Utilization of Weibull Techniques to Describe Stability Distribution of Carbon Resin Electrodes

Abstract

As a follow up to previous studies, in this paper, the stability of carbon-resin electrodes has been statistically analysed using Weibull distribution. Carbon electrodes were developed from used and discarded dry cells and resin using a non-heat treatment process. Stability of the electrodes during and after electrochemical treatment was tested in synthetic wastewater prepared using standard methods. Effects of particle size, percentage of  resin and compaction pressure on the stability of the electrodes were studied and a mathematical model was developed. Results of the stability tests were analysed using Weibull techniques. The techniques were evaluated using known statistical methods (total error, coefficient of determination and model selection criterion) .

The study revealed that the electrodes had a mean of stability after 24 hours of 89.79 % with standard deviation and coefficient of variation of 2.57 and 2.86 % respectively. The mathematical model of stability in use with respect to particle size (S_a), percentage binder (P_c) and compaction pressure (C_u) revealed that stability of the electrodes depends mainly on S_a  (2.38 x 10 ⁴ /m) and  C_u (5.82x 10^-7m²/N), but less on P_c (3.84/%). Correlation coefficient between experimental and predicted stabilities using the model was found to be statistically adequate indicating that there is an agreement between the values statistically. Weibull distribution parameters namely scale ‘ b’  and shape ‘c’ parameters were in the range of 88.99 to 92.49 and 31.80 to 50.62 respectively. This indicates that selected operational factors affect stability distribution of carbon resin electrodes and that at compaction pressure of greater than 90 MN/m² the electrodes will be stable. Statistical evaluation showed that total error, coefficient of determination and model selection criterion were 8.321, 0.998 and 5.739, and 0.606, 1.000 and 11.496 for three and two parameter models respectively. These results show that two parameter model is better than three parameters model because of lower total error, higher coefficient of determination and model of selection criterion. An application of limit state criterion provides information about safe and unsafe regions for the stability, particle size and compaction pressure.

 It was concluded that Weibull distribution can be applied in development of carbon resin electrodes, which are important ingredients in wastewaters treatment.  Mathematical model developed allows researchers to describe the stability of a carbon resin electrodes and provides information for the manufacturers that will help in the production of the electrodes.