JP4272586B2 - Activated carbon for water treatment - Google Patents

Description

  The present invention relates to activated carbon for water treatment. More specifically, the present invention relates to activated carbon for water treatment whose pH is adjusted by a specific method.

  Activated carbon is obtained by activating carbide, but activated carbon immediately after production contains a large amount of alkali metal oxides, and becomes alkaline when the pH is measured, for example, according to JIS K1474. For this reason, when these activated carbons are used in the water treatment step, the pH of the treated water becomes alkaline, which makes it unsuitable as drinking water. Similarly, when used for industrial purposes or for wastewater treatment, alkaline treated water may not be suitable for use.

  For this reason, generally, the activated carbon produced is washed with an acid, and the alkaline component of the activated carbon is neutralized to lower the pH of the activated carbon to a neutral region, and then used for each step. Here, after washing with acid, usually, washing with water is used as various pH adjustment activated carbons.

  Here, the delivery standard of the pH-adjusted activated carbon used in the activated carbon adsorption pond in the water supply field is often pH 5.8 to 8.6 (JIS K1474 or JWWA K113).

  And as a measuring method of pH, it is prescribed | regulated, for example to JISK1747, and it will become as follows when the outline is shown (refer nonpatent literature 1).

(A) Convert the sample to dry mass, weigh 1.0 g for the powder sample and 3.0 g for the granular sample, and transfer to a 200 ml Erlenmeyer flask.
(B) Add 100 ml of water and heat for 5 minutes so that boiling continues gently.
(C) After cooling to room temperature, add water to make 100 ml, stir well, and measure the pH value of the suspension using a pH meter.

Here, in order to obtain the amount of the undried sample collected from the dry mass conversion value, the loss on drying is obtained by the following operation and calculated by the following equation.
S ′ = S × 1 / (100−W) × 100
Here, S ′ represents an undried sample collection amount (g), S represents the mass of the sample (in terms of dry mass) (g), and W represents the loss on drying (%).

  And loss on drying is calculated | required as follows.

(A) About 5 g of a sample is placed in a flat weighing bottle with a known mass, spread to the same thickness as possible on the bottom of the weighing bottle, capped, and weighed to 10 mg.
(B) Remove the lid and dry the balance bottle and lid for 3 hours in a constant temperature drier adjusted to 115 ± 5 ° C.
(C) After allowing to cool in a desiccator (desiccant silica gel), cover and measure the weight to determine the weight loss.
(D) The loss on drying is calculated by the following formula.
F = N / S × 100
Here, F is the loss on drying (%), N is the loss (g), and S is the mass (g) of the sample.

  Then, according to the above JIS K1474, when the pH is measured by converting the dry sample of the pH-adjusted activated carbon into a dry mass and the pH is measured using the dry sample of the pH-adjusted activated carbon, both pH values are compared. It was confirmed that there was a big difference in measured values.

  Table 1 shows an example in which the pH is measured after drying the pH-adjusted activated carbon, and in the case where the pH is measured in terms of dry mass.

As can be seen from Table 1, there was a tendency for the pH to be lower when the pH was measured in terms of dry mass. This is presumably because the water contained in the undried pH-adjusted activated carbon contains the acid used to neutralize the activated carbon. That is, when the activated carbon sample is dried, acid components such as hydrochloric acid contained in the water volatilize, so the pH of the activated carbon measured after drying is high, and the pH measured in terms of dry mass is low. Conceivable.

  Then, in the process of producing pH-adjusted activated carbon, the acid component present between the activated carbon particles is washed away with water after the acid cleaning, but is sorbed in the activated carbon pores or on the surface. The acid component is difficult to remove only by washing with water. For this reason, if pH-adjusted activated carbon that has only been washed with water after acid cleaning is used in, for example, a drinking water treatment process, the remaining acid component gradually leaks into the treated water, and the pH of the treated water is adjusted to the drinking water standard. It was found that there are cases where it is off.

Each pH adjusted activated carbon shown in Table 1 is packed in a column, and water is passed through at SV = 5 h ⁻¹ , and the results of observing changes in pH of treated water over time are shown in FIG.

  In the activated carbon of Comparative Example 1, the pH of the pH-adjusted activated carbon measured in terms of dry mass is 3.9. When water treatment is performed using this, the pH is 5.0 or less at the initial stage of water flow. In order to lower the pH and restore it to around 7, it was necessary to pass water 80 times or more.

