A Simple Spectrometer Using Various LEDs and a Photodiode Sensor for Photocatalytic Performance Evaluation

Abstract

The degradation of pollutants in a waste water with the aid of light as an energy source enabler is one of the photocatalysis processes. Because a textile dye dissolved in water is often used to model the waste water, the degradation of color becomes a major variable to indicate the water clarity after the photocatalysis process occured. Therefore, a sensitive instrument to measure the degradation of color is required. This paper reports a simple spectrometer using a photodiode sensor OPT101 and a light emitting diode (LED). The light emitted by the LED passes through the waste water so that its intensity is reduced. Then, the photodiode sensor receives the light with reduced intensity. In order to test the spectrometer performance, a waste water model was prepared by employing a textile dye in water with various concentrations. Curves showing the relationships between concentration and voltage output of the sensor were obtained for different colors of LEDs (white, blue, orange, red and yellow). A microcontroller is used to process the voltage output of the sensor and an LCD then displays the concentration. The results shows that red LEDs has a smallest error with an error of less than 5%.