DK142049B - PROCEDURE FOR ELECTROCHEMICAL CLEANING OF WASTE CONTAINING HEAVY METAL COMPOUNDS - Google Patents

PROCEDURE FOR ELECTROCHEMICAL CLEANING OF WASTE CONTAINING HEAVY METAL COMPOUNDS Download PDF

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DK142049B
DK142049B DK197372A DK197372A DK142049B DK 142049 B DK142049 B DK 142049B DK 197372 A DK197372 A DK 197372A DK 197372 A DK197372 A DK 197372A DK 142049 B DK142049 B DK 142049B
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mercury
solution
iron
chromium
salts
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DK142049C (en
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N Mastrorilli
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Snam Progetti
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    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/70Treatment of water, waste water, or sewage by reduction
    • C02F1/705Reduction by metals
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/46Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104Devices therefor; Their operating or servicing
    • C02F1/46176Galvanic cells
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/10Inorganic compounds
    • C02F2101/20Heavy metals or heavy metal compounds
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/10Inorganic compounds
    • C02F2101/20Heavy metals or heavy metal compounds
    • C02F2101/22Chromium or chromium compounds, e.g. chromates
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/02Non-contaminated water, e.g. for industrial water supply
    • C02F2103/023Water in cooling circuits

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)
  • Removal Of Specific Substances (AREA)
  • Water Treatment By Sorption (AREA)

Description

(11) FREMLÆGBELSiSSKRIFT 142049 (én i gpHf y V^Ra/ DANMARK (»i) intci.3 i/62 «(21) Anaøgrting nr. I975/72 (22) Indleveret den 21· apr. 1972 (23) Løbødag 21· apr· 1972 (44) Ansøgningen fremlagt og o o a(11) PRESENTATION 142049 (one in gpHf y V ^ Ra / DENMARK ("i) intci.3 i / 62" (21) Appendix No. I975 / 72 (22) Filed on Apr 21, 1972 (23) Running Day 21 · Apr · 1972 (44) The application submitted and also

fremlæggelsesekriftet offentliggjort den 18. aug. 1 SoOthe petition published on 18 Aug. 1 SoO

DIREKTORATET FOR ,„n, D. _ . _ . .DIRECTORATE OF, n, D. _. _. .

PATENT-OG VAREMÆRKEVÆSENET (30> Prioritet begssret fra denPATENT AND TRADE MARKET (30> Priority requested from it

23. apr. 1971s 235W71, ITApr 23 1971s 235W71, IT

7. maj 1971a 24205/71, ITMay 7, 1971a 24205/71, IT

__________ _ _______ (71) SNAM PROGETTI S.P.A., Corso Venezia, 16, Milano, IT.__________ _ _______ (71) SNAM PROGETTI S.P.A., Corso Venezia, 16, Milan, IT.

(72) Opfinder: Nunzio Maetrorilli, Via Rlsorgimento, 10, Milano, IT. _ (74) Fuldmægtig under sagens behandling:(72) Inventor: Nunzio Maetrorilli, Via Rlsorgimento, 10, Milan, IT. (74) Plenipotentiary in the proceedings:

Internationalt Patent-Bureau._ ________________ (54) Fremgangsmåde til elektrokemisk rensning af spildevand indeholdende tungmetalforblndels er.International Patent Bureau._ ________________ (54) Process for the electrochemical treatment of wastewater containing heavy metal blend is.

Den foreliggende opfindelse angår en fremgangsmåde til elektrokemisk rensning af spildevand indeholdende tungmetalforbindelser, navnlig chromater og kviksølvsalte, ved hvilken fremgangsmåde indholdet af tungmetal formindskes ved tilvejebringelse af en redoxproces.The present invention relates to a process for the electrochemical purification of wastewater containing heavy metal compounds, in particular chromates and mercury salts, in which process the content of heavy metal is reduced by providing a redox process.

Det er kendt at tilvejebringe en redoxproces i opløsninger indeholdende tungmetaller, som f.eks. kobbersalte, chromater eller kviksølvsalte eller -komplekser, ved tilsætning af et mindre ædelt metal som sådant, f.eks. zink eller jern, eller i form af ioner, der kan oxideres til en højere valenstilstand, f.eks. ferroioner, eller tilsætning af et andet reduktionsmiddel.It is known to provide a redox process in solutions containing heavy metals such as e.g. copper salts, chromates or mercury salts or complexes, by the addition of a less noble metal as such, e.g. zinc or iron, or in the form of ions that can be oxidized to a higher valence state, e.g. ferrous ions, or the addition of another reducing agent.

På denne måde har man søgt at befri forskellige former for spildevand for tungmetaller, enten med henblik på undgåelse af millieuforgiftning eller på genvinding af værdifulde metaller eller begge dele. F.eks. har man reduceret 2 14 2 Ο Λ 9 chromater til trivalente chromsalte, kobbersalte til metallisk kobber og anioni-ske kviksølvkomplekser, der er i ligevægt med kationen, til metallisk kviksølv.In this way, various forms of waste water have been sought for heavy metals, either for the purpose of avoiding environmental poisoning or for the recovery of valuable metals or both. Eg. For example, 2 14 2 Ο Λ 9 chromates have been reduced to trivalent chromium salts, copper salts to metallic copper and anionic mercury complexes in equilibrium with the cation to metallic mercury.

Nogen helt tilfredsstillende befrielse af spildevand for tungmetaller har man dog ikke opnået ved de kendte fremgangsmåder, ligesom der ofte forekommer andre ulemper. Således kan der ved reduktion af kviksølvforbindelser med et metal, som f.eks. jern, dannes et amalgam, der nødvendiggør yderligere behandling både til adskillelse af amalgamen og til udvindingen af de to bestanddele. Endvidere bruges der ofte en forholdsvis stor mængde reduktionsmiddel pr. vægtenhed tungmetal. En række andre ulemper vil fremgå af den efterfølgende beskrivelse i forbindelse med omtalen af den foreliggende opfindelse.However, no completely satisfactory discharge of wastewater for heavy metals has been achieved by the known methods, and other disadvantages often occur. Thus, by reducing mercury compounds with a metal such as e.g. iron, an amalgam is formed which requires further treatment both for the separation of the amalgam and for the recovery of the two components. Furthermore, a relatively large amount of reducing agent is often used. weight unit heavy metal. A number of other disadvantages will become apparent from the following description in connection with the discussion of the present invention.

