Synthesis and modifications of g-C3N4-based materials and their applications in wastewater pollutants removal

Wastewater remediation and pollutants removal, such as organic pollutants and heavy metals, have become increasingly important for the protection of environment. Numerous technologies, such as adsorption, membrane separation and photocatalysis, have been proposed to solve this problem. However, these methods also have some disadvantages, such as the inability to mineralize the pollutants during the adsorption process and the serious membrane fouling. Therefore, g-C3N4 as a photocatalyst has been widely used to remove pollutants from wastewater due to graphitic like structure, adjustable morphology, low cost, facile preparation and high chemical stability. However, the pristine g-C3N4 suffers from issues such as small specific surface area, low utilization of visible light and serious photogenerated carrier recombination. Hence, various modification strategies, such as doping, defects, morphology control, metal deposition and heterojunction construction, have been developed to improve its photocatalytic activity. In this review, the synthesis and modification techniques of novel g-C3N4 materials were systematically introduced. Their application and related mechanisms in wastewater remediation and pollutant removal were discussed. Their efficiency, limitations and advantages were also compared and discussed. Furthermore, the promising perspectives and the potential directions of g-C3N4-based materials in environmental applications were put forward and discussed. In the future, materials modifications through supramolecular self-assembly method and S-scheme heterojunction structure still need to be further explored. And it is of great significance for industrial applications to design new processes that are conducive to material recovery and simultaneous treatment of multiple pollutants.