Removal of heavy metals from aqueous solution by biochars derived from anaerobically digested biomass

This study examined the ability of two biochars converted from anaerobically digested biomass to sorb heavy metals using a range of laboratory sorption and characterization experiments. Initial evaluation of DAWC (digested dairy waste biochar) and DWSBC (digested whole sugar beet biochar) showed that both biochars were effective in removing a mixture of four heavy metals (Pb2 +, Cu2+, Ni2+, and Cd2+) from aqueous solutions. Compared to DAWC, DWSBC demonstrated a better ability to remove Ni and Cd. Further investigations of lead sorption by the two biochars indicated that the removal was mainly through a surface precipitation mechanism, which was confirmed by batch sorption experiments, mathematical modeling, and examinations of lead-laden biochars samples using SEM–EDS, XRD, and FTIR. The lead sorption capacity of the two biochars was close to or higher than 200 mmol/kg, which is comparable to that of commercial activated carbons.