Ved fremgangsmåden ifølge opfindelsen formindskes disse ulemper i væsentlig grad. Er emgangsmåden er kendetegnet ved, at ved sur pH-værdi to, i kontakt med hinanden værende elektrodematerialer, hvoraf det ene er elektronegativt, og det andet elektropositivt i forhold til hydrogen, bringes i kontakt med spildevandet. De to elektrodematerialer kan f.eks. være zink og carbon eller jern og kviksølv.In the method according to the invention, these disadvantages are substantially reduced. The process is characterized in that at acidic pH two, electrode materials, one of which is electronegative and the other electropositive with hydrogen, are contacted with the wastewater. The two electrode materials can e.g. be zinc and carbon or iron and mercury.

Den af syre -.bevirkede opløsning af den i forhold til hydrogen mindre ædle elektrode fremkalder en strøm af elektroner henimod den anden elektrode, og de i elektrolytten fremkaldte reaktioner forløber uden energitilførsel udefra, idet de tværtimod frembringer elektrisk energi i form af en jævnstrøm, som går fra anoden til den uangribelige katode, og som kan måles gennem den ydre leder, hvis der anvendes to hensigtsmæssige grundstoffer, som adskilt fra hinanden er neddyppet i den væske (elektrolytten), der skal behandles, og som er kortsluttet uden for denne.The acid-effected solution of the less noble electrode relative to hydrogen elicits a flow of electrons toward the other electrode, and the reactions elicited in the electrolyte proceed without outside energy supply, producing, on the contrary, electrical energy in the form of a direct current which passes from the anode to the intangible cathode and can be measured through the outer conductor if two appropriate elements are used, which are separately immersed in the liquid (electrolyte) to be treated and which are short-circuited outside it.

Forbindelsen mellem de to forskellige materialer kan også tilvejebringes i selve opløsningen, især under anvendelse af flere elektroder med meget små dimensioner. Til dette formål kan der hensigtsmæssigt anvendes elektrodematerialer i form af stænger, korn eller pulvere. Når disse anvendes i blanding med hinanden kan væsken kontinuerligt gå gennem blandingen og komme ud fuldstændigt renset.The connection between the two different materials can also be provided in the solution itself, especially using multiple electrodes of very small dimensions. For this purpose, electrode materials in the form of rods, grains or powders may conveniently be used. When used in admixture with one another, the liquid can continuously pass through the mixture and come out completely purified.

Redoxreaktionerne afhænger ikke af den valgte opstilling. Derimod afhænger kinetikken af formen af og eventuelt af afstanden mellem elektroderne.The redox reactions do not depend on the setup chosen. In contrast, the kinetics depend on the shape and possibly the distance between the electrodes.

Fremgangsmåden ifølge opfindelsen er helt almen, hvilket vil sige, at den kan anvendes både ved omdannelsen af oxidative salte til andre salte, i hvilke metallet har en lavere valenstilstand, og til opnåelse af ædelmetaller ud fra de tilsvarende salte. I det følgende anføres reaktionsmekanismen under henvisning til henholdsvis behandling af chromater og behandling af kviksølvsalte.' I nærværelse af en natriumchromatopløsning foregår den følgende reaktion, idet anoden består af metallisk zink, og opløsningen er gjort sur ved hjælp af salpetersyre 3 142049 3 Zn + Na2Cr207 + 14 HN03 = 3 Zn (NO^ + 2 NaNO^ + 2 Cr (NO ) + 7 H20 og på en mere almen form 3 Me + Cr207"" + 14 H+ * 3 Me^ + 2 Cr^ + 7 H20 idet Me er et divalent metal, der er elektropositivt i forhold til hydrogen.The process of the invention is quite general, that is, it can be used both in the conversion of oxidative salts to other salts in which the metal has a lower valence state, and to obtain noble metals from the corresponding salts. The reaction mechanism is described below with reference to the treatment of chromates and the treatment of mercury salts, respectively. In the presence of a sodium chromate solution, the following reaction takes place as the anode consists of metallic zinc and the solution is acidified by nitric acid 3 Zn + Na 2 Cr 2 0 7 + 14 HNO 3 = 3 Zn (NO 2 + 2 NaNO 2 + 2 Cr (NO + 7 H 2 O and in a more general form 3 Me + Cr 2 O 7 "+ 14 H + * 3 Me 2 + 2 Cr 2 + 7 H 2 O, Me being a divalent metal electropositive to hydrogen.

Hvis metallet (Me) har højere valenser, sker der en yderligere reaktion, f.eks. som følger 6 Me"1"1· + Cr207'_ + 14 H+ <= 6 Me444" + 2 Cr+++ + 7 H20If the metal (Me) has higher valences, a further reaction occurs, e.g. as follows 6 Me "1" 1 · + Cr207'_ + 14 H + <= 6 Me444 "+ 2 Cr +++ + 7 H20

Dette sker f.eks., når Me er jern, idet dette først bliver divalent og derefter trivalent.This occurs, for example, when Me is iron, being first divalent and then trivalent.

Belyst ved hjælp af eksempler beskrives i det følgende behandlingen af chro-matholdigt spildevand fra oparbejdningen af chrom- eller nikke1-chrom-stål. Det vil derefter være meget let for en fagmand at anvende det principielle ved opfindelsen ved behandlingen af spildevand, der indeholder chromater fra en anden kilde.Illustrated by way of example, the following describes the treatment of chromate-containing wastewater from the chromium or nickel-1 chromium steel reprocessing. It will then be very easy for a person skilled in the art to apply the principle of the invention in the treatment of wastewater containing chromates from another source.

Den elektrokemiske oparbejdning af chrom- eller nikke1-chrom-stål består i det væsentlige af en anodisk oxidation i et elektrolytisk bad, der udgøres af en vandig 30%'s natriumnitratopløsning.The electrochemical work-up of chromium or nickel-1 chromium steel consists essentially of an anodic oxidation in an electrolytic bath which is made up of an aqueous 30% sodium nitrate solution.

Under oparbejdningen dannes der betydelige mængder opløseligt natriumchromat, og der dannes også slam indeholdende jern- og chromhydroxider samt basiske salte.During the work-up, considerable amounts of soluble sodium chromate are formed, and also mud containing iron and chromium hydroxides as well as basic salts is formed.

Ved en efterfølgende centrifugering af en sådan suspension kan bundfaldene separa-res og den alkalinitratrige eller -chromatrige opløsning recirkuleres.Upon subsequent centrifugation of such a suspension, the precipitates can be separated and the alkaline nitrate-rich or -chromatic-rich solution recycled.

Imidlertid bortledes slammet efter en delvis fortykning, både af hensyn til centrifugeringen og frem for alt til undgåelse af en stadig forøgelse af chro ma tkoncentrat ionen i den recirkulerede elektrolyt. Effluenten, der skal bortledes udgøres derfor af en suspension af jern- og chromhydroxider og basiske nitrater dispergeret i en opløsning af natriumnitrat og -chfomat.However, the sludge is discharged after a partial thickening, both for the sake of centrifugation and, above all, to avoid a continuous increase of the chromate concentration of the recycled electrolyte. The effluent to be derived is therefore a suspension of iron and chromium hydroxides and basic nitrates dispersed in a solution of sodium nitrate and chromate.

