polymer Polymers 0.000 description 3
- 239000003518 caustics Substances 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 239000012085 test solution Substances 0.000 description 3
- 238000004065 wastewater treatment Methods 0.000 description 3
- -1 with ferrous sulfate Chemical compound 0.000 description 3
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 238000011021 bench scale process Methods 0.000 description 2
- 229910052793 cadmium Inorganic materials 0.000 description 2
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 2
- 229920006317 cationic polymer Polymers 0.000 description 2
- AYTAKQFHWFYBMA-UHFFFAOYSA-N chromium dioxide Chemical compound O=[Cr]=O AYTAKQFHWFYBMA-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000004571 lime Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 238000010979 pH adjustment Methods 0.000 description 2
- 238000011020 pilot scale process Methods 0.000 description 2
- 235000010265 sodium sulphite Nutrition 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- KSPIHGBHKVISFI-UHFFFAOYSA-N Diphenylcarbazide Chemical compound C=1C=CC=CC=1NNC(=O)NNC1=CC=CC=C1 KSPIHGBHKVISFI-UHFFFAOYSA-N 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 1
- 229920005372 Plexiglas® Polymers 0.000 description 1
- DWAQJAXMDSEUJJ-UHFFFAOYSA-M Sodium bisulfite Chemical compound [Na+].OS([O-])=O DWAQJAXMDSEUJJ-UHFFFAOYSA-M 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- DGEZNRSVGBDHLK-UHFFFAOYSA-N [1,10]phenanthroline Chemical compound C1=CN=C2C3=NC=CC=C3C=CC2=C1 DGEZNRSVGBDHLK-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000001668 ameliorated effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000010866 blackwater Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
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- 230000007613 environmental effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 229910001447 ferric ion Inorganic materials 0.000 description 1
- 239000008394 flocculating agent Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 229910052976 metal sulfide Inorganic materials 0.000 description 1
- 229960000907 methylthioninium chloride Drugs 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000012545 processing Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 150000003464 sulfur compounds Chemical class 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- 238000012795 verification Methods 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/34—Treatment of water, waste water, or sewage with mechanical oscillations
- C02F1/36—Treatment of water, waste water, or sewage with mechanical oscillations ultrasonic vibrations
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
- C02F1/56—Macromolecular compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S210/00—Liquid purification or separation
- Y10S210/902—Materials removed
- Y10S210/911—Cumulative poison
- Y10S210/912—Heavy metal
- Y10S210/913—Chromium
Definitions
- the present invention relates to a method for treating industrial waste waters containing high levels of hexavalent chromium and other heavy metals, and more particularly to a method for efficient reduction of hexavalent chromium to trivalent chromium in a waste treatment process wherein acceptable sludge levels are produced as compared to processes known in the art.
- Additional methods of Cr +6 reduction include use of ferrous sulfate, sodium sulfide, a combination of both ferrous sulfate and sodium sulfide, and use of sodium borohydride.
- the Cr +6 usually exists as HCrO 4 -
- hexavalent chromium exists as CrO 4 -2 .
- Reduction with ferrous ion, such as with ferrous sulfate, at acidic pH proceeds as,
- the rate of Cr +6 reduction using an amount of ferrous ion substantially in excess of the stoichiometric amount proceeds faster than using a stoichiometric amount.
- the rate is based upon the reaction of HCrO 4 - .
- Sulfur compounds (S +4 ) can reduce Cr +6 at pH less than 3, the rate slowing logarithmically with increased pH.
- H 2 S is the predominant specie at acidic conditions, while at neutral or alkaline pH conditions, the predominant species are HS - and CrO 2 -2 .
- ferrous ion is present as ferrous sulfate
- Cr +6 is rapidly reduced at neutral and alkaline pH. The ferrous ion appears to catalyze the sulfide reaction.
- ferrous ion is not efficient by itself in reducing Cr +6 since only one electron is available per iron atom. A large quantity of iron hydroxide sludge is therefore produced. Ferrous ion and sulfide would appear to be the best combination for reducing and precipitating Cr +6 at neutral or near neutral conditions.
- the free sulfide reacts with a heavy metal to form a precipitate.
- the metal sulfides that precipitate by this process can form extremely fine colloidal particles (pin floc). Under alkaline operating conditions, evolution of hydrogen sulfide gas is minimal.
- the insoluble sulfide (SulfexTM) process uses freshly precipitated ferrous sulfide to precipitate heavy metals from a metal finishing waste stream.
- the freshly precipitated ferrous sulfide has substantially more reactive sites than pulverized iron sulfide and results in Cr +6 reduction and precipitation in one step (see U.S. Pat. Nos. 3,740,331 and 4,102,784).
- a process for treating industrial waste water containing hexavalent chromium (Cr +6 ) and other heavy metals which comprises reduction of Cr +6 to Cr +3 and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9.
- Polymers are added to the solution to assist flocculation and clarification of the waste stream.
- the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1.
- the waste stream pH is preferably maintained in the range of about 7.2 to 7.5.
- Sludge production by the process of the invention is substantially less than that characteristic of prior art processes.
- the sludge bed may be used as a filter to remove floccules from the waste stream after precipitation of heavy metals. A portion of the sludge may be recirculated through the waste water stream to aid flocculation and clarification. Use of ultrasonic energy enhanced the Cr +6 to Cr +3 reduction rate.
- FIG. 1 depicts a bench scale industrial waste treatment plant for illustration of the process of the invention
- FIG. 2 shows graphs of Cr +6 remaining in test solution after partial or total reduction to Cr +3 as functions of ferrous concentration at various sulfide concentrations
- FIG. 3 is a graph of Cr +6 remaining in test solution after partial reduction to Cr +3 as a function of pH
- FIG. 4 is a graph of Cr +6 remaining in test solution after partial reduction to Cr +3 as a function of sulfide concentration in the presence of added heavy metals;
- FIG. 5 shows graphs of Cr +6 remaining in electroplating waste solution after partial or total reduction to Cr +3 as a function of ferrous concentration at various sulfide concentrations
- FIG. 6 is a graph of Cr +6 remaining in electroplating waste solution after partial or total reduction to Cr +3 as a function of pH
- FIG. 7 shows graphs of Cr +6 remaining in a waste treatment plant influent stream after partial or total reduction to Cr +3 as a function of ferrous concentration at various sulfide concentrations
- FIG. 8 shows graphs of total chromium remaining in solution as a function of ferrous concentration at various sulfide concentrations
- FIG. 9 depicts a pilot scale waste treatment plant used in demonstration of the invention.
- FIG. 10 depicts a solids contact clarifier of FIG. 8 used in demonstration of the invention.
- FIG. 11 shows graphs of Cr +6 remaining in solution as a function of pH at two different S:Fe:Cr +6 ratios
- FIG. 12 is a graph of optimum process operational ranges of the invention.
- FIG. 13 is a graph of Cr +6 reduction versus time with and without application of ultrasonic energy.
- the commercially available SulfexTM process is intended for precipitation of heavy metals, (not Cr +6 reduction) and produces a greater quantity of sludge than the conventional acid/SO 2 /lime process.
- the process described in U.S. Pat. No. 4,705,639 referred to above is directed to a waste treatment scheme similar to that described herein; that prior process assumes 90-100% efficiency in transfer of electrons from a donor source to a selective recipient in a waste water stream containing many different and competitive ions. Such a process efficiency is not practical, and substantial excesses over stoichiometric quantities of treatment constituents may be required to effectively precipitate most heavy metal.
- the invention can be illustrated by the following examples performed in demonstration of the invention and in definition of the process parameters thereof.
- the appropriate volume of a 1,000 mg/L ferrous solution (as FeSO 4 /7H 2 O) was added. It may be noted here that in the practice of the invention described herein the ferrous ion may be added in the form either as sulfate or chloride. The volume was brought to 1,000 ml with distilled water and pH adjusted again while the solutions were stirred at 100 rpm. After six minutes, mixing was slowed to 20 rpm for two minutes, during which period final pH adjustments were made. Stirring was stopped and the solutions were allowed to stand for two minutes. If required, the solution was filtered using a funnel with a cotton plug.
- Sludge production was determined using four-liter volumes of the appropriate solution. Sufficient sodium sulfide and ferrous sulfate were added and the pH was adjusted with nitric acid to 7.2-7.5. Flocculant was added and mixing ceased. The floc was allowed to settle before vacuum filtering through a #4 Whatman filter paper. Wet and dry weights were determined by weighing the dry filter paper and the wet filter paper before and after filtering and after drying overnight at 103° C.
