GB2409684A - Method of production of a biocidal liquid medium - Google Patents

Abstract

A process for the preparation of a liquid biocidal medium is defined. The feed liquid, a solution of an alkali metal halide, is electrolysed. The electrolyser 10 comprises; respective anode and cathode chambers 14, 12 each with at least one electrode, said anode and cathode chambers 14, 12 being separated by an ion-permeable membrane 16. The feed liquid is heated to a temperature in the range from 30-60{C before it enters the electrolyser 10 and a direct current of 2-55A is passed though the electrolyser 10 producing a liquid biocidal medium, which is drawn off from at least one of said chambers. The feed liquid can be treated by subjecting it to radio waves in the range 50-500 Hz and may also be post treated through contact with a charged metallic catalyst to remove hydrogen.

Description

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LIQUID MEDIUM, ITS USE AND METHODS FOR ITS PRODUCTION The present invention relates to methods for production by electrolysis of liquid media which have long lasting broad spectrum biocidal properties, to the liquid media and to s their use as biocidal liquids and incorporation in medical wipes. Sterilizing liquids of the type to which the invention relates are often referred to as electrolysed brine or superoxidised water. One aim of the invention is to produce sterilising liquids having a storage life significantly longer than generic liquids made by similar processes. The known generic electrolysed brine liquids made for safe biocidal applications have to be generated on site and last only a few days. The liquids of the present invention have the very powerful sporicidal properties evident for years.

Electro-chemical cells and processes using them for the electrolysis of brine and the like have been around for about 100 years and many types of cells exist. This technology was developed in the 1930's by Austrians and Germans and further work to develop a harmless sporicidal solution for treating components of satellites prior to launch was carried out in Russia as part of its space programme.

There is a need for powerful cold sterilization products which are ecoand human- friendly but which have effective long lasting, biocidal properties with good storage characteristics.

A number of patents exist which cover similar technology and liquids but none of these produce liquid media which have long shelf lives and which can be stored in suitable containers rather than being produced on-site and on demand.

For example W 098/13304 describes a process in which the flow configuration is such that the liquid being electrolysed flows from a cathode chamber at least partly to an Is anode. The process described and liquids produced are different from those of the present inventions and produce liquids with poorer storage stabilities and poorer performance as biocides.

According to the present invention there is provided a process for the preparation of a liquid medium with biocidal properties in which a feed liquid is passed through an electrolyser unit that has at least two electrodes, one of which is an anode and one of which is a cathode each in its own chamber, and applying an electric current to the electrodes, characterized in that the feed liquid is caused to flow into the anode chamber and the liquid medium is created at and collected from the anode chamber or that at least a part of the feed liquid is caused to flow from the anode chamber to the cathode chamber and the liquid medium is collected from the cathode chamber.

According to a further feature of the present invention there is provided a variety of apparatus for preparation of a liquid medium by the process with biocidal properties in which a feed liquid is passed through an electrolyser that has at least two electrodes, which can be plumbed to achieve different flow configurations giving rise to anolytes of varying properties in terms of biocidal strength and longevity. Electrolysers with flat or cylindrical electrodes can be used. The liquid medium produced is a safe, non-toxic, fast-acting, environmentally friendly, broad spectrum biocide effective on a wide range lo of micro organisms including bacteria, fungi, yeasts, moulds, bacterial spores and viruses and which may be used at room temperature in sterilization, disinfection, and big-film removal applications. The biocidal properties of liquid media produced by the present process compare favourably with the performance of materials already used as biocides such as glutaraldehyde, peracetic acid and chlorine dioxide but do not have the disadvantages associated with these materials such as handling and disposal problems.

The feed liquid used in the process is water or comprises water and an alkali metal halide, preferably sodium chloride or potassium chloride and preferably of high purity.

The solution preferably has a conductivity of 5 to 15 pS.

The Electrolytic Cell can produce various biocidal liquids, depending on the electrical power supply, the current drawn, brine feed and flow pattern convention.

In the cathode chamber, the following reactions are thought to take place: 2H2O+2e=H2+20H 2H3O+2e=H3+2H202 In the anode chamber, the following reactions are thought to take place: 2ce=ce2+2e 3H20=/2O2+2H30-+2e 2OH=/202+H20+2e and the formation of active chlorine: c e2+H2O+Hc Lo HCtO+ H++C to as well the formation of hypochlorite, as minor by-product: HC CO+ NaOH=NaC tO+H2O l The electrolyser comprises at least one anode and at least one cathode, each in its own chamber. The chambers are separated by a membrane which may be fabricated from any suitable material which will allow ions to pass through it. The membranes are preferably selected from a rigid ceramic or a flexible polymeric material. Preferred ceramic membranes include metal oxides more preferably aluminium oxide. The ceramic membranes are preferably from I to 2 mm thick. Preferred polymeric materials include fluoropolymers, more preferably polytetrafluoroethylene (PTFE) and perfluorinated polymers that contain small proportions of sulphonic or carboxylic ionic functional groups, especially NAFION perfluorinated polymers (NAFION is a trade mark of lo DuPont Corporation) such as NAFION 810. The flexible polymeric membrane material is preferably from 25 to 500 Em thick.

The preferred family of ceramics are semi permeable membranes are made from Alumina particles of 3 to 5 Em [ 85% w/w] with Zirconium Dioxide 0.3 - to 0.8 micron [15%] made as a slip and fired in sheet or cylindrical form. This has the mechanical strength and at 2 mm thickness is an effective membrane for this electrolytic process.

