The Removal and Recovery of Non-orthophosphate from Wastewater: Current Practices and Future Directions

The critical shortage of phosphorus (P) resources and its associated environmental pollution underscore the urgent need for reducing P emission and recovering P. Non-orthophosphate species (phosphite, hypophosphite, and phosphonate), prevalent in industrial wastewater, contribute to water eutrophication, damage plant growth, and pose serious public health risks after discharging into the aquatic environment. These species are neglected despite their negative influences. Herein, we present a comprehensive review of non-orthophosphate species emphasizing their physicochemical properties, sources, detection methods, and toxicity. Moreover, we summarize and discuss recent advancements in biological, physicochemical (i.e., adsorption, Fenton, photocatalysis, catalytic oxidation, and Fenton-like), and electrochemical (i.e., electo-Fenton, photoelectron-Fenton, anodic oxidation, and electroadsorption) practices to remove and recover non-orthophosphate. In addition, we discuss the potential applications of these technologies, evaluate the processing efficiency and operating costs, and analyze the effects of the operating parameters. Finally, we provide a cutting-edge perspective regarding developing non-orthophosphate removal and recovery technologies that are more effective and affordable. We call for the development of cost-effective chemicals, high-quality electrodes, and enhancement of mass transfer efficiency to improve processing efficiency, deeper understanding of the reaction mechanism, and comprehensive evaluation of the recycled product to improve technology maturity and move toward industrialization.