- FIG. 1 shown therein is a schematic of bench scale plexiglass system 10, simulating an existing ALC industrial waste treatment plant, which was used for dynamic tests in demonstration of the invention.
- Sodium sulfide solution 19 was added through pipe 21 into mixer 11.
- Ferrous sulfate solution 23 was added through pipe 25 into mixer 12 and cationic polymers 27 were added through pipe 29 into mixer 13.
- Effluent 31 of mixer 13 was fed using pump 32 through conduit 33 into clarifier 35.
- Nitric acid was added to mixer 12 to maintain the pH therein at about 7.2-7.5.
- Anionic polymers 37 were fed into conduit 33 in front of clarifier 35 as at inlet 39.
- Effluent 31 from mixer 13 was fed to the center of clarifier 35 where it flowed upwardly through sludge blanket 41.
- Sample ports 43 were provided for withdrawing samples from either sludge blanket 41 or solution 45 thereabove.
- the uppermost sample port 43 functioned as a continuous outlet for solution 45.
- Outlet 47 allowed discharge of sludge 46 from sludge blanket 41.
- FIG. 2 shown therein are graphs of Cr +6 remaining in solution after partial or total reduction to Cr +3 as functions of ferrous concentration at the various designated sulfide concentrations. At relatively low ferrous concentrations, little or no reduction of Cr +6 occurred, even at high sulfide concentrations. Although high concentrations of sulfide were shown to be more efficient in reducing Cr +6 than lower concentrations (see discussion infra re FIG. 5), relatively high sulfide concentrations resulted in fine precipitates and solutions which remained cloudy after filtering through cotton.
- FIG. 2 shown therein are graphs of Cr +6 remaining in solution after partial or total reduction to Cr +3 as functions of ferrous concentration at the various designated sulfide concentrations. At relatively low ferrous concentrations, little or no reduction of Cr +6 occurred, even at high sulfide concentrations. Although high concentrations of sulfide were shown to be more efficient in reducing Cr +6 than lower concentrations (see discussion infra re FIG. 5), relatively
- Residual Cr +6 as a function of pH at optimum sulfide and ferrous concentrations is shown in FIG. 3 and illustrates that Cr +6 can be removed to TABLE I limits between pH 7 and 9. At higher pH (above 9) a black precipitate formed.
- Jar tests on electroplating waste were conducted similarly to those of EXAMPLE I. Day-to-day concentration variations in the waste was ameliorated somewhat by collecting 40 gallons of electroplating waste from the subject ALC plant. Cr +6 concentration in the waste was extremely high (about 350 mg/L). Sufficient waste was diluted with distilled water to form a 100 liter solution of 55 mg/L Cr +6 for use in the tests in order to simulate average electroplating waste. One liter of the diluted waste solution was placed in a beaker and the pH adjusted to 7.2-7.5 with caustic (initial pH was 4.0). The solutions were stirred at 100 rpm while the desired volume of a 2,000 mg/L sulfide solution was added.
- Sulfide and ferrous ion requirements for reduction and precipitation of the electroplating wastes are shown in FIG. 5.
- Optimum reagent requirements for 55 mg/L Cr +6 are shown as 56 mg/L sulfide and 50.0 mg/L ferrous ion as determined by the theoretical sludge production shown in TABLE V.
- ferrous and sulfide ions in higher-than-optimal concentrations although effective to a degree in reducing Cr +6 , result in black water (a fine suspension of FeS that does not filter out or precipitate with the floccules) and corresponding high concentrations of soluble metals in the solutions.
- FIG. 6 shows Cr +6 remaining in solution to be below TABLE I limits between pH 7.2 and 8.2 but to increase dramatically above pH 9.0.
- Waste water typically comprising influent to the subject ALC waste treatment plant was collected for jar testing. Analysis of the influent is shown in TABLE VI.
- the pH was lowered from 9.5 to 7.3 with nitric acid and beakers were filled with one liter of the resulting solution. Each solution was stirred at 100 rpm as the desired volume of 1,000 mg/L sulfide solution was added and stirring was continued for six minutes. The appropriate volume of 1,000 mg/L ferrous solution was added, pH adjusted, and stirring continued for six minutes at 100 rpm. Stirring was slowed to 20 rpm for two minutes to allow floc formation, pH adjustments were made, and stirring was stopped. The solutions sat undisturbed for two minutes, and if necessary were filtered through cotton.
- TABLE IX Data on the jar tests conducted in demonstration of the invention are summarized in TABLE IX.
- Data of TABLE IX show that the chemistry of Cr +6 reduction to Cr +3 according to the process of the invention is concentration dependent for several species, particularly Fe +2 and HS - .
- FIG. 7 shows that high sulfide concentration are efficient in reducing Cr +6 , but that too high a concentration hinders floccule precipitation, as suggested in FIG. 8.
- a pilot scale field verification test unit was constructed at the subject ALC industrial waste treatment plant, designed to replicate flow characteristics and retention times of the on-site waste treatment facility in demonstration of the process of the
- the pilot plant 50 is shown in FIG. 9 and comprises an equalization tank 51, mixer tanks 53, 54, 55, chemical feed tanks 57, a 330-gallon solids contact clarifier 59, activated sludge bed 61 and final clarifier 63.
- equalization tank 51 In order to minimize effects on the operation of pilot plant 50 of day-to-day perturbations in the effluent from the electroplating facility (not shown in FIG. 9), waste therefrom was held in reservoir 52 and periodically pumped to equalization tank 51. Sulfuric acid and caustic were used to control pH of waste influent in tank 51.
- Mixer tanks 53, 54, 55 were operated similarly to that suggested for the FIG.
- FIG. 10 shown is a solids contact clarifier 59 typical of that usable in the system of FIG. 9 in demonstration of the invention.
- Influent 70 from mixer 55 (FIG. 9) fed into center well 71 of clarifier 59 is integrated with anionic polymer 73 (e.g. Betz 1120) and external sludge flow 74 which is circulated from sludge bed 85 through opening 75 in the bottom of clarifier 59 and through valved conduit and pump means 77.
- Waste stream 70, polymer 73 and external sludge flow 74 are mixed in mixing chamber 79.
- An internal sludge flow 80 is moved into mixing chamber 79 and mixed using mixer 81.
- Liquid 82 with entrained floc and metal spills through openings 83 into mixing chamber 79 internally of intermediate skirt 84 and onto sludge bed 85. Fluids within skirt 84 percolate through the sludge bed, which percolation filters out floc, and flows as substantially clear effluent 86 from under the wall defining skirt 84 and into collecting chamber 87. Effluent 86 is collected in weir 89 and withdrawn through conduit 90 to activated sludge bed 61 (FIG. 9).
- Rake 91 moving at slow speed (typically 3 rpm) around the bottom of clarifier 59 moves sludge to the sludge outlets and prevents channeling of sludge bed 85 by effluent 86.
- Ferrous solutions were made using ferrous sulfate heptahydrate while sulfide solutions were prepared from stock sodium sulfide. Concentrated sulfuric acid was added to each batch to decrease the amount of ferrous oxidized to ferric ion.
- FIG. 11 shows the effect of pH using a feed ratio into mixer tank 54 of 1.75 mg/L sulfide to 1 mg/L ferrous to 1 mg/L Cr +6 and a ratio of 2.0 mg/L sulfide to 1.5 mg/L ferrous to 1 mg/L Cr +6 .
- FIG. 12 illustrates preferred operational ranges for the process of the invention.
- the ratios of S -2 and Fe +2 to Cr +6 are expressed in mg/L per mg/L Cr +6 .
- the optimum process operational ranges are from about 1.3-1.7 mg/L S -2 per mg/L Cr +6 and from about 0.85-3.00 mg/L Fe +2 per mg/L Cr +6 at pH of 7.2-8.4. While the process of the invention will operate outside the preferred ranges, FIG. 12 defines operating conditions wherein operation of the process is unexpectedly efficient in accordance with an underlying principle of the invention.
- the invention therefore provides an improved method for treating industrial waste waters containing high levels of hexavalent chromium and other heavy metals by reduction of hexavalent chromium to trivalent chromium in the waste treatment process and wherein acceptably small amounts of sludge are produced. It is understood that modifications to the invention may be made as might occur to one with skill in the field of the invention within the scope of the appended claims. All embodiments contemplated hereunder which achieve the objects of the invention have therefore not been shown in complete detail. Other embodiments may be developed without departing from the spirit of the invention or the scope of the appended claims.