The electrolyser may be of any suitable shape such as a cylinder, disc or flat plate.

Where the electrolyser is cylindrical the electrodes are preferably cylindrical tubes with one electrode having a larger internal and external diameter than the other, the smaller electrode arranged to be placed, essentially coaxially, within the inner bore of the larger electrode with a suitable membrane, which is also a cylindrical tube, placed between the electrodes. The spaces between the cylindrical electrodes and the membrane form the electrode chambers. Spacers typically produce distances of between 5 and 12 mm between electrodes.

2s Where the electrolyser is a flat plate assembly it preferably comprises at least a membrane to separate the electrode chambers, at least one anode and at least one cathode each electrode being within or forming part of an electrode chamber. The flat plate electrolyser may further comprise spacers which can be used in various thicknesses to vary the volume of the electrode chambers.

Optionally flow baffles may be formed within the electrode chamber of any of the above electrolysers for creating a turbulent flow pattern.

The electrolysers may be used singly, or used in combinations with flows of feed liquid passing into the electrolysers either in series or in parallel.

The electrodes used in the above electrolysers may be made of any suitable material which is capable of conducting a current applied to the electrodes. The electrode materials include metals or alloys, particularly those which are resistant to oxidation or corrosion or those which have coatings which are resistant to oxidation or corrosion.

Preferred electrode materials include those with a titanium substrate which are coated with metals, metal oxides or alloys which are resistant to oxidation or corrosion, preferred coatings include Noble metal or metal oxide coatings particularly nickel, Iridium [IrO2 Ir203] palladium [PdO2, PdO] ruthenium [Ru2O] rhodium [RhO2] and platinum. Platinum/ruthenium coatings are particularly suitable as are coatings of finely lo divided platinum such as platinum black. It is preferred that the titanium substrate is of high purity. Makers of anode materials in the USA and in the UK make a number of proprietary brands which can be used to make the electrolysers. These materials used in the correct electrical convention and with the appropriate size and shape should preferably be able to draw up to 0.5 amps per square cm [when both electrode surface s areas are taken into account]without damaging the coating in order to create the range of liquids efficacious to a range of applications.

The electrolysers have a useful lifetime typically of up to five years. They have the advantage that they are recyclable for recovery of the metal from the electrodes.

The El-Tech Corporation in the US and ETB in Runcorn UK both make suitable proprietary electrodes.

In the process of the invention the potential applied between the electrodes causes ion exchange across the membrane, creating a cocktail of chemicals which combine to form the product liquid.

The liquid media produced by the present process have properties which are dependent on a number of factors such as the pipe-work configuration, power absorbed, electrode coating material and physical size, shape and spacing of the electrodes. The membrane material is also an important feature since it affects to mobility of ions passing between the electrodes.

The process is operated by applying a DC current across the electrodes, preferably a full wave rectified DC current. A steady current is applied to the electrodes, and may be adjusted based on the saline content of the liquid feed.

The process is preferably operated at temperatures below 55 C which gives a good cell lifetime. Preferred temperatures are from 25 C to 45 C, more preferably from 30 C to 40 C, and especially from 34 C to 39 C.

The conductivity of the feed liquid is preferably from 0.3 to 13 pS.

A current from 2 to 50 amps flows through the electrolyser, preferably at least 20 amps and more preferably at least 30 amps flows through a low voltage electrolyser. The current is preferably a clean spike-free half or full wave rectified DC current. For a high voltage electrolyser a current of at least 50 amps preferably flows through the electrolyser. The power consumed per unit size of electrode has a bearing on the lo properties of the product. High volts may need low amps and visa versa, the number of watts absorbed is important and this is preferably in the range 40 to 1800 watts depending on electrode design.

The liquid media produced by the present process can maintain their positive redox potential and their biocidal properties for up to 2 years.

The present process uses untreated towns water as part of the liquid feed to the electrolyser and this does not require any pre-treatment to remove hard salts. This is an advantage over other available electrolysers where a pre-treatment is needed.

The present process uses a stock brine solution typically containing up to 20%w/v sodium chloride. This is 70 % saturated brine and is the most stable concentration.

The stock brine solution is diluted with towns water, to give the liquid feed, before feeding the liquid feed to the electrolyser. The dilution of the stock brine solution may be conveniently achieved by mixing in a mixing column which may optionally be packed with an inert support, such as plastics rings to promote good mixing of the stock brine solution and the towns water. The liquid feed preferably comprises up to 26%w/v sodium chloride, more preferably up to 20%w/v sodium chloride.

The flow rate of feed liquor through the electrolyser is typically in a range of 30 to 500 1/h, depending on the size of the cell.

The process may optionally include a means of pre-treating the feed liquid to prevent any hard salts from caking or scaling within the pipework feeding the feed liquid into the electrolyser. A preferred means of pre-treating the feed liquid is via a low band frequency radio wave transmitter which is placed on the feed line to the electrolyser and/or between electrolysers positioned in series. This prevents/minimises salt caking and deposition within the feed lines and on the electrode surfaces. The transmitter works on the principle of induction through the feed line walls via aerials which are wound around the feed lines in both clockwise and anticlockwise directions. The frequencies that the transmitter operates at can be from 50 to 500 hertz, preferably dwelling from X? to 500 hertz.

Where at least a part of the feed liquid is caused to flow from the anode chamber to the cathode chamber the flow may be regulated by a flow control means, such as a valve.

