ELECTROLYSIS OF BRINE USING PLASMA CATHODES
ELECTROLYSIS OF BRINE USING PLASMA CATHODES H. F. M. Silva1*; F. L. G. Menezes2; A. K. Gurgel2; R. R. Melo2 C. Alves Jr 2 1 LabPlasma, Universidade Federal do Rio Grande do Norte, Lagoa Nova, 59066-800, Natal, RN, Brazil. 2 LabPlasma, Universidade Federal Rural do Semiárido, Costa e Silva, 59.625-900, Mossoró, RN, Brazil. In this work was used as DBD plasma jet electrode in the production of the electrolysis in aqueous metal salts. Fructose was used as a stabilizer that prevents uncontrolled particle growth and agglomeration. This new methods have been studied to obtain metalics nanoparticle of Ag and Na when is used water containing AgNO3 and NaCl, respectively. In this study, plasma jet was used as the cathode, and a cylinder of stainless steel as anode. The plasma jet was used with high voltage of 56 kV and frequency of 500Hz. This configuration is applied for different times (5, 10, 15, 20 and 30 minutes). After electrolysis, the samples were analyzed by spectrophotometry and compared to its color. By measuring absorbance at 400 nm and 590 nm, obtained using the spectrophotometer, showed that Ag is stabilized in the solution while Na is sedimented at the bottom of the container.
Keywords: DBD Plasma, Plasma Electrolysis, absorbance Introduction Using electrolysis to extract sea water products is costly, mainly due to the large consumption of electrodes caused by the highly corrosive environment. The possibility of using plasma jets as electrodes in liquid solutions, opens a great opportunity for application in saline solutions as seawater. Experiments conducted by Richmonds et al. [2008 Richmonds] showed that is possible to obtain Ag nanoparticles from an aqueous solution containing AgNO3. In this study the experiment was repeated and extrapolated to other on our interest, such as the seawater electrolysis. In this sense electrolysis was carried out in water containing NaCl when plasma jet produced by dielectric barrier discharge is used as cathode. Experimental part Two solutions were prepared. The first solution was produced by the article that originated this work [Richmonds 2008] and serve as a reference for the second solution, to be tested in this study. The first solution was prepared by adding 50% of 0.1 Mm AgNO3 and 50% of 0.01 M fructose and another one with 50% of 30g / L NaCl and 50% of 0.01 M fructose in distilled water. A cuvette with approximately 04 ml of solution was used to perform the treatment. For this electrolysis, the configuration used was as follows: Plasma jet of He gas was used as the cathode 2 mm between the tube end and the liquid surfasse having a stainless steel cylinder approximately of 20 mm as an anode in solution. The plasma jet was used with high voltage of 56 kV and frequency of 500Hz. At different times 5, 10, 15, 20 and 30 minutes. Absorbance measurements were performed at 400 nm and 590 nm for studies with solutions of AgNO3 and NaCl respectively, with the aid of a spectrophotometer (Figure 1)
Fig. 1 – Schematic model of electrolysis using plasma jet as cathode, and equipment for characterization.
Results and discussion When analyzing the samples of AgNO3 a crescente color gradiente was generated (Figure 2). Furthermore, the absorbance result of Ag shows that there is an increase in it intensity compared to electrolysis time (Figure 3). In electrolysis in NaCl there was no change in color of the solution and it absorbance intensities of Na shows decreasing (Figure 4). These results show that one of the factors that influence directly in the dissolution of the metal in solution is the duration of electrolysis.
Fig. 2 – Silver dissociation evolution as a function of electrolysis time in plasma. Where A1, A2, A3, A4, A5 and A6 represent the samples. A1 is the solution without treatment and the following result from the treatment of 5, 10, 15, 20 and 30 min respectively. Absorbance I Absorbance II
0,010 0,25
0,008 0,006
Absorbance (590 nm)
Absorbance (400nm)
0,20
0,15
0,10
0,05
0,004 0,002 0,000 -0,002 -0,004 -0,006 -0,008
0,00
-0,010 0
5
10
15
20
25
30
Time (min)
Fig. 3 – Absorption spectrophotometry Ag colloid obtained from diferente treatment times.
0
5
10
15
20
25
30
Time (min)
Fig. 4 – Absorption spectrophotometry Na colloid obtained from diferente treatment times.