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Abstract
A process for treating industrial waste water containing hexavalent chromium (Cr+6) and other heavy metals is disclosed which comprises reduction of Cr+6 to trivalent chromium (Cr+3) and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9 under conditions such that sludge production by the process of the invention is substantially less than that characteristic of prior art processes. Polymers are added to the solution to assist flocculation and clarification of the waste stream. More specifically, the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1. The waste stream pH is preferably maintained in the range of about 7.2 to 7.5.
Description
The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.
The present invention relates to a method for treating industrial waste waters containing high levels of hexavalent chromium and other heavy metals, and more particularly to a method for efficient reduction of hexavalent chromium to trivalent chromium in a waste treatment process wherein acceptable sludge levels are produced as compared to processes known in the art.
Industrial waste treatment plants downstream from electroplating facilities are generally subjected to industrial wastes which contain relatively high levels of numerous toxic heavy metals in concentrations which often fail to meet National Pollutant Discharge Elimination Permit levels. Therefore, such waste water must be treated to reduce the levels of heavy metals to within discharge permit limits. The metals typically contained in these waste waters include chromium, cadmium, copper, lead, zinc, nickel and aluminum. Presently known processes for the treatment of such waste waters produce large quantities of metal-bearing sludges which are classified as hazardous wastes requiring special and costly handling and transport and disposal in hazardous waste landfills. While numerous processes exist for the precipitation of most heavy metals, hexavalent chromium (Cr+6) cannot conveniently be precipitated without first reducing the Cr+6 to trivalent chromium (Cr+3). The process for reducing Cr+6 to Cr+3 presently being used by a number of electroplating facilities utilizes sulfur dioxide in the reaction,
2CrO.sub.4.sup.-2 +3SO.sub.2 +2H.sub.2 SO.sub.4 →2Cr.sup.+3 +5SO.sub.4.sup.-2 +2H.sub.2 O (1)
Other methods of acidic reduction of Cr+6 include use of sodium sulfite, sodium bisulfite and ferrous compounds. For example, the reaction utilizing sodium sulfite is,
2CO.sub.4.sup.-2 +3Na.sub.2 SO.sub.3 +5H.sub.2 SO.sub.4 →2Cr.sup.-3 +8SO.sub.4.sup.-2 +5H.sub.2 O+6Na.sup.+ (2)
Additional methods of Cr+6 reduction include use of ferrous sulfate, sodium sulfide, a combination of both ferrous sulfate and sodium sulfide, and use of sodium borohydride. At acidic pH, the Cr+6 usually exists as HCrO4 -, while at alkaline pH, hexavalent chromium exists as CrO4 -2. Reduction with ferrous ion, such as with ferrous sulfate, at acidic pH proceeds as,
3FeSO.sub.4 +HCrO.sub.4.sup.- +7H.sup.+ →3Fe.sup.+3 +Cr.sup.+3 +4H.sub.2 O+3SO.sub.4.sup.-2 (3)
The rate of Cr+6 reduction using an amount of ferrous ion substantially in excess of the stoichiometric amount proceeds faster than using a stoichiometric amount. The rate is based upon the reaction of HCrO4 -. Sulfur compounds (S+4) can reduce Cr+6 at pH less than 3, the rate slowing logarithmically with increased pH. H2 S is the predominant specie at acidic conditions, while at neutral or alkaline pH conditions, the predominant species are HS- and CrO2 -2. When ferrous ion is present as ferrous sulfate, Cr+6 is rapidly reduced at neutral and alkaline pH. The ferrous ion appears to catalyze the sulfide reaction. However, ferrous ion is not efficient by itself in reducing Cr+6 since only one electron is available per iron atom. A large quantity of iron hydroxide sludge is therefore produced. Ferrous ion and sulfide would appear to be the best combination for reducing and precipitating Cr+6 at neutral or near neutral conditions.
Metal precipitation by soluble sulfides require a sulfide source more soluble than the metal to be precipitated. Sodium sulfide dissociates readily into sodium and sulfide ions:
Na.sub.2 S+H.sub.2 O→2Na.sup.+ +S.sup.-2 +H.sub.2 O (4)
The free sulfide reacts with a heavy metal to form a precipitate. The metal sulfides that precipitate by this process can form extremely fine colloidal particles (pin floc). Under alkaline operating conditions, evolution of hydrogen sulfide gas is minimal.
It was previously proposed in U.S. Pat. No. 4,705,639 (Nov. 10, 1987) that a ferrous/sulfide process for reduction of Cr+6 and precipitation of Cr+3 and other heavy metals was possible in heavy metal contaminated waste water at pH of from about 8-10, and using about 90% stoichiometric sulfide and about 10-20% stoichiometric ferrous ion.
The insoluble sulfide (Sulfex™) process uses freshly precipitated ferrous sulfide to precipitate heavy metals from a metal finishing waste stream. The freshly precipitated ferrous sulfide has substantially more reactive sites than pulverized iron sulfide and results in Cr+6 reduction and precipitation in one step (see U.S. Pat. Nos. 3,740,331 and 4,102,784).
It is therefore a principle object of the invention to provide an improved industrial waste treatment process.
It is another object of the invention to provide an improved waste water treatment process for removing heavy metals therefrom.
It is yet another object of the invention to provide a waste water treatment process for reducing contained hexavalent chromium to trivalent chromium and precipitation thereof from the waste water along with other heavy metals.
It is yet another object of the invention to provide a waste water treatment process for removing chromium and other heavy metals from the waste water with the accompanying generation of minimum amounts of sludge.
These and other objects of the invention will become apparent as the detailed description of representative embodiments proceeds.
In accordance with the foregoing principles and objects of the present invention, a process for treating industrial waste water containing hexavalent chromium (Cr+6) and other heavy metals is disclosed which comprises reduction of Cr+6 to Cr+3 and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9. Polymers are added to the solution to assist flocculation and clarification of the waste stream. More specifically, the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1. The waste stream pH is preferably maintained in the range of about 7.2 to 7.5.
Sludge production by the process of the invention is substantially less than that characteristic of prior art processes. In practicing the invention, the sludge bed may be used as a filter to remove floccules from the waste stream after precipitation of heavy metals. A portion of the sludge may be recirculated through the waste water stream to aid flocculation and clarification. Use of ultrasonic energy enhanced the Cr+6 to Cr+3 reduction rate.
FIG. 1 depicts a bench scale industrial waste treatment plant for illustration of the process of the invention;
FIG. 2 shows graphs of Cr+6 remaining in test solution after partial or total reduction to Cr+3 as functions of ferrous concentration at various sulfide concentrations;
FIG. 3 is a graph of Cr+6 remaining in test solution after partial reduction to Cr+3 as a function of pH;
FIG. 4 is a graph of Cr+6 remaining in test solution after partial reduction to Cr+3 as a function of sulfide concentration in the presence of added heavy metals;
FIG. 5 shows graphs of Cr+6 remaining in electroplating waste solution after partial or total reduction to Cr+3 as a function of ferrous concentration at various sulfide concentrations;
FIG. 6 is a graph of Cr+6 remaining in electroplating waste solution after partial or total reduction to Cr+3 as a function of pH;
FIG. 7 shows graphs of Cr+6 remaining in a waste treatment plant influent stream after partial or total reduction to Cr+3 as a function of ferrous concentration at various sulfide concentrations;
FIG. 8 shows graphs of total chromium remaining in solution as a function of ferrous concentration at various sulfide concentrations;
FIG. 9 depicts a pilot scale waste treatment plant used in demonstration of the invention;
FIG. 10 depicts a solids contact clarifier of FIG. 8 used in demonstration of the invention;
FIG. 11 shows graphs of Cr+6 remaining in solution as a function of pH at two different S:Fe:Cr+6 ratios;
FIG. 12 is a graph of optimum process operational ranges of the invention; and
FIG. 13 is a graph of Cr+6 reduction versus time with and without application of ultrasonic energy.
While the invention will be described primarily as related to processing waste streams from an electroplating facility, it will be appreciated that the process is useful for any waste stream containing appreciable amounts of heavy metal in order to minimize sludge generation. The reduction of hexavalent chromium (Cr+6) to trivalent chromium (Cr+3), while important in treating waste water comprising electroplating effluent, is not by itself the primary point of invention herein. The thrust of the invention is the treatment of metal bearing waste water in a novel process wherein significantly lower quantities of sludge are produced than is possible using conventional waste water treating processes.
Environmental Protection Agency (EPA) imposed limits for heavy metal concentrations in effluent from waste treatment plants at the Air Logistics Centers (ALCs) are set forth in TABLE 1.