In a further feature of the present process an in-line heater may advantageously be included to warm the feed liquid before it enters the electrolyser. The performance of the electrolyser is improved if the feed liquid temperature is from 30 C to 60 C, 0 preferably from 30 C to 40 C. Where the feed liquid is warmed the ions in the feed liquid have greater mobility and passage across the membrane is promoted. The salt levels in the liquid feed can be lowered with no detriment to the current drawn through the electrolyser, less energy is consumed and lower salt residues are obtained in the liquid medium.

The liquid medium produced by the process may optionally undergo one or more post treatments.

One post-treatment disengages gases such as hydrogen, oxygen, ozone and chlorine which are produced in the process. This post-treatment may be conveniently achieved by passing the liquid medium through a column, typically made of glass or plastics material which is packed with an inert support, such as plastics rings.

A further post-treatment removes hydrogen from the liquid medium; this post-treatment has advantages where hydrogen cannot be vented to atmosphere. The liquid medium is contacted with a charged metallic catalyst, preferably a catalytic wire, typically a platinum wire. This is conveniently carried out in a column through which the liquid medium is passed. The column may further contain an activated or absorbent material such as charcoal.

A further post-treatment incorporates a surfactant dose device via which a surfactant, preferably a non-ionic low foaming surfactant, can be added to the liquid medium, preferably to the liquid medium produced at the anode. The surfactant is preferably dosed at a ratio of from 500 to 1000, preferably from 700 to 1000 parts of liquid medium to 1 part of surfactant. A liquid medium which further comprises a surfactant has the advantage that it's long lasting broad spectrum biocidal properties, particularly its sporicidal properties, are effective in the presence of organic materials such as fats, oils and greases.

The electrolysers used in the present process are generally low maintenance but where deposits and surface contamination build up for example on the electrode surface these s may be removed easily by reversing the polarity of the electrolyser.

The electrolysers further comprise an outer body. The outer body, particularly for electrolysers of the flat plate design are constructed using an outer body of a corrosion resistant material, typically a plastics material such as polymethyl methacrylate, e.g. Perspex (Perspex is a trade mark of Lucite International UK Limited) which has the lo advantage of being transparent and allows the electrode surfaces to be inspected without disassembling the electrolyser. The components of the electrolysers are bonded together with proprietary resins and/or polymer sealants which has the advantage that no complex gaskets are required and the electrolysers can be assembled relatively easily and without problems arising from leaks. Where multiple electrolysers are used in combination these Is are generally supported and held together generally with stainless steel nuts and bolts, these do not contribute significantly to the mechanical sealing characteristics of the electrolyser.

Where the feed liquid is passed through the anode chamber of the electrolyser and the liquid medium is created at and collected from the anode this liquid medium is hereinafter referred to as acid anolyte (AA).

Where the feed liquid is brine and this is passed through the anode chamber of the electrolyser and at least a part of the feed liquid is caused to flow from the anode chamber to the cathode chamber and the liquid medium is collected from the cathode chamber this liquid medium is hereinafter referred to as anolyte neutral catholyte (ANK 2s or ANC used as abbreviations herein to describe the same liquid media).

ANK is particularly suitable as a disinfectant for endoscope reprocessing, and for use in disinfecting wipes and sprays.

The AA liquid medium is acidic, with a pH typically in the range from pH 2.3 to 6.4 This has a total chlorine content of 50 to 1200ppm, typically from 700 pm to 1000 pm, and a log 6 sporicidal kill in less than I minute.

The ANK liquid medium is essentially pH neutral, with a pH typically in the range from pH 7.5 to 9.0, with a redox potential of +680 to +790mV, and a total active chlorine content typically from 200 ppm to 700 ppm.

A blend (ANB) liquid medium is generated by blending AA with neutral anolyte ANK giving a formulation of high redox and neutral pH. The AND liquid medium is essentially pH neutral, with a pH typically in the range from pH 6.5 to 7.5. This has a total chlorine content typically from 200 ppm to 800 ppm, and a log 6 sporicidal kill in about 10 minutes.

In the liquid medium from the anode chamber the products include hypochloric acid in a complex with oxygen compounds of active chlorine (hypochlorite ions, hypochloric acid, chlorine monoxide), and the basic gases produced during electrolysis (chlorine, oxygen and ozone).

In In the liquid medium from the cathode chamber the products include peroxides, elementary hydrogen and hydroxides of alkaline metals.

In a further feature of the present invention the process is characterized in that the feed liquid is caused to flow into the anode chamber of a first electrolyser and the liquid medium is created at the anode chamber of the first electrolyser is caused to flow into the IS anode chamber of a second electrolyser and collected from the anode of the second electrolyser.

In a further feature of the present invention the process is characterized in that the feed liquid is caused to flow into the anode chamber of a first electrolyser and at least part of the feed liquid is caused to flow from the anode chamber to the cathode chamber the liquid medium is created at the anode chamber of the first electrolyser is caused to flow into the anode chamber of a second electrolyser and collected from the anode of the second electrolyser.

A process and apparatus in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic cross-section through an electrolyser suitable for use in the process according to a first embodiment of the invention, showing flow paths into and out of the anode and cathode chambers; Figure 2 is a diagrammatic cross-section through an electrolyser suitable for use in the process according to a second embodiment of the invention, showing a flow path from anode chamber to cathode chamber; Figure 3 illustrates, with additional detail, the electrolyser of Figure 2 with the flow reversed; Figure 4 is a part- exploded side view of an electrolyser; Figure 5 is a schematic showing fluid flow through the assembled electrolyser of Figure 4; Figures 6a, 6b and 6c illustrate individual components of the assembly of Figures 4 and 5; and Figure 7 is a schematic flow diagram showing an electrolyser system.

