Hydrothermal synthesis of a novel ecological revetment material by sediment mixed with biochar

Abstract

Ecological revetments, as a sustainable way of ecological construction of water conservancy projects, have attracted much attention. Herein, we synthesized a novel revetment material hydrothermally with the local sediment enriched with biochar made from waste biomass. The effect of Ca(OH)2 content, biochar content, curing temperature and curing time on the strength and porous structure of the material was studied, and with 25 mass% Ca(OH)2 and 2 mass% biochar cured at 200 °C for 12 h, the synthesized materials possess a lower pH (≤9.32), higher flexural strength (20.8 MPa) and superior removal performance of ammonia nitrogen (45%), phosphorus (100%) and heavy metals (≥90%). The formation of C–S–H and tobermorite in the matrix were found to enhance the strength of the materials, and the porous structure was attributed to the original porous structure of sediment, further the formed tobermorite and added biochar. The Sorption kinetics and equilibria of the material for heavy metals followed pseudo-second order and Langmuir isotherm equations respectively, which indicates that the mechanism of adsorption for heavy metals mainly is attributed to the chemical adsorption. In addition, the synthesized materials were used as revetments in Beiheng River (Shanghai, China), which provides a site for demonstration of the flood control and ecological restoration.