Utilisation of residue gas sludge (BOS sludge) for removal of heavy metals from acid mine drainage (AMD)

• Batchmode kinetic studieswere performed to assess the functionality of BOS sludge as a low cost sorbent for real AMD treatment.
• Results showed high pH obtained due to the dissolution of the BOS sludge (neutralising potential) during the agitation of AMD solution and BOS.
• Results revealed that the efficiency and adsorption rates were favoured with an increase in BOS mass and an increase in the initial solution pH.
• Residue gas sludge has the potential to function as an effective adsorbent in removal of heavy metal ions from real acid mine drainage solutions.

This investigation employed waste gas sludge (BOS sludge) which is an end-waste from steelmaking process as a novel adsorbent to study adsorption phenomena on real acid mine drainage. BOS sludge was used to treat Wheal Jane mine (Cornwall, UK) AMD in this work. Batch experiments were conducted as function of initial solution pH, adsorbent loading, regeneration and thermal treatment to study the performance of BOS sludge in removing manganese, copper, iron, and zinc.Kinetic studies indicated that the rate of adsorption of the heavy metals by BOS sludge was rapid. A high pH promoted adsorption and removal of the heavy metal ions was not only due to ion exchange or adsorption but also partly due to co-precipitation effect. The treatment of Wheal Jane mine AMD demonstrated that about 100% of Cu and Fe, 97% of Zn and 94% of Mn were removed from solution. The results show that BOS sludge has great potential as an alternative material in the treatment of real waste water streams. Thus BOS sludge could be used as a sustainable sorbent for the more expensive materials in AMD treatment technologies due to its adsorptive properties, high availability, large quantities and low cost.