Abstract: A reactivation method for an electrolyzer for the production of sodium hydrochlorite and chlorate, equipped with interleaved plates acting as anodes and cathodes, wherein at least the anode plates are provided with foraminous sheets having an electrocatalytic coating and a planar profile, said sheets being applied to the anode plates by means of a multiplicity of connection points.

Abstract: The present invention relates to an improved electrolyzer for the production of sodium hydrochlorite and chlorate, equipped with interleaved plates acting as anodes and cathodes, wherein at least the anode plates are provided with foraminous sheets having an electrocatalytic coating and a planar profile, said sheets being applied to the anode plates by means of a multiplicity of connection points. The invention further discloses a reactivation method for electrolyzers fabricated according to the prior art teachings.

Abstract: Electrolyzer for the electrolysis of a solution of a salt for the production of a solution containing an acid and a solution of a base, said electrolyzer comprising at least one elementary cell divided into three compartments by two cation-exchange membranes, the first of said compartments contains the first of said membranes and a cathode for hydrogen evolution and the production of the base, a central compartment is defined by said cation-exchange membranes and has an inlet for the solution of the salt and has an outlet for the withdrawal of the solution containing the acid, a third compartment contains the second of said cation exchange membranes and an anode, said anode comprises a porous electrocatalytic sheet for hydrogen ionization and a porous rigid current collector, said third compartment further has an inlet for a hydrogen-containing gaseous stream and an outlet for the venting of the rest of gas characterized in that said current collector has a multiplicity of contact points and said porous elect

Abstract: Electrolyzer comprising at least one elementary cell divided into electrolyte compartments by cation-exchange membranes, said compartments are provided with a circuit for feeding electrolytic solutions and a circuit for withdrawing electrolysis products, said cell is equipped with a cathode and a hydrogen-depolarized anode assembly forming a hydrogen gas chamber fed with a hydrogen-containing gaseous stream, characterized in that said assembly comprises a cation-exchange membrane, a porous, flexible electrocatalytic sheet, a porous rigid current collector having a multiplicity of contact points with said electrocatalytic sheet, said membrane, sheet and current collector are held in contact together by means of pressure without bonding.

Abstract: A chlor-alkali diaphragm electrolysis cell comprising pairs of interleaved cathodes (C) and anodes (B), said cathodes having surfaces with openings and are provided with porous corrosion resistant diaphragms, said cell further comprising feed brine inlets and outlets (H, I, L) for the removal of produced chlorine, hydrogen and caustic, said anodes (B) are expanded by internal extenders (F) and have electrode surfaces with openings for releasing produced gaseous chlorine, characterized in that each of said expanded anodes (B) comprises a plurality of pressing means (O,Q) made of corrosion resistant material having elastic properties to maintain the electrode surfaces of the anodes against the diaphragm and said pressing means are longitudinally positioned inside the anodes having very low operating voltages.

Abstract: A process for the electrolytic recovery of metals from solutions containing metal ions and fluorides and/or anionic flurocomplexes in diaphragmless cells wherein the deposition of the metals at the cathodes and the oxygen evolution at the anodes is effected, the improvement comprising the use of insoluble anodes made of sintered powders of doped tin dioxide optionally provided with coating of zirconyl phosphate and metal oxides which prevents the deposition of metal oxides on the anode surface and catalyze the oxygen evolution reaction.

Abstract: In a process of chlor-alkali electrolysis carried out in a diaphragm cells comprising pairs of interleaved anodes and cathodes, the cathodes being provided with openings and coated with a porous diaphragm resistant to corrosion, at least part of the said anodes being provided with hydrodynamic circular to produce circulation of the anodic brine, the cell having inlets for feeding the fresh brine, and outlets for the removal of produced chlorine, hydrogen and caustic, the improvement comprising controlling the oxygen content in the chlorine and chlorate concentration in the caustic independently from the the fresh brine introduced and the concentration of the the brine by adding an aqueous solution of hydrochloric acid to the brine in the anodic compartment of the cell through a distributor positioned over the hydrodynamic circulator.

