Remediation of Cd(II), Zn(II) and Pb(II) in contaminated soil by KMnO4 modified biochar: Stabilization efficiency and effects of freeze–thaw ageing

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-05, Vol.487, p.150619, Article 150619
• Main Authors: Wang, Yipeng, Wang, Xuchan, Bing, Zetao, Zhao, Qingliang, Wang, Kun, Jiang, Junqiu, Jiang, Miao, Wang, Qiao, Xue, Ruiyuan
• Format: Article
• Language: English
• Subjects: Cd/Zn/Pb co-contaminated soil; Freeze–thaw cycles; KMnO4-modified biochar; Stabilization; Two-dimensional correlation spectroscopy
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2024.150619

[Display omitted] •Stability of biochar to Cd, Zn and Pb in soil enhanced after KMnO4 modification.•Biotoxicity of metals was reduced by 28%-95% at 10% KMnO4-modified biochar dose.•Biochar was oxidized and C-O stretching change was prior during freeze–thaw cycles.•Ion exchange and precipitation were mechanisms for MBC to stabilize Cd, Zn and Pb.•KMnO4-modified biochar resisted the adverse effects of freeze–thaw cycles in soil. Biochar has been widely used in soil remediation because of its porosity and impressive efficiency. Many studies have demonstrated the good affinity of biochar for heavy metals (HMs), but efficient modification methods to increase the stability of multiple HMs are lacking. Moreover, few studies focus on biochar’s potential ability to ageing resistance and changes in its physicochemical properties during freeze–thaw (F/T) cycles. Here, KMnO4-modification biochar (MBC) was prepared and the immobilization and anti-freeze performance of MBC on Cd, Zn and Pb in soil were investigated. The addition of 10 % MBC decreased concentrations of toxicity characteristic leaching procedure (TCLP) by 66.80 %, 25.39 % and 99.68 % for Cd, Zn and Pb, respectively, after 28 days, accompanied by a significant decrease in the phytoavailability and bioaccessibility of HMs in soil. Soil fertility was also improved by MBC application. Furthermore, frequent F/T cycles obviously induced the fragmentation of soil particles and enhanced the activity of HMs. Conversely, MBC particles became finer, accompanied by further oxidation and higher alkalinity but degraded pore structures during F/T cycles. The oxidation of lignocellulose and changes in C-O stretching were greatest among all functional groups in biochar. Therefore, MBC could suppress the migration of HMs through precipitation, cohesion of soil particles, and stronger complexation by oxygen-containing functional groups. Moreover, fractions of HMs were also transferred from exchangeable to potentially labile or nonlabile species. Overall, MBC displayed advantages in the stabilization of HMs and showed higher resistance to F/T cycles and promise for long-term remediation of HM-contaminated soils in cold regions.