Harnessing Natural Sunlight for Solar-Driven Photocatalysis in Sustainable Agricultural Runoff Remediation

This study evaluates the real-world performance of a TiO2 compound parabolic collector (CPC) photocatalytic reactor operated under natural sunlight for the treatment of agricultural runoff. The three objectives are to determine whether photocatalytic performance can be reliably predicted using a spectrally relevant UVA dose, quantify the impact of water-matrix optical attenuation on degradation efficiency, and lastly, to assess whether an adaptive irradiance-gated control strategy can improve operational throughput. Field Analytical Models are conducted by using a 5 L recirculating CPC slurry reactor treating three model agro-pollutants under mid-latitude outdoor conditions. Kinetics followed pseudo-first-order behaviour when analysed against cumulative UVA dose, which reduced inter-day variability in apparent rate constants from more than 30% (time-based analysis) to less than 10%. Natural river water shows a 20–35% reduction in removal efficiency relative to synthetic runoff, which was correlated with lower UV transmittance and higher UV254 absorbance. Catalyst reusability tests indicated only an 18% loss of activity after five cycles, with partial recovery after rinsing. Importantly, the proposed adaptive UVA dose control increased the daily treated volume by 25–35% compared with continuous operation. These results demonstrate that solar photocatalysis can be transformed into a predictable, optimisable treatment process when spectral irradiance, matrix optics, and intelligent operation are considered together.