Koncentrationen af natriumchromatet, der er tilstede i en sådan suspensions flydende fase, afhænger af de behandlede legeringers chromindhold, og den er sædvanligvis .større end 250 ppm Cr svarende til ca. 750 ppm NajCrO^.The concentration of the sodium chromate present in the liquid phase of such a suspension depends on the chromium content of the treated alloys, and is usually greater than 250 ppm Cr, corresponding to approx. 750 ppm NajCrO ^.

Denne elektrokemiske oparbejdning foregår eksemplevis som skematisk vist i tegningens fig. 1.This electrochemical work-up is carried out, for example, as schematically shown in the drawing of FIG. First

I fig. 1 indeholder en beholder 1 den rene elektrolyt, og der ledes na-truimnitrat til beholderen gennem en ledning 14. Gennem en ledning 2 sendes elektrolytten til et apparat 3, i hvilket den elektrolytiske oparbejdning sker.In FIG. 1, a container 1 contains the pure electrolyte, and sodium hydroxide nitrate is passed to the container through a conduit 14. Through a conduit 2, the electrolyte is sent to an apparatus 3 in which the electrolytic reprocessing takes place.

Den urene elektrolyt, der udgøres af opløseligt natriumchromat og slam indeholdende jern- og chromhydroxider, kommer ud fra apparatet 3 og ledes gennem en ledning 4 til en beholder 5. Gennem en ledning 6 sendes suspensionen til en centrifuge 7, der i vaskefasen fødes med vand gennem en ledning 15. Ved den 4 142049 efterfølgende centrifugering af suspensionen separeres bundfaldene, og den alka-linitratrige og -chromatrige opløsning recirkuleres gennem ledningerne 8 og 9 til beholderen 1. Slammet, der gennem en ledning 10 sendes til en beholder 11, udgøres af en suspension af jern- og chromhydroxider og basiske nitrater disper-geret i en opløsning af natriumnitrat og -chromat.The impure electrolyte, composed of soluble sodium chromate and sludge containing iron and chromium hydroxides, exits the apparatus 3 and is passed through a conduit 4 to a container 5. Through the conduit 6, the suspension is sent to a centrifuge 7 which is fed with water in the wash phase. through a conduit 15. At the subsequent centrifugation of the suspension, the precipitates are separated and the alkaline nitrate-rich and chromatically rich solution is recycled through conduits 8 and 9 to the container 1. The sludge sent through a conduit 10 to a container 11 is constituted by a suspension of iron and chromium hydroxides and basic nitrates dispersed in a solution of sodium nitrate and chromate.

Rensningen i beholderen 11 udføres på den ovenfor angivne måde. I væsken ned-dyppes der to elektroder, jern som anode og amalgeret kobber som katode, og ved kortslutning af elektroderne sker den følgende reaktion 3 Fe + Cr207~‘ + 14 H+^=>· 3 Fe** + 2 Cr+++ + 7 H20 idet chromater således reduceres til trivalente chromsalte.The cleaning in the container 11 is carried out in the manner indicated above. Two electrodes are immersed in the liquid, iron as anode and amalgamated copper as cathode, and by shorting the electrodes, the following reaction occurs 3 Fe + Cr207 ~ '+ 14 H + ^ => · 3 Fe ** + 2 Cr +++ + 7 H20 thus chromates are reduced to trivalent chromium salts.

Det i opløsningen tilstedeværende divalente jern oxideres til trivalent jern som følge af et overskud af nitrationer, og de ved denne redoxreaktion dannede nitrogenoxider opløses i systemet og forbliver heri. Nitrationerne gendannes kvantitativ, når systemet gøres alkalisk i nærværelse af luft med det formål at opnå de trivalente chrom- og jernhydroxider og separere dem fra systemet.The divalent iron present in the solution is oxidized to trivalent iron as a result of an excess of nitrate rations, and the nitrogen oxides formed by this redox reaction dissolve in the system and remain therein. The nitrations are quantitatively restored when the system is made alkaline in the presence of air for the purpose of obtaining the trivalent chromium and iron hydroxides and separating them from the system.

Den til dannelsen af jern- og chromsalte nødvendige syrning kan være sådan, at der ikke sker en opløsning af de allerede tilstedeværende jernforbindelser.The acidification necessary for the formation of iron and chromium salts may be such that no solution of the iron compounds already present occurs.

Efter reaktionen fjernes jern og chrom som nævnt ovenfor ved tilsætning af natriumhydroxid, til udfældning i form af metalhydroxider.After the reaction, as mentioned above, iron and chromium are removed by addition of sodium hydroxide, to precipitate in the form of metal hydroxides.

I denne fase er hele salpetersyremængden, inden den anvendes, tilstede i opløsningen i form af natriumnitrat, der gennem ledninger 12 og 13 recirkuleres til beholderen 1. Elektrolyttens alkalinitratmængde genoprettes derfor automatisk, og dette bevirker, at de ellers nødvendige nitrattilsætninger til opløsningen, der skal recirkuleres, undgås.During this phase, the entire amount of nitric acid, before use, is present in the solution in the form of sodium nitrate which is recycled through conduits 12 and 13 to the container 1. The electrolyte's alkaline nitrate amount is therefore automatically restored and this causes the otherwise necessary nitrate additions to the solution to be used. recirculated, avoided.

Efter separeringen af metalhydroxiderne, f.eks. ved hjælp af de allerede tilstedeværende centrifuger, kan der ved den førnævnte behandling opnås en opløsning, som kun indeholder natriumnitrat, og opløsningen er som sådan egnet til genanvendelse i en lukket cyklus.After the separation of the metal hydroxides, e.g. by means of the centrifuges already present, a solution containing only sodium nitrate can be obtained in the aforementioned treatment and the solution as such is suitable for recycling in a closed cycle.

En for den i fig. 1 skematiserede fremgangsmåde interessant variant, der gør en sådan fremgangsmåde helt almen, består i også at anvende den omhandlede fremgangsmåde ved behandling af suspensionen i beholderen 5. Efter reduktionen og neutraliseringen er det på denne måde muligt at foretage en separering i centrifugen 7 af slam, som kan bortledes, idet der i den tilbageblivende flydende fase hverken findes chromater eller tungmetalsalte.One for the one shown in FIG. In the schematic procedure, an interesting variant which makes such a procedure quite general consists in also using the method according to the treatment of the suspension in the container 5. After the reduction and neutralization it is possible in this way to make a separation in the centrifuge 7 of sludge. which can be deduced since in the residual liquid phase there are no chromates or heavy metal salts.

