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MY RESEARCH :-)

Japanese Version

BACHELOR COURSE

[SURFACE TREATMENT OF ACTIVATED CARBON USING DIELECTRIC BARRIER DISCHARGE]

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INTRODUCTION

Activated carbon can adsorb an extremely wide range of hazardous compound. In the present study, we used plasma in order to improve  the adsorption ability of activated carbon. Plasma treatment probably will gives change to the surface chemical structure and pore structure, as for these structures  give  a big influence in adsorption property. There are many types of plasma, but in this research the plasma dielectric barrier discharge was utilized in generation process. In this treatment process, the interchange discharge was put between the electrodes. Plasma usually generates under high temperature and low pressure conditions, but as for dielectric barrier discharge with the dielectric current is restricted,  the discharge is maintained to occur at normal temperature and atmospheric pressure, so it is not necessary to provide the vacuum devices. Furthermore, the plasma treatment   becomes  more possible at  low cost  due  to  small  energy. In this research, the pH and  specific surface area etc are measured in order to know the changes in surface character by plasma treatment. Furthermore, we used plasma treated activated carbon on adsorption of  the arsenic and  compared it with the untreated activated carbon.  

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EXPERIMENTAL METHOD

The apparatus of this experiment is shown in Fig.1. In the discharge section, two  copper plates were arranged parallel. As for treatment method, activated carbon were put between electrodes. Let O2 through and then impressed the voltage in the reactor. After  specified time, stopped the discharge and then fetched the activated carbon. Plasma treatment condition is shown in Table 1. On the other hand, pH 10.38 of arsenic solution is used in adsorption experiment, the adsorption experimental condition is shown in Table 2.

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RESULTS AND DISCUSSION

Chemical property like pH also gives an influence in adsorption  phenomenon instead of  pore structure of activated carbon (surface area, pore volume, pore diameter distribution).  Fig.2 shows the variation of pH of activated carbon as a function of treatment time. It can be concluded that the increase in pH with time is due to the  oxidation reaction  occurred, as a result of forming phenol type hydroxyl (- OH) and carboxyl group (-COOH) etc  (from previous result of low temperature  oxygen plasma experiment). On the other hand, the specific  surface  area  did  not  change  abruptly  even  if  it  was treated by plasma. The result of adsorption experiment of arsenic is shown in Fig.3. As Fig.3 shows, the increase of adsorption quantity is not excessively seeing at 10.7kV, whereas at 12.4kV, the adsorption quantity is gradually increased with treatment time. It can be concluded that all the pore volume was increased.

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CONCLUSION

As a conclusion, when the activated carbon is  treated by plasma, the pH of the activated  carbon decreased and the mesopore volume increased. This time, from the result of arsenic adsorption experiment we could see slightly improvement of adsorption properties.                         

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Fig.1 Experimental apparatus

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Discharge voltage 10.7 - 12.4 kV
Plasma gas Oxygen
Gas flow rate 0.5 L/h
Treatment time 10 - 30 min
Table 1 Plasma treatment condition
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Temperature 25Ž
Pressure Atmospheric pressure
Adsorption time 6 - 96h
Adsorbent weight 0.1 g
Table 2 Adsorption experimental condition ( pH 10.38)

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MASTER COURSE

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