DE102006033904A1 - Production of bactericidal charcoal by silver impregnation for absorbing substances such as halogen containing organic substances and microorganisms from water, comprises impregnating the charcoal by introducing silver lactate solution - Google Patents

Abstract

The production of bactericidal charcoal by silver impregnation for absorbing substances such as halogen containing organic substances and microorganisms from water in water filtration system, comprises impregnating the charcoal by introducing silver lactate solution with an excess of lactic acid into the charcoal under reduced pressure by ultrasonic nozzle, thermally drying the impregnated charcoal and treating the dried charcoal with microwave in a discontinuous charging process for fixing the silver on the charcoal. The production of bactericidal charcoal by silver impregnation for absorbing substances such as halogen containing organic substances and microorganisms from water in water filtration system, comprises impregnating the charcoal by introducing silver lactate solution with an excess of lactic acid into the charcoal under reduced pressure by ultrasonic nozzle, thermally drying the impregnated charcoal and treating the dried charcoal with microwave in a discontinuous charging process for fixing the silver on the charcoal. The charcoal is discharged from calcium carbonate through an acid wash or through the addition of acid to silver lactate solution by the carbonate contamination. The charcoal is treated after idle phase. The charcoal is subjected with silver that is dejected on the coal through a chemical reaction.

Description

The The invention relates to a process for the production of bactericidal Activated carbon with an adhesive silver.

State of the art

to Quality improvement of drinking water come ion exchangers and also activated carbon as well Combinations of the components mentioned used. The ion exchangers serve to ionic components such as heavy metal salts from the To remove water while the activated carbon for the adsorption of non-ionic substances such as halogen-containing organic compounds or microorganisms. That in his quality to be improved water is over Ion exchanger and activated carbon filtered, whereby naturally a discontinuous Operation is the rule. Especially the resulting downtime the water filter systems can be a source of contamination. Since the filter systems are often in immediate Related to food, put bacteria in the filter systems a hazard represents.

Around To prevent germination of the activated carbon, it becomes bactericidal equipped. This can be done especially by exposure to precious metals such as Silver done. Particularly suitable is silver, since the very low delivery Amounts of antibacterial activity. A well-known technology poses the loading of the activated carbon with elemental silver or with silver oxides dar. The technical implementation however, is complicated and presents considerable difficulties in practice.

A another method involves the application of silver by means of soluble Silver salts dar. Especially the very soluble silver nitrate comes to Impregnate for use. However, it should be noted that such registered nitrate ions because of their toxicity in the food industry are subject to strict limits, so when using silver nitrate removal of the nitrate ions must be done with a relatively high cost.

To circumvent this problem, other soluble silver salts were used. For example, the use of soluble organic silver salts such as silver acetate is possible. One more way ( DE 198 52 526 A1 ) is to use silver solutions of other organic acids such as silver lactate also prepared in situ for charging activated carbon and to fix formed silver by subsequent drying. The disadvantages of these methods are firstly that complex technical apparatuses such as drying ovens are required and also large amounts of energy must be expended for drying and fixing the silver. Since the heat is supplied from the "outside", these processes are particularly energetically unfavorable.On the other hand, the practice has shown that the fixation succeeds only imperfectly and the filtered water still contain unacceptably high amounts of silver.

The invention

Of the presented invention is the object of a method for producing a bactericidal activated carbon by using Silver salt solutions, in particular with the aid of silver lactate solution, by which the applied silver is firmly adhered so that it is also at Use of activated carbon in filter processes permanently on the coal remains and also during a permanent filtering process is not washed out.

According to the invention was the task solved by the use of microwave technology.

• • Durch die Mikrowellentechnologie wird das leicht lösliche Silbersalz vollständig in elementares Silber bzw. in unlösliche Silberverbindungen überführt, wobei niedrige Energiemengen und keine hohen Temperaturen eingesetzt werden.
• • Durch den Einsatz von Mikrowellentechnologie wird die lösliche Silberverbindung sicher zersetzt und in unlösliches Silber umgewandelt, ohne dass die Aktivkohle stofflich verändert oder in ihrer Struktur und ihren Adsorptionseigenschaften beeinträchtigt wird.
• • Bei der Behandlung der silberhaltigen Kohle mit Mikrowellen werden möglichst keine toxischen oder sonstwie gefährlichen Stoffe gebildet.
• • Während der Mikrowellen – Behandlung verflüchtigen sich alle auftretenden Zersetzungsprodukte der löslichen Silberverbindungen entweder während der Reaktion, oder sie werden durch einfache Waschprozesse von der Kohle separiert.