Ved anvendelse af den omhandlede fremgangsmåde på opløsninger eller suspensioner af kviksølvsalte dannes der metallisk kviksølv. Reaktionerne sker tilsyneladende uden anvendelse af syre, f.eks. ifølgeBy applying the method of the present invention to solutions or suspensions of mercury salts, metallic mercury is formed. The reactions apparently occur without the use of acid, e.g. according to

HgSO^ + Zn.+ H2S04 - ZnS04 + H2S04 + Hg men egentlig er den dannede mængde metallisk kviksølv støkiometrisk ækvivalent med 5 142049 den mængde syre , der omsættes med zink, hvilket fremgår afHgSO4 + Zn. + H2SO4 - ZnSO4 + H2SO4 + Hg but, in fact, the amount of metallic mercury formed is stoichiometric equivalent to zinc, the amount of acid reacted with zinc, as shown in

Zn + H2S0^ = ZnSO^ + 2 H+ 2 H+ + HgS04 = H2S04 + HgZn + H2SO4 = ZnSO4 + 2H + 2H ++ HgSO4 = H2SO4 + Hg

Dette forhold kan belyses ved hjælp af tegningens fig. 2.This relationship can be illustrated by means of the drawing of FIG. 2nd

I fig. 2 indeholder en ydre beholder 1 kviksølvsaltopløsningen, medens en beholder 2 af et porøst materiale indeholder en syre. Førstnævnte beholder indeholder en uangribelig elektrode 3, medens den anden beholder indeholder en af syrer angribelig metalelektrode 4. Pilene angiver elektronstrømmens retning.In FIG. 2, an outer container 1 contains the mercury salt solution, while a container 2 of a porous material contains an acid. The first container contains an inaccessible electrode 3, while the second container contains one of the acids attackable metal electrode 4. The arrows indicate the direction of the electron current.

Forudsat at kviksølvsaltet hydrolyseres vanskeligt, er opløsningen i beholderen 2 i begyndelsen af forsøget sur, medens opløsningen i beholderen 1 er neutral.Provided that the mercury salt is difficult to hydrolyze, the solution in the container 2 at the beginning of the experiment is acidic, while the solution in the container 1 is neutral.

Under forsøget sker der en vandring af elektroner fra elektroden 4 til elektroden 3 og en passage af hydrogenioner fra beholderen 2 til beholderen 1. Hvis de oprindelige opløsninger i beholderne 2 og 1 har samme normalitet, og hvis forholdet mellem rumfangene af opløsningerne i beholderne 2 og 1 er l:n, idet n er meget større end 1, er opløsningen i beholderen 2 neutral, efter at 1/n af det oprindeligt tilstedeværende kviksølv findes i beholderen 1 i reduceret form, medens syremængden fra beholderen 2 er gendannet i beholderen 1.During the experiment, a migration of electrons from the electrode 4 to the electrode 3 and a passage of hydrogen ions from the container 2 to the container 1. takes place if the original solutions in the containers 2 and 1 have the same normality and if the ratio of the volumes of the solutions in the containers 2 and 1 is l: n, with n being much greater than 1, the solution in the container 2 is neutral after 1 / n of the mercury initially present in the container 1 is in reduced form, while the amount of acid from the container 2 is recovered in the container 1.

Man kan derfor uden energitilførsel få metallisk kviksølv fra kviksølvsaltopløsninger under anvendelse af et andet metal, der er angribeligt af syrer, og en syremængde, der er ækvivalent med den kviksølvmængde, som skal separeres i metallisk tilstand.Therefore, without mercury, metallic mercury can be obtained from mercury salt solutions using another metal attackable by acids and an amount of acid equivalent to the amount of mercury to be separated in metallic state.

En aciditet, der er ækvivalent med den indførte aciditet, er konstant tilstede i systemet, og den kan uden hensyn til den indre beholders porøsitetsgrad tilskrives syrer, som teoretisk kan stamme fra kombinationen af hydrogenionerne fra den tilsatte syre med anionerne fra det eller de oprindeligt tilstedeværende kviksølvsalt eller kviksølvsalte. Den frie syre indgår i den førnævnte proces, men systemets virkelige aciditet holdes konstant, hvorfor der sædvanligvis ikke kræves en syretiIsætning.An acidity equivalent to the introduced acidity is constantly present in the system and it can be attributed, without regard to the degree of porosity of the inner container, which theoretically can be derived from the combination of the hydrogen ions of the added acid with the anions of the originally present one (s). mercury salts or mercury salts. The free acid is part of the aforementioned process, but the real acidity of the system is kept constant, so an acid addition is usually not required.

Når det drejer sig om vand, der indeholder kviksølvsalte, vil det væne klart, at fordelen ved anvendelse af den omhandlede fremgangsmåde er betydelig, fordi det uden energitilførsel udefra er muligt at isolere kviksølv i metallisk tilstand.In the case of water containing mercury salts, it will be appreciated that the advantage of using the process of the present invention is considerable, because without the addition of energy it is possible to isolate mercury in metallic state.

Ifølge det førnævnte system får man det metalliske kviksølv direkte i ren tilstand i den zone, i hvilken carbonelektroderne er neddyppet, især ved indskydelse af en porøs væg imellem zonerne, i hvilke elektroderne af zink og carbon er anbragt.According to the aforementioned system, the metallic mercury is obtained directly in the pure state in the zone in which the carbon electrodes are immersed, especially by the insertion of a porous wall between the zones in which the zinc and carbon electrodes are placed.

Man kunne ved ingen af de hidtil kendte fremgangsmåder få et sådant resultat, og heller ikke ved udfældningsprocessen kunne der kannes metallisk kviksølv, selv om den tilsyneladende ligner den ovenfor beskrevne fremgangsmåde med hensyn til 6 142049 nogle af de angivne parametre, idet den består i reduktion af kviksølvsalte ved hjælp af et mindre ædelt metal. Som tidligere nævnt dannes der herved et amalgam, som nødvendiggør yderligere behandlinger. Desuden formindskes oparbejdningshastigheden, medens amalgameringen forløber.No such result could be obtained in any of the known methods, nor could the metallic mercury be precipitated by the precipitation process, although it appears to be similar to the above described method with respect to some of the parameters stated, since it consists in reduction. of mercury salts using a less noble metal. As mentioned earlier, an amalgam is formed which necessitates further treatments. In addition, the reprocessing rate decreases as the amalgamation proceeds.