TABLE I ______________________________________ Concentration Constituent (mg/L) ______________________________________ Cadmium. Total 0.03 Chromium. Total 1.0 Chromium. Hexavalent 0.1 Copper. Total 0.1 Lead. Total 0.1 Nickel. Total 1.0 Zinc. Total 1.0 ______________________________________
Since 1980, the EPA has classified sludges bearing concentrations of such metals above permit limits as hazardous wastes and have required disposal in hazardous waste landfills, typically at a cost greater than $168 per ton. While certain processes, such as sludge dewatering, have been implemented to reduce the amount of sludge produced, no processes to date have been effective to reduce appreciably the amounts of generated sludge.
The commercially available Sulfex™ process is intended for precipitation of heavy metals, (not Cr+6 reduction) and produces a greater quantity of sludge than the conventional acid/SO2 /lime process. The process described in U.S. Pat. No. 4,705,639 referred to above is directed to a waste treatment scheme similar to that described herein; that prior process assumes 90-100% efficiency in transfer of electrons from a donor source to a selective recipient in a waste water stream containing many different and competitive ions. Such a process efficiency is not practical, and substantial excesses over stoichiometric quantities of treatment constituents may be required to effectively precipitate most heavy metal.
The invention can be illustrated by the following examples performed in demonstration of the invention and in definition of the process parameters thereof.
Analyses were made of Cr+6 reduction and heavy metal removal in distilled water and electroplating wastes. Jar tests were conducted using Phipps and Bird six-paddle stirrer with an illuminated base. Beakers were filled with 800 ml of distilled water and 10 ml of a 2,000 milligrams per liter (mg/L) Cr+6 solution. The pH of each solution was adjusted with either caustic or lime. Appropriate volumes of 1,000 mg/L S-2 solution (Na2 S/9H2 O) was added to each beaker. The solutions were stirred at 100 rpm while the pH of each was adjusted as desired. After six minutes of stirring, the appropriate volume of a 1,000 mg/L ferrous solution (as FeSO4 /7H2 O) was added. It may be noted here that in the practice of the invention described herein the ferrous ion may be added in the form either as sulfate or chloride. The volume was brought to 1,000 ml with distilled water and pH adjusted again while the solutions were stirred at 100 rpm. After six minutes, mixing was slowed to 20 rpm for two minutes, during which period final pH adjustments were made. Stirring was stopped and the solutions were allowed to stand for two minutes. If required, the solution was filtered using a funnel with a cotton plug.
Cr+6 was determined using the 1,5-diphenyl carbohydrazide method and standard Hach Chemical Company procedures. Ferrous concentration was determined using the Hach procedures for the 1,10-phenanthroline method. Sulfide was determined using the Hach procedure for the methylene blue method for low concentrations and the Orion Specific ion electrode for high concentrations (above 150 mg/L S-2). Metal concentrations were determined using a Perkin Elmer 4000 atomic absorption spectrophotometer.
Sludge production was determined using four-liter volumes of the appropriate solution. Sufficient sodium sulfide and ferrous sulfate were added and the pH was adjusted with nitric acid to 7.2-7.5. Flocculant was added and mixing ceased. The floc was allowed to settle before vacuum filtering through a #4 Whatman filter paper. Wet and dry weights were determined by weighing the dry filter paper and the wet filter paper before and after filtering and after drying overnight at 103° C.
Referring now to FIG. 1, shown therein is a schematic of bench scale plexiglass system 10, simulating an existing ALC industrial waste treatment plant, which was used for dynamic tests in demonstration of the invention. Three mixers 11, 12 13 arranged in sequence, were fed a mixture 15 of metals including Cr+6 through inlet 17. Sodium sulfide solution 19 was added through pipe 21 into mixer 11. Ferrous sulfate solution 23 was added through pipe 25 into mixer 12 and cationic polymers 27 were added through pipe 29 into mixer 13. Effluent 31 of mixer 13 was fed using pump 32 through conduit 33 into clarifier 35. Nitric acid was added to mixer 12 to maintain the pH therein at about 7.2-7.5. Anionic polymers 37 were fed into conduit 33 in front of clarifier 35 as at inlet 39. Effluent 31 from mixer 13 was fed to the center of clarifier 35 where it flowed upwardly through sludge blanket 41. Sample ports 43 were provided for withdrawing samples from either sludge blanket 41 or solution 45 thereabove. The uppermost sample port 43 functioned as a continuous outlet for solution 45. Outlet 47 allowed discharge of sludge 46 from sludge blanket 41.
Referring now to FIG. 2 shown therein are graphs of Cr+6 remaining in solution after partial or total reduction to Cr+3 as functions of ferrous concentration at the various designated sulfide concentrations. At relatively low ferrous concentrations, little or no reduction of Cr+6 occurred, even at high sulfide concentrations. Although high concentrations of sulfide were shown to be more efficient in reducing Cr+6 than lower concentrations (see discussion infra re FIG. 5), relatively high sulfide concentrations resulted in fine precipitates and solutions which remained cloudy after filtering through cotton. FIG. 2 illustrates that for residual Cr+6 remaining in solution after 15 minutes was dependent upon the level of sulfide used, to attain EPA (TABLE I) levels of Cr+6 (0.1 mg/L), doubling the sulfide concentration (from 24.7 to 50.0 mg/L) resulted in an almost halving of the ferrous ion requirement (from about 17 mg/L to about 9 mg/L). Excess sulfide concentrations, however, hindered floccule precipitation (see discussion infra re FIG. 8, TABLE IX). Chromium reduction was found to be optimum when sulfide was added to the Cr+6 solution prior to addition of the ferrous ion.
Residual Cr+6 as a function of pH at optimum sulfide and ferrous concentrations is shown in FIG. 3 and illustrates that Cr+6 can be removed to TABLE I limits between pH 7 and 9. At higher pH (above 9) a black precipitate formed.
The jar tests for theoretical sludge production indicate that optimum sulfide and ferrous iron concentrations are 24.7 mg/L and 20.0 mg/L, respectively (for a 20 mg/L Cr+6 solution), as shown in TABLE II.
These optimums correspond to a pH within the range 7.2 to 7.5 for optimum polymer flocculant concentrations. Of the polymers tested, high molecular weight powder flocculants produced the best floc and settled without leaving pin floc in suspension.
TABLE II ______________________________________ STOICHIOMETRY AND THEORETICAL SLUDGE PRODUCTION (DISTILLED WATER).sup.a Theore- Electrons Electrons Electrons tical S.sup.-2 Available Fe.sup.+2 Available Excess Sludge (mg/L) (mole).sup.b (mg/L) (mole) (mole) (lb/day).sup.c ______________________________________ 24.7 0.0015 20.0 0.0004 0.0007 640 31.0 0.0019 20.0 0.0004 0.0011 679 37.3 0.0023 15.0 1.0003 0.0014 659 37.3 0.0023 20.0 0.0004 0.0015 718 50.0 0.0031 10.0 0.0002 0.0021 678 50.0 0.0031 15.0 0.0003 0.0022 738 50.0 0.0031 20.0 0.0004 0.0023 797 ______________________________________ .sup.a 20 mg/L Cr.sup.+6 (0.0012 moles e.sup.- required) .sup.b 2 electrons per mole of sulfide .sup.c 750,000 gal/day
The effect of additional metal ions on chromium reduction and reagent requirements were determined. The metals of TABLE III, when added to the Cr+6 solution, increased the sulfide requirement for Cr+6 reduction below TABLE I limits from 24.7 mg/L to 28.0 mg/L, as shown in FIG. 4.
TABLE III ______________________________________ Metal Concentration Added (mg/L) ______________________________________ Ni 2.0 Cd 0.1 Cu 0.2 Pb 0.4 Zn 0.4 Al 1.5 Cr.sup.+6 20.0 ______________________________________
When treating a distilled water solution containing 20 mg/L Cr+6 in system 10 of FIG. 1, Cr+6 was reduced to less than 0.06 mg/L using optimal concentrations of 24.7 mg/L sulfide and 20.0 mg/L ferrous ion. System 10 was operated at 40 ml/min, 60 ml/min and 100 ml/min which correspond to flows of 500,000, 800,000 and 1,250,000 gallons per day through the clarifier of the subject ALC plant. Samples taken from clarifier 35 reported in TABLE IV indicate that total chromium carried through clarifier 35 and into the plant effluent was well below TABLE I requirement of 1.0 mg/L.