Referring to the drawings, Figure 1 shows schematically an electrolytic cell generally indicated by 10, comprising a cathode compartment 12 and download compartment 13, separated by an ion-permeable membrane 16.

The anode and cathode chambers have respective inlets 18 and 15 at their lower ends for lo the feed liquid, which usually comprises brine. At its upper end, the cathode chamber has an outlet 17 for the catholyte product, referred to as caustic catholyte (CC). The anode chamber has an outlet 19 at its upper end for the electrolysis product from that chamber, which is referred to as acid anolyte (AA). The application of a direct electric current to the cell thus provides two separate electrolysis products.

The electrolytic cell of Figure 2 is similar to that of Figure 1, except that the outlet 25 from the anode chamber is collected by a line 26 to the inlet 22 to the cathode chamber.

The cell operated as in Figure 2 thus has a single feed solution which passes in turn through both the anode compartment and the cathode compartment, producing an anolyte from outlet 24 referred to as anolyte neutral catholyte (ANC) or Suprox ANK, the composition and properties of which will be described in more detail below.

The arrangement of Figure 3 is similar to that of Figure 2, except that the flow is reversed so that the feed liquid is fed into the inlet 31 of the cathode chamber 32, and after leaving the cathode compartment by the outlet 33, is split into two streams. The first stream goes directly to a product outlet line 35 whereas the second stream goes via a valve 36 to the inlet 38 of the anolyte compartment 34. The output from this compartment passes from the outlet 39 of the anolyte compartment, via a valve 37 to the product outlet line 35. The outlet from the system of Figure 3 thus comprises a blend of solutions, known as catholyte neutral anolyte (CAN), or Suprox B. the B standing for "Blend".

Figure 4 illustrates the components of an electrolytic cell as might be used in the apparatus of Figures 1 to 3. The cell in this case is a flat plate electrolyser, comprising a cathode chamber and an anode chamber, separated by an ion-permeable membrane 50.

On the left hand side of Figure 4 there is shown an outer plate 42, which is fitted with an inlet connection 43 and an outlet connection 41.

Figure 6a shows the outer plate 42 rotated through 90 , and shows on the inwardly facing surface of the plate a series of flow baffles 60 intended to increase the dwell time of the s liquid passing through the cell from inlet 43 to outlet 41. As can also be seen in Figure 6a, the outer plate 42 is of rectangular shape, and has around its inner periphery a rectangular spacer 44.

On the opposite side of the cell is a second outer plate 57, the shape and configuration of which is essentially the same as that of outer plate 42.

0 The inlet and outlet fitting may be of the type supplied by John Guest International Limited. The inlet fittings each comprise an inward projection 58, to convey the feed liquid to the inner part of the respective electrode chamber nearest the membrane.

The gasket 44 on the outer plate 42 bears against the periphery of a primary cathode 45, which has a spacer 46, 47 on each side, the spacer 46 fitting within the spacer 44. The spacers may be made of any suitable gasket material to form water-tight seals.

The electrode 45 is also shown in Figure 6b, rotated through 90 . Here it can be seen that the anode has a lower aperture 62 for passage of the projection from inlet 43, and a set of smaller apertures 63 at its upper end to allow circulation of the liquid within the cathode chamber.

The spacer 47 bears against an outwardly facing surface of a secondary cathode 48, and is rounded by a peripheral spacer 49 on the secondary cathode. The inner part of the anode chamber is defined within these two spacers.

Secondary cathode 48 bears directly against the membrane 50 and, as can be seen in Figure 6c, has a series of six larger apertures 64, with pairs of smaller apertures 66 in 2s between, to allow the catholyte access to the membrane whereby ion transfer can take place across the membrane during electrolysis.

On the opposite side of the membrane is a secondary anode 52, with apertures similar to those shown in Figure tic.

The membrane, secondary anode and secondary cathode 48, 52 and spacers 49, 53 can be constructed as a prefabricated module which can be assembled together with four other modules as shown in Figure 4. Thus, there is a primary anode module comprising the primary anode 54 with rectangular peripheral spacers 55, 56 on each side of it. The primary anode 45 is also assembled in a similar module with its respective spacers 46, 47. Finally, the outer plate 57 is assembled with its John Guest fittings and inner spacer to form a module similar to that which comprises the outer plate 42.

The modular construction illustrated in Figure 4 means that many different arrangements of electrode, spacer, flow baffles and membranes can easily be assembled to vary the size and construction of the electrolyser, and in particular can be used to form multiple anode and cathode chambers.

The modules of Figure 4 are shown in their assembled state in Figure 5, forming an electrolysis cell with a single anode chamber and a single cathode chamber. In the embodiment shown in Figure 5, a Brand solution is fed into inlet 58 of the anode lo compartment, and passes up through the compartment on each side of the primary electrode 54 while being electrolysed, mixing of the solution being aided by the baffle 60 on the inside of outer plate 57. The electrolysed anolyte leaves the anode compartment via outlet 59 and is then fed to the inlet 60 to the cathode compartment where a similar electrolysis takes place. The final product stream of ANC anolyte leaves the cell via the IS outlet 62.