The invention includes the knowledge that the activated carbon treated with silver obtains the following properties by the use of microwave technology:

• • Microwave technology converts the easily soluble silver salt completely into elemental silver or into insoluble silver compounds, using low energy levels rather than high temperatures.
• • By using microwave technology, the soluble silver compound is safely decomposed and converted into insoluble silver without the activated carbon being altered or impaired in its structure and adsorption properties.
• • In the treatment of silver-containing coal with microwaves as possible no toxic or otherwise dangerous substances are formed.
• • During the microwave treatment, any decomposition products of the soluble silver compounds are either volatilized during the reaction or they are separated from the carbon by simple washing processes.

According to the invention are for use for Fixing the silver on the activated carbon conventional microwave ovens, such as they are used in engineering or the food industry, without additional technical effort suitable. The activated carbon can be both discontinuous, this means in smaller or larger batches, or in a continuous manner, for example by a continuous conveyor the Microwave devices are supplied.

In the microwave treatment of the activated carbon, the energy supply must be controlled so that an optimal fixation of the silver on the Koh le takes place. This energy input depends on the type of impregnation of the coal and on the pretreatment of the coal prior to microwave use. If inorganic silver salts are used to impregnate the coal, or if the coal is moist, which is particularly the case after direct impregnation of the coal, correspondingly higher energies must be used. If the coal is pre-dried or subject to a period of rest or maturity, lower amounts of energy must be entered through the microwave. If organic silver salt solutions or easily decomposable silver compounds are used in the silver impregnation of the coal, smaller amounts of energy are also needed to fix the silver.

to Charging silver with activated carbon comes from silver 0.01 to 1%, preferably 0.01 to 0.05% silver used. The Concentrations of silver salt solutions, which to impregnate the coal can be used vary within a wide range. Preferably, 15 to 25 % silver salt solutions used to uniform impregnation to reach.

at the use of sensitive coal, for example with special Adsoption properties, or in the supply of high amounts of energy through the microwave, which may be required as described above it is possible, that the coal is burning up or a strong sparking is observed. in the case of air access can it then too unwanted oxidation processes come on the coal, or there is a change of silver. These operations can both to an impairment the adsorption properties as well as to reduce the antibacterial Effect of silver exposure lead. To avoid these evils, it is advisable to carry out the microwave treatment under protective gas. When Protective gases can Nitrogen, but also noble gases such as argon or helium or carbon dioxide be used.

A another possibility the additional treatment the coal while The silver fixation by microwaves is the use of vacuum. By the use of vacuum will also be the contact of the coal with Reduced air or oxygen, resulting in better fixation results of the silver. Get to the silver impregnation organic silver salts are used, a series of volatile Decomposition products. By applying vacuum they become very cheap removed, so also the quality of the resulting silver-containing Coal cheap affected becomes. The use of vacuum also causes an odor nuisance during the Microwave treatment reduced or completely avoided. Upon decomposition of the silver salt on the activated carbon as a further positive effect, a shift in the reaction equilibrium by removing individual reaction products when using vacuum to observe. The fixation reaction is thereby faster and more complete, which to a shortening the reaction time and thus the energy saving within the Process leads.

at Use of inorganic silver salts for silver impregnation, such as silver nitrate, it may in the subsequent microwave treatment the coal to form toxic or otherwise harmful Reaction products come. While the silver is firmly fixed, the by-products are only superficially tied the coal. It is therefore recommended in such cases, the To combine microwave technology with an integrated or immediately subsequent suitable washing process.

to Charging activated carbon with silver by using microwaves Particularly suitable are organic silver salt solutions in which as an acid component simple carboxylic acids like acetic acid or propionic acid, but also polybasic acids like tartaric acid or citric acid be used. Particularly preferred is the lactic acid, which is widespread in nature and non-toxic. She forms with Silver, the readily soluble silver lactate, which is well absorbed by the activated carbon and when applied of microwaves into a firmly fixed silver component and largely gaseous reaction products decays, which can be easily separated. Silver lactate presents under the Treatment with microwaves is a redox system in which in one coupled redox reaction turn the silver ions reduced to insoluble silver and at the same time the lactate is oxidized to the unstable pyruvate, which is influenced by the Converts microwaves into acetaldehyde and carbon dioxide. The latter At the same time, it acts as a shielding gas in the system and thus prevents it from acting effectively harmful Oxidation processes.

conventional Activated carbon contains significant amounts of carbonate through their manufacturing process, in the silver salt impregnation of Coal to a failure lead the silver salt in the form of silver carbonate, which is initially insoluble, but not permanently fixed on the coal. By the application from microwaves this carbonate is completely decomposed and solidified into Converted silver and carbon dioxide.