Foruden at udvinde det ædle metal direkte i metallisk tilstand kan man ved den omhandlede fremgangsmåde erstatte disse metaller i opløsning med ionerne af et metal, der kan vælges i forvejen under hensyn til de følgende ved den yderligere rensning af affaldet anvendte metoder.In addition to extracting the precious metal directly in the metallic state, in the present process, these metals in solution can be replaced with the ions of a metal which may be pre-selected, taking into account the following in the further purification of the methods used.

Vedrensning ifølge den kendte teknik ve<l en f lokku lerende behandling af effluenterne, indeholder det i forvejen for de ædle metaller rensede affald en ækvivalent mængde ioner af et mindre ædelt metal, f.eks. zink. Dette udfældes under flokkuleringen i form af uopløseligt hydroxid.Prior purification according to the prior art involves a local treatment of the effluents, it contains in advance of the precious metals purified waste an equivalent amount of ions of a less noble metal, e.g. zinc. This is precipitated during flocculation in the form of insoluble hydroxide.

Hvis der anvendes calciumhydroxid ved flokkuleringen, er de ædle metaller efter den fuldstændige behandling af effluenten erstattet med calciumioner, og zink er omdannet til zinkhydroxid, der kan udvindes som et oxid fra røgen fra en · ved forbrænding af slammet anvendt forbrændingsovn.If calcium hydroxide is used in the flocculation, after the complete treatment of the effluent, the precious metals are replaced with calcium ions, and zinc is converted into zinc hydroxide which can be recovered as an oxide from the smoke from a combustion furnace used in the sludge.

Nedenfor er vist et skema over den mulige reaktion, i hvilken kobber er det ædle metalBelow is a diagram of the possible reaction in which copper is the precious metal

CuS04 + H2S04 + -Zn = ZnS04 + H2S(>4 + CuCuS04 + H2S04 + -Zn = ZnS04 + H2S (> 4 + Cu

ZnS04 + H2S04 + 2 Ca(0H)2 = 2 CaS04 + Zn(0H>2 + 2 H20ZnSO4 + H2SO4 + 2 Ca (OH) 2 = 2 CaSO4 + Zn (OH> 2 + 2 H2 O

Zn(0H)2 = ZnO + Η2<3Zn (OH) 2 = ZnO + Η2 <3

Forholdet er som følger:The relationship is as follows:

CuS04 + Zn + Ca(0H)2 = CaSC>4 i den flydende effluent + ZnO i den faste tilstand + Gu i den faste tilstand + HjO'i damptilstandenCuSO4 + Zn + Ca (OH) 2 = CaSC> 4 in the liquid effluent + ZnO in the solid state + Gu in the solid state + HjO'i in the vapor state

Den behandlede effluents saltholdighed ændres således praktisk taget ikke, da kationen af et ædelt metal ganske enkelt erstattes af calciumioner.Thus, the salinity of the treated effluent is virtually unchanged since the cation of a noble metal is simply replaced by calcium ions.

Dette gør det muligt at rense det bortledte materiale, også med henblik på en eventuel biologisk rensning, der ikke ville være mulig i nærværelse af salte af metaller, såsom Cu, Hg, Ag osv, der er giftige overfor bakterierne.This makes it possible to purify the derived material, also for any biological purification that would not be possible in the presence of salts of metals, such as Cu, Hg, Ag, etc., which are toxic to the bacteria.

Én tredje betydelig fordel ved den omhandlede fremgangsmåde er, at der intet rensningsapparatur kræves, idet der blot i effluenten indføres en række forskellige elektroder.A third significant advantage of the present process is that no purification apparatus is required, simply introducing into the effluent a number of different electrodes.

De samme resultater kan opnås ved som anode at anvende et metal, der ikke danner amalgam med kviksølv, f.eks. jern. Netop en sådan anvendelse gør-det miiligt at anvende enkle kolonner, der er fyldt med små korn af de to materialer med anodisk og katodisk beskaffenhed (henholdsvis jern og et andet materiale, som ikke korro 7 142049 deres, og som virker som en kviksølvelektrode), som rensningsapparatur: materialerne bringes i meget intim indbyrdes kontakt. Da jern ikke danner amalgam, kan kviksølv udvindes i metallisk tilstand.The same results can be obtained by using as an anode a metal which does not form amalgam with mercury, e.g. iron. Just such an application makes it easy to use simple columns filled with small grains of the two materials of anodic and cathodic nature (iron and other non-corrosive materials, respectively, which act as a mercury electrode). , as a cleaning device: the materials are brought into very intimate contact with one another. Since iron does not form amalgam, mercury can be extracted in metallic state.

Uanset det forurenende grundstof } der skal reduceres, er det sædvanligvis fordelagtigt som katode at anvende et materiale, der virker son en kviksølvelektrode, med det formål at opnå en høj overspænding i forhold til hydrogen, hvorved der kan arbejdes i et bredere pH-område uden udvikling af hydrogen.Regardless of the pollutant element to be reduced, it is usually advantageous as a cathode to use a material which acts as a mercury electrode, for the purpose of obtaining a high voltage over hydrogen, thereby allowing it to operate in a wider pH range without development of hydrogen.

Med dette formål for øje kan der anvendes amalgamerede metaller, carbon der. er imprægneret med kviksølv, eller slet og ret metallisk kviksølv. Katodebestand-delene kan også fremstilles ved overtrækning eller imprægnering af en bærer med en metalbes tanddel, der kan danne amalgam, og derefter ved amalgamering af metal-bestanddelen.For this purpose, amalgamated metals, carbon there, can be used. is impregnated with mercury, or simply metallic mercury. The cathode components may also be prepared by coating or impregnating a support with a metal berry tooth portion capable of forming amalgam, and then by amalgamating the metal component.

Hvis der anvendes apparaturer, der udgøres af fyldte kolonner, i hvilke kontakten mellem elektroderne tilvejebringes i selve den vandige fase, er det hensigtsmæssigt som anode at anvende en bestanddel, der ikke danner amalgam, med det formål at bevare en konstant potentialforskel mellem elektroderne, og der kan fordelagtigt anvendes jern.If apparatus made up of filled columns are used in which contact between the electrodes is provided in the aqueous phase itself, it is appropriate as an anode to use a non-amalgam constituent for the purpose of maintaining a constant potential difference between the electrodes, and advantageously, iron can be used.

Under alle omstændigheder kan anoden fordelagtigt bestå af zink, nikkel, tin, bly, jern, chrom og alle de metaller, der kan angribes af ikke-oxidative syrer, hvilket vil sige de metaller, der er elektropositive i forhold til hydrogen. De kan eventuelt amalgameres med det formål at styre korrosionshastigheden.In any case, the anode may advantageously consist of zinc, nickel, tin, lead, iron, chromium and all the metals which can be attacked by non-oxidative acids, that is, the metals which are electropositive to hydrogen. They may optionally be amalgamated for the purpose of controlling the corrosion rate.

