Application of Biomass Ashes for Treatment of Acid Mine Drainage

摘要

Acid mine drainage (AMD) is the largest environmental problem facing the world mining and processing industry because it has low pH and can contain high concentrations of potential pollutants (e.g., Zn, Pb, Cd, Cu, As, Sb, Hg). Biomass ash (BA), which is a by-product of burning biomass in conventional power station, can be considered as a potential material for AMD treatment. The main goal of this work was to investigate potential use of BAs for AMD remediation. Four UK biomass ashes from different fuels (i.e., straw, meat and bone meal, mixed biomass) were characterised. All biomass ashes contain high concentrations of P, Ca, and K. The bulk crystalline phases in the biomass ashes include portlandite, calcite, arcanite, quartz, apatite, and other phosphates. We used a synthetic AMD which is comparable in composition to AMD from the Almasu Mare region in Romania. Batch experiments showed that a biomass ash from straw combustion (L/S = 250) can effectively neutralise the synthetic acid mine drainage (pH=2.7; Fe=310 mg/L; Zn=95 mg/L; Mn=54 mg/L), with removal of potential pollutants (pH=7.4; Fe=0.01 mg/L; Zn=0.58 mg/L; Mn=17 mg/L) in less than 1 hour. Other series of experiments were carried out on real AMDs from the Ursk Tailings of the Gold concentration plant and from the Belovo sludge pond from the Belovo zinc processing plant which have low pH (2.73-3.83) and high concentration of heavy metals. The biomass ashes from straw and mixed biomass combustion can effectively remove pollutants from the Ursk AMD at L/S = 100 and adjust pH=5.7-7.8. For the Belovo AMD, an appropriate L/S ratio is 10-30 and pH can be adjusted to 6.0-10. The metal concentrations of these treated AMDs met water quality standards. Pollutants mainly present as phosphate which usually have very low solubility product constant.