Of particular importance for the successful use of microwave technology to fix silver on activated carbon is the introduction of the silver salt into the pore systems of the coal. By simply spraying with the silver salt solution is this purpose only imperfectly achieved. As a particularly effective method, two special methods can be used:
In a continuous process, the activated carbon is sprayed before the microwave treatment with the silver salt solution by means of an ultrasonic nozzle. This allows a particularly fine distribution of the silver salt solution in the form of fine droplets, which penetrate due to their small size in the pore system of the activated carbon.

The second option the particularly effective preparation of the activated carbon for the microwave treatment consists in the application of negative pressure during the spraying process. Again, a particularly favorable Penetration of the silver salt solutions into the pores of the activated carbon.

Based on the silver salt impregnated activated carbon, four different methods are used for fixing the silver on the coal using microwave technology:
In the first way, the coal is treated with microwaves immediately after impregnation. The advantage of this way is that it is very time-economical and the process of fixing can be done without intermediate storage and laborious storage times. For the conversion of the silver salt into silver by means of microwaves, however, a higher energy must be expended, since the coal additionally has to be dried.

The second option consists of the activated carbon after the silver salt thermally pre-dried and then the microwave treatment perform. This saves energy in microwave technology. These However, method requires a further process step.

The third possibility consists of spraying the activated carbon after spraying with the silver salt solution before Intermediate microwave treatment in a resting phase. By This resting phase can affect the adsorption balance between Set coal and silver salt. Frequently be after this method the preparation good results in the subsequent fixation of the silver achieved by microwaves. Disadvantage here, however, is that a longer one Period for the production of the silver coal is needed.

The fourth possibility The pretreatment of coal consists of a combination of resting phase and thermal predrying, these process steps both in the order of resting phase with subsequent predrying as well can be performed in reverse order.

Which the described method steps before the actual microwave treatment for Use, hangs of different factors such as structure and type of coal, type of Silbersalzbeaufschlagung, the silver compounds used and the intended use of coal and must be empirical on a case-by-case basis be determined.

The Invention is based on embodiments explained without being limited to these examples:

example 1

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver nitrate solution in distilled water containing 0.5 g of silver in 100 ml of water, in a Mixing drum mixed for 5 minutes. Thereafter, the drying of the Activated carbon in the drying cabinet at elevated temperature.

Subsequently, will add the dried coal in a microwave with 800 watts of power consumption reduced power for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 2

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water, in a Mixing drum mixed for 5 minutes. Thereafter, the drying of the Activated carbon in the drying cabinet at elevated temperature.

Subsequently, will add the dried coal in a microwave with 800 watts of power consumption reduced power for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 3

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water, in a Mixing drum mixed for 5 minutes. Thereafter, the drying of the Activated carbon in the drying cabinet at elevated temperature.

Subsequently, the dried coal is treated in a special microwave with continuous feed, whereby the power is regulated that the coal retains its adsorption-determining structure.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 4

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water and contains an excess of lactic acid, in one Mixing drum mixed for 5 minutes. Thereafter, the drying takes place the activated carbon in the drying oven at elevated temperature.

Subsequently, will add the dried coal in a microwave with 800 watts of power consumption reduced power for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 5

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water, in a Mixing drum mixed for 5 minutes. This is followed by several days of storage at room temperature followed by Drying of the activated carbon in the drying oven at elevated temperature.

Subsequently, will add the dried coal in a microwave with 800 watts of power consumption reduced power for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 6

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water, in a Mixing drum mixed for 5 minutes. Thereafter, the drying of the Activated carbon in the drying oven at elevated temperature, followed by a multi-day Store at room temperature.

Subsequently, will add the dried coal in a microwave with 800 watts of power consumption reduced power for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 7

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water with Help an ultrasonic nozzle with the silver salt solution applied. Thereafter, the drying of the activated carbon takes place in the drying oven at elevated Temperature.

Subsequently, will the dried coal in a microwave with 800 watts of power consumption (at reduced power) for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 8

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water, under Use of a vacuum device mixed with the silver salt solution. Thereafter, the drying of the activated carbon in the drying cabinet at increased Temperature.

