To conclusively demonstrate that the photocatalytic degradation of methylene blue using a photocatalyst derived from solid waste red mud follows zero-order kinetics, several key steps must be undertaken. Initially, it is crucial to gather concentration versus time data for the degradation process at consistent intervals. When this data is plotted, the concentration of methylene blue should exhibit a linear decrease over time, characteristic of a zero-order reaction. Conducting a linear regression analysis on this plot will allow you to determine the correlation coefficient (R²), where a value close to 1 indicates strong linearity, supporting zero-order kinetics. The rate constant (k) can then be extracted from the slope of this plot.

Further validation involves repeating experiments with varying initial concentrations of methylene blue. In a zero-order reaction, the degradation rate should remain constant regardless of these initial concentrations. Additionally, performing experiments with different photocatalyst loadings while maintaining a continuous initial dye concentration should yield a consistent reaction rate, indicating that the rate is dependent on the surface saturation of the photocatalyst rather than the dye concentration.

Complementary control experiments without the photocatalyst or light exposure are essential to ensure that observed degradation is due to the photocatalytic process. Additional data, such as absorbance changes monitored via UV-Vis spectroscopy, should consistently show a decline in the absorbance peak corresponding to methylene blue over time. By rigorously following these experimental protocols and analyses, you can robustly demonstrate that the photocatalytic degradation reaction adheres to zero-order kinetics.