Remediation of multi-metal(loid) contaminated soils using Mn-modified biochar: Mechanistic insights and influencing factors

Mn-modified biochar could impact soil quality and metal(loid) migration in contaminated soils. However, the remediation efficiency, mechanism, and influencing factors of Mn-modified biochar on multi-metal(loid) contaminated soils were largely unknown. In this study, three Mn-modified biochar were prepared by using MnCl2-impregnated 2-impregnated rubber, tobacco rod, and coconut shell biochar, respectively. The remediation efficiency of Mn-modified biochar on Pb, As, Cd, Cu, and Zn contaminated soil was also compared. Our data revealed that the addition of Mn-modified biochar increased the effective cation exchange capacity (ECEC), organic matter (OM), alkaline hydrolyzed nitrogen (AHN), and the mobility of the nutrient Zn in the soil. Furthermore, Mn-modified rubber biochar and Mn-modified coconut shell biochar reduced acid extractable or Diethylenetriamine Pentaacetic Acid (DTPA) leached Pb, As, Cd, and Cu However, Mn-modified tobacco rod biochar increased the acid extractable or DTPA leached Pb, Cd, and Cu. The study showed that three Mn-modified biochars could effectively improve soil physicochemical properties and significantly increase soil nutrient activity. Mn-modified rubber and coconut shell biochar can effectively immobilize metal(loid)s and reduce their damage to soil. However, the Mnmodified tobacco rod biochar instead increased the mobility of metal(loid)s. The results indicate that feedstock is an important factor influencing the application of Mn-modified biochar and should be considered in the production.