Heavy metal sorption by biochars in mixed metal solutions

James A. Ippolitoa, L. Cuia,b, and K. Scheckelc

a Department of Soil and Crop Sciences, Colorado State University, USA

b School of Environmental Science and Engineering, Yancheng Institute of Technology, China

c USA States Environmental Protection Agency, National Risk Management Research Laboratory, Land and Materials Management Division, USA

jim.ippolito@colostate.edu

Biochars have the proven capacity to sorb and thus reduce trace and heavy metal bioavailability, with the intent to improve environmental quality and human health. The majority of laboratory-based studies have focused attention on one or two trace elements within soil or water systems; what is desperately lacking are focused studies with the use of biochar for metal sorption in mixed metal matrices (e.g., matrices that might be found in urban or environmental runoff). We focused attention on the use of five different biochars for trace/heavy metal sorption in a mixed solution phase – solutions contained varying amounts of biochar in the presence of varying concentrations of Zn, Cu, Cd, Pb, Al, and Fe (we are currently adding Cr, Ni, and Hg into the solution matrix). Our intent was to quantify sorption phenomenon and maximum metal sorption in the presence of other potentially competing metal ions. Results show that biochar-heavy metal sorption varied considerably based, likely on, inherent biochar properties. However, some of the best performing biochars resulted in sorption of Al and Cu up to ~ 680 and 1140 mg/kg, respectively. These high-performing biochars linearly sorbed Cd, Fe, Pb, and Zn up to 100, 1400, 800, and 1200 mg/kg, respectively, with sorption maximum not yet met. Sorption mechanisms are currently being quantified. Regardless, some biochars obviously have the propensity to sorb a multitude of heavy/trace metals in the presence of mixed metal solution phases. These results suggest that biochars could be created or designed to reduce metal bioavailability in mixed metal matrices, and ultimately improve environmental quality.

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