Homogeneous Photosensitized Oxidation for Water Reuse in Cellars: A Study of Different Photosensitizers

The demand for fresh water is increasing daily, requiring industries to take action to reduce the need for fresh water. Winemaking industries represent a massive hydric impact by combining the water consumed and the high volume of wastewater produced. The sun-driven photooxidation process has been widely employed in removing wastewater pollutants. This work employed four photosensitizers, Rose Bengal, AlPcS4, ZnPcS4, and TPP, for water reuse in cellars. A secondary effluent has been investigated as a water matrix. Of all the photosensitizers (PS) employed, ZnPcS4 showed better chemical oxygen demand (COD) (23%) and phenolic (TPh) (81%) removal. The effect of pH and concentration was also assessed for ZnPcS4. The phenolic content removal was found to be highly dependent on the solution's pH, as alkaline solutions improve the singlet oxygen quantum yield where the use of a pH = 11 reached 42% and 81% of COD and TPH removal. However, a pH higher than 7 showed higher PS bleaching than pH = 7. Three different PS concentrations were evaluated: 3 x 10(-6), 5 x 10(-6), and 1 x 10(-5) mol/L. The optimal PS concentration was found to be 5 x 10(-6) mol/L.

Automated summary

The increasing demand for fresh water requires industries to reduce the need for it, especially in the winemaking industry, which has a significant impact on water resources due to high water consumption and wastewater production. The sun-driven photooxidation process is widely used for wastewater treatment, and this study employed four photosensitizers to remove pollutants from wastewater for water reuse. Among the photosensitizers used, ZnPcS4 showed better removal of chemical oxygen demand (COD) and phenolic compounds (TPH). The study also evaluated the effect of pH and concentration on ZnPcS4, finding that alkaline solutions improved the removal efficiency but also caused bleaching of the photosensitizer.