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WO2006103713A2 - Utilisation de dechets chromes de tannerie pour l'obtention d'un produit a base d'oxyde de chrome, principalement destine a l'industrie des ceramiques - Google Patents

Utilisation de dechets chromes de tannerie pour l'obtention d'un produit a base d'oxyde de chrome, principalement destine a l'industrie des ceramiques Download PDF

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Publication number
WO2006103713A2
WO2006103713A2 PCT/IT2006/000204 IT2006000204W WO2006103713A2 WO 2006103713 A2 WO2006103713 A2 WO 2006103713A2 IT 2006000204 W IT2006000204 W IT 2006000204W WO 2006103713 A2 WO2006103713 A2 WO 2006103713A2
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WO
WIPO (PCT)
Prior art keywords
solid
washing
chromium
reactive
heating
Prior art date
Application number
PCT/IT2006/000204
Other languages
English (en)
Other versions
WO2006103713A3 (fr
Inventor
Leonardo Regoli
Luca Lemmi
Original Assignee
Leonardo Regoli
Luca Lemmi
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leonardo Regoli, Luca Lemmi filed Critical Leonardo Regoli
Publication of WO2006103713A2 publication Critical patent/WO2006103713A2/fr
Publication of WO2006103713A3 publication Critical patent/WO2006103713A3/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G37/00—Compounds of chromium
    • C01G37/02—Oxides or hydrates thereof
    • C01G37/033—Chromium trioxide; Chromic acid
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/22—Nature of the water, waste water, sewage or sludge to be treated from the processing of animals, e.g. poultry, fish, or parts thereof
    • C02F2103/24—Nature of the water, waste water, sewage or sludge to be treated from the processing of animals, e.g. poultry, fish, or parts thereof from tanneries