Figure 7 shows an example of an electrolyser system and a typical flow through such a system. The process of the present invention may be operated as illustrated by and with reference to Figure 7 as follows: A water supply 70, such as towns water, is fed via a pre-heater 72 which is typically controlled at from 30 to 40 C through feed lines around which are wound aerials of a low band frequency radio wave transmitter 74. The water is optionally passed through a hard salt deioniser 76. The towns water supply feeds both the mixer column 78, and the brine tank 80. The towns water supply to the mixer column 78 is used to dilute the brine solution feed. The towns water supply to the brine tank is used to prepare the brine solution, typically from sodium chloride and towns water. The towns water feed line has a T-connector 75 to direct the towns water feed to the mixer column and to the brine tank. A first valve 77, in a first feed line after the T-connector in the towns water feed line controls the flow of towns water to the mixer column 78; a second valve 79, in a second feed line after the T-connector 75, in the towns water feed line controls the flow of towns water to the brine tank. Regulation of these valves controls the flow of towns water to the mixer column and to the brine tank. A second T-connector 81 is situated downstream of the valve 77 between the towns water supply and the mixer column. A feed line from the brine tank 80, via this second T-connector, provides a supply of brine, via a third valve 82 to the mixer column 78. Regulation of the first and third valves allows the concentration of brine fed to and exiting from the mixer column to be controlled. It will be appreciated that closing the third valve 82 will isolate the brine feed to the mixer column and result in only towns water being fed into the mixer column.

It will also be appreciated that the first, second and third valves may be automated and controlled in response to a suitable signal from the electrolyser system. For example, the second valve 79 may be controlled by a level detector 83 in the brine tank, the valve closing when a particular pre-set level is reached. The first and third valves 79, 82 may be controlled by a suitable means such as a conductivity detector 84 situated before or after the mixer column which adjusts the relative flows of towns water to obtain a pre-set range of conductivity. Further the first and third valves may be controlled by a redox meter or pH meter measuring the redox or pH value of the liquid medium exiting the electrolyser(s) (E). In this example the feed liquid exiting the mixer column 78 is caused to flowinto the anode chamber 85 of the first electrolyser 90 and from the anode Is chamber to the cathode chamber 88 of the first electrolyser. The liquid exiting the cathode chamber 88 of the first electrolyser is caused to flow into the anode chamber 92 of a second electrolyser 91 and from the anode chamber to the cathode chamber 94 of the second electrolyser. On its way from the mixer column to the first electrolyser the feed liquid is subjected to further radio waves from a generator 86.

The liquid medium exiting the electrolyser, or if more than one electrolyser the last electrolyser 91, is caused to flow into a gas entrainment column 9S where gases such as hydrogen, oxygen, ozone and chlorine which are produced in the process are disengaged.

The gas entrainment column, is typically made of glass or plastics material which is packed with an inert support, such as plastics rings.

A non-foaming non-ionic surfactant held in a surfactant tank 100 may be fed into the liquid medium exiting the electrolyser 90 either before or after the gas entrainment column 95 (shown as before in Figure 7). The surfactant may be fed into the liquid medium via a T-connector 102 and using a suitable pump, such as a peristaltic pump, to transfer the surfactant. The liquid medium exiting the gas entrainment column is ready for use as a broad spectrum biocide in sterilization, disinfection, and big-film removal applications and the like.

A central power supply and control unit 150 controls the power supply to the electrolysers 90, 92 via transformers 152, 154, and also controls the operation of the valves and radio wave generators.

It will be appreciated that any number of electrolysers may be operated in series or in parallel as part of the electrolyser system. It will be further appreciated that the pipework connecting the electrolysers may be arranged in different ways to provide liquid media with different characteristics.

In a second example the liquid medium exiting the anode chamber is collected via an outlet from the anode chamber (not shown in Figure 6).

lo In a third example part of the liquid medium exiting the anode chamber is collected and part is fed into the cathode chamber via a T-connector and outlet (not shown in Figure 6).

In a fourth example the feed liquid exiting the mixer column 78 is fed via a manifold device into electrolysers connected in parallel.

The liquid media produced by the present process may comprise additional components such as surfactants and fragrances. Those which additionally contain a surfactant preferably contain a surfactant such as a Synperonic (Synperonic is a trade mark of ICI Chemicals & Polymers Limited) preferably Synperonic 850. As an example a 0. 1% of a 30% Synperonic 850 solution may be added to the liquid media.

The liquid media produced by the present process have been evaluated for their effectiveness and storage stability. The ANK liquid medium is a neutral anolyte which has a long shelf life as determined by its sporicidal activity. This was assessed against Bacillus subtilis var niger under clean conditions, without organic contamination, and under 'dirty' conditions in which horse serum was present. Contact times of 30 seconds, 1, 2, 5, 10 or 15 minutes from contacting the B. subtilis with the liquid medium under test were used and the ability of the liquid medium to obtain a kill rate (log reduction) of log 6 or more over a given contact time under clean conditions (no horse serum) and dirty conditions ( 1% horse serum) was assessed.

General Method for assessing sporicidal activity Fresh cultures of B. subtilis spore solutions (obtained from Don Whitely Scientific, Shipley, West Yorkshire, England) were used and kept in a refrigerator until needed.