Katoden kan udgøres af carbon, metaller, der er elektronegative i forhold til hydrogen, deres amalgamer, materialer, der er imprægneret af kviksølv, og alle de materialer, der ikke korroderes af syrer og er ledere.The cathode may be carbon, metals that are electronegative to hydrogen, their amalgams, mercury-impregnated materials, and all materials that are not corroded by acids and conductors.

Såfremt elektrokemisk rensning alene udførtes under anvendelse af anode-bestanddelen med metallisk beskaffenhed ifølge de ovenfor angivne reaktionsskemaer, ville fordelene ikke være særlig bemærkelsesværdige. Først og fremmest er forholdet det, at når der ikke anvendes en katode, der virker som en elektrode, der er elektronegativ i forhold til hydrogen, foreligger der lavere potential-forskelle, hvad angår anodebestanddelen, og som følge heraf er reaktionshastighederne lavere. Når der yderligere ikke anvendes en katode med en betydelig overspænding i forhold til hydrogen, således som det er tilfældet ved en katode, der virker som en kviksølvelektrode, kan der frigøres hydrogen af anoden, hvorved syreforbruget forøges, og anoden polariseres. Når det drejer sig om vand indeholdende ædelmetalsalte, ville der kunne ske en udfældning eller dannes et amalgam, hvorved alle de ovenfor angivne ulemper ville kunne forekomme. Hvis der behandledes opløsninger, der indeholdt oxidative forbindelser i høje koncentrationer, f.eks. chromater i en koncentration på 1000 ppm Cr, så at de ovenfor angivne reaktioner forløb, og syreforbruget var ækvivalent med mængden af reducerede 8 142049 chromater, ville hydrogenionkoncentrationen formindskes, hvilket vil sige, at pH-værdien ville forøges, især på anodeoverfladen, hvis metallet antager højere • « · +++ valenser, når det gik i opløsning. Når det drejer sig om jern, dannes der Fe --ioner ved sådanne pH-værdier, ved hvilke der kan dannes trivalente jemhydroxi-der eller basiske salte. Da disse er uopløselige stoffer, der er dannet nær metaloverfladen, på hvilken Fe+++-ioner er blevet dannet, ville opløsningsprocessen kunne sinkes som følge af overfladepolymerisationsfænomener. I dette tilfælde kan der så ganske vist tilsættes et kompleksdannende middel, f.eks. na-truimsaltet af ethylendiamintetråeddikesyre, med det formål at undgå, at der dannes uopløselige jemhydroxider og basiske salte.If electrochemical purification alone was performed using the anode component of metallic nature according to the above reaction schemes, the advantages would not be particularly noteworthy. First of all, the fact is that when a cathode acting as an electrode that is electronegative to hydrogen is not used, there are lower potential differences with respect to the anode component, and as a result, the reaction rates are lower. Further, when a cathode having a significant voltage over hydrogen is not used, as is the case with a cathode which acts as a mercury electrode, hydrogen can be released from the anode, thereby increasing the acid consumption and polarizing the anode. In the case of water containing precious metal salts, a precipitate or amalgam could be formed, whereby all the disadvantages mentioned above could occur. If solutions containing oxidative compounds at high concentrations, e.g. chromates at a concentration of 1000 ppm Cr so that the above reactions proceeded and the acid consumption was equivalent to the amount of reduced chromates, the hydrogen ion concentration would be reduced, that is, the pH would be increased, especially on the anode surface if the metal assumes higher • «· +++ valences when dissolved. In the case of iron, Fe ions are formed at such pH values at which trivalent iron hydroxides or basic salts can be formed. Since these are insoluble substances formed near the metal surface on which Fe +++ ions have been formed, the dissolution process could be slowed down due to surface polymerization phenomena. In this case, a complexing agent, e.g. the post-salt salt of ethylene diamine tetraacetic acid, with the aim of avoiding the formation of insoluble iron hydroxides and basic salts.

For ved fremgangsmåden ifølge opfindelsen at undgå størstedelen af katodé-overfladen bringes i kontakt med anoderne er det hensigtsmæssigt at anvende særligt udformede katoder, også hvis der anvendes kolonner, der på vilkårlig måde er fyldt med katodiske og anodiske materialer.In order to avoid contacting most of the cathode surface with the anodes in the method according to the invention, it is advisable to use specially designed cathodes, even if columns which are arbitrarily filled with cathodic and anodic materials are used.

Det er f.eks. muligt at anvende et katodisk materiale i form af små rørstyk-ker, og hvis det anodibke materiale har sådanne dimensioner, at det ikke kan komme ned i de således tilvejebragte små hule cylindre, kan der anvendes en katodisk overflade, som udgøres af indervæggene af rørstykkerne, der ikke er i kontakt med anoderne, også selv om de er påtrykt en spænding som følge af kontakten mellem disse anoder og de hule cylindres ydervægge. Ved et sådant arrangement reduceres den chromatholdige opløsning ved kontakt med cylinderens indervæg, og derefter reduceres jemioner, der allerede er til stede i opløsningen, medens de ikke reduceres under dannelsen.It is e.g. it is possible to use a cathodic material in the form of small tubes, and if the anodic material has such dimensions that it cannot fall into the small hollow cylinders thus provided, a cathodic surface made up of the inner walls of the tubes can be used. that are not in contact with the anodes, even if they are applied to a voltage due to the contact between these anodes and the outer walls of the hollow cylinders. In such an arrangement, the chromate-containing solution is reduced by contact with the inner wall of the cylinder, and then chemistries already present in the solution are reduced while not reduced during formation.

Det eventuelt dannede jernhydroxid og de eventuelt dannede basiske salte samler sig så mellem den flydende fase og anodevæskerummet.The optionally formed iron hydroxide and the optionally formed basic salts then assemble between the liquid phase and the anode liquid compartment.

Fremgangsmåden ifølge opfindelsen forklares nærmere i de følgende eksempler.The process according to the invention is explained in more detail in the following examples.

Eksempel 1.Example 1.

Den i fi& 1 skitserede proces, omhandlende en elektrokemisk behandling af chrom- og nikkel-chrom-stål, udførtes med det formål at give stålet en ønsket kontur ved hjælp af en anodisk opløsning, og koncentrationen af natriumchromatet, der fandtes i den flydende fase af suspensionen, der skulle bortledes (11 i figuren), var ca. 750 ppm, svarende til ca. 250 ppm Cr.The process outlined in FIG. 1, dealing with electrochemical treatment of chromium and nickel-chromium steels, was carried out with the aim of giving the steel a desired contour by means of an anodic solution and the concentration of the sodium chromate present in the liquid phase of the suspension to be discharged (11 in the figure) was approx. 750 ppm, corresponding to approx. 250 ppm Cr.

