Preparation of Potassium Ferrate from Spent Steel Pickling Liquid

• Published in: Metals (Basel ) 2015-09, Vol.5 (4), p.1770-1787
• Main Authors: Wei, Yu-Ling, Wang, Yu-Shun, Liu, Chia-Hung
• Format: Article
• Language: English
• Subjects: Fe k-edge XAS; ferric chloride; ferrous chloride; potassium ferrate; steel pickling liquid; wet oxidation method
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met5041770

Potassium ferrate (K2FeO4) is a multi-functional green reagent for water treatment with considerable combined effectiveness in oxidization, disinfection, coagulation, sterilization, adsorption, and deodorization, producing environment friendly Fe(III) end-products during the reactions. This study uses a simple method to lower Fe(VI) preparation cost by recycling iron from a spent steel pickling liquid as an iron source for preparing potassium ferrate with a wet oxidation method. The recycled iron is in powder form of ferrous (93%) and ferric chlorides (7%), as determined by X-ray Absorption Near Edge Spectrum (XANES) simulation. The synthesis method involves three steps, namely, oxidation of ferrous/ferric ions to form ferrate with NaOCl under alkaline conditions, substitution of sodium with potassium to form potassium ferrate, and continuously washing impurities with various organic solvents off the in-house ferrate. Characterization of the in-house product with various instruments, such as scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS), proves that product quality and purity are comparative to a commercialized one. Methylene blue (MB) de-colorization tests with in-house potassium ferrate shows that, within 30 min, almost all MB molecules are de-colorized at a Fe/carbon mole ratio of 2/1.