Novel integrating sphere structure solar photocatalytic reactor design: Efficient conversion of nitrate wastewater into high-value ammonia

Solar photocatalytic nitrate technology represents a promising, eco-friendly approach with wide application potential. However, in practical applications, non-concentrated photocatalytic reactors often suffer from low surface solar energy flow density and significant optical losses due to material reflection. To address these issues, this paper proposes a photocatalytic reactor with an integral sphere structure, designed to enhance solar energy flow density during the photocatalytic process and minimize light loss caused by photocatalyst reflection. This study evaluated the optical performance of this structure and found that the optical losses at standard and 10° incident angles are 34.13 % and 34.64 %, respectively, which meet the design requirements. The successful loading of Cu2+ enhances the responsiveness of Cu-TiO2 to ultraviolet and visible light. In practical environments, the total ammonia production after 3 h, 4 h, and 5 h of reaction under concentration condition were 175.42 μg, 251.15 μg, and 280.28 μg. In addition, through testing in non-concentration mode under the same irradiance, the total ammonia production was 82.66 μg, 90.35 μg, and 101.22 μg, respectively. Compared with non-concentration conditions, the total ammonia production of the system increased by 113.2 %, 177.9 %, and 176.62 %, respectively. These findings underscore the potential of the integral sphere photocatalytic reactor for practical environmental treatment applications.