TABLE IV ______________________________________ TOTAL CHROMIUM CARRYOVER AS A FUNCTION OF FLOWRATE Flowrate Port 4Port 6 Port 8 (ml/min) Cr mg/L Cr mg/L Cr mg/L ______________________________________ 40 0.06 0.06 0.06 64 0.15 0.16 0.15 100 0.36 0.28 0.20 ______________________________________
Jar tests on electroplating waste were conducted similarly to those of EXAMPLE I. Day-to-day concentration variations in the waste was ameliorated somewhat by collecting 40 gallons of electroplating waste from the subject ALC plant. Cr+6 concentration in the waste was extremely high (about 350 mg/L). Sufficient waste was diluted with distilled water to form a 100 liter solution of 55 mg/L Cr+6 for use in the tests in order to simulate average electroplating waste. One liter of the diluted waste solution was placed in a beaker and the pH adjusted to 7.2-7.5 with caustic (initial pH was 4.0). The solutions were stirred at 100 rpm while the desired volume of a 2,000 mg/L sulfide solution was added. Stirring continued for six minutes, at which time the appropriate volume of a 2,000 mg/L ferrous solution was added. The pH was adjusted and stirring continued for six minutes at 100 rpm. Stirring was slowed to 20 rpm for two minutes to allow floc formation; stirring was then stopped and the solutions were left undisturbed for two minutes. If necessary, resulting solutions were filtered through cotton.
Sulfide and ferrous ion requirements for reduction and precipitation of the electroplating wastes are shown in FIG. 5. Optimum reagent requirements for 55 mg/L Cr+6 are shown as 56 mg/L sulfide and 50.0 mg/L ferrous ion as determined by the theoretical sludge production shown in TABLE V. As suggested above relative to the EXAMPLE I tests, ferrous and sulfide ions in higher-than-optimal concentrations, although effective to a degree in reducing Cr+6, result in black water (a fine suspension of FeS that does not filter out or precipitate with the floccules) and corresponding high concentrations of soluble metals in the solutions.
The effect of pH on Cr+6 reduction in the electroplating waste was determined using the optimum reagent concentration. FIG. 6 shows Cr+6 remaining in solution to be below TABLE I limits between pH 7.2 and 8.2 but to increase dramatically above pH 9.0.
TABLE V ______________________________________ STOICHIOMETRY AND THEORETICAL SLUDGE PRODUCTION (ELECTROPLATING WASTE).sup.a Theore- Electrons Electrons Electrons tical S.sup.-2 Available Fe.sup.+2 Available Excess Sludge (mg/L) (mole).sup.b (mg/L) (mole) (mole) (lb/day).sup.c ______________________________________ 56.0 0.0035 50.0 0.0009 0.0012 1626 56.0 0.0035 60.0 0.0011 0.0014 1746 70.0 0.0044 40.0 0.0007 0.0019 1594 70.0 0.0044 50.0 0.0009 0.0021 1713 70.0 0.0044 60.0 0.0011 0.0023 1833 84.0 0.0053 30.0 0.0005 0.0026 1562 84.0 0.0053 40.0 0.0007 0.0028 1681 84.0 0.0053 50.0 0.0009 0.0030 1801 84.0 0.0053 60.0 0.0011 0.0032 1920 ______________________________________ .sup.a 35 mg/L Cr.sup.+6 (0.0032 moles e.sup.- required) .sup.b 2 electrons per mole of sulfide .sup.c 750,000 gal/day
Waste water typically comprising influent to the subject ALC waste treatment plant was collected for jar testing. Analysis of the influent is shown in TABLE VI. The pH was lowered from 9.5 to 7.3 with nitric acid and beakers were filled with one liter of the resulting solution. Each solution was stirred at 100 rpm as the desired volume of 1,000 mg/L sulfide solution was added and stirring was continued for six minutes. The appropriate volume of 1,000 mg/L ferrous solution was added, pH adjusted, and stirring continued for six minutes at 100 rpm. Stirring was slowed to 20 rpm for two minutes to allow floc formation, pH adjustments were made, and stirring was stopped. The solutions sat undisturbed for two minutes, and if necessary were filtered through cotton.
TABLE VI ______________________________________ Metal Concentration Constituent (mg/L) ______________________________________ Cr.sup.+6 9.00 Cr 9.10 Fe 1.42 Cd 0.10 Cu 0.02 Ni 0.97 Pb 0.15 Zn 0.13 ______________________________________
The corresponding theoretical sludge production shown in TABLE VII and the graphs of Cr+6 remaining in the influent stream after partial or total reduction to Cr+3 as functions of ferrous concentration at various sulfide concentrations of in FIG. 7 indicate that optimum requirements were 12,36 mg/L sulfide and 10.0 mg/L ferrous ion.
A summary of optimum conditions for reduction of Cr+6 to less than 0.1 mg/L for the three experimental waste streams described in EXAMPLES I, II, III is presented in TABLE VIII.
Data on the jar tests conducted in demonstration of the invention are summarized in TABLE IX. Data of TABLE IX show that the chemistry of Cr+6 reduction to Cr+3 according to the process of the invention is concentration dependent for several species, particularly Fe+2 and HS-. For example, FIG. 7 shows that high sulfide concentration are efficient in reducing Cr+6, but that too high a concentration hinders floccule precipitation, as suggested in FIG. 8.
TABLE VII ______________________________________ STOICHIOMETRY AND THEORETICAL SLUDGE PRODUCTION (WASTEWATER).sup.a Theore- Electrons Electrons Electrons tical S.sup.-2 Available Fe.sup.+2 Available Excess Sludge (mg/L) (mole).sup.b (mg/L) (mole) (mole) (lb/day).sup.c ______________________________________ 10.40 0.00065 12.0 0.00021 0.00034 461 10.40 0.00065 14.0 0.00025 0.00038 515 12.36 0.00077 10.0 0.00018 0.00043 582 12.36 0.00077 12.0 0.00021 0.00046 623 12.36 0.00077 14.0 0.00025 0.00050 678 ______________________________________ .sup.a 9 mg/L Cr.sup.+6 (0.00052) moles e.sup.- required) .sup.b 2 electrons per mole of sulfide .sup.c 750,000 gal/day
TABLE VIII ______________________________________ SUMMARY OF OPTIMUM CONDITIONS FOR GIVEN Cr.sup.+6 CONCENTRATIONS EXAMPLE I EXAMPLE II EXAMPLE III Parameter (20 mg/L) (55 mg/L) (9 mg/L) ______________________________________ S.sup.-2 (mg/L) 24.7 56.0 12.4 Fe.sup.+2 (mg/L) 20.0 55.0 10.0 pH 7.2-9.0 7.2-8.1 7.2-7.5 Polymer Betz 1120.sup.R Betz 1120.sup.R Betz 1195.sup.R (1.0 mg/L) (1.0 mg/L) (15 mg/L) Betz 1120.sup.R (0.5 mg/L) ______________________________________
A pilot scale field verification test unit was constructed at the subject ALC industrial waste treatment plant, designed to replicate flow characteristics and retention times of the on-site waste treatment facility in demonstration of the process of the
TABLE IX ______________________________________ REACTION CONDITIONS AND RESULTS OF JAR TESTS WITH HEXAVALENT CHROMIUM, SODIUM SULFIDE AND FERROUS SULFATE Initial Conditions Final Conditions (a,b,c) (d) Run Cr.sup.-0 Cr Fe.sup.+2 Fe S.sup.-2 Floc Number S.sup.-2 Fe.sup.+1 (e) (f) (g) (f) (h) wt (i) ______________________________________ 1 0 0 21 22 0.0 0.0 0 None 2 0 10 18 21 4.4 7.8 0 100 3 0 20 13 9 0.1 6.0 0 660 4 0 30 11 11 0.2 6.3 0 -- 5 0 40 8 7 0.0 2.3 0 250 6 10 0 19 22 0.0 0.0 10 None 7 10 10 8 1 0.0 2.0 1 470 8 10 20 2 4 0.2 0.8 1 750 9 10 30 0 3 0.2 1.0 1 970 10 10 40 0 3 0.0 0.8 1 1170 11 20 0 17 20 0.0 0.8 19 None 12 20 10 6 8 0.1 1.0 7 530 13 20 20 0 3 0.0 1.0 1 830 14 20 30 0 3 0.0 1.0 1 830 15 20 40 0 3 0.0 0.8 1 1280 16 30 0 15 22 0.0 0.0 16 None 17 30 10 3 7 0.0 2.3 8 620 18 30 20 0 1 0.0 0.8 5 820 19 30 30 0 1 0.3 2.7 2 1140 20 30 40 0 1 1.2 2.9 2 1250 21 40 0 12 11 0.0 0.0 22 240 22 40 10 0 3 0.5 1.2 15 640 23 40 20 0 2 0.2 2.8 11 870 24 40 30 0 1 0.9 4.4 5 1000 25 40 40 0 1 0.1 0.8 2 1400 26 50 0 13 15 0.0 0.0 41 200 27 50 10 0 4 0.0 2.0 22 620 28 50 20 0 17 2.2 16.8 16 560 29 50 30 0 22 2.1 27.8 3 560 30 50 40 0 16 3.0 35.4 2 990 ______________________________________ (a) Concentrations are in ppm. (b) Initial Cr.sup.-0 concentration was 20.0 ppm. (c) PH adjusted with H.sub.2 SO.sub.4 or NaOH to 7.2-7.5 after Fe.sup.- added. (d) After the initial reagents had been mixed for 5 minutes. (e) As determined by Hach method for Cr.sup.-0 total chromium or iron. (f) As determined by A.A.S. (g) As determined by Hach method forFe.sup.+ 2. (h) As determined by Hach method for S.sup.-2. (i) Dry weight of floc.