Immediately before use the B. subtilis were placed in a pre-heated incubator set at 70 C for 30 minutes and allowed to cool to room temperature for 30 minutes. 1.7ml of liquid medium was used and to it 0. 2ml of sterile water was added for tests under clean conditions, and 0. 2ml of horse serum (obtained from Oxoid Limited, Basingstoke Hampshire, RG24 8PW, England) was added for tests under dirty conditions. lml of spore solution was added to either the clean or the dirty test solutions and samples taken at time intervals. The samples were added to a neutralization broth (containing nutrient broth Oxoid no2 (from Oxoid Limited), lecithin, tween 80, 1% sodium thiosulphate) which deactivated the liquid medium, after 5 minutes a portion of the neutralization broth was removed and added to MRD [max recovery diluent] (which contains Peptone and sodium chloride from Oxoid Limited). After mixing thoroughly samples of the MRD 0 mixture and the neutralization broth were plated out on to Tryptone Soya agar (TSA) plate and incubated for 18 hours at 37 C. The plates were examined after 18, 24 and 48 hours and the spores counted. Controls were prepared by substituting the liquid medium with MRD. The control and test plates were compared and the log reduction in spores calculated.

The results obtained (for SUPROX Blend) are summarised in Table 1: Time since liquid Sporicidal Sporicidal medium produced activity activity minutes, 5 minutes clean 1% horse conditions serum dirty conditions

_

days >log 6 Log6 reduction reduction weeks >log 6 Log 6 reduction reduction 9 weeks >log 6 Log 2.19.

reduction reduction 12 weeks >log 6 Log 0.5 reduction reduction Further testing of this liquid medium gave the following: After 4 months for a 5 minute contact time a log 4 reduction was obtained under dirty conditions with 0.8% horse serum.

Up to 6 months for a 30 minute contact time a log 6 reduction was obtained under dirty conditions with 1.0% horse serum.

By comparison use of an industry standard steriliser, glutaraldehyde, takes 2 hours to achieve a log 6 reduction in spores where 1.0% horse serum is present.

The results obtained for ANK for sporicidal activity and bactericidal activity using 0 European standard EN1276 for Chemical disinfectants and antiseptics against S. aureus and P. aeruginosa is summarised in Table 2: Time since S. aureus and P. B. subtilis B. subtilis liquid medium aerugirosa Dirty Dirty conditions Clean conditions produced conditions 0.3% 1.0% horse serum, 5 1.0% horse serum, horse serum, 5 minutes 5 minutes minutes 2 months pass pass 8 months pass pass 12 months pass 18 months Log 6 reduction in mine A pass indicates that a greater than log 6 reduction in spores or a greater than log 5 reduction in bacteria was obtained in 5 minutes.

European standard EN1276 test procedures was used to evaluate the performance of the liquid medium against other microorganisms. Under clean conditions in the presence of 0.3g/1 bovine albumin with a 5 minute contact time a greater than log 5 reduction was obtained for E. colt, S. typhimurium, K pneumonias and C. albicans. Under dirty conditions, in the presence of 3.0g/1 bovine albumin with a 5 minute contact time a greater than log 5 reduction was obtained for E. colt, S. typhimurium, and K pneumonias and a greater than log 4 reduction for C. albicans.

Wipe Technology In a further feature of this invention the Suprox ANK can be used to impregnate a paper product in its neat or in the form of surfactant / fragrance blend such that this paper product can be packaged as a wipe in a pouch or a tub. The preferred type of paper is a polyesterbased absorbent paper. One suitable proprietary paper is Jettex 1005 FAVC.

Preferred impregnation rates are 30 to 80 g/m2, typically about 50 g/m2. l

This invention allows for at least a six month shelf life matching the sporicidal properties of the liquid.

The paper chosen to give the best storage life is Italian made and based on Polyseter It has the trade name Jettex. It has the density of 50g per square meter 1005AVC. Other s densities in this range can be used.

Summary of the Evaluation of Suprox_ Sporcidal Wipes. Lab Work to date

Introduction:

Suprox_ wipes are sporicidal wipes designed to effectively clean heavily contaminated surfaces and disinfect the surface after a final wipe with a fresh clean wipe.

The aim for this work has been to evaluate the performance of the wipes against Bacillus subtilis containing 1% horse serum to simulate heavy contamination of surfaces with soils such as blood, mucous and tissue deposits. The type of wipe material has been crucial. Jettex spun-laced medical grade paper was selected and impregnated with Suprox_ ANK. Such wipes have been used thorough out all this work. Suprox_ did not contain surfactant / citric acid blend. No testing has been earned out in-house against S. aureus or P. aenginosa.

Performance on endoscope insertion tubing: A solution of Bacillus subtilis spores containing 1% horse serum was applied using a sterile cotton wool swab. Swabs were pre-weighed to determine the weight of liquid applied to the test piece. The actual weight of spores / horse serum mixture applied to the test surface was found to be 0.04g. The tubing was dried for 30 minutes at SAC. The test area was wiped and the wipe discarded. Any remaining chlorine was neutralised and remaining spores enumerated by swabbing the surface and serial dilution. Dip slides were used to pick up any remaining spores on the wiped surface.

Trigene wipes (also claiming sporicidal activity), water-soaked wipe and an IPA-soaked wipe were all tested in duplicate alongside the Suprox_ wipe.

This test proves that Suprox_ wipes can effectively remove all of the spores from the surface of the insertion tubing. This was comparable with the Trigene wipe. IPA and water soaked wipes were not effective at fully removing all spores and only partially reduced the numbers. An initial count of 108 spores per ml was added to the test surface.

3s Therefore the initial count for 0.04g applied to the test piece was 4 x 107.

Performance on laminated work surface material: Initial experiments look promising showing that Suprox_ ANK wipes are comparable with Trigene wipes reducing the numbers on the surface significantly more than water and IPA soaked wipes.

Further work is required looking at Suprox_ ANK containing 0.1% surfactant / citric acid blend. The wipes will be used and tested, as they would be used in a hospital environment. The surface will be wiped for 10 seconds and not 30 seconds as previous 4s and left to dry before enumerating what is left on the treated surface.

