The invention relates to a method for pickling steel sheets 8, the steel sheets being continuously dipped in a pickling bath 1, containing a pickling solution 10, the bath being connected to a treatment unit including a recirculation tank 3, circulators 12 and 13, a continuous entering flow 11 of the solution being fed into an ultrafiltration device 2 from the recirculation tank 3 and two flows exiting the ultrafiltration device, one filtered exiting flow 21 being then fed back inside the recirculation tank 3 and one unfiltered flow 22, the treatment unit including no storage tank.

The invention relates to a method for pickling steel sheets 8, the steel sheets being continuously dipped in a pickling bath 1, containing a pickling solution 10, the bath being connected to a treatment unit including a recirculation tank 3, circulators 12 and 13, a continuous entering flow 11 of the solution being fed into an ultrafiltration device 2 from the recirculation tank 3 and two flows exiting the ultrafiltration device, one filtered exiting flow 21 being then fed back inside the recirculation tank 3 and one unfiltered flow 22, the treatment unit including no storage tank.

The present invention relates to a method of purifying waste hydrochloric acid, and more particularly, to a method of purifying waste hydrochloric acid which includes preparing an extraction solution by dissolving an extractant in an organic solvent (S1), extracting metallic components with the organic solvent by adding the extraction solution to the waste hydrochloric acid (S2), separating a waste hydrochloric acid layer and the organic solvent containing the metallic components (S3), and obtaining purified hydrochloric acid by recovering the separated (fractionated) waste hydrochloric acid layer (S4), wherein the extractant is used in an amount of 40 moles or more based on 1 mole of iron (Fe) included in the waste hydrochloric acid, and the waste hydrochloric acid and the extraction solution are mixed in a volume ratio of 1:0.1 to 1:1.

Methods, systems and apparatuses are disclosed for treating aluminum desmutting solutions by reacting, mixing and filtering an aluminum desmutting solution flow from an aluminum desmutting solution tank and controlling the amount of copper ions in an aluminum desmutting solution tank by directing a portion of the desmutting solution from a desmutting solution tank to a treatment line, reacting a portion of the desmutting solution in the treatment line and recirculating a filtered aluminum desmutting solution to the aluminum desmutting solution tank during active desmutting operation of the aluminum desmutting solution tank.

Methods, systems and apparatuses are disclosed for treating aluminum desmutting solutions by reacting, mixing and filtering an aluminum desmutting solution flow from an aluminum desmutting solution tank and controlling the amount of copper ions in an aluminum desmutting solution tank by directing a portion of the desmutting solution from a desmutting solution tank to a treatment line, reacting a portion of the desmutting solution in the treatment line and recirculating a filtered aluminum desmutting solution to the aluminum desmutting solution tank during active desmutting operation of the aluminum desmutting solution tank.

Disclosed is a method of regenerating a nitric and hydrofluoric acid bath contained in a machining vessel, the method including, when the etching bath is spent, performing steps of: transferring a portion of the spent etching bath, referred to as the spent solution, from the machining vessel into a reactor; adding NaF and NaNO.sub.3 to the spent solution, to form HF, HNO.sub.3, and Na.sub.2TiF.sub.6; separating the resulting precipitate from the supernatant; transferring the supernatant, which is a regenerated solution, into a tank; measuring the concentrations of HF, of HNO.sub.3, and of dissolved titanium in the tank and in the machining vessel; and determining the volume of regenerated solution that can be added to the spent etching bath to obtain a regenerated bath in which the concentrations of HF, of HNO.sub.3, and of dissolved titanium lie in acceptable concentration ranges, and transferring the regenerated solution into the machining vessel.

Disclosed is a method of regenerating a nitric and hydrofluoric acid bath contained in a machining vessel, the method including, when the etching bath is spent, performing steps of: transferring a portion of the spent etching bath, referred to as the spent solution, from the machining vessel into a reactor; adding NaF and NaNO.sub.3 to the spent solution, to form HF, HNO.sub.3, and Na.sub.2TiF.sub.6; separating the resulting precipitate from the supernatant; transferring the supernatant, which is a regenerated solution, into a tank; measuring the concentrations of HF, of HNO.sub.3, and of dissolved titanium in the tank and in the machining vessel; and determining the volume of regenerated solution that can be added to the spent etching bath to obtain a regenerated bath in which the concentrations of HF, of HNO.sub.3, and of dissolved titanium lie in acceptable concentration ranges, and transferring the regenerated solution into the machining vessel.

The invention relates to a method for pickling steel sheets 8, the steel sheets being continuously dipped in a pickling bath 1, containing a pickling solution 10, the bath being connected to a treatment unit including a recirculation tank 3, circulators 12 and 13, a continuous entering flow 11 of the solution being fed into an ultrafiltration device 2 from the recirculation tank 3 and two flows exiting the ultrafiltration device, one filtered exiting flow 21 being then fed back inside the recirculation tank 3 and one unfiltered flow 22, the treatment unit including no storage tank.

The invention relates to a method for pickling steel sheets 8, the steel sheets being continuously dipped in a pickling bath 1, containing a pickling solution 10, the bath being connected to a treatment unit including a recirculation tank 3, circulators 12 and 13, a continuous entering flow 11 of the solution being fed into an ultrafiltration device 2 from the recirculation tank 3 and two flows exiting the ultrafiltration device, one filtered exiting flow 21 being then fed back inside the recirculation tank 3 and one unfiltered flow 22, the treatment unit including no storage tank.

The current invention concerns a method for increasing an iron content of a solution by converting low iron containing solutions into highly concentrated ferric chloride solutions by adding iron containing substances. The invention concerns also methods for transporting and storage of said highly concentrated ferric chloride solutions.