Definitions

  • the present invention relates to a new system for obtaining a chromium-oxide based product for use in various industrial sectors, especially but not exclusively the ceramics industry.
  • Chromium-oxide (Cr 2 O 3 ) based products are widely used for the synthesis of dyes and pigments in the ceramics industry, but also and more in general, in the glass industry, in the industry of colorant substances for metal foil and in the refractory materials industry, as well known by any expert in these sectors .
  • chromite a mineral with the chemical formula FeCr 2 O 4 .
  • Various methods for producing chromium oxide are known, the most common being those that pass through the synthesis of sodium chromate and dichromate
  • a process has now been developed for obtaining a chromium-oxide based solid product with optimal characteristics for the synthesis of ceramic dyes and pigments, at extremely reduced prices, and above all with extremely advantageous results from the standpoint of ecology and impact on the environment .
  • a chromium-oxide based product is obtained from chromiferous tanning bath wastes.
  • the advantages resulting from the present invention consist basically in the fact that it is possible to obtain a chromium-oxide based product in solid state, in a simple and economic way, recovering it from tanning waste, without any kind of negative effects, and on the contrary, with the advantage that the above mentioned waste recovery reduces the problems of the disposal thereof in the environment.
  • the waste water to be eliminated will have a chromium content which is lower than the minimum limit normally imposed by the authorities for discharge in sewer systems.
  • the invention provides for the possibility of supplying users of chromium-oxide for ceramic dyes and pigments, with a product having outstanding characteristics.
  • the content of organic matter present in the product obtained does not affect the good result of the inorganic syntheses of ceramic dyes and pigments, because these syntheses occur at temperatures far higher than 600 0 C, temperatures at which organic matter degrades to volatile compounds (mainly water and carbon oxides) ; in other words, to substances that, in practice, remain inert in the synthesis.
  • the syntheses of inorganic pigments are performed in reducing environments to the establishment of which the organic compounds already present in the product may also contribute.
  • the organic content is not necessary, it is possible to remove almost all of it by means of a simple heat treatment consisting in keeping the product at a temperature under 500 0 C for a few seconds.
  • the product obtained with the said method has a granulometry sufficiently fine to permit the product to attain a high reactivity level in the characteristic solid-solid reactions that occur during ceramic pigment and dyes syntheses.
  • the granulometric distribution of the solid is not deemed sufficiently homogeneous for the specific purposes, it will still possible to add a final dry grinding step after drying or possible heat treatment.
  • Another essential aspect is represented by the fact that the metal salt content that may interfere with pigment preparation can be diminished by simple washing with water based solutions of binding and complexant agents used under appropriate reaction conditions. Therefore, it is possible to choose the most suitable purification method according to the final use.
  • the considerations above are applicable also to possible uses of the product in the glass and refractory material industries, and in colorants for metal foils.
  • the process uses chemical reactives not considered toxic or harmful to the environment, and no hexavalent chromium is produced at any stage. From an economical viewpoint this permits the supply of a low cost raw material for the ceramics industry, or for other industrial fields, such as those previously mentioned, with the full elimination of a waste product from the tanning productive cycle.
  • the whole process with the exception of the final heating step (that is in any case optional) , is performed in cold conditions, thus providing considerable energy saving during the processing stage.
  • the possible heating treatment given the temperatures involved and above all the short time the products are exposed to said temperatures, cannot have a significant influence on the economical aspects of the process.
  • the chemical products used in the process are easily and cheaply available on the market .
  • the industrial plant for the preparation of the final product is composed of simple, easily accessible modules.
  • FIG. 1 shows a layout scheme of a plant for carrying out a method according to the invention. Description of a preferred embodiment
  • the chromium contained in the wastes derived from chromiferous tanning baths used in the tanning industry is recovered and made suitable as a raw material to be used mainly for the synthesis of chromium-oxide based ceramic pigments and dyes.
  • This product can also be used as a raw material in glass industry, the industry of colorants for metal foils and in the refractory materials industry.
  • the industrial waste (staring point of the process) has a composition that is not constant. Consequently, the specific operating conditions for the recovery process will be subject to slight variations, due to the nature of the waste processed, or the type of tanning process in question. Then, the reaction parameters (pH and concentrations) will be indicated in the form of ranges, and not with a single exact value, in order to take into consideration the nature of the treated waste.
  • the final reaction conditions in the industrial application of the invention will reasonably not be very distant from a given average value. Said average value will be subject to slight changes over a period of time, due to the different leather articles treated in the tanning process that originates the waste, or due to changes in the productive processes applied in the reference district.
  • a complex system can be found, composed mainly of trivalent chromium hydroxides and sulphates, coordinated to organic ⁇ molecules (proteins from leathers, sugars and agents used in tanning processes as masking agents, and water) .
  • the average chromium content is about 40 g/1 in equivalent Cr 2 O 3 .