Work carried out to date: Surnrnary of the Evaluation of Suprox_ Sporicldal Wipes.

Independent testing on plastic laminated worktop material: HIRL. T. Bradley.

(CRB/HIRL/August2003/Medipure Ltd) s It is assumed that testing carried out by HIRL of wipes and sprays is done so following SOP's and protocols.

Suprox_ wipes, Alcowipes, Sanichlor (1000 ppm chlorine) and 1% neutral detergent were tested against S. aureus and P. aeruginosa with 1% horse serum. The broths were lo inoculated and dried onto a plastic laminated surface. The area was wiped and rinsed with a water-soaked wipe and dried with dry paper. Results showed that Suprox_ is comparable with the chlorine-releasing agent, Sanichlor, but not as effective as 70% alcohol when tested against a heavy and light inoculated surface.

When tested at 108 per ml, Suprox_ wipes are more effective at reducing S. aureus than P. aeruginosa with an average of 133 P. aenginosa colonies remaining compared to 9 S. aureus colonies. At the lower inoculum of 104, Suprox_ wipes completely remove all organisms from the surface for both species.

No testing was carried 'out against Bacillus subtilis. Don Whiteley Scientific will independently carry this out.

Discussion: Medipure has followed this protocol to some degree with the exception of the rinse and dry. It is considered that this part of the protocol does not give the test biocide sufficient contact time to kill the bacteria on the surface. By wiping and drying, the full efficacy of a test biocide is not being explored. If this represents empirical practice, poor performing biocides would spread infection over a larger surface area.

Recommended cleaning regimes for biocides encompass good covering power and sufficient exposure time (for 3 -5 minutes is very effective).

Further work: The protocol used by Medipure will allow any remaining liquid on the surface to dry before the surface is sampled for surviving bacteria. The time taken for the surface to dry will be recorded with all other test data. The surface will not be rinsed or dried as we consider this not to be common practice. Suprox_ will remain on the surface and will not affect the properties of the surface in any way.

Stainless steel surface: Testmg on this type of surface has yet to be carred out. The protocol for larnnated work surface material will be used (Medlpure m-house protocol SOP025).

Date: May 2004 Evaluation of Suprox_ wipes and Suprox_ ANK /S on P. aeruginosa & 5. aureus inoculated laryagoscopes. r Aim:

To determine the efficacy of Suprox_ wipes and Suprox_ ANK/S on P. aenginosa & 5. aureus inoculated laryngoscope insertion tubmg.

Procedure: Inoculation of Laryugoscope with P. aerugizesa & 5. aureus: P aerugnosa & S aureus at a concentration of 106 was inoculated on to the insertion tubmg of a laryngoscope using a sterile swab. The tubing was left to dry Inside the class 2 safety cabinet. The tubing was left to dry for 30 minutes. After this time a Suprox_ wipe was used to clean the insertion tubmg.

Once the scope was dry It was swabbed and placed m Suprox_ ANK/S for a soak time of 10 mans. The scope was rmsed under the tap and wiped with kitchen paper before re-swabbing. (This procedure was followed, as It IS an m-use method recommended for using Nucdex for cleaning laryngoscopes at Countess of Chester Hospital m the ENT clinic).

Table 1. Sample repeated 8 times various protocols Sample Procedure Count from swab No's. 106 mixed culture P. aerugnosa /5. aureus.

1-8 Wipe with Suprox_ wipe - handle 2ctu's /cc 5-8 Wipe with Suprox_ wipe msert tube Ictu's /cc 1-8 Wipe with Suprox_ wipe + 10 mine soak in Suprox_ 0cfu's /cc ANK/S + rmse under tap + wipe with kitchen paper 9- 12 Wipe with Suprox_ wipe only msert tube and handle 2ctu's /cc Concluslon.

If careful cleaning is carried out a log 6 or better reduction can be achieved on microorganisms over 8 samples.

Very good agreement means process IS robust.

Current practices show high levels of contamination on none soaked areas of the scope.

Rec o mmend ah on Introduce Suprox ANK Liquid and Wipes Suprox Composition and Inarediants Drawing 2: ANK-AnolYte Drawing Figure 1: A- AnolYte + K-Catholvte Blocldal liquids Production technology Composition / ingredients produced on cylindrical CELLS. Symbol Cas-No EINICS- No Wt/Vol% A - AnolYte Anode treatment of <90% NaCE 7647-14-5 231-598-3 0. 26 of NaCL solution; the main electrochemlcally part of the current IS C e2 7782-50-5 231-959-5 0.05 activated acidic transferred though the HC eo 7782-50-5 231-959-5 anolyte diaphragm by Cl and Na lon pH < 5 counter movement H2O 7732-18-5 231-791-2 99.69 ORP > 1100mV AA on drawmg K Catholvte Cathode treatment of>10% NaCt 7647-14-5 231-598-3 0.26 NaCL solution; the main alkahne catholyte part of the current is HNaO 1310-732 215-185-5 0 10 pH > 9 transferred though the ORP < -9OOmV daphragm by Cl and Na on CC on drawmg counter movement HzO 7732- 18-5 231 -791-2 99. 64 Drawing Fgure 2 ANK Anolyte - Suprox ANK Biocidal liquids Production technology Composition / ingredients produced on cylindrical CELLS Symbol Cas-No EINICS-No Wt/Vol % AISK - Anolyte# Catllode treatmellt of the NaCt 7647- 14-5 231 -598-3 0.26 NaCL sohton; anode clectrochemically treatment ofthe catholyte HCtO 7782-50-5 231-959-5 0.05 activated neutral anolvc wth gaseous hydrogen pH 8.7 * 0.7 and dissolved hydrogen OCt 7681 -52-9 231 -668-3 ORP > 730mV \N( o'drav'',,.fg, 12O 7732-18-5 231-791-2 99.69 Ar,1 f y 5 Drawng2a AND- Anolyte Biocidal liquids Production technology Composition / ingredients produced on cylindrical CELLS Symbol Cas-No EINICS-No Wt/Vol % ANI) - Anolyte Cathode treatment of the NaCt 7647-14-5 231 -598-3 0.26 NaCL solution; anode electrochemically treatment of thc catholyte HCtO 7782-50 5 231-959-5 0.05 activated neutral anolvte without gaseous hydrogen pH 7. 3 * 0.5 but with dissolved OCt 7681-52-9 23 1-668-3 ORP 800mV hydrogen H2O 7732- 18-5 231 -791 -2 99 69 lieferred to as Suprox B 1 131end1

