Potential to remove heavy metals and cyanide from gold mining wastewater using biochar

Abstract

Gold processing results in the generation of tailings wastewater which contain cyanide (CN−) and heavy metals ions such as chromium (Cr3+), iron (Fe2+), zinc (Zn2+), nickel (Ni3+), lead (Pb2+), manganese (Mn2+) and copper (Cu2+). On the other hand, low cost-based bio adsorbents have received a lot of interest as a source of bio-based wastewater treatment for removal of wastewater contaminants. This study looks at the potential to remove contaminants from gold processing tailing dams using saw dust-based bio char. The bio char was produced through slow pyrolysis at 500 °C for 2 h. The bio char was then ground to particle sizes in the range of 0.5–2.0 mm before use as the bio adsorption media. The tailings wastewater was then passed through wastewater at various bio char loadings ranging from 10 to 50 mg/L at a pH of 7.0 for a period of 2–14 h. The wastewater was characterised using the APHA standard methods before and after bio adsorption. The CN, Cr, Fe, Zn, Ni, Pb, Mn and Cu ions concentration significantly reduced after the bio adsorption process with efficiency decreases as high as 75%, 78%, 74%, 87%, 82%, 70%, 85% and 90% respectively. Bio adsorbents can be successfully used to remove contaminants in gold tailings dam wastewater.