  • the waste from chromium tanning or pre- tanning processing in the tanning industry is treated initially with a precipitant reactive, more precisely a basifying solution for bringing the pH to a value between 6.8 and 7.8, under agitation.
  • a precipitant reactive more precisely a basifying solution for bringing the pH to a value between 6.8 and 7.8, under agitation.
  • the nature of the basifying agent can vary according to the reaction conditions and/or the economy of the process. In any case the choice should be directed to minimizing the metallic impurities present in the final product.
  • the concentration of the basifying agent can be appropriately chosen according to the volumes of the liquid fraction that is required: the greater the concentration, the lesser the liquid volume obtained although with increasing difficulty in the handling of more concentrated base solutions.
  • the separation of the solid from the liquid can be performed using any method suitable for the process : decanting, filtering, centrifuge, filter pressing, etc.
  • the more effective is the technique the greater is the amount of recovered product, and therefore the lower is chromium content in the liquid fraction to be discharged.
  • suitable solutions of chelating or complexant agents used in the appropriate reaction conditions for example ambi- or multident complexant reactives, EDTA solutions buffered at suitable pH
  • EDTA solutions will remove most of the metal salts present (such as sodium, calcium, potassium, iron, aluminum, manganese, magnesium and zinc sulphates or hydroxides, etc.) or any organic matter.
  • washing should be performed depends on the subsequent process that the recovered chromium must undergo, by establishing an economic balance between the advantages of the purification and the cost of the process. On the other hand, even with the use of simple water there will be a reduction, though a very slight one, in the salts inside the solid produced.
  • This treatment step should be envisaged only when the granulometric distribution requires a determined homogeneity, or when the average size of the particles needs to be especially fine for particular applications.
  • the following is a treatment formula exemplifying the process, with the relevant resulting data.
  • an aqueous solution of sodium hydroxide at 30% as a basifying agent in the amount of 23 ml for each liter of tanning bath waste (in order to obtain the complete liquid/solid separation) an amount of about 35 grams of dry solid product is obtained for each liter of tanning bath waste.
  • the concentration of the residual chromium in the waste is approximately 0.2 mg/liter.
  • an aqueous washing solution is obtained with a chromium concentration equal to 1.1 mg/liter, and an amount of dry solid product is obtained equal to 57% in relation to the starting amount subjected to the washing process.
  • the following data are obtained after a washing treatment using water only (50 ml of water per gram of dry solid) .
  • the aqueous washing solution will have a chromium concentration of 0.9 mg/liter, producing an amount of dry solid product equal to 60% of the initial amount subjected to washing.
  • Sodium hydroxide represents the cheapest basifying agent and also the easiest to use in these specific conditions.
  • the reactive precipitants can also generally include other alkaline hydroxides or earth alkalines and magnesium oxide, adapting the reaction conditions to the reactive used.
  • a plant for carrying out the invention can be made up according to a very simple layout, that is also quite versatile depending on the amount of waste to be processed and on the type of product that is to be obtained.
  • a storage tank 2 for the waste 1 coming from the tanning plant that can be discharged into a basin 3 equipped with a feeding device 4 for the addition of the reactive precipitant solution.
  • the basin 3 is provided with an agitating system (not shown) and an internal pH control system 5 for assisting and controlling the formation of the solid chromium hydroxide.
  • the basin 3 can be emptied using a pump if the product (pumpable solid) is passed through a filter, filter press or centrifuge 8. Alternatively, a liquid pump can be sufficient to extract the surplus liquid in cases where the solid washing action is performed in the same precipitation basin 3.
  • the subsequent washing step can be carried out in a second basin 6 according to installation choices, (depending on the amounts to be processed and the efficiency required in the installation) .
  • This washing step can also be carried out in the first basin 3, thereby, in practice, the whole group included within the square in dotted lines, indicated at "A", can be replaced by a single basin with appropriate feeding and control means .
  • the second basin 6, also equipped with a mechanical agitating device, is fed with washing liquid stored in an adjacent tank 7.
  • the second basin 6 must be equipped with a pump for the successive transfer of the pumpable solid to the aforesaid filter, filter press or centrifuge 8.
  • the solid obtained on exit from the filtration unit 8 already possesses the characteristics necessary to be employed as a raw material for the applications envisaged above. If necessary, in order to optimize the transport costs of the product, a drying or desiccation unit 9 can be positioned directly at the exit of the plant to completely eliminate the water contained in the solid.
  • the drying unit 9 can be equipped with a forced ventilation system or an oven able to attain temperatures up to 100 0 C.
  • a further module can be added to heat the material to at least 600° C (this system can be realized simultaneously and in the same device envisaged for the drying action, by adopting a more powerful heating system) .
  • the further addition of a unit for dry-grinding the product (not shown) will provide a material with a more homogeneous granulometry .
  • the filtration can be performed by a single unit 8 for both the solid/liquid separation steps (the first after precipitation, and the second after the washing action) , or two separate filter sub-units can be installed.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Processing Of Solid Wastes (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Treatment And Processing Of Natural Fur Or Leather (AREA)
  • Glass Compositions (AREA)

