Optimized nano-scale zero-valent iron supported on treated activated carbon for enhanced nitrate and phosphate removal from water

Supported nano-scale zero-valent (nZVI) iron is a suitable material for groundwater and wastewater treatment applications. It can prevent the agglomeration of nanoparticles and increase their hydraulic conductivity. However, these supported nZVI particles suffer corrosion and greater pore diffusion resistance. Synthesis in ethanol medium, thermal treatment, acid treatment and acid thermal treatment were applied to deal with these problems and produce several treated composites of different nZVI to activated carbon (AC) mass ratios. Produced composites were characterized and applied in batch experiments to remove nitrate (200 mg NO3-/L), phosphate (50 mg PO43--P/L) and a mixture of nitrate and phosphate from their aqueous solutions. Among 25 composites, AC-supported nZVI (F(1)(2)AT(2)(950)) was selected at optimum nZVI/AC mass ratio of 2:1 and treatment conditions of 950 degrees C for 2 h. This study introduced thermal treatment of AC before supporting nZVI, which modified its textural and surface chemistry properties to attract contaminant anions with a higher affinity towards nZVI. F(1)(2)AT(2)(950) composite succeeded to increase removal efficiency of nitrate by 50% and of phosphate by 100% from their aqueous solutions and of nitrate by 170% along with a complete removal of phosphate from their solution. Interference studies were executed for actual field applications. The novel composite was tested in the presence of hardness, humic acid, phosphorus, sulfate ions, domestic wastewater and cuprous and cupric ions. The latter interference enhanced the removal efficiencies by about 10-50% according to concentrations and the type of copper compounds. The novel composite can be implemented as a promising reagent in environmental wastewater and groundwater technologies. (C) 2016 Elsevier B.V. All rights reserved.