Reducing the migration of cadmium, lead and nickel in soil using rice straw-based humic acid modified bentonite

With the continuous advancement of industrial development, the contamination of soil by potentially toxic element ions has emerged as an escalating issue, posing significant threats to both ecological systems and human health. Clay minerals have long been considered as green and economic remediation agents for polluted soil. However, their current application is hampered by low and inconsistent fixation efficiency. Here, a new clay composite BHA@B was prepared by modifying bentonite with biomass humic acid (BHA) prepared from rice straw. The BHA@B was characterized by FTIR, SEM and XRD and then tested as a remediation agent for potentially toxic element ion-contaminated soil. The effect of BHA@B on the prevalence of different fractions of Cd, Pb and Ni in soil and its ability to stabilize these metals were investigated using the BCR sequential extraction method. Treatment with BHA@B reduced the weak acid-extractable and reducible fractions of cadmium, lead and nickel by 22.5 and 8.1%, 17 and 11.4%, and 19.8 and 14%, respectively, compared with untreated soil. BHA@B transforms potentially toxic elements into oxidizable, residual, and other stable fractions, which greatly reduces the ability of potentially toxic element ions in the soil to migrate into the groundwater. BHA@B is a new, green, low-cost and efficient soil remediation agent.