Ved at gå frem som tidligere beskrevet reduceredes chromaterne fuldstændigt i løbet af ca. 2 timer, og det var imens muligt at påvise en passage af en strøm på 100 mA ved en potentialforskel på 1 V.Proceeding as previously described, the chromates were completely reduced in about 2 hours, and it was possible to detect a passage of a current of 100 mA at a potential difference of 1 V.

Der bemærkedes ingen reduktion af ferrisalte eller nitrater.No reduction of ferric salts or nitrates was observed.

9 1420499 142049

Eksempel 2 I anlæg til fremstilling af acetaldehyd fra acetylen afgiver katalysatorafdelingerne diskontinuerligt kviksølvsulfatrige opløsninger, der kan indeholde indtil 200 mg Hg/i,Example 2 In systems for preparing acetaldehyde from acetylene, the catalyst compartments discontinuously deliver mercury sulfate-rich solutions which may contain up to 200 mg Hg / l.

Eksemplet angår behandlingen af en kviksølvsulfatopløsning indeholdende 200 mg Hg/1. Hvis kviksølvsulfatet er opløst, er opløsningen sur som følge af hydrolyse.The example relates to the treatment of a mercury sulfate solution containing 200 mg Hg / l. If the mercury sulfate is dissolved, the solution is acidic due to hydrolysis.

Den mindste syremængde, der er nødvendig til undgåelse af hydrolysen, er en sådan, som giver opløsningen et pH på ca. 2, d.v.s. en surhedsgrad, ved hvilken processen kan udføres.The minimum amount of acid needed to avoid the hydrolysis is one which gives the solution a pH of approx. 2, i.e. an acidity at which the process can be performed.

22

Det var derfor nødvendigt at anvende en række zinkplader (5 m / m opløsning) og en række carbonstænger. Zn og C er elektrisk forbundet udenfor opløsningen.It was therefore necessary to use a number of zinc plates (5 m / m solution) and a number of carbon bars. Zn and C are electrically connected outside the solution.

Zn-C-systemet gjorde det muligt i nærværelse af opløsningen at udvinde metallisk Hg på carbonoverfladen, først i form af et gråt pulver og derefter i form af små dråber, hvorefter det udskiltes som metallisk Hg og samlede sig i rummet under carbon. pH holdt sig konstant uden syretilsætning. Efter 8 timer var reaktionen tilendebragt (99,5%). Der gik mindst 65 g Zn i opløsning, og der blev dannet 200 g metallisk kviksølv pr. m tilført effluent.The Zn-C system, in the presence of the solution, allowed metallic Hg to be recovered on the carbon surface, first in the form of a gray powder and then in the form of small droplets, after which it was separated as metallic Hg and collected in the space under carbon. The pH remained constant without acid addition. After 8 hours, the reaction was complete (99.5%). At least 65 g of Zn was dissolved and 200 g of metallic mercury was formed per ml. m added effluent.

Eksempel 3 I anlæg til fremstilling af vinylchlorid fra acetylen har rørene, der forbinder reaktorerne og vasketårnet, betydelige HgClg-belægninger, da der anvendes kviksølvsalte som katalysatorer. Under reparationsstoppene udvaskes HgC^ med vand, og man f^r på den måde et affald, der i betydelig grad er forurenet med Hg, da de førnævnte belægninger kan ; være 10 til 15 mm tykke.Example 3 In plants for the production of vinyl chloride from acetylene, the tubes connecting the reactors and the washing tower have significant HgClg coatings as mercury salts are used as catalysts. During the repair stops, HgCl 2 is washed out with water, and thus a waste which is considerably contaminated with Hg is obtained, as the aforementioned coatings can; be 10 to 15 mm thick.

Apparaturet ifølge det foregående eksempel anvendtes, og der kunne opnås et bedre resultat, hvis carbonstængerne indførtes i en porøs beholder.The apparatus of the preceding example was used and a better result could be obtained if the carbon rods were introduced into a porous container.

Det første reduktionsproduktvar det inden i den porøse beholder dannede uopløselige mercurochlorid, der derefter omdannedes til metallisk kviksølv. Omrøringen af væsken i den i nærheden af carbonelektroderne liggende zone forøgede hastigheden af reaktionerne, der her fandt sted i et heterogent system på grund af nærværelsen af det uopløselige mercurochlorid.The first reduction product is the insoluble mercuric chloride formed within the porous container which is then converted to metallic mercury. The stirring of the liquid in the vicinity of the carbon electrodes increased the rate of the reactions which took place here in a heterogeneous system due to the presence of the insoluble mercurochloride.

Hvis den forurenede opløsning indeholdt 1000 ppm Hg, anvendtes der i det 3 mindste 310 g Zn pr. ra behandlet effluent, og der blev udvundet ca. 1000 g kviksølv.If the contaminated solution contained 1000 ppm Hg, at least 310 g of Zn was used per day. ra treated effluent, and approx. 1000 g of mercury.

Eksempel 4Example 4

Dette forsøg er udelukkende et sammenligningsforsøg og viser det almindelige forløb i forbindelse med et chrompletteringsanlæg.This experiment is purely a comparative experiment and shows the ordinary course of a chromium plating plant.

10 14204910 142049

Ved den mest anvendte fremgangsmåde til rensning af det tilsvarende spildevand reguleres pH til en lavere værdi end 3, og der tilsættes gasformig SO^ eller en opløsning af natriumsulfit eller -hydrogensulfit i en koncentration på 50 til 100 g/1.In the most commonly used process for purifying the corresponding wastewater, the pH is adjusted to a value lower than 3, and a gaseous SO 2 or a solution of sodium sulfite or hydrogen sulfite is added at a concentration of 50 to 100 g / l.

Reaktionerne er som følger:The reactions are as follows:

Cr20" + 3 HS03" + 5 H+->. 2 Cr^4 + 3 SO^" + 4 H20Cr20 "+ 3 HS03" + 5 H + ->. 2 Cr ^ 4 + 3 SO ^ „+ 4 H2 O

Cr207~~ + 3 S02 + 2 H+ -K 2 Cr444 + 3 S04" + R20 17,35 g hexavalent chrom, som metal, behøver 63,02 g vandfrit natriumsulfit.Cr207 ~~ + 3 SO2 + 2 H + -K 2 Cr444 + 3 SO4 "+ R20 17.35 g hexavalent chromium, as metal, needs 63.02 g anhydrous sodium sulfite.

I virkeligheden må mængden af reduktionsmiddel forøges med ca. 257« til fuldstændig reduktion af chrom til den trivalente tilstand.In reality, the amount of reducing agent must be increased by approx. 257 «for the complete reduction of chromium to the trivalent state.