Claims (22)

1. CLAIMS: 1. A process for the preparation of a liquid biocidal medium

   wherein a feed liquid comprising a solution of an alkali metal halide is electrolysed in an electrolyser s comprising respective anode and cathode chambers each with at least one electrode, said anode and cathode chambers being separated by an ion-permeable membrane, wherein: a) the feed liquid is fed to at least one of the anode and cathode chambers and a liquid biocidal medium is drawn off from at least one of said chambers; to b) a direct current of 2 to 55 A is passed through the electrolyser; and c) the feed liquid is heated to a temperature in the range from 30 to 60 C before it enters the electrolyser.
2. 2. A process according to claim 1 wherein the electrolysis is operated at a temperature below 55 C.
3. A process according to claim 2 wherein the electrolysis temperature is from 34 to 39 C.
4. 4. A process according to any preceding claim wherein the electrolysis current is at least 30 A.
5. 5. A process according to any preceding claim wherein the feed liquid comprises sodium chloride at a concentration of up to 26% w/v.
6. 6. A process according to any preceding claim wherein the feed liquid is pre-treated by subjecting it to radio waves at a frequency in the range of 50 to 500 Hz.
7. 7. A process according to any preceding claim wherein the temperature of the feed liquid is 30 to 40 C.
8. 8. A process according to any preceding claim wherein the feed liquid has a conductivity from 0.3 to 15 US.
9. 9. A process according to any preceding claim wherein the feed liquid is passed through the anode chamber of the electrolyser and at least a part of the feed liquid is then caused to flow from the anode chamber to the cathode chamber and the resulting liquid medium is collected from the cathode chamber in the form of an anolyte neutral catholyte solution.

   lo
10. 10. A process according to any preceding claim wherein the ionpermeable membrane is a rigid ceramic membrane having a thickness of 1 to 2mm.
11. 1 1. A process according to claim 10 wherein the membrane is a semipermeable membrane formed from particles of alumina and/or of zirconium dioxide.
12. 12. A process according to any one of claims 1 to 9 wherein the ionpermeable membrane is a flexible fluorinated polymer membrane having a thickness to 25 to 500 m.
13. 13. A process according to any preceding claim wherein the electrolyser comprises coaxial cylindrical electrodes, separated by a coaxial membrane dividing the electrolyser into coaxial annular anode and cathode chambers.
14. 14. A process according any one of claims 1 to 12 wherein the electrolyser comprises a flat plate assembly wherein the anode and cathode are separated by said membrane and spaced therefrom by means of spacers selected to define anode and cathode chambers of predetermined size.
15. 15. A process according to any preceding claim wherein one or both of the anode and so cathode comprise titanium coated with a noble metal, metal alloy or metal oxide which is resistant to oxidation or corrosion.
16. 16. A process according to claim 15 wherein said anode and/or cathode comprises titanium coated with nickel, iridium, IrO2, Ir2O3' palladium, PdO, PdO2, ruthenium, RuO2, rhodium, RhO2 or platinum.
17. 17. A process according to claim 1 S wherein said anode and/or cathode comprises titanium with a platinum/black coating.
18. 18. A process according to any preceding claim wherein the liquid medium collected from the anode and/or cathode compartment is post-treated by passing it through a 0 column packed with an inert support, to disengage hydrogen, oxygen, ozone and chlorine produced in the process.
19. 19. A process according to any preceding claim wherein the liquid medium from the electrolysis is subjected to a post treatment by contacting it with a charged metallic catalyst to remove hydrogen.
20. 20. A process according to any preceding claim wherein a surfactant is added to the liquid medium from the anode or cathode chamber.
21. 21. An aqueous superoxygenated sterilising solution produced in the anode chamber in a process according to any preceding claim comprising sodium chloride and hypochloric acid in a complex with oxygen compounds of active chlorine, the solution having a total chlorine content of 700 to 1200 ppm and a pH of 2.3 to 6.4.

    2s 22. An aqueous superoxygenated sterilising solution produced from the cathode chamber in a process according to any one of claims 1 to 20, comprising sodium chloride and hypochloric acid in a complex with oxygen compounds of active chlorine, said solution having a pH of 7 to 8.9 and a total chlorine content of 200 to 800 ppm.
22. 22. A sporicidal wipe comprising a polyester-based absorbent paper, impregnated with an aqueous sterilising solution according to claim 19.