Pickling acids used

The degree of pickle, ie, the amount and type of acid used, depends on the type of hides or skins and the taimage to be used. The pickle is in preparation for tanning and the chemistry of the subsequent taimage determines the pickle method. 

The speed of the pickle reaction is also dependent on the concentration and temperature of the pickle, the degree of agitation of either the metal part or the pickle solution, the alloy being pickled, and the acid used. Pickling solutions may be appHed by either spray or immersion techniques. However, because of the noxious fumes emitted, there must be adequate ventilation. Sometimes, particularly when spraying techniques are used, an enclosure to contain the fumes and mist is employed. 

Acid Dips and Acid Pickles. Acids are used to remove inorganic soils. A distinction is made between acid dips and acid pickels. Where there is no mst or scales, a dilute acid dip is used for activation and as a rinse aid. Caustic residues from cleaners are notoriously difficult to remove with water rinsing alone. By contrast, strong acid pickles are used to remove mst and scale. 

Use closed-loop systems for pickling regenerate and recover acids from spent pickling liquor using resin bed, retorting, or other regeneration methods such as vacuum crystallization of sulfuric acid baths. 

As further confirmation of this Rozenfeld has reviewed Russian work on this subject and reports that in pickling with sulphuric acid the amount of acid used in scale dissolution is only about one-tenth that consumed by the dissolution (corrosion) of the underlying metal. However, in hydrochloric acid the direct scale dissolution occurs to a much greater degree, and is responsible for about 40% of the acid consumption. 

Pickle, Pickling a solution (usually acidic) used to remove or loosen corrosion products from the surface of a metal. 

Acid Pickling Tanks Using Hydrochloric Acid. 1202... 

MANAGEMENT AND TREATMENT OF WASTEWATER AND AIR EMISSIONS FROM ACID PICKLING TANKS USING HYDROCHLORIC ACID... 

AQUATECH Systems first commercial application is recycling waste HF/HNO- steel pickling acid as shown in Figure 7 above. As described earlier, the acid is neutralized with KOH to pH 10-11, filtered and sent to the AQUATECH cellstack for regeneration. The KF/KNO, mixed salt produces an HF/HNO, mixed acid suitable for stainless steel pickling Jand an equivalent amount of KOH used to neutralize the next batch of waste acid. The water balance is maintained by conventional electrodialysis which rejects excess water from the KF/KNO salt. This water is... 

The two water desalination applications described above represent the majority of the market for electrodialysis separation systems. A small application exists in softening water, and recently a market has grown in the food industry to desalt whey and to remove tannic acid from wine and citric acid from fruit juice. A number of other applications exist in wastewater treatment, particularly regeneration of waste acids used in metal pickling operations and removal of heavy metals from electroplating rinse waters [11]. These applications rely on the ability of electrodialysis membranes to separate electrolytes from nonelectrolytes and to separate multivalent from univalent ions. 

Bipolar membrane synthesis also holds promise for regenerating spent pickling liquors in stainless steel manufacture. As shown in Fig. 43(b), waste acid laden with metal ions can be continuously neutralized, filtered to remove the precipitated metal oxide, and the clarified salt solution split into its acid and base components in a bipolar membrane unit [Type (IV) shown in Table IX], As much as 95% of the hydrofluoric and nitric acid used are returned to the pickling bath, thereby solving a waste... 

Method 3 Preparation of chloroform from Rubbing alcohol, potassium dichromate, pickling salt, and dilute sulfuric acid using an electrochemical cell... 

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