Sustainability assessment of the recovery and utilisation of acid from acid mine drainage

Acid mine drainage (AMD) presents serious threats to the environment due to its toxic constituents. Traditional wastewater treatment methods such as neutralization, precipitation, membrane processes, ion exchange and biological sulphate removal, etc., have been applied to remediate AMD and reduce its negative impact on the receiving environment. However, the challenge with most of these methods is that the constituents of AMD have not been viewed as valuable resources. The constituents, though toxic can be recovered and transformed into valuable materials which could be marketed. Amongst the various AMD constituents, is sulphuric acid which has an appreciable market in the chemical and metallurgical industry. The acid value could be recovered from AMD and used to meet the demands of various sulphuric acid consumers. The financial benefits obtained could then be used to offset the overall AMD treatment cost. Hence, this paper reviews some of the techniques used to recover sulphuric acid from various wastewater solutions. The techniques reviewed include: rectification, membrane separation, solvent extraction, crystallization and acid retardation. The technical and economic feasibility of each process for application to AMD is also evaluated. Subsequently, the acid retardation and crystallization technologies are recommended as the most promising technologies for acid recovery from AMD.