Reduction crystallization of manganese and aluminum from waste water using hydrazine

Removal and recovery of heavy metals from wastewater has been a priority in recent years due to environmental and economic reasons. The scarcity of fresh water resources, pollution of water sources and the dwindling mineral reserves are some of the issues that has led to an increased interest in heavy metal removal and recovery. The use of hydrazine as a reducing agent to remove and recover aluminum and manganese metal was investigated. A 5 L batch reactor was used to conduct experiments where 100 mg/l of Al and Mn metal solutions were reduced using 1M hydrazine as a reducing agent. It was found that the metals were reduced to their elemental form. Hydrazine proved to be an effective reducing agent for Mn with average removal efficiencies of 99.8 and 99.5% in the single metal (Mn-only) and mixed metal systems (Mn and Al) respectively. However, the removal efficiency for Al was low with average removal efficiencies of 17 and 19% in the single and mixed metal system.