  In addition, in the activated carbons of Comparative Examples 3 and 4, the pH measured in terms of dry mass was 7.5 and 8.2, respectively, and when water treatment was performed using this, near neutrality at the initial stage of water flow However, when the water flow was continued, the pH of the treated water increased and the drinking water standard was deviated to the alkali side.

  Thus, when there is a lot of remaining acid, the pH of the treated water becomes too low, while the acid concentration in the acid washing is lowered to bring the treated water pH in the initial stage of water flow to near neutral, The treated water pH may deviate to the alkali side.

  Therefore, if the amount of acid retained in the activated carbon changes, the pH of the activated carbon treated water will change from time to time, so it will be difficult to specify the delivery standard or product standard of activated carbon by conventional methods. .

For this reason, when pH-adjusted activated carbon is obtained by neutralization with acid and washing with water, the pH range of the activated carbon for maintaining the pH of the treated water within the beverage standards will be very narrow, and conventional water purification plants It was found that it was difficult to comply with the pH delivery standards. In addition, when the pH deviates from the drinking water standard, a large amount of water is required to return it to the drinking water standard, which increases the time and the amount of water used.
Therefore, an activated carbon for water treatment suitable for keeping the pH within a specific standard has been desired.
JIS K1474 activated carbon test method, published by the Japanese Standards Association, revised on November 1, 1991

  The subject of this invention is providing the activated carbon for water treatment which makes easy pH adjustment of the treated water by activated carbon, and its manufacturing method. Moreover, the subject of this invention is providing the water treatment apparatus and the water treatment method using these activated carbons for water treatment.

  The present invention is an activated carbon for water treatment obtained by neutralizing activated carbon with an acid and then removing the acid retained on the activated carbon.

  Further, the present invention provides the activated carbon for water treatment as described above, wherein the acid is removed by at least one selected from the group consisting of water cleaning, alkali cleaning, ultrasonic cleaning, heat cleaning and drying. It is.

  Moreover, this invention is activated carbon for water treatment as described above, wherein the acid is a volatile acid.

  The present invention also provides the activated carbon for water treatment as described above, wherein the acid is hydrochloric acid and / or carbonic acid.

  By these inventions, it is possible to obtain activated carbon for water treatment that facilitates pH adjustment.

  Further, the present invention is the above activated carbon for water treatment, characterized in that the pH measured by JIS K1474 is 4.0 to 7.0.

  Further, the present invention is the above activated carbon for water treatment, characterized in that the pH measured in accordance with JIS K1474 is 4.0 to 7.0 after drying at 115 ± 5 ° C. for 3 hours. .

  By these inventions, the activated carbon for water treatment of the stable product specification can be provided.

  Moreover, this invention is a manufacturing method of the activated carbon for water treatment characterized by including the process of neutralizing activated carbon with an acid, and the process of removing the acid hold | maintained at the said neutralized activated carbon.

  Further, the present invention is the above production method, wherein the acid is removed by at least one selected from the group consisting of water cleaning, alkali cleaning, ultrasonic cleaning, heat cleaning and drying. .

  Moreover, this invention is said manufacturing method characterized by the acid being a volatile acid.

  The present invention is also the above production method, wherein the acid is hydrochloric acid and / or carbonic acid.

  By these inventions, it becomes possible to produce activated carbon for water treatment that facilitates pH adjustment.

  Moreover, this invention is a water treatment apparatus provided with the column filled with said activated carbon for water treatment, and the pump which supplies to-be-processed water to the said column.

  Moreover, this invention is a water treatment method characterized by using said activated carbon for water treatment.

  These inventions can provide a water treatment apparatus and a water treatment method that facilitate the pH adjustment.

  ADVANTAGE OF THE INVENTION By this invention, the activated carbon for water treatment which makes easy pH adjustment of the treated water by activated carbon, and its manufacturing method can be provided. Moreover, according to the present invention, a water treatment apparatus and a water treatment method using these activated carbons for water treatment can be provided.

  There is no restriction | limiting in particular as activated carbon used for this invention, The thing normally used for a water treatment can be utilized. Moreover, there is no restriction | limiting in particular as a shape of activated carbon, The thing of any shape, such as a granular thing and a powder form, can be used.

