Investigating Biochar As a Tool for Environmental Remediation.

Biochar is a cost-effective, carbon negative soil amendment that can lead to improved soil quality.  Research has also demonstrated the efficacy of biochar to sorb heavy metals and agricultural chemicals from contaminated soils, thus effectively reducing the potential for metal and chemical contamination of surface and ground waters.  In this study we investigated the ability of biochar produced from a single feedstock (Doulas fir wood chips) across a range of charring temperatures (300 – 700 °C) to bind with metals.  Our goal in this research is to link metal sorption to specific biochar properties, and then use these relationships to engineer biochar with specific properties to achieve various remediation and soil quality outcomes.  We characterized our biochars using a variety of techniques including total elemental analysis, pH, FTIR spectroscopy, surface area and pore size analysis, and proximal carbon analysis.  We used batch experiments of biochar with either Cu (II) solutions or simulated rainwater extracts of soils contaminated with mine tailings to investigate metal sorption.   Sorbed metals were characterized using synchrotron-based XAS, XANES, EXAFS and XRF-Tomography.  We found that higher temperature biochars, while having a decreased abundance of oxygen containing functional groups, had an increased capacity for metal sorption over biochar produced at lower temperatures.  Concomitantly, these biochars also have greater ash contents, surface areas, abundance of small pores and higher pH values.  Results of our sorption studies indicate that metal sorption on biochar may be competitive and preferential, and that as the charring temperature goes up, physisorption may become more important as a mechanism of metal sorption to biochar.