Abstract

La présente invention concerne l'utilisation des déchets des bains de tannerie pour l'obtention d'un produit à base d'oxyde de chrome destiné à d'autres domaines industriels, et en particulier au domaine des céramiques, des matériaux réfractaires, et à l'utilisation sous forme pigmentaire pour le verre et des colorants pour tôles de métal. A cette fin, il est possible d'utiliser un traitement par lequel la précipitation d'un solide est induite au moyen d'un précipitant réactif, le traitement comprenant en outre les opérations de séparation solide/liquides, de lavage, de nouveau de séparation solide/liquide, et d'une action de séchage. Si nécessaire, le solide peut également être chauffé pour séparer les impuretés organiques résiduelles.
PCT/IT2006/000204 2005-04-01 2006-03-30 Utilisation de dechets chromes de tannerie pour l'obtention d'un produit a base d'oxyde de chrome, principalement destine a l'industrie des ceramiques WO2006103713A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITPI20050035 ITPI20050035A1 (it) 2005-04-01 2005-04-01 Procedimento per la sintesi di un concentrato in ossido di cromo ottenuto da reflui di bagni di concia al cromo ed utilizzabile principalmente come materia prima nell' industria ceramica
ITPI2005A000035 2005-04-01

Publications (2)

Publication Number Publication Date
WO2006103713A2 true WO2006103713A2 (fr) 2006-10-05
WO2006103713A3 WO2006103713A3 (fr) 2006-12-07

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PCT/IT2006/000204 WO2006103713A2 (fr) 2005-04-01 2006-03-30 Utilisation de dechets chromes de tannerie pour l'obtention d'un produit a base d'oxyde de chrome, principalement destine a l'industrie des ceramiques

Country Status (2)

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IT (1) ITPI20050035A1 (fr)
WO (1) WO2006103713A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014199193A1 (fr) 2013-06-10 2014-12-18 Trivalent Chrome Cc Production d'oxyde de chrome

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE426081C (de) * 1922-10-19 1926-03-05 Georges Croulard Verfahren zur Wiedergewinnung des Chroms aus chromat- oder bichromathaltigen Abwaessern oder Laugen
US2110187A (en) * 1933-08-23 1938-03-08 Dudley A Willams Method of treating chrome liquors
US4108596A (en) * 1975-07-11 1978-08-22 Revere Copper And Brass, Incorporated Recovery of chromium values from waste streams by the use of alkaline magnesium compounds
US4401573A (en) * 1980-05-12 1983-08-30 Luigi Stoppani S.P.A. Continuous process for the removal of chromium from waste waters and valorization of the recovered chromium
US4569830A (en) * 1982-12-30 1986-02-11 Giovanni Tibaldi Method and plant to recover chromium salts from tannery reflux water

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE426081C (de) * 1922-10-19 1926-03-05 Georges Croulard Verfahren zur Wiedergewinnung des Chroms aus chromat- oder bichromathaltigen Abwaessern oder Laugen
US2110187A (en) * 1933-08-23 1938-03-08 Dudley A Willams Method of treating chrome liquors
US4108596A (en) * 1975-07-11 1978-08-22 Revere Copper And Brass, Incorporated Recovery of chromium values from waste streams by the use of alkaline magnesium compounds
US4401573A (en) * 1980-05-12 1983-08-30 Luigi Stoppani S.P.A. Continuous process for the removal of chromium from waste waters and valorization of the recovered chromium
US4569830A (en) * 1982-12-30 1986-02-11 Giovanni Tibaldi Method and plant to recover chromium salts from tannery reflux water

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014199193A1 (fr) 2013-06-10 2014-12-18 Trivalent Chrome Cc Production d'oxyde de chrome

Also Published As

Publication number Publication date
ITPI20050035A1 (it) 2006-10-02
WO2006103713A3 (fr) 2006-12-07

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