Abstract: The present invention relates to metal anodes for oxygen evolution from solutions containing fluorides or artionic fluorocomplexes such as tetrafluoroborates and hexafluorosilicates, the anodes having a metal substrate or matrix selected in the group comprising nickel-copper alloys with a copper content in the range of 2.5 and 30% by weight, tungsten or tantalum, niobium or titanium, combinations thereof or alloys of the same with palladium, nickel or yttrium. The anodes further comprise electrocatalytic compounds for oxygen evolution dispersed in the metal matrix. In the case of nickel- copper alloys, useful electrocatalytic compounds are cerium or tin dioxides, with suitable additives, while for tungsten, cobalt added with nickel, iron, copper or palladium may be used.

Abstract: The present invention relates to a device for removing gas-liquid mixtures from electrolysis cells divided into compartments, particularly membrane type cells, without producing pressure fluctuations, wherein each compartment of said cells is characterized in that it is provided with two different ducts for removing the mixture after separation into liquid-rich and gas-rich phases, each duct being connected with its first end to the upper part of the cell, while the other end of the gas-rich phase duct (4) is inserted into the liquid-rich phase duct (3) so that liquid is present only in the portion of the duct comprised between the connection to the cell and the point of inlet of the gas-rich phase. In the subsequent portion the flow consists in the gas-liquid mixture which is forwarded to a gas-disengaging vessel.

Abstract: The present invention discloses a method for identifying defective ion exchange membranes installed in monopolar and/or bipolar electrolyzers for chlor-alkali production. The method of the present invention comprises reducing the electric load of the electrolyzer down to 2 to 10% of the normal load and under these reduced load conditions, a measurement of the single electric current load absorbed by each elementary cell in a monopolar electrolyzer is effected as well as the measurement of the single electric voltage of the elementary cell in the case of bipolar electrolyzers. The method further comprises calculating the deviations of the single current or voltages with respect to average values. All membranes which present values comprised between a determined threshold value are considered as suitable for operation.

Abstract: A dimensionally stable anode for high-speed galvanizing processes comprising a plurality of substantially parallel, foraminous layers, in electrical contact with each other, each layer comprising an inert, electroconductive substrate with an oxygen evolving electrocatalytic coating, characterized in that the current density of each individual layer is substantially the same and does not exceed the value corresponding to the minimum desired lifetime of the anode. The number of layers is sufficient to provide the total current density required for the high-speed galvanizing. The anode further comprises spacers suitable for preventing short-circuits.

Abstract: A method of reducing ferric ions in a sulfuric acid ilmenite leach solution to ferrous ions comprising circulating a sulfuric acid ilmenite leach catholyte solution through the cathodic compartment of an electrolysis cell separated by a fluid-impervious anion exchange membrane from the anodic compartment, circulating a ferrous sulfate anolyte solution through the anodic compartment of the electrolysis cell and impressing an electrolysis current across the cell to reduce the ferric ions in the catholyte to ferrous ions and to oxidize a portion of the ferrous ions to ferric ions in the anolyte to prevent oxygen evolution in the anodic compartment and to an off-peak method of electrolysis operation to reduce energy consumption and to reduce or eliminate ferrous sulfate by-product.

Abstract: Describes an electrochemical process operated at relatively low cathodic current density and high anodic current density, particularly for electrowinning and electrorefining processes using dimensionally stable metal anodes with reduced anodic electrocatalytic surfaces to allow full exploitation of the advantages of insoluble metal anodes, such as lower overvoltages, high current density capability, and purer deposits, together with an economical employment of expensive anode materials. Cathodic/anodic current densityratios down to 1/20 are used without materially decreasing overall process efficiency or product's morphology. Choice of geometric parameters, practical aspects, typical embodiments and examples are disclosed.

Abstract: There is disclosed an electrochemical apparatus including two or more electrochemical cells arranged in series. Each of the cells has at least one particulate electrode and is separated from its adjacent cells by a bipolar member which constitutes a current feeder for at least one particulate electrode. The apparatus is particularly useful in processes for the electrodeposition of metal onto the particles of a particulate cathode.