Solar Desalination and Porphyrin Mediated Visible-Light Photocatalysis in Decolouration of Dyes as Biological Analogues Applied in Advanced Water Treatment

Engineering can be made simple and more impactful by observing and understanding how organisms in nature solve eminent problems. For example, scientists around the world have observed green plants thriving without organic food inputs using the complex photosynthesis process to kick-start a self-sustaining biochemical food chain. In this study, two biological analogues for advanced water treatment, i.e., visible-light photocatalysis using porphyrin-Bi12O17Cl2 and BiOIO3 compounds and interfacial solar desalination by a by Reduced Graphene Oxide-Black TiO2 (rGO-Black TiO2) were investigated. For the visible-light photocatalytic process for dye decolouration, a porphyrin@Bi12O17Cl2 system was applied to successfully degrade Rhodamine B dye in batch experiments, achieving up to 79% degradation within 240 minutes. These results show that more advances and more efficient engineered systems can be achieved by observing nature and how these systems have survived over billions of years. The rGO-Black TiO2 system achieved increases in temperature for 25oC to 60oC in less than 5 seconds. Based on these observations, the research group from the Water Utilisation Group at the University of Pretoria have studied and developed fundamental processes for the degradation and remediation of unwanted compounds such as disinfection byproducts (DBPs), volatile organic compounds (VOCs) and pharmaceutical products from water.