Subsequently, will add the dried coal in a microwave with 800 watts of power consumption reduced power for 5 minutes.

The Treated coal has its original at a low mass loss Preserved appearance.

Example 9

1000 g of activated carbon (dedusted, with a water content of approx. 5%) with silver lactate solution in distilled water containing 0.5 g of silver in 100 ml of water, under Use of a vacuum device mixed with the silver salt solution.

Subsequently, will the coal directly, without drying, in a microwave with 800 watts of power consumption at reduced power several Minutes treated.

The treated coal has its at a considerable mass loss her original Preserved appearance.

Example 10

With 0.05% silver activated carbon is after pretreatment eluted several times with 1 liter of water. The last liter of water gives a silver content of the eluate of 14 μg silver per liter.

The determination is carried out by means of atomic absorption tion spectroscopy (AAS).

With 0.05% silver activated carbon is after pretreatment using a microwave with 800 watts of power at a reduced Performance treated for several minutes. After that, several times with each 1 liter of water eluted. The last liter of water gives a silver content of the eluate of 5 μg Silver per liter, showing the special fixation of the silver becomes.

The Determination by atomic absorption spectroscopy (AAS).

Example 11

With 0.05% silver activated carbon is after pretreatment eluted several times with 1 liter of water. The last liter of water gives a silver content of the eluate of 14 μg silver per liter. The determination carried out by atomic absorption spectroscopy (AAS).

With 0.05% silver activated carbon is after pretreatment using a microwave with 800 watts of power at a reduced Performance treated several times with brief interruptions. After that will eluted several times with 1 liter of water. The last liter of water gives a silver content of the eluate of 4 ug silver per liter, which the special fixation of the silver is shown.

The Determination by atomic absorption spectroscopy (AAS).

Example 12

With 0.05% silver activated carbon is after pretreatment eluted with 1 liter of water, which has a silver content of the eluate of 39 μg Silver per liter yields.

The Determination by atomic absorption spectroscopy (AAS).

With 0.05% silver activated carbon is after pretreatment using a microwave with 800 watts of power at a reduced Performance treated for several minutes. After that, use 1 liter of water which elutes a silver content of the eluate of 9 μg silver per liter, which shows the special fixation of the silver becomes.

The Determination by atomic absorption spectroscopy (AAS).

Claims (14)

A process for the production of a bactericidal activated carbon with a silver impregnation, in which the activated carbon is exposed to a silver salt solution consisting of inorganic and organic silver salt solutions and in further steps silver is firmly adhered to the activated carbon, characterized in that the fixation of the silver by the The use of microwave technology is carried out by treating the activated carbon impregnated with silver salt solutions discontinuously or continuously with microwaves either directly after silver salt application or by using further process steps in such a way that permanent fixation of the silver on the coal takes place. Method according to claim 1, characterized in that that the activated carbon in a continuous process by microwaves is treated. Method according to claim 1, characterized in that that the activated carbon in a discontinuous batch operation is treated with microwaves. Method according to Claims 1 to 3, characterized that the activated carbon immediately after the silver salt impregnation is treated with microwaves. Method according to Claims 1 to 3, characterized that the activated carbon after the silver salt impregnation and a subsequent thermal Predrying is treated with microwaves. Method according to Claims 1 to 3, characterized that the activated carbon after the silver salt impregnation and a rest phase is treated with microwaves. Method according to Claims 1 to 3, characterized that the activated carbon after the silver salt impregnation, a resting phase and a subsequent thermal predrying is treated with microwaves. Method according to one of the preceding claims, characterized characterized in that an inorganic silver salt solution for impregnation the activated carbon is used. Method according to one of the preceding claims, characterized characterized in that an organic silver salt solution for impregnation the activated carbon is used. Method according to one of the preceding claims, characterized in that the silver salt used for impregnating the activated carbon solution is applied to the coal by means of an ultrasonic nozzle. Method according to one of the preceding claims, characterized characterized in that used for impregnating the activated carbon Silver salt solution under reduced pressure) is applied to the coal. Method according to one of the preceding claims, characterized characterized in that a silver lactate solution with a lactic acid excess for impregnation the activated carbon is used. Method according to one of the preceding claims, characterized characterized in that the activated carbon of potassium carbonate by a Acid wash or by the addition of the acid to the silver salt solution was freed from carbonate contamination. Method according to one of the preceding claims, characterized characterized in that the activated carbon was treated with silver, which was precipitated by a chemical reaction on the coal.