Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/36—Regeneration of waste pickling liquors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J41/00—Anion exchange; Use of material as anion exchangers; Treatment of material for improving the anion exchange properties
  • B01J41/04—Processes using organic exchangers
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/30—Fluxes or coverings on molten baths

Definitions

• the present invention relates to a purification process for spent pickling baths , preferably based on hydrochloric acid, which have been used for pickling steel articles.
• the .steel In hot dip galvanizing of steel articles, the .steel must be pretreated if the zinc is to adhere.
• This pretreat- ment can for example include the steps of degreasing, pickling, washing, neutralization, flux bath treatment, and thereafter immersion in molten zinc.
• Pickling consists of dipping into a pickling bath which is usually hydro ⁇ chloric acid, but which also can be sulphuric acid.
• the flux bath has a high concentration of zinc chloride and ammonium chloride. When pickling steel articles, the normal starting concentration of hydrochloric acid in the pickling bath is about 10-15 %.
• the bath is contaminated with among other things iron ions and the pickling bath can be said to be spent when its concentra ⁇ tion of Fe is about 80-120 g/1 and when the hydrochloric acid concentration has gone down to about 5-10 %.
• the pickling bath is also unavoidably contaminated with zinc, which comes primarily from unsuccessful galvanizations where the zinc must be removed by pickling before a new galvanization can be attempted (so-called burning-off pickling bath) .
• the pickling bath- is also contaminated by the zinc cloud surrounding the hot dip galvanizing process and from the hooks which convey the articles past the various stations.
• the amount of zinc in a spent pickling bath can be about 1-20 g/1 Zn. in modern day chemical processes it is especially important that the waste solutions produced be able to be reused, encapsuled, incinerated or otherwise prevented from affecting the external invironment.
• the purpose of the present invention is to achieve a simple and inexpensive process for purification of spent, preferably hydrochloric acid based, pickling baths, which gives rise to residual material which can be reused in the process and/or used for other purposes, and which is independent of the amounts of metal ions contaminating the pickling bath.
• the method according to the invention is characterized in that metal ions present in the spent pickling bath in the form of anion complexes are brought in contact with an anion-adsorbing material, which selectively adsorbs one of the metal ion complexes, whereafter the adsorbed metal ion complex is washed out during the formation of a concentrate solution which can be used without further treatment.
• the spent pickling bath is thus primarily contaminated with iron- and zinc ions, and the method according to the invention is primarily directed to the separation of the same.
• the metal ions are present more or less in the form of chloride complexes.
• normal contents in a spent pickling bath are 1-20 g/1 Zn an
• the chloride content of the pickling bath must be about 100-500 g/1 and the hydrochloric acid concentration be about 1-5 ekv.
• the zinc concentration can be very low, e.g. 0.5 g/1 or even 0.1 g/1. Even at these low concentrations, the invention works satisfactorily and from a content of about 0.1 g/1 Zn prior to purification, a content on the order of 0.001 g/1 zinc can be obtained after purification.
• the zinc content in the bath is instead quite high, for 'example about 80 g/1 or sometimes even higher, at the same time as the iron content can be very low, for example, about 20-30 g/1- Even in these cases the process according to the invention works just as satisfactorily, as it does in those cases where the iron content reaches up to 150 g/1 or higher. If the chloride content of the spent pickling bath is not sufficient for th.e complex formation, the chloride content can be adjusted quite easily by the simple addition of HC1.
• the metal ions are present in the form of anion complexes, they can be separated with the aid of an anion adsorbing material, which provides a substantially better selectivity than with the previously mentioned separation by means of cation exchangers.
• anion adsorbing materials which can be used are activated charcoal, molecular sieves and the like.
• the ion exchanger is eluted-or--washed with wate
• the ion concentration is thus diluted and the zinc chlorid complexes disintegrate.
• the wash water carries with it zin chloride and hydrochloric acid at the same time as the ion exchanger is regenerated and again contains chloride ions.
• the ion exchanger is thereby completely restored wit the same activity and mere water.is used as an elution agent, a very inexpensive raw material.
• the hot dip galvanization process comprises a flux step, in which the flux bath has a high concentration of zinc chloride and ammonium chlorid
• the washing liquid can be recirculated directly back to the hot dip galvanizing process.
• this. is achieved by carryin out the washing in steps countercurrent to the normal flow through the ion exchanger. Only limited amounts of water are used, which are kept separate and used so that the volume with the highest degree of contamination washes first, whereby the contaminant content is additionally increased. Thus in each regeneration cycle only a small amount of washing liquid with high zinc content is removed and a small amount of pure water is added. This results in about 10-100 liters washing liquid having a high enough zinc chloride content that it can be directly added to the flux bath, per 1 m spent pickling bath. That this is a major step forward is revealed for example by a comparis
• OMPI used for the production of water purification chemicals, for example.
• Example 1 To illuminate the invention further, several examples are described below, carried out on a laboratory scale.
• Example 1 To illuminate the invention further, several examples are described below, carried out on a laboratory scale.
• 100 ml pickling bath was allowed to flow through a bed containing 20 ml anion exchanger substance.
• the composition of the pickling bath was 147 g/1 Fe, whereof 6 g/1 was Fe , 2.64 g/1 Zn and 42 g/1 HCl.
• the zinc content in the treated pickling bath i.e. that which has flowed through the substance, rose during the test from 0.75 mg/1 after 20 ml to 195 mg/1 after 100 ml.
• the bed was then washed with 100 ml pure water which was allowed to run-through the bed.
• the zinc content in the washing liquid was after 40 ml 50 mg/1 and after 60 ml, 4700 mg/1. 93 % of the added zinc was washed out.
• ther was obtained from 20 liters of pickling bath with 7.3 g/1 Zn, 20 liters purified .pickling bath with 1.6 g/1 Zn and 6 liters washing liquid with 19 g/1 Zn.
• the invention is not limited to hydrochloric acid base pickling baths, but can also be used for sulphuric acid based pickling baths. In that case, however, the entire amount of chloride required for transferring the metal ion to anion complexes must be added.
• the invention is not limited solely to the separation of iron- and zinc ions.
• the pickling bath becomes contaminated with lead for example when wire is to be galvanized, due to the fact that when wire is drawn it is often passed through a bath of molten lead to lubricate the " same. Drops of lead adhering to the wire are then pickled off the wire in the pickling bath. Lead also forms chloride complexes, and through properly balanced conditio can be separated from the iron in the pickling bath.
• the invention should not be regarded as being limited solely to purification of spent pickling baths either. It can of course be used in any situation requiring the separation of metal ions from each other in hydrochloric acid solution.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• General Chemical & Material Sciences (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Detergent Compositions (AREA)
• Cosmetics (AREA)

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• 1979
  • 1979-09-13 SE SE7907619A patent/SE7907619L/xx unknown
• 1980
  • 1980-09-04 WO PCT/SE1980/000220 patent/WO1981000728A1/en not_active Ceased
  • 1980-09-09 FI FI802821A patent/FI802821A7/fi not_active Application Discontinuation
• 1981
  • 1981-03-23 EP EP80901669A patent/EP0035515A1/en not_active Withdrawn
  • 1981-05-11 NO NO811606A patent/NO811606L/no unknown
  • 1981-05-12 DK DK209180A patent/DK209181A/da unknown

Non-Patent Citations (1)

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