Reduktionen kan også udføres på en anden måde,nemlig under anvendelse af ferro-sulfat, og reaktionen er som følger:The reduction can also be carried out in another way, namely using ferro-sulfate, and the reaction is as follows:

Cr20?" + 6 Fe + 14 H -fc. 2 Crm + 6 Fe^ + 7 H20 Ved freffl_ gangsmåden ifølge opfindelsen er zinkforbruget under anvendelse af elektrodeparret C/Zn afhængig af den i den afgivne opløsning indeholdte chrommængde og af pH.Cr20? + 6 Fe + 14 H -fc. 2 Crm + 6 Fe ^ + 7 H20 In the freffl method of the invention, the zinc consumption using the electrode pair C / Zn is dependent on the amount of chromium contained in the delivered solution and on the pH.

Ved et pH på 3 til 3,5 forbruger 17,35 g hexavalent chrom, som metal, 41 g metallisk zink. Forbruget forøges i betydelig grad, når pH bringes ned under 2.At a pH of 3 to 3.5, 17.35 g of hexavalent chromium, like metal, consumes 41 g of metallic zinc. Consumption is significantly increased when the pH is lowered below 2.

Anvender man derimod elektrodeparret Cu, Hg/Fe er jernforbruget til reduktion af 17,35 g chrom til den trivalente tilstand 20 g ved pH-værdier for den afgivne opløsning på 3 eller mindre.By contrast, if the electrode pair Cu, Hg / Fe is used, the iron consumption for reducing 17.35 g of chromium to the trivalent state is 20 g at pH values of the delivered solution of 3 or less.

Indholdet af hexavalent chrom i den afgivne opløsning var mindre end 0,05 ppm.The content of hexavalent chromium in the delivered solution was less than 0.05 ppm.

Eksempel 5Example 5

Under anvendelse af elektrodeparret Cu, Hg/Fg reduceredes hexavalent chrom indeholdt i en koncentreret opløsning af natriumnitrat til trivalent chrom. Affaldsopløsningen indeholdt 30 vægt?« natriumnitrat, og koncentrationen af hexavalent chrom 250 ppm udtrykt som metal. Her anvendtes der 30 g jern til fuldstændig reduktion af 17,35 g hexavalent chrom.Using the electrode pair Cu, Hg / Fg, hexavalent chromium contained in a concentrated solution of sodium nitrate was reduced to trivalent chromium. The waste solution contained 30% by weight sodium nitrate and the concentration of hexavalent chromium 250 ppm expressed as metal. Here, 30 g of iron was used to completely reduce 17.35 g of hexavalent chromium.

Indholdet af hexavalent chrom i den afgivne opløsning var mindre end 0,05 ppm.The content of hexavalent chromium in the delivered solution was less than 0.05 ppm.

Eksempel 6Example 6

Eksemplet angår fjernelsen af kviksølvsalte fra spildevand, der indeholder dette i en mængde på 25 ppm. Under anvendelse af elektrodeparret Cu/Fe bemærkedes det, at kobberkatoden i løbet af forsøget blev amalgameret, mens den afgivne opløsning blev rig på divalent jern. Forbruget af metallisk jern til reduktion af 100,30 g divalens kviksølv var ca. 30 g.The example relates to the removal of mercury salts from wastewater containing this in an amount of 25 ppm. Using the Cu / Fe electrode pair, it was noted that during the experiment, the copper cathode was amalgamated while the dissolved solution became rich in divalent iron. The consumption of metallic iron to reduce 100.30 g of divalent mercury was approx. 30 g.

DK197372A 1971-04-23 1972-04-21 PROCEDURE FOR ELECTROCHEMICAL CLEANING OF WASTE CONTAINING HEAVY METAL COMPOUNDS DK142049C (en)

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IL (1) IL39131A (en)
LU (1) LU65207A1 (en)
NL (1) NL153829B (en)
NO (1) NO139679C (en)
PL (1) PL83655B1 (en)
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SE (1) SE386153B (en)
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DE2430848C2 (en) * 1974-06-27 1986-02-27 Levrini, Valter, Castellarano Process for the chemical purification of waste water
CH649976A5 (en) * 1981-03-05 1985-06-28 Hans Lueber DEVICE FOR LIMESTONE PREVENTION IN WATER TANKS.
US4525254A (en) * 1982-10-07 1985-06-25 Gosudarstvenny Nauchno-Issledovatelsky I Proektny Institut Po Obogascheniju Rud Tsvetnykh Metallov "Kazmekhanobr" Process and apparatus for purifying effluents and liquors
DE10005681B4 (en) * 2000-02-07 2005-06-16 Atc Dr. Mann E.K. Method and device for the decontamination of metal-containing waters
CN115418483B (en) * 2022-08-30 2023-06-30 中南大学 Method for preparing ferrochrome from chromium-containing waste liquid

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DE1459451A1 (en) * 1962-05-29 1968-12-19 Asendorf Dr Erich Process for removing copper from sulfuric acid and nitric acid waste water with simultaneous destruction of water-insoluble copper compounds
AT240059B (en) * 1963-08-02 1965-05-10 Donau Chemie Ag Process for the electrolytic deposition of sulfo-salt-forming metals
US3392102A (en) * 1967-03-16 1968-07-09 Koch Rudolf Galvanic action water purifier

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IE36316B1 (en) 1976-10-13
TR17282A (en) 1975-03-24
RO63778A (en) 1978-10-15
SE386153B (en) 1976-08-02
IL39131A (en) 1975-08-31
BE782358A (en) 1972-08-16
NL7205539A (en) 1972-10-25
GB1376998A (en) 1974-12-11
NO139679B (en) 1979-01-15
NL153829B (en) 1977-07-15
CS178869B2 (en) 1977-10-31
CA1028278A (en) 1978-03-21
YU36674B (en) 1984-08-31
JPS5235945B1 (en) 1977-09-12
AT324969B (en) 1975-09-25
PL83655B1 (en) 1975-12-31
DD96694A5 (en) 1973-04-05
CH539001A (en) 1973-07-15
YU105172A (en) 1982-02-25
HU164830B (en) 1974-04-11
DE2219095A1 (en) 1972-11-16
FR2133922A1 (en) 1972-12-01
NO139679C (en) 1979-04-25
IE36316L (en) 1972-10-23
FI62810C (en) 1983-03-10
FR2133922B1 (en) 1974-10-18
LU65207A1 (en) 1972-07-13
FI62810B (en) 1982-11-30
ES402789A1 (en) 1975-10-16
DK142049C (en) 1981-01-12
IL39131A0 (en) 1972-06-28

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