Effect of pruning-derived biochar on heavy metals removal and water dynamics

Biomass-derived biochar is considered as a promisingheavy metal adsorbent, due to abundance of polar functionalgroups, such as carboxylic, hydroxyl, and aminogroups, which are available for heavy metal removal. Theaims of this study were to evaluate the effectiveness of anorchard pruning-derived biochar in removing some heavymetals (through the evaluation of isotherms) and to studywater dynamics at the solid-liquid interface as affected byheavy metal adsorption (through an innovative nuclear magneticresonance (NMR) relaxometry approach). Both isothermsand NMR spectra revealed that Pb and Cr showed agood affinity for the biochar surface (Pb > Cr), while Cu wasless affine. Accordingly, higher amounts of Pb and Cr wereadsorbed by biochar as compared to those of Cu in the singlesystems. In binary systems (i.e., when two metals were appliedsimultaneously), Pb showed the highest inhibition of theadsorption of the other two metals, whereas the opposite wasevidenced when Cu was used; the competitive adsorption wasalso strongly influenced by the metal residence time on biocharsurface. In ternary systems (i.e., when all metals wereapplied simultaneously), even in the presence of high amountsof Pb and Cr, considerable adsorption of Cu occurred, indicatingthat some biochar adsorption sites were highly specificfor a single metal.