Conclusions It was observed that the color of the samples and the absorbance of AgNO3 gradually increased. In parallel there was no change in the color of the NaCl solution. However, it was noted that there was a precipitation of small particles. Initially, the particles remain dispersed in the solution, and then was decanted from the same container. Therefore, two absorbance measurements were performed. These phenomena were attributed to the effect of fructose as stabilizing agent. References [1] C. Richmonds and R. Mohan. Sankaran Plasma-liquid electrochemistry: Rapid synthesis of colloidal metal nanoparticles by microplasma reduction of aqueous cations. Applied Physics Letters, vol. 93, nº. 131501,2008. Acknowledgement: CNPq, UFERSA.
Keywords: DBD Plasma, Plasma Electrolysis, absorbance Introduction Using electrolysis to extract sea water products is costly, mainly due to the large consumption of electrodes caused by the highly corrosive environment. The possibility of using plasma jets as electrodes in liquid solutions, opens a great opportunity for application in saline solutions as seawater. Experiments conducted by Richmonds et al. [2008 Richmonds] showed that is possible to obtain Ag nanoparticles from an aqueous solution containing AgNO3. In this study the experiment was repeated and extrapolated to other on our interest, such as the seawater electrolysis. In this sense electrolysis was carried out in water containing NaCl when plasma jet produced by dielectric barrier discharge is used as cathode. Experimental part Two solutions were prepared. The first solution was produced by the article that originated this work [Richmonds 2008] and serve as a reference for the second solution, to be tested in this study. The first solution was prepared by adding 50% of 0.1 Mm AgNO3 and 50% of 0.01 M fructose and another one with 50% of 30g / L NaCl and 50% of 0.01 M fructose in distilled water. A cuvette with approximately 04 ml of solution was used to perform the treatment. For this electrolysis, the configuration used was as follows: Plasma jet of He gas was used as the cathode 2 mm between the tube end and the liquid surfasse having a stainless steel cylinder approximately of 20 mm as an anode in solution. The plasma jet was used with high voltage of 56 kV and frequency of 500Hz. At different times 5, 10, 15, 20 and 30 minutes. Absorbance measurements were performed at 400 nm and 590 nm for studies with solutions of AgNO3 and NaCl respectively, with the aid of a spectrophotometer (Figure 1)
Fig. 1 – Schematic model of electrolysis using plasma jet as cathode, and equipment for characterization.
Results and discussion When analyzing the samples of AgNO3 a crescente color gradiente was generated (Figure 2). Furthermore, the absorbance result of Ag shows that there is an increase in it intensity compared to electrolysis time (Figure 3). In electrolysis in NaCl there was no change in color of the solution and it absorbance intensities of Na shows decreasing (Figure 4). These results show that one of the factors that influence directly in the dissolution of the metal in solution is the duration of electrolysis.
Fig. 2 – Silver dissociation evolution as a function of electrolysis time in plasma. Where A1, A2, A3, A4, A5 and A6 represent the samples. A1 is the solution without treatment and the following result from the treatment of 5, 10, 15, 20 and 30 min respectively. Absorbance I Absorbance II
0,010 0,25
0,008 0,006
Absorbance (590 nm)
Absorbance (400nm)
0,20
0,15
0,10
0,05
0,004 0,002 0,000 -0,002 -0,004 -0,006 -0,008
0,00
-0,010 0
5
10
15
20
25
30
Time (min)
Fig. 3 – Absorption spectrophotometry Ag colloid obtained from diferente treatment times.
0
5
10
15
20
25
30
Time (min)
Fig. 4 – Absorption spectrophotometry Na colloid obtained from diferente treatment times.
Conclusions It was observed that the color of the samples and the absorbance of AgNO3 gradually increased. In parallel there was no change in the color of the NaCl solution. However, it was noted that there was a precipitation of small particles. Initially, the particles remain dispersed in the solution, and then was decanted from the same container. Therefore, two absorbance measurements were performed. These phenomena were attributed to the effect of fructose as stabilizing agent. References [1] C. Richmonds and R. Mohan. Sankaran Plasma-liquid electrochemistry: Rapid synthesis of colloidal metal nanoparticles by microplasma reduction of aqueous cations. Applied Physics Letters, vol. 93, nº. 131501,2008. Acknowledgement: CNPq, UFERSA.
