Study on Phosphorus Removal Pathway in Constructed Wetlands with Thermally Modified Sepiolite

Abstract

Constructed wetlands, as natural sewage treatment ecosystems, have been widely used in the fields of rural domestic sewage and sewage plant tailwater treatment. However, the synchronous removal of phosphorus in most constructed wetlands is not ideal. This study aimed to prepare thermally modified sepiolites with high phosphorus adsorption capacities and design a constructed wetland based on them. Thermal modification was adopted to enhance the adsorption capacity of sepiolite based on its high specific surface area and ion exchange capacity. The physicochemical properties and adsorption performance of thermally modified sepiolite were studied. The results showed that the specific surface area and adsorption capacity of thermally modified sepiolite were higher than those of natural sepiolite, reaching 19.494 mg·g−1. The concentration of effluent and the removal of constructed wetlands based on thermally modified sepiolite was 0.07 mg·g−1 and 91.05%. An analysis of the phosphorus forms in constructed wetlands proved that the main phosphorus removal pathway is the adsorption of substrate, and the form of phosphorus was mainly Ca/Mg-P and Fe/Al-P.