invention. The pilot plant 50 is shown in FIG. 9 and comprises an equalization tank 51, mixer tanks 53, 54, 55, chemical feed tanks 57, a 330-gallon solids contact clarifier 59, activated sludge bed 61 and final clarifier 63. In order to minimize effects on the operation of pilot plant 50 of day-to-day perturbations in the effluent from the electroplating facility (not shown in FIG. 9), waste therefrom was held in reservoir 52 and periodically pumped to equalization tank 51. Sulfuric acid and caustic were used to control pH of waste influent in tank 51. Mixer tanks 53, 54, 55 were operated similarly to that suggested for the FIG. 1 system, wherein effluent from mixer 11 flowed over the top of a weir to mixer 12 and similarly to mixer 13 to prevent back mixing. Sodium sulfide was added to mixer tank 53, ferrous sulfate and sulfuric acid were added to mixer tank 54 and a cationic polymer was added to mixer tank 55. Anionic polymer was added between mixer tank 55 and clarifier 59 as at 65. Clarifier 59 had a retention time of 2.75 hours at a flow rate of 2 gallons per minute.
Referring now to FIG. 10, shown is a solids contact clarifier 59 typical of that usable in the system of FIG. 9 in demonstration of the invention. Influent 70 from mixer 55 (FIG. 9) fed into center well 71 of clarifier 59, is integrated with anionic polymer 73 (e.g. Betz 1120) and external sludge flow 74 which is circulated from sludge bed 85 through opening 75 in the bottom of clarifier 59 and through valved conduit and pump means 77. Waste stream 70, polymer 73 and external sludge flow 74 are mixed in mixing chamber 79. An internal sludge flow 80 is moved into mixing chamber 79 and mixed using mixer 81. Liquid 82 with entrained floc and metal spills through openings 83 into mixing chamber 79 internally of intermediate skirt 84 and onto sludge bed 85. Fluids within skirt 84 percolate through the sludge bed, which percolation filters out floc, and flows as substantially clear effluent 86 from under the wall defining skirt 84 and into collecting chamber 87. Effluent 86 is collected in weir 89 and withdrawn through conduit 90 to activated sludge bed 61 (FIG. 9). Rake 91 moving at slow speed (typically 3 rpm) around the bottom of clarifier 59 moves sludge to the sludge outlets and prevents channeling of sludge bed 85 by effluent 86. Ferrous solutions were made using ferrous sulfate heptahydrate while sulfide solutions were prepared from stock sodium sulfide. Concentrated sulfuric acid was added to each batch to decrease the amount of ferrous oxidized to ferric ion.
The effect of pH on Cr+6 reduction was studied by holding pH of the influent to mixer tank 54 (FIG. 9) at 8.0 while varying pH within tank 54. FIG. 11 shows the effect of pH using a feed ratio into mixer tank 54 of 1.75 mg/L sulfide to 1 mg/L ferrous to 1 mg/L Cr+6 and a ratio of 2.0 mg/L sulfide to 1.5 mg/L ferrous to 1 mg/L Cr+6. At the higher sulfide and ferrous ratios, Cr+6 was reduced to less than TABLE I levels between pH of 7.2-8.4; in accordance with a governing principle of the invention, however, Cr+6 was substantially completely reduced only at pH 7.2-7.5 For the lower sulfide to ferrous ratio TABLE I levels were achieved only at pH 7.2-7.6 and Cr+6 was substantially completely reduced only at pH 7.2.
Typical electroplating waste stream metals fed to clarifier 59 were removed by precipitation as shown in TABLE X.
TABLE X ______________________________________ Influent Effluent Metal (mg/L) (mg/L) ______________________________________ Cr.sup.+6 0.50 0.00* Cr (Total) 3.37 0.15 Ni 3.71 0.38 Cd 0.96 0.02 Cu 0.77 0.00* Fe 1.31 1.93 Zn 0.59 0.05 ______________________________________ *Below detection limits
Because floc formed in the sodium sulfide/ferrous sulfate process is extremely fine, effluent 86 quality, as judged by clarity, is difficult to achieve, even at optimized parameters, without filtration. Therefore, the process of the invention appears optimized with sufficient sludge depth within bed 85 at least a few inches above the bottom of skirt 84 as suggested in FIG. 10, which requires effluent 86 to flow through sludge bed 85 so as to filter out pin floc produced by the process.
The effect of suspended solids in mixing chamber 79 (FIG. 10) on turbidity of effluent 86 was determined. In order to increase concentration of suspended solids, external sludge recirculation 74 was initiated. With insufficient sludge recirculation 74, proper sludge depth within sludge bed 85 was difficult to maintain. As external sludge recirculation 74 rate increased to about 10-20% of influent 70 flow (1,320-2,640 mil/min) turbidity decreased markedly and heavy metal precipitation increased. It was also determined that relatively high (95° F.) and low (41° F.) temperatures had no significant effect on metal precipitation in clarifier 59 within TABLE I levels. In the use of Na3 PO4, no appreciable effect on Cr+6 reduction was noticed with concentrations as high as 176 mg/L PO4 -3. Adding EDTA (a typical chelating agent in electroplating baths) up to 50 mg/L caused no change in effluent quality from clarifier 59. Cyanide, typically used in metal stripping prior to electroplating, may contaminate the waste water. The sodium sulfide/ferrous sulfate process will not eliminate cyanide, but it may complex with metals in the waste water and not be presented at full strength to the activated sludge when introduced into influent 70. Levels as high as 10 mg/L cyanide were reduced to 1.85 mg/L in clarifier 59 and to 0.5 mg/L in activated sludge bed 61, where it apparently had little or no effect.
FIG. 12 illustrates preferred operational ranges for the process of the invention. The ratios of S-2 and Fe+2 to Cr+6 are expressed in mg/L per mg/L Cr+6. The optimum process operational ranges are from about 1.3-1.7 mg/L S-2 per mg/L Cr+6 and from about 0.85-3.00 mg/L Fe+2 per mg/L Cr+6 at pH of 7.2-8.4. While the process of the invention will operate outside the preferred ranges, FIG. 12 defines operating conditions wherein operation of the process is unexpectedly efficient in accordance with an underlying principle of the invention.
In a test to observe the effect of ultrasonic energy on the reduction of Cr+6 in the presence of sodium sulfide, a marked increase in the rate of reduction of Cr+6 to Cr+3. As shown in FIG. 13, the reduction Cr+6 to Cr+3 proceeded about seven times faster with about 20 KHz of ultrasonic energy at about 25 watts/cm2 imparted to a 235 ml vessel containing an aqueous solution of 20 mg/L Cr+6 and 40 mg/L sulfide.
The invention therefore provides an improved method for treating industrial waste waters containing high levels of hexavalent chromium and other heavy metals by reduction of hexavalent chromium to trivalent chromium in the waste treatment process and wherein acceptably small amounts of sludge are produced. It is understood that modifications to the invention may be made as might occur to one with skill in the field of the invention within the scope of the appended claims. All embodiments contemplated hereunder which achieve the objects of the invention have therefore not been shown in complete detail. Other embodiments may be developed without departing from the spirit of the invention or the scope of the appended claims.
