Electrode for electrochlorination processes and method of manufacturing thereof

Patent metadata

Field	Value
Publication number	US-10287188-B2
Application number	US-201515516161-A
Country	US
Kind code	B2
Filing date	Oct 23, 2015
Priority date	Oct 27, 2014
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

The invention relates to an electrode suitable for electrolytic treatments of dilute solutions of sodium chloride even at low temperatures. The electrode can be used in the generation of active chlorine-based biocidal agents in ballast water for marine applications. The electrode has a titanium substrate, an inner catalytic coating containing oxides of tantalum, ruthenium and iridium, and an outer catalytic coating containing oxides of titanium, ruthenium and of at least one of nickel, iron and cobalt.

First claim

The invention claimed is:

1. An electrode in electrochlorination cells comprising:
a titanium substrate
an inner catalytic coating applied onto said substrate containing a mixture of oxides of tantalum, ruthenium and iridium and
an outer catalytic coating applied on top of said inner catalytic coating containing a mixture of oxides of titanium, ruthenium and of at least one element selected from the group consisting of nickel, iron and cobalt.

2. The electrode according to claim 1 wherein said titanium substrate is characterised by a value of average roughness R a of 4 to 10 μm.

3. The electrode according to claim 1 wherein said inner catalytic coating has a total loading of noble metal expressed as the sum of ruthenium and iridium of 1 to 5 g/m 2 .

4. The electrode according to claim 1 , wherein the weight composition of said outer catalytic coating comprises 30-60% Ru, 35-70% Ti and 1-8% as the sum of Fe, Co and Ni.

5. The electrode according to claim 1 , wherein the weight ratio of ruthenium content in said outer catalytic coating to noble metal content expressed as the sum of ruthenium and iridium in said inner catalytic coating is 3 to 10.

6. A method for the production of an electrode according to claim 1 comprising the following sequential steps:
etching the titanium substrate in an acid solution until imparting a controlled roughness profile;
applying a solution of tantalum, ruthenium and iridium compounds to the etched substrate, with subsequent thermal decomposition at a temperature above 400° C. and formation of an inner catalytic coating; and
applying a solution of compounds of titanium, ruthenium and at least one element selected from the group consisting of nickel, iron and cobalt to the inner catalytic coating, with subsequent thermal decomposition at a temperature above 400° C. and formation of an outer catalytic coating.

7. The method according to claim 6 wherein said acid solution comprises 20-30% by weight sulphuric acid and said etching step is carried out at 80-90° C. until a weight loss of said substrate between 150 and 250 g/m 2 is obtained.

8. A process of biocidal treatment on an aqueous sodium chloride solution comprising electrolyzing the solution in an electrolytic cell equipped with a pair of electrodes according to claim 1 and forming of active chlorine.

9. The process according to claim 8 , further comprising the periodic reversal of the polarity of the electrodes of said pair.

10. The process according to claim 8 in which said aqueous solution of sodium chloride is a ballast water for marine applications.

Assignees

• Industrie De Nora Spa

Inventors

• Iacopetti Luciano
• Calderara Alice

Classifications

• C25B1/26

  Chlorine; Compounds thereof (by simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine C25B1/34) · CPC title

• C02F2103/008

  Originating from marine vessels, ships and boats, e.g. bilge water or ballast water · CPC title

• C02F1/4674 Primary

  with halogen or compound of halogens, e.g. chlorine, bromine · CPC title

• C02F2001/46142

  Catalytic coating · CPC title

• C02F2201/4613

  Inversing polarity · CPC title