  The acid used in the present invention is not particularly limited as long as it can neutralize the alkaline component of activated carbon. For example, inorganic acids such as hydrochloric acid, carbonic acid, sulfuric acid, and nitric acid, and organic acids such as formic acid, acetic acid, and citric acid. An acid can be mentioned, Among these, it is preferable that it is a volatile acid, and hydrochloric acid or carbonic acid can be mentioned as a more preferable example.

  In the present invention, the method for neutralizing activated carbon with an acid is not particularly limited, and examples include immersing activated carbon in an acid aqueous solution.

  The concentration of the acid used at this time is appropriately determined depending on the amount and strength of the alkali component contained in the activated carbon to be neutralized, and generally includes 0.01 to 0.3 N.

  By this neutralization operation, the alkali component contained in the activated carbon is neutralized, but usually excess acid is retained in the activated carbon.

  Next, the activated carbon for water treatment of the present invention can be obtained by removing the acid retained on the activated carbon. The acid removal method used in the present invention is not particularly limited, and examples thereof include water washing, alkali washing, ultrasonic washing, heat washing and drying.

  That is, after neutralization with an acid, the activated carbon is filtered off and washed with water or alkaline water to remove the acid retained on the activated carbon. The amount of water used here is not particularly limited as long as the acid retained on the activated carbon can be removed, but, for example, 1 to 10000 times, preferably 10 to 1000 times, more than the volume of the activated carbon. Preferably, the amount of water can be 50 to 500 times. In addition, the alkaline water used here is not particularly limited as long as it can remove the acid retained on the activated carbon, and examples thereof include alkaline water having a pH of about 8 to 10. Further, the alkali component used in this case is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate and the like. For example, when using sodium hydroxide, 0.0001-10N, preferably 0.001-1N, more preferably 0.01-0.1N can be mentioned.

  In the case of cleaning by irradiating with ultrasonic waves, for example, a method of dispersing activated carbon in water or alkaline water and irradiating with ultrasonic waves can be mentioned. The energy amount of the ultrasonic wave irradiated at this time is not particularly limited as long as the acid retained on the activated carbon can be removed.

  Moreover, when heat-washing, the method of disperse | distributing activated carbon to water or alkaline water, and heating this can be mentioned, for example. The temperature heated at this time is not particularly limited as long as the acid retained on the activated carbon can be removed. For example, the temperature is 40 to 110 ° C, preferably 50 to 100 ° C, more preferably 70 to 90 ° C. Can be mentioned.

  Moreover, when removing an acid by drying, the method of hold | maintaining activated carbon in a dry atmosphere can be mentioned, for example. The degree of drying in this case is not particularly limited. For example, the moisture content is 10% or less, preferably 5% or less, more preferably 3% or less. Specifically, using activated air dryer, heating type dryer, fluid dryer, etc., the activated carbon after washing in a wet state is put in an atmosphere of about 200 ° C. and dried for several tens of minutes to several hours. Thus, dried activated carbon having a water content of 3% or less can be obtained.

  When the pH of the activated carbon for water treatment of the present invention is measured according to JIS K1474, it is preferably 4.0 to 7.0, more preferably 4.5 to 6.5.

  Furthermore, the activated carbon for water treatment according to the present invention is preferably 4.0 to 7.0 when pH is measured according to JIS K1474 after drying at 115 ± 5 ° C. for 3 hours. What becomes 6.5 is more preferable.

  There is no restriction | limiting in particular as a method of performing water treatment using the activated carbon for water treatment of this invention, Water treatment can be performed like the activated carbon for normal water treatment. For example, the water treatment can be performed by filling the activated carbon for water treatment of the present invention into a column and passing water to be treated through the column. Moreover, the activated carbon for water treatment of this invention is thrown into to-be-processed water, and water treatment can also be performed by filtering activated carbon after stirring.

Next, the water treatment apparatus of the present invention will be described.
An example of the water treatment apparatus of the present invention is shown in FIG. In FIG. 2, a water treatment apparatus 10 of the present invention includes a pump 2, a column 6 connected to the pump 2 via a pipe 4, and a pH meter 12 connected to the column 6 via a pipe 8. 6 is filled with activated carbon 14 for water treatment.