Claims (9)
1. A process of reducing hexavalent chromium to trivalent chromium and precipitating the trivalent chromium from a waste water stream to form a sludge for disposal, said process comprising the steps of:
(a) adding soluble sulfide ion to said stream in a ratio of sulfide ion to hexavalent chromium of from about 0.7 to 2.5;
(b) adding soluble ferrous ion to said stream in a ratio of ferrous ion to hexavalent chromium of from about 0.5 to 5.0;
(c) thereafter adjusting pH of said stream to about 7.2 to .[.7.5.]..Iadd.8.4.Iaddend.;
(d) adding a flocculating polymer to said stream to promote formation of a floc comprising precipitated trivalent chromium;
(e) forming a sludge bed comprising sad precipitated trivalent chromium; and
(f) thereafter filtering the floc from said stream using said sludge bed containing said precipitated trivalent chromium.
2. The process of claim 1 wherein said ferrous ion is added from a material selected from the group consisting of ferrous sulfate and ferrous chloride.
3. The process of claim 1 further comprising the step of recirculating sludge from said sludge bed into said stream at a rate of about 10 to 20 percent by volume of the flow rate of said stream to promote clarification of said stream.
4. The process of claim 1 further comprising the step of introducing ultrasonic energy into said stream in the presence of said sulfide ion and said ferrous ion to enhance the rate of reduction of hexavalent chromium to trivalent chromium.
5. A process of reducing hexavalent chromium to trivalent chromium and precipitating the trivalent chromium and other heavy metals from a waste water stream to form a sludge for disposal, said process comprising the steps of:
(a) adding soluble sulfide to said stream in a ratio of sulfide to hexavalent chromium of from about 0.7 to 2.5;
(b) thereafter adding soluble ferrous ion to said stream in a ratio of ferrous ion to hexavalent chromium of about 0.5 to 5.0;
(c) thereafter adjusting pH of said stream to about 7.2 to .[.7.5.]..Iadd.8.4.Iaddend.;
(d) adding a flocculating polymer to said stream to promote formation of a floc comprising precipitated trivalent chromium and other heavy metals and to aid in removal of said floc from said stream by forming a sludge bed containing said precipitated trivalent chromium and other heavy metals therein;
(e) filtering the floc from said stream using said sludge bed;
(f) recirculating sludge into said stream to aid in removal of said floc therefrom; and
(g) introducing ultrasonic energy into said stream in the presence of said sulfide ion and said ferrous ion to enhance the rate of reduction of hexavalent chromium to trivalent chromium.
6. The process of claim 5 wherein said ferrous ion is added from a material selected from the group consisting of ferrous sulfate and ferrous chloride.
7. A process of operating a solids contact clarifier having a mixer chamber disposed within a sludge bed, said process being effective to reduce hexavalent chromium to trivalent chromium and to precipitate the trivalent chromium and other heavy metals from a waste water stream into the sludge bed, said process comprising the steps of:
(a) adding soluble sulfide to said stream to provide a ratio of sulfide ion to hexavalent chromium of about 0.7:1 to 2.5:1;
(b) thereafter adding soluble ferrous ion to said stream to provide a ration of ferrous ion to hexavalent chromium of about 0.5:1 to 5.0:1;
(c) adjusting pH of said stream to about 7.2 to .[.7.5.]..Iadd.8.4.Iaddend.;
(d) adding a flocculating polymer to said stream to promote formation of a floc comprising precipitated trivalent chromium and other heavy metals and clarification of said stream;
(e) forming a sludge bed comprising said precipitated trivalent chromium and other heavy metals separated from the stream; and
(f) recirculating sludge into said stream at a rate of about 10 to 20 percent by volume of the flow rate of said stream to aid in removal of said floc therefrom.
8. The process of claim 7 wherein said ferrous ion is added from a material selected from the group consisting of ferrous sulfate and ferrous chloride.
9. The process of claim 7 further comprising the step of introducing ultrasonic energy into said stream in the presence of said sulfide ion and said ferrous ion to enhance the rate of reduction of hexavalent chromium to trivalent chromium.
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US08/032,581 USRE36915E (en) | 1988-10-26 | 1993-03-17 | Process for sodium sulfide/ferrous sulfate treatment of hexavalent chromium and other heavy metals |
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US07/263,161 US5000859A (en) | 1988-10-26 | 1988-10-26 | Process for sodium sulfide/ferrous sulfate treatment of hexavalent chromium and other heavy metals |
US08/032,581 USRE36915E (en) | 1988-10-26 | 1993-03-17 | Process for sodium sulfide/ferrous sulfate treatment of hexavalent chromium and other heavy metals |
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US08/032,581 Expired - Lifetime USRE36915E (en) | 1988-10-26 | 1993-03-17 | Process for sodium sulfide/ferrous sulfate treatment of hexavalent chromium and other heavy metals |
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Citations (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1932531A (en) * | 1932-01-05 | 1933-10-31 | Herschel C Parker | Apparatus for extracting gold from solutions |
US2110187A (en) * | 1933-08-23 | 1938-03-08 | Dudley A Willams | Method of treating chrome liquors |
US2346320A (en) * | 1941-04-24 | 1944-04-11 | Nat Lead Co | Clarification and purification of industrial liquors |
US2977202A (en) * | 1956-07-02 | 1961-03-28 | Pfaulder Permutit Inc | Apparatus for conditioning precipitates and separating same from liquids |
US3023089A (en) * | 1958-07-28 | 1962-02-27 | Int Minerals & Chem Corp | Reaction vessel |
US3027321A (en) * | 1959-11-09 | 1962-03-27 | Wilson & Company | Treatment of chromate solutions |
US3218252A (en) * | 1962-08-31 | 1965-11-16 | Coal Industry Patents Ltd | Process for the bacteriological oxidation of ferrous salts in acidic solution |
US3294680A (en) * | 1964-11-18 | 1966-12-27 | Lancy Lab | Treatment of spent cooling waters |
US3575853A (en) * | 1968-12-24 | 1971-04-20 | Lab Betz Inc | Waste water treatment |
US3740331A (en) * | 1971-06-23 | 1973-06-19 | Sybron Corp | Method for precipitation of heavy metal sulfides |
JPS4916714A (en) * | 1972-06-02 | 1974-02-14 | ||
US4102784A (en) * | 1976-04-27 | 1978-07-25 | Schlauch Richard M | Colloid free precipitation of heavy metal sulfides |
US4362629A (en) * | 1980-10-08 | 1982-12-07 | Murata Manufacturing Co., Ltd. | Method for processing solution including heavy metal |
US4705639A (en) * | 1985-05-10 | 1987-11-10 | The United States Of America As Represented By The Secretary Of The Air Force | Ferrous and sulfide treatment of electroplating wastewater |
-
1988
- 1988-10-26 US US07/263,161 patent/US5000859A/en not_active Ceased
-
1993
- 1993-03-17 US US08/032,581 patent/USRE36915E/en not_active Expired - Lifetime
Patent Citations (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1932531A (en) * | 1932-01-05 | 1933-10-31 | Herschel C Parker | Apparatus for extracting gold from solutions |
US2110187A (en) * | 1933-08-23 | 1938-03-08 | Dudley A Willams | Method of treating chrome liquors |
US2346320A (en) * | 1941-04-24 | 1944-04-11 | Nat Lead Co | Clarification and purification of industrial liquors |
US2977202A (en) * | 1956-07-02 | 1961-03-28 | Pfaulder Permutit Inc | Apparatus for conditioning precipitates and separating same from liquids |
US3023089A (en) * | 1958-07-28 | 1962-02-27 | Int Minerals & Chem Corp | Reaction vessel |
US3027321A (en) * | 1959-11-09 | 1962-03-27 | Wilson & Company | Treatment of chromate solutions |
