Effects of Cationic Polypeptide on CaCO3 Crystallization and Sand Solidification by Microbial-Induced Carbonate Precipitation

摘要

The use of organic additives to improve microbial-induced carbonate precipitation (MICP) is a novel and innovative idea. This study is the first to address the effects of the cationic biopolymer polylysine (poly-Lys) on CaCO3 crystallization and sand solidification by MICP. CaCO3 was precipitated with and without poly-Lys by hydrolysis of urea by using ureolytic bacteria, Pararhodobacter sp., in the presence of CaCl2 under different experimental conditions. The morphologies and polymorphs of the oven dried precipitates were investigated using scanning electron microscopy and X-ray diffraction. A larger amount of precipitate was obtained with poly-Lys than with the conventional MICP method. The curve for the relationship between the poly-Lys concentration and amount of precipitate was bell shaped. In the presence of poly-Lys, the morphology changed from rhombohedral crystals to twin spherical crystals. The effects of poly-Lys on sand solidification were also investigated by syringe solidification at different bacterial injection intervals with and without poly-Lys. The addition of poly-Lys gave strongly cemented sand specimens that were stronger than those obtained by the conventional method. The results confirm that poly-Lys addition is an effective and sustainable way to improve the MICP efficiency and production of green materials for engineering applications.