Use of Biochar for Limiting the Pathway of Exposure and Reducing the Risk of Heavy Metal Contamination from Mines

Field-scale experiments were conducted to assess biochar’s ability with and without supplements to sequester heavy metals of lead (Pb 2+ ) and zinc (Zn 2+ ) from stream water contaminated by abandoned mines. The study was conducted at the Frongoch mine watercourse site in central Wales for 1104 h (46 days). The methods employed include pyrolysis of waste Leylandii feedstocks at 700 °C and post-amendment ash at ratios in mass (kg/kg) 1:10, 1:35, 1:50, and 1:100 of biophos to biochar (BC) and 1:1:100 mixed biophos and cockleshell ash to biochar (CBB). The collected data were analyzed by ASTM Brunauer-Emmett-Teller (BET), XRF spectrometer, R-stat, and SPSS statistical procedures. The results showed that non-amended samples are better suitable as adsorbent materials of lead and zinc. Overall, this field study showed that 33 g/kg of lead and 30 g/kg of zinc could be sequestered by 50 g of biochar (BC) and activated carbon (AC) from the contaminated mine watercourse containing 0.62 mg/L and 15.8 mg/L of lead and zinc metals flowing at 0.014 m 3 /s. These adsorbent materials BC and AC applications are variably recommended at an optimal replacement interval of 1104 h (46 days) and 72 h (3 days) for lead and zinc sorption, respectively. Graphical abstract