Harnessing Natural Sunlight for Solar-Driven Photocatalysis in 2 Sustainable Agricultural Runoff Remediation

This study evaluates the real-world performance of a TiO₂ compound parabolic collector 23 (CPC) photocatalytic reactor operated under natural sunlight for the treatment of agricul- 24 tural runoff. Three objectives are to determine whether photocatalytic performance can be 25 reliably predicted using spectrally relevant UVA dose, quantify the impact of water-ma- 26 trix optical attenuation on degradation efficiency, and lastly to assess whether an adaptive 27 irradiance-gated control strategy can improve operational throughput. Field Analytical 28 Models are conducted by using a 5 L recirculating CPC slurry reactor treating three model 29 agro-pollutants under mid-latitude outdoor conditions. Kinetics followed pseudo-first- 30 order behaviour when analysed against cumulative UVA dose, which reduced inter-day 31 variability in apparent rate constants from more than 30% (time-based analysis) to less 32 than 10%. Natural river water shows a 20–35% reduction in removal efficiency relative to 33 synthetic runoff, which correlated with lower UV transmittance and higher UV254 ab- 34 sorbance. Catalyst reusability tests indicated only an 18% loss of activity after five cycles, 35 with partial recovery after rinsing. Importantly, the proposed adaptive UVA-dose control 36 increased daily treated volume by 25–35% compared with continuous operation. These 37 results demonstrate that solar photocatalysis can be transformed into a predictable, opti- 38 misable treatment process when spectral irradiance, matrix optics, and intelligent opera- 39 tion are considered together.