Calciphilic plant biomass inherent metal cross-linked manganese oxide modification of biochar for heavy metal immobilization

• KMnO4-modified calcium-rich plant biochar was prepared • Intrinsic metallic calcium and exogenous metals promote the modification • Surface complexation and precipitation were the main adsorption mechanisms • Calciphilic plant biochar serves as an environment-friendly adsorbent Pristine biochar generally has disadvantages such as low adsorption capacity, a restricted number of functional groups, poor stability, and its application is very limited. To address this issue, the interaction between biomass endogenous metals and modifiers (metal oxide) was combined to remove target contaminants. Herein, Pteroceltis tatarinowii wood, a biowaste material, was utilized to make a new modified Ca-rich biochar by adding manganese oxide, effectively removing Cu (II)/Zn (II). In comparison with unmodified biochar, the adsorption capacity of modified biochar was enhanced according to the findings. The reason behind this phenomenon is that manganese oxide and biomass endogenous metals interact in concert. The endogenous mineral CaCO 3 in calcium-rich biochar will form a large amount of CaO and CO 3 2 − under the action of the KMnO 4 modifier, which is conducive to the complexation and precipitation reactions between biochar and heavy metals. Moreover, MnO x has the advantages of a rich micropore structure and multiple adsorption sites. Cu (II)/Zn (II) adsorption mechanism was mainly through precipitation, ion exchange, cation-π electron interaction, and complexation of surfaces with functional groups that contain oxygen. It can serve as a reference for analyzing the mechanisms of endogenous metals in the preparation and modification of biochar.