Valorization of Acid Mine Drainage into an Iron Catalyst to Initiate the Solar Photo-Fenton Treatment of Municipal Wastewater

Abstract

Acid mine drainage was utilized to catalyze the solar photo-Fenton treatment of wastewater coming from a sludge dewatering system. Acid mine drainage in the form of iron-rich liquid or synthesized minerals (namely magnetite, hematite, and goethite) was added in the wastewater, which was treated by means of the solar photo-Fenton process. The effects of operational parameters such as the amount of acid mine drainage, the wastewater matrix (i.e., synthetic and real wastewater), and the initial H2O2 concentration municipal wastewater’s organic content were explored. The results showed that using acid mine drainage (liquid phase) for wastewater treatment was more efficient than using the acid-mine-drainage-recovered minerals. Moreover, it was observed that the addition of acid mine drainage above 10.7 mL/L wastewater, which is equivalent to 50 mg/L iron, could substantially reduce the removal percentage of the chemical oxygen demand (COD). At the best conditions assayed, COD removal reached 99% after 90 min of photo-Fenton treatment under simulated solar light, in the presence of 30 mg/L Fe (i.e., 6.4 mL drainage/L of real wastewater) and 1000 mg/L H2O2 at a pH of 2.8. Therefore, the solar photo-Fenton treatment of municipal wastewater catalyzed by acid mine drainage may appear to be a promising method to effectively improve wastewater management, especially in areas with high solar energy potential.