US3218252A (en) * | 1962-08-31 | 1965-11-16 | Coal Industry Patents Ltd | Process for the bacteriological oxidation of ferrous salts in acidic solution |
US3294680A (en) * | 1964-11-18 | 1966-12-27 | Lancy Lab | Treatment of spent cooling waters |
US3575853A (en) * | 1968-12-24 | 1971-04-20 | Lab Betz Inc | Waste water treatment |
US3740331A (en) * | 1971-06-23 | 1973-06-19 | Sybron Corp | Method for precipitation of heavy metal sulfides |
JPS4916714A (en) * | 1972-06-02 | 1974-02-14 | ||
US4102784A (en) * | 1976-04-27 | 1978-07-25 | Schlauch Richard M | Colloid free precipitation of heavy metal sulfides |
US4362629A (en) * | 1980-10-08 | 1982-12-07 | Murata Manufacturing Co., Ltd. | Method for processing solution including heavy metal |
US4705639A (en) * | 1985-05-10 | 1987-11-10 | The United States Of America As Represented By The Secretary Of The Air Force | Ferrous and sulfide treatment of electroplating wastewater |
Non-Patent Citations (39)
Title |
---|
"Alkaline Chromium (VI) Reduction by Ferrous Iron and Sulfide", Thomas E. Higgins et al, Arizona State University Rept No ERC-R-81028 (Oct. 1981). |
"An EPA Demonstration Plant for Heavy Metals Removal by Sulfide Precipitation", Murray C. Scott, Second Conference on Advanced Pollution Control for the Metal Finishing Industry, Rept No EPA-600/8-79-014, pp. 106-113 (Jun. 1979). |
"Combined Removal of Cr, Cd and Ni by Alkaline Reduction, Precipitation and Upflow Filtration", Thomas E. Higgins et al, Arizona State University, Rept No CR-R-83015 (Mar. 1983). |
"Ferrous and Sulfide Treatment of Industrial Wastewater at OC-ALC", CENTEC Applied Technologies (Oct. 15, 1985). |
"Final Report, Research and Development Design and Evaluation Report, Ferrous and Sulfide Treatment of Hexavalent Chromium", CENTEC Corporation (Jan. 1986). |
"Final Report--Ferrous and Sulfide Treatment of Industrial Wastewater at OC-ALC", CENTEC Corporation (Dec. 16, 1985). |
"Pilot Field Verification Studies of the Sodium Sulfide/Ferrous Sulfate Treatment Process", P.M. Wikoff et al (unpublished), dated Aug. 1988. |
"Potential Transformations of Chromium in Natural Waters", David C. Schroeder and G. Fred Lee, Water, Air, and Soil Pollution 4:3/4 (Jul./Aug. 1975). |
"Rate Studies on the Primary Step of the Reduction of Chromium (VI) by Iron (II)", James H. Espenson, J Am Chem Soc 92:7 (Apr. 8, 1970). |
"Sludge Generation from Ferrous/Sulfide Chromium Treatment", J.R. Aldrich, Rept No ESL-TR-84-27 (Aug. 1984). |
"Sodium Sulfide/Ferrous Sulfate Treatment of Hexavalent Chromium and Other Heavy Metals at Tinker AFB", P.M. Wikoff et al, Rept No ESL-TR-87-39 (Mar. 1988). |
"Sulfide Process Removes Metals, Produces Disposable Sludge", M.C. Scott, Industrial Wastes (Jul./Aug. 1979). |
"Sulfide vs Hydroxide Precipitation of Heavy Metals From Industrial Wastewater", A.K. Robinson, 1st Annual Conference on Advanced Pollution Control for the Metal Finishing Industry, Jan. 1978, Rept No EPA-600/8-78-010, pp. 59-65 (May 1978). |
"Summary Report--Control and Treatment Technology for the Metal Finishing Industry--Sulfide Precipitation", Rept No EPA-625/8-80-003 (Apr. 1980). |
"Treatment of Electroplating Wastewaters by Alkaline Ferrous Reduction of Chromium & Sulfide Precipitation", Thomas E. Higgins et al, Rept No ESL-TR-83-21 (Jun 1983). |
"Treatment of Metal Finishing Wastes by Sulfide Precipitation", Richard M. Schlauch and Arthur C. Epstein, Rept No EPA600/2-77-049 (Feb. 1977). |
"Treatment of Plating Wastewaters by Ferrous Reduction, Sulfide Precipitation, Coagulation and Upflow Filtration", Thomas E. Higgins, Arizona State Univ Rept No ERC-R-81014 (May 1981). |
Alkaline Chromium (VI) Reduction by Ferrous Iron and Sulfide , Thomas E. Higgins et al, Arizona State University Rept No ERC R 81028 (Oct. 1981). * |
An EPA Demonstration Plant for Heavy Metals Removal by Sulfide Precipitation , Murray C. Scott, Second Conference on Advanced Pollution Control for the Metal Finishing Industry, Rept No EPA 600/8 79 014, pp. 106 113 (Jun. 1979). * |
Combined Removal of Cr, Cd and Ni by Alkaline Reduction, Precipitation and Upflow Filtration , Thomas E. Higgins et al, Arizona State University, Rept No CR R 83015 (Mar. 1983). * |
Espenson et al., Kinetics and Mechanisms of Reactions of Chromium(VI) & Iron(II) Species in Acidic Solutions, J Am. Chem Soc. 85(21) 3328 33, 1963. * |
Espenson et al., Kinetics and Mechanisms of Reactions of Chromium(VI) & Iron(II) Species in Acidic Solutions, J Am. Chem Soc. 85(21) 3328-33, 1963. |
Ferrous and Sulfide Treatment of Industrial Wastewater at OC ALC , CENTEC Applied Technologies (Oct. 15, 1985). * |
Final Report Ferrous and Sulfide Treatment of Industrial Wastewater at OC ALC , CENTEC Corporation (Dec. 16, 1985). * |
Final Report, Research and Development Design and Evaluation Report, Ferrous and Sulfide Treatment of Hexavalent Chromium , CENTEC Corporation (Jan. 1986). * |
Peters et al. Removal of Heavy Metals form Industrial Plating Waste Waters by Sulfide Precip., Proc. Ind. Waste Sympos. 5th Wate Pollution Fed. Ann. Conf. 1984. * |
Pilot Field Verification Studies of the Sodium Sulfide/Ferrous Sulfate Treatment Process , P.M. Wikoff et al (unpublished), dated Aug. 1988. * |
Potential Transformations of Chromium in Natural Waters , David C. Schroeder and G. Fred Lee, Water, Air, and Soil Pollution 4:3/4 (Jul./Aug. 1975). * |
Rate Studies on the Primary Step of the Reduction of Chromium (VI) by Iron (II) , James H. Espenson, J Am Chem Soc 92:7 (Apr. 8, 1970). * |
Scott, "Sulflex™--A New Process Technology For Removal of Heavy Metals From Waste Streams," Proc. 32nd Ind Waste Conf. Purdue Univ. May 1977. |
Scott, Sulflex A New Process Technology For Removal of Heavy Metals From Waste Streams, Proc. 32nd Ind Waste Conf. Purdue Univ. May 1977. * |
Sludge Generation from Ferrous/Sulfide Chromium Treatment , J.R. Aldrich, Rept No ESL TR 84 27 (Aug. 1984). * |
Sodium Sulfide/Ferrous Sulfate Treatment of Hexavalent Chromium and Other Heavy Metals at Tinker AFB , P.M. Wikoff et al, Rept No ESL TR 87 39 (Mar. 1988). * |
Sulfide Process Removes Metals, Produces Disposable Sludge , M.C. Scott, Industrial Wastes (Jul./Aug. 1979). * |
Sulfide vs Hydroxide Precipitation of Heavy Metals From Industrial Wastewater , A.K. Robinson, 1st Annual Conference on Advanced Pollution Control for the Metal Finishing Industry, Jan. 1978, Rept No EPA 600/8 78 010, pp. 59 65 (May 1978). * |
Summary Report Control and Treatment Technology for the Metal Finishing Industry Sulfide Precipitation , Rept No EPA 625/8 80 003 (Apr. 1980). * |
Treatment of Electroplating Wastewaters by Alkaline Ferrous Reduction of Chromium & Sulfide Precipitation , Thomas E. Higgins et al, Rept No ESL TR 83 21 (Jun 1983). * |
Treatment of Metal Finishing Wastes by Sulfide Precipitation , Richard M. Schlauch and Arthur C. Epstein, Rept No EPA600/2 77 049 (Feb. 1977). * |
Treatment of Plating Wastewaters by Ferrous Reduction, Sulfide Precipitation, Coagulation and Upflow Filtration , Thomas E. Higgins, Arizona State Univ Rept No ERC R 81014 (May 1981). * |
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US6884352B1 (en) | 2002-03-07 | 2005-04-26 | Lonnie G. Kennedy | Treating toxic solvents and heavy metal contaminants in groundwater and soil using iron sulfides microbial geochemical treatment zone |
US6896817B2 (en) | 2002-04-15 | 2005-05-24 | Gregory S. Bowers | Essentially insoluble heavy metal sulfide slurry for wastewater treatment |
US20050173350A1 (en) * | 2002-04-15 | 2005-08-11 | Bowers Gregory S. | Essentially insoluble heavy metal sulfide slurry for wastewater treatment |
US20050289659A1 (en) * | 2004-05-18 | 2005-12-29 | Jacks E T | Cre-lox based method for conditional RNA interference |
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