Pyrolysis or not: Comparison between biomass and biochar for vanadium stabilization in soil

Abstract

Vanadium (V) ore mining and processing result in abandoned V in soil, whose immobilization is crucial for pollution control. Utilizing recyclable biomass and biochar materials as (bio)stabilization agents for V is promising, but their efficacies have rarely been comparatively investigated. In this study, the efficacy of raw biomass (rice husk and sawdust) and their pyrolytic derivatives (biochar produced at 300 °C and 600 °C) in stabilizing V within contaminated soil matrices was systematically examined. The results indicated that rice husk outperforms wood chips, achieving a stabilization efficiency of 47.7 ± 2.84 % within 42 d. Mechanistic analyses indicated the reduction of mobile pentavalent V to insoluble tetravalent V precipitates, a process mediated by redox-active organic functional groups inherent to biomass substrates. Furthermore, soil microbiomes played a pivotal role in V stabilization, with taxa including KD4-96, MND1, Comamonadaceae, Methylotenera, and Pseudolabrys demonstrating exceptional V tolerance and serving as key drivers of microbial-mediated V reduction. Comparative assessment highlighted that biomass amendments not only enhanced V immobilization but also positively modulated microbial community composition and diversity, outperforming biochar treatments. This study is helpful to choose proper materials for remediation of V-contaminated soil.