  Then, the water to be treated supplied by the pump 2 is introduced into the column 6 through the pipe 4. The treated water put into the column 6 is treated with the activated carbon 14 for water treatment, and the treated water is discharged through the pipe 8 and the pH is measured by the pH meter 12. Thereby, a series of water treatment processes will be completed.

<Reference Examples 1-4>
1 kg of activated carbon (“Evadia LG-20”: manufactured by Ebara Manufacturing Co., Ltd. (activated carbon not washed with acid)) was neutralized with 4 L of 0.15 N hydrochloric acid, and then washed with 4 L of water. After filtering the activated carbon, a part of it was measured for pH according to JIS K1474. The result was pH = 5.5. Next, activated carbon for water treatment of the present invention was obtained by adding 4 L of hot water at 80 ° C. to the filtered activated carbon, washing for about 20 minutes, and further filtering the activated carbon.

  About the obtained activated carbon for water treatment, it was pH = 6.8 when pH was measured by dry mass conversion according to JISK1474. Furthermore, after drying at 115 degreeC for 3 hours, when pH was measured according to JISK1474, it was pH = 6.6 (Example 1).

By performing the same operation while increasing the hydrochloric acid concentration, three types of activated carbon for water treatment with different pH were obtained (Reference Examples 2 to 4).
The measurement results of pH are also shown in Table 2.

Next, the water treatment apparatus shown in FIG. 2 was filled with 500 ml of the activated carbon for water treatment obtained above, and a water treatment test was performed. The column diameter used was 40 mm, and SV = 5h-1. The results are shown in FIG.

  From this, it is understood that when the water treatment is performed using the activated carbon for water treatment of the present invention, it falls within the drinking water standard.

<Reference Examples 5-7, Example 1>
By the same operation as in Reference Example 1, the activated carbon was neutralized with acid and washed with water. Next, water washing, alkali washing, heat washing, and drying were performed to obtain activated carbon for water treatment of the present invention (Reference Examples 5 to 7, Example 1).

  Table 3 shows the pH measurement results in terms of dry weight after acid neutralization and water washing, the pH measurement results after drying after each operation, and the pH measurement results in terms of dry mass after each operation.

Next, the obtained activated carbon for water treatment was subjected to a water treatment test in the same manner as in Reference Example 1. The maximum and minimum values of the treated water pH at this time are also shown in Table 3.

  From this, it can be seen that activated carbon for water treatment that facilitates pH adjustment can be obtained by performing an acid removal operation.

  As described above, according to the present invention, the pH measured according to JIS K1474 is 4.0 to 7.0, and after drying at 115 ± 5 ° C. for 3 hours, the pH measured according to JIS K1474 is 4. It turns out that the activated carbon for water treatment which is 0-7.0 is obtained, and when water treatment is performed using this, it falls within the drinking water standard.

FIG. 1 is a diagram showing the results of a water treatment test using conventional pH-adjusted activated carbon. FIG. 2 is a diagram showing an example of the water treatment apparatus of the present invention. FIG. 3 is a diagram showing the results of a water treatment test using the activated carbon for water treatment of the present invention.

Claims (6)

Neutralizing activated carbon with 0.01 to 0.15 N aqueous hydrochloric acid and / or aqueous carbonate,
Washing the activated carbon with water or alkaline water;
Drying the activated carbon to remove the acid retained on the activated carbon;
The activated carbon for water treatment obtained by the above, wherein the activated carbon has a water content of 3% or less. The activated carbon for water treatment according to claim 1, wherein the pH measured by JIS K1474 is 4.0 to 7.0. 3. The activated carbon for water treatment according to claim 1, wherein the pH measured in accordance with JIS K1474 is 4.0 to 7.0 after drying at 115 ± 5 ° C. for 3 hours. Neutralizing activated carbon with 0.01 to 0.15 N aqueous hydrochloric acid and / or aqueous carbonate,
Washing the activated carbon with water or alkaline water;
Drying the activated carbon to remove the acid retained on the activated carbon;
A step of further drying such that the moisture content of the activated carbon is 3% or less;
For producing activated carbon for water treatment. A water treatment apparatus comprising: a column filled with the activated carbon for water treatment according to any one of claims 1 to 3; and a pump for supplying water to be treated to the column. A water treatment method using the activated carbon for water treatment according to claim 1.