Abstract
This work describes the design and testing of a low-cost light-emitting diode (LED)-based nephelometer for turbidity analysis. It also describes the use of this nephelometer for context-based learning (CBL) experiments designed for teaching laboratories. The LED nephelometer is simple, low-cost, and robust, providing similar results as a commercial device. Data collection and analysis is quick and intuitive, allowing time and opportunity for discussion about the analytical process and the chemistry involved. The experiments described here are based on real-world applications to emphasize the usefulness of chemical analysis and quantification of turbidity in everyday life.
Highlights
Turbidity is an expression of the optical properties of a medium due to the presence of suspended particles, which cause light to be scattered rather than transmitted. It is defined by the International Organization for Standardisation (ISO) as the “reduction of transparency of a liquid caused by the presence of undissolved matter”
It is proposed that “Mie scattering” is the dominant form of light diffusion occurring within the light-emitting diode (LED) nephelometer since the particle sizes used throughout this work have previously been reported as having similar or larger diameters than the wavelength of the light source (860 nm).[32−34] The proposed directions and intensity of the light diffusion are represented in the schematic (Figure 1)
The kaolinite suspension produces a steady and linear flocculation profile over time for all the flocculants tested here. This is achieved by measuring the decrease in the turbidity levels of the suspension using the LED nephelometer (Figure 6)
Summary
Turbidity is an expression of the optical properties of a medium due to the presence of suspended particles, which cause light to be scattered rather than transmitted. It is proposed that “Mie scattering” is the dominant form of light diffusion occurring within the LED nephelometer since the particle sizes used throughout this work have previously been reported as having similar or larger diameters than the wavelength of the light source (860 nm).[32−34] The proposed directions and intensity of the light diffusion are represented in the schematic (Figure 1) This is based on a standard Mie scattering plot where the most intense scattering takes place in the forward direction, away from the incident radiation. The kaolinite suspension produces a steady and linear flocculation profile over time for all the flocculants tested here This is achieved by measuring the decrease in the turbidity levels of the suspension using the LED nephelometer (Figure 6). The results obtained here through turbidity analysis with the LED nephelometer confirm previously reported flocculation differences between kaolinite and montmorillonite with different cations.[52,53]
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